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1

Supernova Cosmology Project  

NLE Websites -- All DOE Office Websites (Extended Search)

The Hubble Space Telescope Cluster Supernova Survey: The Hubble Space Telescope Cluster Supernova Survey: An Intensive HST Survey for z>1 Type Ia Supernovae by Targeting Galaxy Clusters Survey Paper: Dawson et al. (The Supernova Cosmology Project) 2009, AJ, 138, 1271 [ADS] [arXiv] We present a new survey strategy to discover and study high redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 0.95, nine of which were in galaxy clusters. This strategy provides a SN sample that can be used to decouple the effects of host galaxy extinction and intrinsic color in high redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology.

2

Four Papers by the Supernova Cosmology Project  

E-Print Network (OSTI)

Study Institute Thermonuclear Supernovae Conference,STUDY INSTITUTE THERMONUCLEAR SUPERNOVAE Aiguablava, SPAIN20-30, 1995 To appear-in Thermonuclear Supernovae (NATO ASI)

Perlmutter, S.; Deustua, S.; Gabi, S.; Goldhaber, G.

2008-01-01T23:59:59.000Z

3

Supernovae and cosmology with future European facilities  

Science Journals Connector (OSTI)

...high-redshift SN samples into the NIR. (i) Dark Energy Survey and VISTA The Dark Energy Survey (DES, see http://www.darkenergysurvey...Supernova simulations and strategies for the Dark Energy Survey. Astrophys. J. 753, 152. 10.1088...

2013-01-01T23:59:59.000Z

4

Fitting oscillating string gas cosmology to supernova data  

E-Print Network (OSTI)

In string gas cosmology, extra dimensions are stabilised by a gas of strings. In the matter-dominated era, competition between matter pushing the extra dimensions to expand and the string gas pulling them back can lead to oscillations of the extra dimensions and acceleration in the visible dimensions. We fit this model to supernova data, taking into account the Big Bang Nucleosynthesis constraint on the energy density of the string gas. The fit to the Union set of supernova data is acceptable, but the fit to the ESSENCE data is poor.

Francesc Ferrer; Tuomas Multamaki; Syksy Rasanen

2008-12-22T23:59:59.000Z

5

Fitting oscillating string gas cosmology to supernova data  

Science Journals Connector (OSTI)

In string gas cosmology, extra dimensions are stabilised by a gas of strings. In the matter-dominated era, competition between matter pushing the extra dimensions to expand and the string gas pulling them back can lead to oscillations of the extra dimensions and acceleration in the visible dimensions. We fit this model to supernova data, taking into account the Big Bang Nucleosynthesis constraint on the energy density of the string gas. The fit to the Union set of supernova data is acceptable, but the fit to the ESSENCE data is poor.

Francesc Ferrer; Tuomas Multamäki; Syksy Räsänen

2009-01-01T23:59:59.000Z

6

Cosmological Parameters From Supernovae Associated With Gamma-ray Bursts  

E-Print Network (OSTI)

We report estimates of the cosmological parameters $\\Omega_m$ and $\\Omega_{\\Lambda}$ obtained using supernovae (SNe) associated with gamma-ray bursts (GRBs) at redshifts up to 0.606. Eight high-fidelity GRB-SNe with well-sampled light curves across the peak are used. We correct their peak magnitudes for a luminosity-decline rate relation to turn them into accurate standard candles with dispersion $\\sigma = 0.18$ mag. We also estimate the peculiar velocity of the host galaxy of SN 1998bw, using constrained cosmological simulations. In a flat universe, the resulting Hubble diagram leads to best-fit cosmological parameters of $(\\Omega_m, \\Omega_{\\Lambda}) = (0.52^{+0.34}_{-0.31},0.48^{+0.31}_{-0.34})$. This exploratory study suggests that GRB-SNe can potentially be used as standardizable candles to high redshifts to measure distances in the universe and constrain cosmological parameters.

Li, Xue; Wojtak, Rados?aw

2014-01-01T23:59:59.000Z

7

Lightcurves of thermonuclear supernovae as a probe of the explosion mechanism and their use in cosmology  

E-Print Network (OSTI)

Thermonuclear supernovae are valuable for cosmology but their physics is not yet fully understood. Modeling the development and propagation of nuclear flame is complicated by numerous instabilities. The predictions of supernova light curves still involve some simplifying assumptions, but one can use the comparison of the computed fluxes with observations to constrain the explosion mechanism. In spite of great progress in recent years, a number of issues remains unsolved both in flame physics and light curve modeling.

S. Blinnikov; E. Sorokina

2002-12-30T23:59:59.000Z

8

Dimming of supernovae and gamma ray busts by Compton Scattering and its cosmological implications  

E-Print Network (OSTI)

Free electrons deplete photons from type Ia supernovae through the (inverse) Compton scattering. This Compton dimming increases with redshift and reaches 0.004 mag at $z=1$ and 0.01 mag at $z=2$. Although far from sufficient to invalidate the existence of dark energy, it can bias constraint on dark energy at a level non-negligible for future supernova surveys. This effect is correctable and should be incorporated in supernova analysis. The Compton dimming has similar impact on cosmology based on gamma ray bursts as standard candles.

Pengjie Zhang

2008-02-18T23:59:59.000Z

9

Cosmological Constant Problems and Renormalization Group  

E-Print Network (OSTI)

The Cosmological Constant Problem emerges when Quantum Field Theory is applied to the gravitational theory, due to the enormous magnitude of the induced energy of the vacuum. The unique known solution of this problem involves an extremely precise fine-tuning of the vacuum counterpart. We review a few of the existing approaches to this problem based on the account of the quantum (loop) effects and pay special attention to the ones involving the renormalization group.

Ilya L. Shapiro; Joan Sola

2007-01-05T23:59:59.000Z

10

Science magazine names Supernova Cosmology Project "Breakthrough of the  

NLE Websites -- All DOE Office Websites (Extended Search)

December 17, 1998 December 17, 1998 Go to Berkeley Lab Home Page Contacts: Saul Perlmutter, (510) 486-5203, s_perlmutter@lbl.gov Paul Preuss, (510) 486-6249, paul_preuss@lbl.gov Lynn Yarris, (510) 486-5375, lcyarris@lbl.gov Additional Information: Down-to-Earth Benefits from Far-Out Science Supernova Cosmology Project Research Site Jan 98 news release: Universe To Last Forever Search for Omega: Will the Universe Last Forever Fate of the Universe and the Cosmological Constant Revolution in Telescopes: The Keck The oldest, farthest supernova NERSC: Computers and Cosmology Images: High-resolution versions of image on this page Still images from the Supernova Cosmology Project website Online movie clip BERKELEY, CA -- By observing distant, ancient exploding stars, physicists and astronomers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory and elsewhere have determined that the universe is expanding at an accelerating rate -- an observation that implies the existence of a mysterious, self-repelling property of space first proposed by Albert Einstein, which he called the cosmological constant. This extraordinary finding has been named Science magazine's "Breakthrough of the Year for 1998."

11

Supernovae, an accelerating universe and the cosmological constant  

Science Journals Connector (OSTI)

...attributes the hydrogen-free type Ia supernovae to the thermonuclear detonation of white dwarf stars and the type II (as well...explode if a binary companion adds to its mass. When a thermonuclear burning wave destroys such a star, by burning approximately...

Robert P. Kirshner

1999-01-01T23:59:59.000Z

12

A review of "1604-2004: Supernovae as Cosmological Lighthouses." by Massimo Turatto, Stefano Benetti, Luca Zampieri, William Shea, eds.  

E-Print Network (OSTI)

in the history of early modern science. Massimo Turatto, Stefano Benetti, Luca Zampieri, William Shea, eds. 1604- 2004: Supernovae as Cosmological Lighthouses. Astronomical Society of the Pacific Conference Series, Vol. 342. San Francisco: ASP, 2005. 512 pp... in the history of early modern science. Massimo Turatto, Stefano Benetti, Luca Zampieri, William Shea, eds. 1604- 2004: Supernovae as Cosmological Lighthouses. Astronomical Society of the Pacific Conference Series, Vol. 342. San Francisco: ASP, 2005. 512 pp...

Giostra, Alessandro

2006-01-01T23:59:59.000Z

13

Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey  

Science Journals Connector (OSTI)

We present constraints on the dark energy equation-of-state parameter, w = P/(?c2), using 60 SNe Ia from the ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat universe. By including constraints on (?M, w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1.05 (stat 1 ?) ± 0.13 (sys) and ?M = 0.274 (stat 1 ?) with a best-fit ?2/dof of 0.96. These results are consistent with those reported by the Supernova Legacy Survey from the first year of a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the first-results Supernova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1.07 (stat 1 ?) ± 0.13 (sys), ?M = 0.267 (stat 1 ?) with a best-fit ?2/dof of 0.91. The current global SN Ia data alone rule out empty (?M = 0), matter-only ?M = 0.3, and ?M = 1 universes at >4.5 ?. The current SN Ia data are fully consistent with a cosmological constant.

W. M. Wood-Vasey; G. Miknaitis; C. W. Stubbs; S. Jha; A. G. Riess; P. M. Garnavich; R. P. Kirshner; C. Aguilera; A. C. Becker; J. W. Blackman; S. Blondin; P. Challis; A. Clocchiatti; A. Conley; R. Covarrubias; T. M. Davis; A. V. Filippenko; R. J. Foley; A. Garg; M. Hicken; K. Krisciunas; B. Leibundgut; W. Li; T. Matheson; A. Miceli; G. Narayan; G. Pignata; J. L. Prieto; A. Rest; M. E. Salvo; B. P. Schmidt; R. C. Smith; J. Sollerman; J. Spyromilio; J. L. Tonry; N. B. Suntzeff; A. Zenteno

2007-01-01T23:59:59.000Z

14

A Renormalization Group Approach to Relativistic Cosmology  

E-Print Network (OSTI)

We discuss the averaging hypothesis tacitly assumed in standard cosmology. Our approach is implemented in a "3+1" formalism and invokes the coarse graining arguments, provided and supported by the real-space Renormalization Group (RG) methods. Block variables are introduced and the recursion relations written down explicitly enabling us to characterize the corresponding RG flow. To leading order, the RG flow is provided by the Ricci-Hamilton equations studied in connection with the geometry of three-manifolds. The properties of the Ricci-Hamilton flow make it possible to study a critical behaviour of cosmological models. This criticality is discussed and it is argued that it may be related to the formation of sheet-like structures in the universe. We provide an explicit expression for the renormalized Hubble constant and for the scale dependence of the matter distribution. It is shown that the Hubble constant is affected by non-trivial scale dependent shear terms, while the spatial anisotropy of the metric influences significantly the scale-dependence of the matter distribution.

Mauro Carfora; Kamilla Piotrkowska

1995-02-08T23:59:59.000Z

15

Discovery of a Supernova Explosion at Half the Age of the Universe and its Cosmological Implications  

E-Print Network (OSTI)

and Bounds on qo. in Thermonuclear Supernovae (eds P. Ruiz-novae as clocks. in Thermonuclear Supernovae (eds P. Ruiz-distance indicators. in Thermonuclear Supernovae (eds P.

Perlmutter, S.

2010-01-01T23:59:59.000Z

16

Verifying the Cosmological Utility of Type Ia Supernovae: Implications of a Dispersion in the Ultraviolet Spectra  

SciTech Connect

We analyze the mean rest-frame ultraviolet (UV) spectrum of Type Ia Supernovae (SNe) and its dispersion using high signal-to-noise ratio Keck-I/LRIS-B spectroscopy for a sample of 36 events at intermediate redshift (z=0.5) discovered by the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We introduce a new method for removing host galaxy contamination in our spectra, exploiting the comprehensive photometric coverage of the SNLS SNe and their host galaxies, thereby providing the first quantitative view of the UV spectral properties of a large sample of distant SNe Ia. Although the mean SN Ia spectrum has not evolved significantly over the past 40percent of cosmic history, precise evolutionary constraints are limited by the absence of a comparable sample of high-quality local spectra. The mean UV spectrum of our z~;;=0.5 SNe Ia and its dispersion is tabulated for use in future applications. Within the high-redshift sample, we discover significant UV spectral variations and exclude dust extinction as the primary cause by examining trends with the optical SN color. Although progenitor metallicity may drive some of these trends, the variations we see are much larger than predicted in recent models and do not follow expected patterns. An interesting new result is a variation seen in the wavelength of selected UV features with phase. We also demonstrate systematic differences in the SN Ia spectral features with SN light curve width in both the UV and the optical. We show that these intrinsic variations could represent a statistical limitation in the future use of high-redshift SNe Ia for precision cosmology. We conclude that further detailed studies are needed, both locally and at moderate redshift where the rest-frame UV can be studied precisely, in order that future missions can confidently be planned to fully exploit SNe Ia as cosmological probes.

Nugent, Peter E; Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam, A.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R.; Conley, A.; Fouchez, D.; Guy, J.; Hardin, D.; Hook, I.; Pain, R.; Perrett, K.; Pritchet, C.J.; Regnault, N.

2008-02-28T23:59:59.000Z

17

Supernova Simulations from the T-6 Group at Los Alamos National Laboratory (LANL)  

DOE Data Explorer (OSTI)

LANL's primary effort to numerically model supernova explosions is based in the Theoretical Astrophysics Group (T-6). Both thermonuclear supernovae and core- collapse supernovae are studied, with special emphasis placed on multi-dimensional simulations. Both types of supernova require a wide range of input physics, which is provided by research efforts throughout the lab. In particular this research benefits from other LANL efforts studying massive star evolution, equations of state and aspects of neutrino physics. [From http://laastro.lanl.gov/science/computation.html

Woosley, Stanford

18

Observational Constraints on the Nature of the Dark Energy: First Cosmological Results From the ESSENCE Supernova Survey  

SciTech Connect

We present constraints on the dark energy equation-of-state parameter, w = P/({rho}c{sup 2}), using 60 Type Ia supernovae (SNe Ia) from the ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat Universe. By including constraints on ({Omega}{sub M}, w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1.05{sub -0.12}{sup +0.13} (stat 1{sigma}) {+-} 0.13 (sys) and {Omega}{sub M} = 0.274{sub -0.020}{sup +0.033} (stat 1{sigma}) with a best-fit {chi}{sup 2}/DoF of 0.96. These results are consistent with those reported by the Super-Nova Legacy Survey in a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic currently with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the SuperNova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1.07{sub -0.09}{sup +0.09} (stat 1{sigma}) {+-} 0.13 (sys), {Omega}{sub M} = 0.267{sub -0.018}{sup +0.028} (stat 1{sigma}) with a best-fit {chi}{sup 2}/DoF of 0.91. The current SNe Ia data are fully consistent with a cosmological constant.

Wood-Vasey, W.Michael; Miknaitis, G.; Stubbs, C.W.; Jha, S.; Riess, A.G.; Garnavich, P.M.; Kirshner, R.P.; Aguilera, C.; Becker, A.C.; Blackman, J.W.; Blondin, S.; Challis, P.; Clocchiatti, A.; Conley, A.; Covarrubias, R.; Davis, T.M.; Filippenko, A.V.; Foley, R.J.; Garg, A.; Hicken, M.; Krisciunas, K.; /Harvard-Smithsonian Ctr. Astrophys.

2007-01-05T23:59:59.000Z

19

Type Ia supernovae selection and forecast of cosmology constraints for the Dark Energy Survey  

Science Journals Connector (OSTI)

We present the results of a study of selection criteria to identify Type Ia supernovae photometrically in a simulated mixed sample of Type Ia supernovae and core collapse supernovae. The simulated sample is a mockup of the expected results of the Dark Energy Survey. Fits to the \\{MLCS2k2\\} and SALT2 Type Ia supernova models are compared and used to help separate the Type Ia supernovae from the core collapse sample. The Dark Energy Task Force Figure of Merit (modified to include core collapse supernovae systematics) is used to discriminate among the various selection criteria. This study of varying selection cuts for Type Ia supernova candidates is the first to evaluate core collapse contamination using the Figure of Merit. Different factors that contribute to the Figure of Merit are detailed. With our analysis methods, both SALT2 and \\{MLCS2k2\\} Figures of Merit improve with tighter selection cuts and higher purities, peaking at 98% purity.

Eda Gjergo; Jefferson Duggan; John D. Cunningham; Steve Kuhlmann; Rahul Biswas; Eve Kovacs; Joseph P. Bernstein; Harold Spinka

2013-01-01T23:59:59.000Z

20

Verifying the Cosmological Utility of Type Ia Supernovae:Implications of a Dispersion in the Ultraviolet Spectra  

SciTech Connect

We analyze the mean rest-frame ultraviolet (UV) spectrum ofType Ia Supernovae(SNe) and its dispersion using high signal-to-noiseKeck-I/LRIS-B spectroscopyfor a sample of 36 events at intermediateredshift (z=0.5) discoveredby the Canada-France-Hawaii TelescopeSupernova Legacy Survey (SNLS). Weintroduce a new method for removinghost galaxy contamination in our spectra,exploiting the comprehensivephotometric coverage of the SNLS SNe and theirhost galaxies, therebyproviding the first quantitative view of the UV spectralproperties of alarge sample of distant SNe Ia. Although the mean SN Ia spectrumhas notevolved significantly over the past 40 percent of cosmic history,preciseevolutionary constraints are limited by the absence of acomparable sample ofhigh quality local spectra. The mean UV spectrum ofour z 0.5 SNe Ia and itsdispersion is tabulated for use in futureapplications. Within the high-redshiftsample, we discover significant UVspectral variations and exclude dust extinctionas the primary cause byexamining trends with the optical SN color. Although progenitormetallicity may drive some of these trends, the variations we see aremuchlarger than predicted in recent models and do not follow expectedpatterns.An interesting new result is a variation seen in the wavelengthof selected UVfeatures with phase. We also demonstrate systematicdifferences in the SN Iaspectral features with SN lightcurve width inboth the UV and the optical. Weshow that these intrinsic variations couldrepresent a statistical limitation in thefuture use of high-redshift SNeIa for precision cosmology. We conclude thatfurther detailed studies areneeded, both locally and at moderate redshift wherethe rest-frame UV canbe studied precisely, in order that future missions canconfidently beplanned to fully exploit SNe Ia as cosmological probes.

Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam,A.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R.G.; Conley,A.; Fouchez, D.; Guy, J.; Hardin, D.; Hook, I.; Pain, R.; Perrett, K.; Pritchet, C.J.; Regnault, N.

2007-11-02T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

TESTING MODELS OF INTRINSIC BRIGHTNESS VARIATIONS IN TYPE Ia SUPERNOVAE AND THEIR IMPACT ON MEASURING COSMOLOGICAL PARAMETERS  

SciTech Connect

For spectroscopically confirmed Type Ia supernovae we evaluate models of intrinsic brightness variations with detailed data/Monte Carlo comparisons of the dispersion in the following quantities: Hubble-diagram scatter, color difference (B - V - c) between the true B - V color and the fitted color (c) from the SALT-II light curve model, and photometric redshift residual. The data sample includes 251 ugriz light curves from the three-season Sloan Digital Sky Survey-II and 191 griz light curves from the Supernova Legacy Survey 3 year data release. We find that the simplest model of a wavelength-independent (coherent) scatter is not adequate, and that to describe the data the intrinsic-scatter model must have wavelength-dependent variations resulting in a {approx}0.02 mag scatter in B - V - c. Relatively weak constraints are obtained on the nature of intrinsic scatter because a variety of different models can reasonably describe this photometric data sample. We use Monte Carlo simulations to examine the standard approach of adding a coherent-scatter term in quadrature to the distance-modulus uncertainty in order to bring the reduced {chi}{sup 2} to unity when fitting a Hubble diagram. If the light curve fits include model uncertainties with the correct wavelength dependence of the scatter, we find that this approach is valid and that the bias on the dark energy equation-of-state parameter w is much smaller ({approx}0.001) than current systematic uncertainties. However, incorrect model uncertainties can lead to a significant bias on the distance moduli, with up to {approx}0.05 mag redshift-dependent variation. This bias is roughly reduced in half after applying a Malmquist bias correction. For the recent SNLS3 cosmology results, we estimate that this effect introduces an additional systematic uncertainty on w of {approx}0.02, well below the total uncertainty. This uncertainty depends on the choice of viable scatter models and the choice of supernova (SN) samples, and thus this small w-uncertainty is not guaranteed in future cosmology results. For example, the w-uncertainty for SDSS+SNLS (dropping the nearby SNe) increases to {approx}0.04.

Kessler, Richard; Frieman, Joshua A. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)] [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Guy, Julien; Betoule, Marc; El-Hage, Patrick [Laboratoire de Physique Nucleaire et des Hautes Energies, UPMC Univ. Paris 6, UPD Univ. Paris 7, CNRS IN2P3, 4 place Jussieu, F-75005 Paris (France)] [Laboratoire de Physique Nucleaire et des Hautes Energies, UPMC Univ. Paris 6, UPD Univ. Paris 7, CNRS IN2P3, 4 place Jussieu, F-75005 Paris (France); Marriner, John [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)] [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Brinkmann, Jon [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States)] [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Cinabro, David [Department of Physics, Wayne State University, Detroit, MI 48202 (United States)] [Department of Physics, Wayne State University, Detroit, MI 48202 (United States); Jha, Saurabh [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)] [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Mosher, Jennifer [Department of Physics and Astronomy, University of Pennsylvania, 203 South 33rd Street, Philadelphia, PA 19104 (United States)] [Department of Physics and Astronomy, University of Pennsylvania, 203 South 33rd Street, Philadelphia, PA 19104 (United States); Schneider, Donald P., E-mail: kessler@kicp.uchicago.edu [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

2013-02-10T23:59:59.000Z

22

Effects of systematic uncertainties on the supernova determination of cosmological parameters  

Science Journals Connector (OSTI)

......cosmological parameters Alex G. Kim 1 Eric V. Linder 1 Ramon Miquel 1 Nick Mostek 2 E-mail: rmiquel@lbl.gov 1 Lawrence Berkeley...at high redshifts. This point is of sufficient importance to merit a formal proof in the Appendix. 4.1 Monte Carlo analysis......

Alex G. Kim; Eric V. Linder; Ramon Miquel; Nick Mostek

2004-01-21T23:59:59.000Z

23

Testing Models of Intrinsic Brightness Variations in Type Ia Supernovae, and their Impact on Measuring Cosmological Parameters  

E-Print Network (OSTI)

For spectroscopically confirmed type Ia supernovae we evaluate models of intrinsic brightness variations with detailed data/Monte-Carlo comparisons of the dispersion in the following quantities: Hubble-diagram scatter, color difference (B-V-c) between the true B-V color and the fitted color (c) from the SALT-II light curve model, and photometric redshift residual. The data sample includes 251 ugriz light curves from the 3-season Sloan Digital Sky Survey-II, and 191 griz light curves from the Supernova Legacy Survey 3-year data release. We find that the simplest model of a wavelength independent (coherent) scatter is not adequate, and that to describe the data the intrinsic scatter model must have wavelength-dependent variations. We use Monte Carlo simulations to examine the standard approach of adding a coherent scatter term in quadrature to the distance-modulus uncertainty in order to bring the reduced chi2 to unity when fitting a Hubble diagram. If the light curve fits include model uncertainties with the c...

Kessler, Richard; Marriner, John; Betoule, Marc; Brinkmann, Jon; Cinabro, David; El-Hage, Patrick; Frieman, Joshua; Jha, Saurabh; Mosher, Jennifer; Schneider, Donald P

2012-01-01T23:59:59.000Z

24

Thermonuclear Supernovae  

E-Print Network (OSTI)

The application of Type Ia supernovae (SNe Ia) as distance indicators in cosmology calls for a sound understanding of these objects. Recent years have seen a brisk development of astrophysical models which explain SNe Ia as thermonuclear explosions of white dwarf stars. While the evolution of the progenitor is still uncertain, the explosion mechanism certainly involves the propagation of a thermonuclear flame through the white dwarf star. Three-dimensional hydrodynamical simulations allowed to study a wide variety of possibilities involving subsonic flame propagation (deflagrations), flames accelerated by turbulence, and supersonic detonations. These possibilities lead to a variety of scenarios. I review the currently discussed approaches and present some recent results from simulations of the turbulent deflagration model and the delayed detonation model.

F. K. Roepke

2008-04-14T23:59:59.000Z

25

The supernova that destroyed a galaxy  

NLE Websites -- All DOE Office Websites (Extended Search)

The supernova that destroyed a galaxy The supernova that destroyed a galaxy The supernova that destroyed a galaxy The research may solve the long-standing puzzle of how supermassive black holes were formed in the centers of some galaxies less then a billion years after the Big Bang. August 5, 2013 Supernova of a 55,000 solar-mass star in a primitive galaxy (explosion in a low-density region) Supernova of a 55,000 solar-mass star in a primitive galaxy (explosion in a low-density region) The Los Alamos simulation is the most realistic cosmological supernova simulation ever performed of this process. New supercomputer simulations by Los Alamos scientists and collaborators capture in unprecedented detail extremely powerful supernovae explosions in the early universe and their effect on the nascent galaxies that gave birth

26

The supernova that destroyed a galaxy  

NLE Websites -- All DOE Office Websites (Extended Search)

August » August » The supernova that destroyed a galaxy The supernova that destroyed a galaxy The research may solve the long-standing puzzle of how supermassive black holes were formed in the centers of some galaxies less then a billion years after the Big Bang. August 5, 2013 Supernova of a 55,000 solar-mass star in a primitive galaxy (explosion in a low-density region) Supernova of a 55,000 solar-mass star in a primitive galaxy (explosion in a low-density region) The Los Alamos simulation is the most realistic cosmological supernova simulation ever performed of this process. New supercomputer simulations by Los Alamos scientists and collaborators capture in unprecedented detail extremely powerful supernovae explosions in the early universe and their effect on the nascent galaxies that gave birth

27

The distant type Ia supernova rate  

SciTech Connect

We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample,which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1 supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.

Pain, R.; Fabbro, S.; Sullivan, M.; Ellis, R.S.; Aldering, G.; Astier, P.; Deustua, S.E.; Fruchter, A.S.; Goldhaber, G.; Goobar, A.; Groom, D.E.; Hardin, D.; Hook, I.M.; Howell, D.A.; Irwin, M.J.; Kim, A.G.; Kim, M.Y.; Knop, R.A.; Lee, J.C.; Perlmutter, S.; Ruiz-Lapuente, P.; Schahmaneche, K.; Schaefer, B.; Walton, N.A.

2002-05-20T23:59:59.000Z

28

The Distant Type Ia Supernova Rate  

DOE R&D Accomplishments (OSTI)

We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample, which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1 supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.

Pain, R.; Fabbro, S.; Sullivan, M.; Ellis, R. S.; Aldering, G.; Astier, P.; Deustua, S. E.; Fruchter, A. S.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I. M.; Howell, D. A.; Irwin, M. J.; Kim, A. G.; Kim, M. Y.; Knop, R. A.; Lee, J. C.; Perlmutter, S.; Ruiz-Lapuente, P.; Schahmaneche, K.; Schaefer, B.; Walton, N. A.

2002-05-28T23:59:59.000Z

29

Supernova bangs as a tool to study big bang  

SciTech Connect

Supernovae and gamma-ray bursts are the most powerful explosions in observed Universe. This educational review tells about supernovae and their applications in cosmology. It is explained how to understand the production of light in the most luminous events with minimum required energy of explosion. These most luminous phenomena can serve as primary cosmological distance indicators. Comparing the observed distance dependence on red shift with theoretical models one can extract information on evolution of the Universe from Big Bang until our epoch.

Blinnikov, S. I., E-mail: Sergei.Blinnikov@itep.ru [Institute for Theoretical and Experimental Physics (Russian Federation)

2012-09-15T23:59:59.000Z

30

Resource Letter: OTS-1: Observations and theory of supernovae  

Science Journals Connector (OSTI)

This Resource Letter provides a guide to the literature on the observations of supernovae and the theory of their explosion mechanisms. Journal articles and books are cited for the following topics: observations of the spectra spectropolarimetry and light curves of supernovae of various types theory of thermonuclear explosions core collapse and radioactive decay applications to cosmology and possible connections to gamma-ray bursts.

J. Craig Wheeler

2003-01-01T23:59:59.000Z

31

{chi}{sup 2} versus median statistics in supernova type Ia data analysis  

SciTech Connect

In this paper we compare the performances of the {chi}{sup 2} and median likelihood analysis in the determination of cosmological constraints using type Ia supernovae data. We perform a statistical analysis using the 307 supernovae of the Union 2 compilation of the Supernova Cosmology Project and find that the {chi}{sup 2} statistical analysis yields tighter cosmological constraints than the median statistic if only supernovae data is taken into account. We also show that when additional measurements from the cosmic microwave background and baryonic acoustic oscillations are considered, the combined cosmological constraints are not strongly dependent on whether one applies the {chi}{sup 2} statistic or the median statistic to the supernovae data. This indicates that, when complementary information from other cosmological probes is taken into account, the performances of the {chi}{sup 2} and median statistics are very similar, demonstrating the robustness of the statistical analysis.

Barreira, A. [Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Avelino, P. P. [Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

2011-10-15T23:59:59.000Z

32

Dark energy, gravitation and supernovae  

E-Print Network (OSTI)

The discovery of the acceleration of the rate of expansion of the Universe fosters new explorations of the behavior of gravitation theories in the cosmological context. Either the GR framework is valid but a cosmic component with a negative equation of state is dominating the energy--matter contents or the Universe is better described at large by a theory that departs from GR. In this review we address theoretical alternatives that have been explored through supernovae.

Pilar Ruiz-Lapuente

2007-04-09T23:59:59.000Z

33

The ESSENCE Supernova Survey: Survey Optimization, Observations, and Supernova Photometry  

SciTech Connect

We describe the implementation and optimization of the ESSENCE supernova survey, which we have undertaken to measure the equation of state parameter of the dark energy. We present a method for optimizing the survey exposure times and cadence to maximize our sensitivity to the dark energy equation of state parameter w = P/{rho}c{sup 2} for a given fixed amount of telescope time. For our survey on the CTIO 4m telescope, measuring the luminosity distances and redshifts for supernovae at modest redshifts (z {approx} 0.5 {+-} 0.2) is optimal for determining w. We describe the data analysis pipeline based on using reliable and robust image subtraction to find supernovae automatically and in near real-time. Since making cosmological inferences with supernovae relies crucially on accurate measurement of their brightnesses, we describe our efforts to establish a thorough calibration of the CTIO 4m natural photometric system. In its first four years, ESSENCE has discovered and spectroscopically confirmed 102 type Ia SNe, at redshifts from 0.10 to 0.78, identified through an impartial, effective methodology for spectroscopic classification and redshift determination. We present the resulting light curves for the all type Ia supernovae found by ESSENCE and used in our measurement of w, presented in Wood-Vasey et al. (2007).

Miknaitis, Gajus; Pignata, G.; Rest, A.; Wood-Vasey, W.M.; Blondin, S.; Challis, P.; Smith, R.C.; Stubbs, C.W.; Suntzeff, N.B.; Foley, R.J.; Matheson, T.; Tonry, J.L.; Aguilera, C.; Blackman, J.W.; Becker, A.C.; Clocchiatti, A.; Covarrubias, R.; Davis, T.M.; Filippenko, A.V.; Garg, A.; Garnavich, P.M.; /Fermilab /Chile U., Catolica /Cerro-Tololo

2007-01-08T23:59:59.000Z

34

Supernova Simulations and Strategies for the Dark Energy Survey  

Science Journals Connector (OSTI)

We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 deg2 search area in the griz filter set. We forecast (1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05 z

J. P. Bernstein; R. Kessler; S. Kuhlmann; R. Biswas; E. Kovacs; G. Aldering; I. Crane; C. B. D'Andrea; D. A. Finley; J. A. Frieman; T. Hufford; M. J. Jarvis; A. G. Kim; J. Marriner; P. Mukherjee; R. C. Nichol; P. Nugent; D. Parkinson; R. R. R. Reis; M. Sako; H. Spinka; M. Sullivan

2012-01-01T23:59:59.000Z

35

SUPERNOVA SIMULATIONS AND STRATEGIES FOR THE DARK ENERGY SURVEY  

SciTech Connect

We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 deg{sup 2} search area in the griz filter set. We forecast (1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05 supernova with an identified host galaxy will be obtained from spectroscopic observations of the host. A supernova spectrum will be obtained for a subset of the sample, which will be utilized for control studies. In addition, we have investigated the use of combined photometric redshifts taking into account data from both the host and supernova. We have investigated and estimated the likely contamination from core-collapse supernovae based on photometric identification, and have found that a Type Ia supernova sample purity of up to 98% is obtainable given specific assumptions. Furthermore, we present systematic uncertainties due to sample purity, photometric calibration, dust extinction priors, filter-centroid shifts, and inter-calibration. We conclude by estimating the uncertainty on the cosmological parameters that will be measured from the DES supernova data.

Bernstein, J. P.; Kuhlmann, S.; Biswas, R.; Kovacs, E.; Crane, I.; Hufford, T. [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Kessler, R.; Frieman, J. A. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Aldering, G.; Kim, A. G.; Nugent, P. [E. O. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); D'Andrea, C. B.; Nichol, R. C. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Finley, D. A.; Marriner, J.; Reis, R. R. R. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Jarvis, M. J. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Mukherjee, P.; Parkinson, D. [Department of Physics and Astronomy, Pevensey 2 Building, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Sako, M. [Department of Physics and Astronomy, University of Pennsylvania, 203 South 33rd Street, Philadelphia, PA 19104 (United States); and others

2012-07-10T23:59:59.000Z

36

Thermonuclear Burning Regimes and the Use of SNe Ia in Cosmology  

E-Print Network (OSTI)

The calculations of the light curves of thermonuclear supernovae are carried out by a method of multi-group radiation hydrodynamics. The effects of spectral lines and expansion opacity are taken into account. The predictions for UBVI fluxes are given. The values of rise time for B and V bands found in our calculations are in good agreement with the observed values. We explain why our results for the rise time have more solid physical justification than those obtained by other authors. It is shown that small variations in the chemical composition of the ejecta, produced in the explosions with different regimes of nuclear burning, can influence drastically the light curve decline in the B band and, to a lesser extent, in the V band. We argue that recent results on positive cosmological constant Lambda, found from the high redshift supernova observations, could be wrong in the case of possible variations of the preferred mode of nuclear burning in the earlier Universe.

E. I. Sorokina; S. I. Blinnikov; O. S. Bartunov

1999-10-02T23:59:59.000Z

37

Supernova: Carbon detonation redux  

Science Journals Connector (OSTI)

... A DECADE ago carbon detonation was all the rage among supernova theorists. The idea was that the characteristic burst ... wind.

J. Craig Wheeler

1983-03-17T23:59:59.000Z

38

Magnetized String Cosmological Model in Cylindrically Symmetric Inhomogeneous Universe with Variable Cosmological-Term $?$  

E-Print Network (OSTI)

Cylindrically symmetric inhomogeneous magnetized string cosmological model is investigated with cosmological term $\\Lambda$ varying with time. To get the deterministic solution, it has been assumed that the expansion ($\\theta$) in the model is proportional to the eigenvalue $\\sigma^{1}_{1}$ of the shear tensor $\\sigma^{i}_{j}$. The value of cosmological constant for the model is found to be small and positive which is supported by the results from recent supernovae Ia observations. The physical and geometric properties of the model are also discussed in presence and absence of magnetic field.

Anirudh Pradhan

2007-08-01T23:59:59.000Z

39

Observational constraints on late-time {lambda}(t) cosmology  

SciTech Connect

The cosmological constant {lambda}, i.e., the energy density stored in the true vacuum state of all existing fields in the Universe, is the simplest and the most natural possibility to describe the current cosmic acceleration. However, despite its observational successes, such a possibility exacerbates the well-known {lambda} problem, requiring a natural explanation for its small, but nonzero, value. In this paper we study cosmological consequences of a scenario driven by a varying cosmological term, in which the vacuum energy density decays linearly with the Hubble parameter, {lambda}{proportional_to}H. We test the viability of this scenario and study a possible way to distinguish it from the current standard cosmological model by using recent observations of type Ia supernova (Supernova Legacy Survey Collaboration), measurements of the baryonic acoustic oscillation from the Sloan Digital Sky Survey, and the position of the first peak of the cosmic microwave background angular spectrum from the three-year Wilkinson Microwave Anisotropy Probe.

Carneiro, S.; Pigozzo, C. [Instituto de Fisica, Universidade Federal da Bahia, Salvador-BA, 40210-340 (Brazil); Dantas, M. A. [Departamento de Astronomia, Observatorio Nacional, Rio de Janeiro-RJ, 20921-400 (Brazil); Alcaniz, J. S. [Departamento de Astronomia, Observatorio Nacional, Rio de Janeiro-RJ, 20921-400 (Brazil); Instituto Nacional de Pesquisas Espaciais/CRN, 59076-740, Natal-RN (Brazil)

2008-04-15T23:59:59.000Z

40

Groups  

Open Energy Info (EERE)

groups/all/feed en Buildings groups/all/feed en Buildings http://en.openei.org/community/group/buildings Description: This group is dedicated to discussions about green buildings, energy use in buildings, occupant comfort in buildings, and building technologies. The OpenEI Buildings Community Group will be dedicated to discussions, blogs, and postings about new building technologies, green buildings, energy use in buildings, and occupant experience (comfort levels) in green buildings.group/buildings" target="_blank">read more architecture building reviews buildings technology comfort energy use facilities management green building LEED technologies usgbc

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Overview of the Nearby Supernova Factory G. Alderinga, G. Adamb, P. Antilogusc, P. Astierd, R. Baconb, S. Bongardc, C. Bonnaudb,  

E-Print Network (OSTI)

. Their cosmological use was developed in the early 1990's, paving the way for the discovery of dark energy.1, 4­10 Now, cosmology, integral-field-unit, spectrograph 1. PROBING DARK ENERGY WITH SUPERNOVAE A coherent view of the universe is emerging in which a mysterious form of "dark energy" accounts for about 2/3 of the total energy

Paris-Sud XI, Université de

42

Laser Cosmology  

E-Print Network (OSTI)

Recent years have seen tremendous progress in our understanding of the cosmos, which in turn points to even deeper questions to be further addressed. Concurrently the laser technology has undergone dramatic revolutions, providing exciting opportunity for science applications. History has shown that the symbiosis between direct observations and laboratory investigation is instrumental in the progress of astrophysics. We believe that this remains true in cosmology. Current frontier phenomena related to particle astrophysics and cosmology typically involve one or more of the following conditions: (1) extremely high energy events; (2) very high density, high temperature processes; (3) super strong field environments. Laboratory experiments using high intensity lasers can calibrate astrophysical observations, investigate underlying dynamics of astrophysical phenomena, and probe fundamental physics in extreme limits. In this article we give an overview of the exciting prospect of laser cosmology. In particular, we showcase its unique capability of investigating frontier cosmology issues such as cosmic accelerator and quantum gravity.

Pisin Chen

2014-02-24T23:59:59.000Z

43

Supernova Bounds on the Dark Photon Using its Electromagnetic Decay  

E-Print Network (OSTI)

The hypothetical massive dark photon ($\\gamma'$) which has kinetic mixing with the SM photon can decay electromagnetically to $e^+e^-$ pairs if its mass $m$ exceeds $2m_e$ and otherwise into three SM photons. These decays yield cosmological and supernovae associated signatures. We briefly discuss these signatures, particularly in connection with the supernova SN1987A and delineate the extra constraints that may then arise on the mass and mixing parameter of the dark photon. In particular, we find that for dark photon mass $m_{\\gamma'}$ in the 5-20 MeV range, arguments based on supernova 1987A observations lead to a bound on $\\epsilon$ which is about 300 times stronger than the presently existing bounds based on energy loss arguments.

Kazanas, Demos; Nussinov, Shmuel; Teplitz, Vic; Zhang, Yongchao

2014-01-01T23:59:59.000Z

44

Physics of supernovae  

SciTech Connect

Presupernova models of massive stars are presented and their explosion by ''delayed neutrino transport'' examined. A new form of long duration Type II supernova model is also explored based upon repeated encounter with the electron-positron pair instability in stars heavier than about 60 Msub solar. Carbon deflagration in white dwarfs is discussed as the probable explanation of Type I supernovae and special attention is paid to the physical processes whereby a nuclear flame propagates through degenerate carbon. 89 refs., 12 figs.

Woosley, S.E.; Weaver, T.A.

1985-12-13T23:59:59.000Z

45

Conformal cosmological model and SNe Ia data  

SciTech Connect

Now there is a huge scientific activity in astrophysical studies and cosmological ones in particular. Cosmology transforms from a pure theoretical branch of science into an observational one. All the cosmological models have to pass observational tests. The supernovae type Ia (SNe Ia) test is among the most important ones. If one applies the test to determine parameters of the standard Friedmann-Robertson-Walker cosmological model one can conclude that observations lead to the discovery of the dominance of the {Lambda} term and as a result to an acceleration of the Universe. However, there are big mysteries connected with an origin and an essence of dark matter (DM) and the {Lambda} term or dark energy (DE). Alternative theories of gravitation are treated as a possible solution of DM and DE puzzles. The conformal cosmological approach is one of possible alternatives to the standard {Lambda}CDM model. As it was noted several years ago, in the framework of the conformal cosmological approach an introduction of a rigid matter can explain observational data without {Lambda} term (or dark energy). We confirm the claim with much larger set of observational data.

Zakharov, A. F., E-mail: zakharov@itep.ru [National Astronomical Observatories of Chinese Academy of Sciences (China); Pervushin, V. N. [Joint Institute for Nuclear Research, Bogoliubov Laboratory for Theoretical Physics (Russian Federation)

2012-11-15T23:59:59.000Z

46

Evolution of density perturbations in decaying vacuum cosmology  

SciTech Connect

We study cosmological perturbations in the context of an interacting dark energy model, in which the cosmological term decays linearly with the Hubble parameter, with concomitant matter production. A previous joint analysis of the redshift-distance relation for type Ia supernovas, barionic acoustic oscillations, and the position of the first peak in the anisotropy spectrum of the cosmic microwave background has led to acceptable values for the cosmological parameters. Here we present our analysis of small perturbations, under the assumption that the cosmological term, and therefore the matter production, are strictly homogeneous. Such a homogeneous production tends to dilute the matter contrast, leading to a late-time suppression in the power spectrum. Nevertheless, an excellent agreement with the observational data can be achieved by using a higher matter density as compared to the concordance value previously obtained. This may indicate that our hypothesis of homogeneous matter production must be relaxed by allowing perturbations in the interacting cosmological term.

Borges, H. A.; Pigozzo, C. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Carneiro, S. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); International Centre for Theoretical Physics, Trieste (Italy); Fabris, J. C. [Institut d'Astrophysique de Paris, Paris (France)

2008-02-15T23:59:59.000Z

47

Supernova Caught in the Act  

NLE Websites -- All DOE Office Websites (Extended Search)

Supernova Caught in Supernova Caught in the Act Supernova Caught in the Act Earliest-ever Detection Made Possible by Computing, Networks August 25, 2011 Contact: Linda Vu, +1 510 495 2402, lvu@lbl.gov ptf11kly.jpg Before and after images of supernova PTF 11kly as it appeared in the nearby M101 galaxy. Click to enlarge. (Images: Peter Nugent) A supernova discovered yesterday is closer to Earth-approximately 21 million light-years away-than any other of its kind in a generation. Astronomers believe they caught the supernova within hours of its explosion, a rare feat made possible by a specialized survey telescope and state-of-the-art computational tools. The discovery of such a supernova so early and so close has energized the astronomical community as they are scrambling to observe it with as many

48

Essential ingredients in core-collapse supernovae  

SciTech Connect

Carrying 10{sup 44} joules of kinetic energy and a rich mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up our solar system and ourselves. Signaling the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae combine physics over a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer-scale nuclear reactions. We will discuss our emerging understanding of the convectively-unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have recently motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of the births of neutron stars and the supernovae that result. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

Hix, W. Raphael [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States) [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Lentz, Eric J.; Chertkow, M. Austin; Harris, J. Austin [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States)] [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Endeve, Eirik [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6008 (United States)] [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6008 (United States); Baird, Mark [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6003 (United States)] [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6003 (United States); Messer, O. E. Bronson [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States) [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831-6008 (United States); Mezzacappa, Anthony [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States) [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Joint Institute for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6173 (United States); Bruenn, Stephen [Department of Physics, Florida Atlantic University, 777 W Glades Road, Boca Raton, FL 33431-0991 (United States)] [Department of Physics, Florida Atlantic University, 777 W Glades Road, Boca Raton, FL 33431-0991 (United States); Blondin, John [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)] [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)

2014-04-15T23:59:59.000Z

49

Theoretical models for supernovae  

SciTech Connect

The results of recent numerical simulations of supernova explosions are presented and a variety of topics discussed. Particular emphasis is given to (i) the nucleosynthesis expected from intermediate mass (10sub solar less than or equal to M less than or equal to 100 Msub solar) Type II supernovae and detonating white dwarf models for Type I supernovae, (ii) a realistic estimate of the ..gamma..-line fluxes expected from this nucleosynthesis, (iii) the continued evolution, in one and two dimensions, of intermediate mass stars wherein iron core collapse does not lead to a strong, mass-ejecting shock wave, and (iv) the evolution and explosion of vary massive stars (M greater than or equal to 100 Msub solar of both Population I and III. In one dimension, nuclear burning following a failed core bounce does not appear likely to lead to a supernova explosion although, in two dimensions, a combination of rotation and nuclear burning may do so. Near solar proportions of elements from neon to calcium and very brilliant optical displays may be created by hypernovae, the explosions of stars in the mass range 100 M/sub solar/ to 300 M/sub solar/. Above approx. 300 M/sub solar/ a black hole is created by stellar collapse following carbon ignition. Still more massive stars may be copious producers of /sup 4/He and /sup 14/N prior to their collapse on the pair instability.

Woosley, S.E.; Weaver, T.A.

1981-09-21T23:59:59.000Z

50

Photo-heating and supernova feedback amplify each other's effect on the cosmic star formation rate  

E-Print Network (OSTI)

Photo-heating associated with reionisation and kinetic feedback from core-collapse supernovae have previously been shown to suppress the high-redshift cosmic star formation rate. Here we investigate the interplay between photo-heating and supernova feedback using a set of cosmological, smoothed particle hydrodynamics simulations. We show that photo-heating and supernova feedback mutually amplify each other's ability to suppress the star formation rate. Our results demonstrate the importance of the simultaneous, non-independent inclusion of these two processes in models of galaxy formation to estimate the strength of the total negative feedback they exert. They may therefore be of particular relevance to semi-analytic models in which the effects of photo-heating and supernova feedback are implicitly assumed to act independently of each other.

Andreas H. Pawlik; Joop Schaye

2008-12-15T23:59:59.000Z

51

Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission  

E-Print Network (OSTI)

We forecast dark energy constraints that could be obtained from a new large sample of Type Ia supernovae where those at high redshift are acquired with the Euclid space mission. We simulate a three-prong SN survey: a zsurveys are assumed to be conducted from the ground, while the high-z is a joint ground- and space-based survey. This latter survey, the "Dark Energy Supernova Infra-Red Experiment" (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing program. We simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints. We account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the supernova model used to fit the supernovae li...

Astier, P; Brescia, M; Cappellaro, E; Carlberg, R G; Cavuoti, S; Della Valle, M; Gangler, E; Goobar, A; Guy, J; Hardin, D; Hook, I M; Kessler, R; Kim, A; Linder, E; Longo, G; Maguire, K; Mannucci, F; Mattila, S; Nichol, R; Pain, R; Regnault, N; Spiro, S; Sullivan, M; Tao, C; Turatto, M; Wang, X F; Wood-Vasey, W M

2014-01-01T23:59:59.000Z

52

Modern cosmology: Interactive computer simulations that use recent observational surveys  

Science Journals Connector (OSTI)

We present a collection of new open-source computational tools for numerically modeling recent large-scale observational data sets using modern cosmology theory. These tools allow both students and researchers to constrain the parameter values in competitive cosmological models thereby discovering both the accelerated expansion of the universe and its composition (e.g. dark matter and dark energy). These programs have several features to help the non-cosmologist build an understanding of cosmological models and their relation to observational data including a built-in collection of several real observational data sets. The current list of built-in observations includes several recent supernovae Type-Ia surveys baryon acoustic oscillations the cosmic microwave background radiation gamma-ray bursts and measurements of the Hubble parameter. In this article we discuss specific results for testing cosmological models using these observational data.

2013-01-01T23:59:59.000Z

53

Testing the cosmological constant as a candidate for dark energy  

SciTech Connect

It may be difficult to single out the best model of dark energy on the basis of the existing and planned cosmological observations, because many different models can lead to similar observational consequences. However, each particular model can be studied and either found consistent with observations or ruled out. In this paper, we concentrate on the possibility to test and rule out the simplest and by far the most popular of the models of dark energy, the theory described by general relativity with positive vacuum energy (the cosmological constant). We evaluate the conditions under which this model could be ruled out by the future observations made by the Supernova/Acceleration Probe SNAP (both for supernovae and weak lensing) and by the Planck Surveyor cosmic microwave background satellite.

Kratochvil, Jan; Linde, Andrei; Linder, Eric V.; Shmakova, Marina

2003-12-03T23:59:59.000Z

54

Learning from the scatter in type Ia supernovae  

SciTech Connect

Type Ia Supernovae are standard candles so their mean apparent magnitude has been exploited to learn about the redshift-distance relationship. Besides intrinsic scatter in this standard candle, additional scatter is caused by gravitational magnification by large scale structure. Here we probe the dependence of this dispersion on cosmological parameters and show that information about the amplitude of clustering, {sigma}{sub 8}, is contained in the scatter. In principle, it will be possible to constrain {sigma}{sub 8} to within 5% with observations of 2000 Type Ia Supernovae. We identify three sources of systematic error - evolution of intrinsic scatter, baryon contributions to lensing, and non-Gaussianity of lensing - which will make this measurement difficult.

Dodelson, Scott [Particle Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637-1433 (United States); Vallinotto, Alberto [Particle Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States); Department of Physics, The University of Chicago, Chicago, Illinois 60637-1433 (United States)

2006-09-15T23:59:59.000Z

55

Supernova Science Center  

SciTech Connect

The Supernova Science Center (SNSC) was founded in 2001 to carry out theoretical and computational research leading to a better understanding of supernovae and related transients. The SNSC, a four-institutional collaboration, included scientists from LANL, LLNL, the University of Arizona (UA), and the University of California at Santa Cruz (UCSC). Intitially, the SNSC was funded for three years of operation, but in 2004 an opportunity was provided to submit a renewal proposal for two years. That proposal was funded and subsequently, at UCSC, a one year no-cost extension was granted. The total operational time of the SNSC was thus July 15, 2001 - July 15, 2007. This document summarizes the research and findings of the SNSC and provides a cummulative publication list.

S. E. Woosley

2008-05-05T23:59:59.000Z

56

Snapping Supernovae at z>1.7  

E-Print Network (OSTI)

redshift supernovae — both thermonuclear and core collapse —between core-collapse and thermonuclear supernovae (Iben &such SNe — both thermonuclear and core collapse — will be

Aldering, Greg

2009-01-01T23:59:59.000Z

57

Supernova Neutrinos Detection On Earth  

E-Print Network (OSTI)

In this paper, we first discuss the detection of supernova neutrino on Earth. Then we propose a possible method to acquire information about $\\theta_{13}$ smaller than $1.5^\\circ$ by detecting the ratio of the event numbers of different flavor supernova neutrinos. Such an sensitivity cannot yet be achieved by the Daya Bay reactor neutrino experiment.

Xin-Heng Guo; Ming-Yang Huang; Bing-Lin Young

2009-05-12T23:59:59.000Z

58

Cosmological parameters are dressed  

E-Print Network (OSTI)

In the context of the averaging problem in relativistic cosmology, we provide a key to the interpretation of cosmological parameters by taking into account the actual inhomogeneous geometry of the Universe. We discuss the relation between `bare' cosmological parameters determining the cosmological model, and the parameters interpreted by observers with a ``Friedmannian bias'', which are `dressed' by the smoothed-out geometrical inhomogeneities of the surveyed spatial region.

Thomas Buchert; Mauro Carfora

2002-10-15T23:59:59.000Z

59

Nuclear astrophysics of supernovae  

SciTech Connect

In this paper, I'll give a general introduction to Supernova Theory, beginning with the presupernova evolution and ending with the later stages of the explosion. This will be distilled from a colloquium type of talk. It is necessary to have the whole supernova picture in one's mind's eye when diving into some of its nooks and crannies, as it is quite a mess of contradictory ingredients. We will have some discussion of supernova 1987a, but will keep our discussion more general. Second, we'll look at the infall and bounce of the star, seeing why it goes unstable, what dynamics it follows as it collapses, and how and why it bounces back. From there, we will go on to look at the equation of state (EOS) in more detail. We'll consider the cases T = 0 and T > 0. We'll focus on /rho/ < /rho//sub 0/, and then /rho/ > /rho//sub 0/ and the EOS of neutron stars, and whether or not they contain cores of strange matter. There are many things we could discuss here and not enough time. If I had more lectures, the remaining time would focus on two more questions of special interest to nuclear physicists: the electron capture reactions and neutrino transport. If time permitted, we'd have some discussion of the nucleosynthetic reactions in the explosion's debris as well. However, we cannot cover such material adequately, and I have chosen these topics because they are analytically tractable, pedagogically useful, and rather important. 23 refs., 14 figs., 3 tabs.

Cooperstein, J.

1988-01-01T23:59:59.000Z

60

LXCDM cosmologies: solving the cosmological coincidence problem?  

E-Print Network (OSTI)

We explore the possibility of having a composite (self-conserved) dark energy (DE) whose dynamics is controlled by the quantum running of the cosmological parameters. We find that within this scenario it is feasible to find an explanation for the cosmological coincidence problem and at the same time a good qualitative description of the present data.

Javier Grande; Joan Sola; Hrvoje Stefancic

2006-09-25T23:59:59.000Z

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61

Cosmological model-independent Gamma-ray bursts calibration and its cosmological constraint to dark energy  

SciTech Connect

As so far, the redshift of Gamma-ray bursts (GRBs) can extend to z ? 8 which makes it as a complementary probe of dark energy to supernova Ia (SN Ia). However, the calibration of GRBs is still a big challenge when they are used to constrain cosmological models. Though, the absolute magnitude of GRBs is still unknown, the slopes of GRBs correlations can be used as a useful constraint to dark energy in a completely cosmological model independent way. In this paper, we follow Wang's model-independent distance measurement method and calculate their values by using 109 GRBs events via the so-called Amati relation. Then, we use the obtained model-independent distances to constrain ?CDM model as an example.

Xu, Lixin, E-mail: lxxu@dlut.edu.cn [Institute of Theoretical Physics, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian, 116024 (China)

2012-04-01T23:59:59.000Z

62

Evolution of density perturbations in decaying vacuum cosmology: The case of nonzero perturbations in the cosmological term  

SciTech Connect

We extend the results of a previous paper where a model of interacting dark energy, with a cosmological term decaying linearly with the Hubble parameter, is tested against the observed mass power spectrum. In spite of the agreement with observations of type Ia supernovas, baryonic acoustic oscillations, and the cosmic microwave background, we had shown previously that no good concordance is achieved if we include the mass power spectrum. However, our analysis was based on the ad hoc assumption that the interacting cosmological term is strictly homogeneous. Now we perform a more complete analysis, by perturbing such a term. Although our conclusions are still based on a particular, scale-invariant choice of the primordial spectrum of dark energy perturbations, we show that a cosmological term decaying linearly with the Hubble parameter is indeed disfavored as compared to the standard model.

Borges, H. A. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Centro de Formacao de Professores, Universidade Federal do Reconcavo da Bahia, Amargosa, BA (Brazil); Carneiro, S. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, London (United Kingdom); Fabris, J. C. [Departamento de Fisica, Universidade Federal do Espirito Santo, Vitoria, ES (Brazil); Institut d'Astrophysique de Paris, Paris (France)

2008-12-15T23:59:59.000Z

63

Long Gamma-Ray Bursts Calibrated by Pade Method and Constraints on Cosmological Models  

E-Print Network (OSTI)

Gamma-ray bursts (GRBs) are among the most powerful sources in the universe. In the recent years, GRBs have been proposed as a complementary probe to type Ia supernovae (SNIa). However, as is well known, there is a circularity problem in the use of GRBs to study cosmology. In this work, based on the Pad\\'e approximant, we propose a new cosmology-independent method to calibrate GRBs. We consider a sample consisting 138 long GRBs and obtain 79 calibrated long GRBs at high redshift $z>1.4$ (named Mayflower sample) which can be used to constrain cosmological models without the circularity problem. Then, we consider the constraints on several cosmological models with these 79 calibrated GRBs and other observational data. We show that GRBs are competent to be a complementary probe to the other well-established cosmological observations.

Jing Liu; Hao Wei

2014-10-15T23:59:59.000Z

64

Long Gamma-Ray Bursts Calibrated by Pade Method and Constraints on Cosmological Models  

E-Print Network (OSTI)

Gamma-ray bursts (GRBs) are among the most powerful sources in the universe. In the recent years, GRBs have been proposed as a complementary probe to type Ia supernovae (SNIa). However, as is well known, there is a circularity problem in the use of GRBs to study cosmology. In this work, based on the Pad\\'e approximant, we propose a new cosmology-independent method to calibrate GRBs. We consider a sample consisting 138 long GRBs and obtain 79 calibrated long GRBs at high redshift $z>1.4$ (named Mayflower sample) which can be used to constrain cosmological models without the circularity problem. Then, we consider the constraints on several cosmological models with these 79 calibrated GRBs and other observational data. We show that GRBs are competent to be a complementary probe to the other well-established cosmological observations.

Liu, Jing

2014-01-01T23:59:59.000Z

65

Thermonuclear supernova models, and observations of Type Ia supernovae  

E-Print Network (OSTI)

In this paper, we review the present state of theoretical models of thermonuclear supernovae, and compare their predicitions with the constraints derived from observations of Type Ia supernovae. The diversity of explosion mechanisms usually found in one-dimensional simulations is a direct consequence of the impossibility to resolve the flame structure under the assumption of spherical symmetry. Spherically symmetric models have been successful in explaining many of the observational features of Type Ia supernovae, but they rely on two kinds of empirical models: one that describes the behaviour of the flame on the scales unresolved by the code, and another that takes account of the evolution of the flame shape. In contrast, three-dimensional simulations are able to compute the flame shape in a self-consistent way, but they still need a model for the propagation of the flame in the scales unresolved by the code. Furthermore, in three dimensions the number of degrees of freedom of the initial configuration of the white dwarf at runaway is much larger than in one dimension. Recent simulations have shown that the sensitivity of the explosion output to the initial conditions can be extremely large. New paradigms of thermonuclear supernovae have emerged from this situation, as the Pulsating Reverse Detonation. The resolution of all these issues must rely on the predictions of observational properties of the models, and their comparison with current Type Ia supernova data, including X-ray spectra of Type Ia supernova remnants.

E. Bravo; C. Badenes; D. Garcia-Senz

2004-12-07T23:59:59.000Z

66

A Second Poincare' Group  

E-Print Network (OSTI)

Solutions of the sourceless Einstein's equation with weak and strong cosmological constants are discussed by using In\\"on\\"u-Wigner contractions of the de Sitter groups and spaces. The more usual case corresponds to a weak cosmological-constant limit, in which the de Sitter groups are contracted to the Poincar\\'e group, and the de Sitter spaces are reduced to the Minkowski space. In the strong cosmological-constant limit, however, the de Sitter groups are contracted to another group which has the same abstract Lie algebra of the Poincar\\'e group, and the de Sitter spaces are reduced to a 4-dimensional cone-space of infinite scalar curvature, but vanishing Riemann and Ricci curvature tensors. In such space, the special conformal transformations act transitively, and the equivalence between inertial frames is that of special relativity.

R. Aldrovandi; J. G. Pereira

1998-09-21T23:59:59.000Z

67

On the geometry of cosmological model building  

E-Print Network (OSTI)

This article analyzes the present anomalies of cosmology from the point of view of integrable Weyl geometry. It uses P.A.M. Dirac's proposal for a weak extension of general relativity, with some small adaptations. Simple models with interesting geometrical and physical properties, not belonging to the Friedmann-Lema\\^{\\i}tre class, are studied in this frame. Those with positive spatial curvature (Einstein-Weyl universes) go well together with observed mass density $\\Omega_m$, CMB, supernovae Ia data, and quasar frequencies. They suggest a physical role for an equilibrium state of the Maxwell field proposed by I.E. Segal in the 1980s (Segal background) and for a time invariant balancing condition of vacuum energy density. The latter leads to a surprising agreement with the BF-theoretical calculation proposed by C. Castro (2002).

Erhard Scholz

2005-11-21T23:59:59.000Z

68

Supernova Remnants And GLAST  

SciTech Connect

It has long been speculated that supernova remnants represent a major source of cosmic rays in the Galaxy. Observations over the past decade have ceremoniously unveiled direct evidence of particle acceleration in SNRs to energies approaching the knee of the cosmic ray spectrum. Nonthermal X-ray emission from shell-type SNRs reveals multi-TeV electrons, and the dynamical properties of several SNRs point to efficient acceleration of ions. Observations of TeV gamma-ray emission have confirmed the presence of energetic particles in several remnants as well, but there remains considerable debate as to whether this emission originates with high energy electrons or ions. Equally uncertain are the exact conditions that lead to efficient particle acceleration. Based on the catalog of EGRET sources, we know that there is a large population of Galactic gamma-ray sources whose distribution is similar to that of SNRs.With the increased resolution and sensitivity of GLAST, the gamma-ray SNRs from this population will be identified. Their detailed emission structure, along with their spectra, will provide the link between their environments and their spectra in other wavebands to constrain emission models and to potentially identify direct evidence of ion acceleration in SNRs. Here I summarize recent observational and theoretical work in the area of cosmic ray acceleration by SNRs, and discuss the contributions GLAST will bring to our understanding of this problem.

Slane, Patrick; /Harvard-Smithsonian Ctr. Astrophys.

2011-11-29T23:59:59.000Z

69

Type Ia Supernova Explosion: Gravitationally Confined Detonation  

Science Journals Connector (OSTI)

We present a new mechanism for Type Ia supernova explosions in massive white dwarfs. The scenario follows from relaxing assumptions of symmetry and involves a detonation born near the stellar surface. The explosion begins with an essentially central ignition of a deflagration that results in the formation of a buoyancy-driven bubble of hot material that reaches the stellar surface at supersonic speeds. The bubble breakout laterally accelerates fuel-rich outer stellar layers. This material, confined by gravity to the white dwarf, races along the stellar surface and is focused at the location opposite to the point of the bubble breakout. These streams of nuclear fuel carry enough mass and energy to trigger a detonation just above the stellar surface that will incinerate the white dwarf and result in an energetic explosion. The stellar expansion following the deflagration redistributes mass in a way that ensures production of intermediate-mass and iron group elements with ejecta having a strongly layered structure and a mild amount of asymmetry following from the early deflagration phase. This asymmetry, combined with the amount of stellar expansion determined by details of the evolution (principally the energetics of deflagration, timing of detonation, and structure of the progenitor), can be expected to create a family of mildly diverse Type Ia supernova explosions.

T. Plewa; A. C. Calder; D. Q. Lamb

2004-01-01T23:59:59.000Z

70

Thermonuclear supernova simulations with stochastic ignition  

E-Print Network (OSTI)

We apply an ad hoc model for dynamical ignition in three-dimensional numerical simulations of thermonuclear supernovae assuming pure deflagrations. The model makes use of the statistical description of temperature fluctuations in the pre-supernova core proposed by Wunsch & Woosley (2004). Randomness in time is implemented by means of a Poisson process. We are able to vary the explosion energy and nucleosynthesis depending on the free parameter of the model which controls the rapidity of the ignition process. However, beyond a certain threshold, the strength of the explosion saturates and the outcome appears to be robust with respect to number of ignitions. In the most energetic explosions, we find about 0.75 solar masses of iron group elements. Other than in simulations with simultaneous multi-spot ignition, the amount of unburned carbon and oxygen at radial velocities of a few 1000 km/s tends to be reduced for an ever increasing number of ignition events and, accordingly, more pronounced layering results.

W. Schmidt; J. C. Niemeyer

2005-10-14T23:59:59.000Z

71

Lectures on Quantum Cosmology  

E-Print Network (OSTI)

The problems encountered in trying to quantize the various cosmological models, are brought forward by means of a concrete example. The Automorphism groups are revealed as the key element through which G.C.T.'s can be used for a general treatment of these problems. At the classical level, the time dependent automorphisms lead to significant simplifications of the line element for the generic spatially homogeneous geometry, without loss of generality. At the quantum level, the ''frozen'' automorphisms entail an important reduction of the configuration space --spanned by the 6 components of the scale factor matrix-- on which the Wheeler-DeWitt equation, is to be based. In this spirit the canonical quantization of the most general minisuperspace actions --i.e. with all six scale factor as well as the lapse function and the shift vector present-- describing the vacuum type II, I geometries, is considered. The reduction to the corresponding physical degrees of freedom is achieved through the usage of the linear constraints as well as the quantum version of the entire set of all classical integrals of motion.

T. Christodoulakis

2001-09-18T23:59:59.000Z

72

Observational Constraints on Cosmological Models with the Updated Long Gamma-Ray Bursts  

E-Print Network (OSTI)

In the present work, by the help of the newly released Union2 compilation which consists of 557 Type Ia supernovae (SNIa), we calibrate 109 long Gamma-Ray Bursts (GRBs) with the well-known Amati relation, using the cosmology-independent calibration method proposed by Liang {\\it et al.}. We have obtained 59 calibrated high-redshift GRBs which can be used to constrain cosmological models without the circularity problem (we call them ``Hymnium'' GRBs sample for convenience). Then, we consider the joint constraints on 7 cosmological models from the latest observational data, namely, the combination of 557 Union2 SNIa dataset, 59 calibrated Hymnium GRBs dataset (obtained in this work), the shift parameter $R$ from the WMAP 7-year data, and the distance parameter $A$ of the measurement of the baryon acoustic oscillation (BAO) peak in the distribution of SDSS luminous red galaxies. We also briefly consider the comparison of these 7 cosmological models.

Hao Wei

2010-08-16T23:59:59.000Z

73

Density Perturbations for Running Cosmological Constant  

E-Print Network (OSTI)

The dynamics of density and metric perturbations is investigated for the previously developed model where the decay of the vacuum energy into matter (or vice versa) is due to the renormalization group (RG) running of the cosmological constant (CC) term. The evolution of the CC depends on the single parameter \

Julio C. Fabris; Ilya L. Shapiro; Joan Sola

2007-01-26T23:59:59.000Z

74

Spectropolarimetric diagnostics of thermonuclear supernova explosions  

E-Print Network (OSTI)

Even at extragalactic distances, the shape of supernova ejecta can be effectively diagnosed by spectropolarimetry. We present here results for 17 Type Ia supernovae that allow a statistical study of the correlation among the geometric structures and other observable parameters of Type Ia supernovae. These observations suggest that their ejecta typically consist of a smooth, central iron rich core and an outer layer with chemical asymmetries. The degree of this peripheral asphericity is correlated with the light-curve decline rate of Type Ia supernovae. These observations lend strong support to delayed-detonation models of Type Ia supernovae.

Lifan Wang; Dietrich Baade; Ferdinando Patat

2006-11-29T23:59:59.000Z

75

Averaging Hypotheses in Newtonian Cosmology  

E-Print Network (OSTI)

Average properties of general inhomogeneous cosmological models are discussed in the Newtonian framework. It is shown under which circumstances the average flow reduces to a member of the standard Friedmann--Lema\\^\\i tre cosmologies. Possible choices of global boundary conditions of inhomogeneous cosmologies as well as consequences for the interpretation of cosmological parameters are put into perspective.

T. Buchert

1995-12-20T23:59:59.000Z

76

Testing the consistency between cosmological measurements of distance and age  

E-Print Network (OSTI)

We present a model independent method to test the consistency between cosmological measurements of distance and age, assuming the distance duality relation. We use type Ia supernovae, baryon acoustic oscillations, and observational Hubble data, to reconstruct the luminosity distance D_L(z), the angle averaged distance D_V(z) and the Hubble rate H(z), using Gaussian processes regression technique. We obtain estimate of the distance duality relation in the redshift range 0.1

Nair, Remya; Jain, Deepak

2015-01-01T23:59:59.000Z

77

THE LOCAL HOSTS OF TYPE Ia SUPERNOVAE  

SciTech Connect

We use multi-wavelength, matched aperture, integrated photometry from the Galaxy Evolution Explorer (GALEX), the Sloan Digital Sky Survey, and the RC3 to estimate the physical properties of 166 nearby galaxies hosting 168 well-observed Type Ia supernovae (SNe Ia). The ultraviolet (UV) imaging of local SN Ia hosts from GALEX allows a direct comparison with higher-redshift hosts measured at optical wavelengths that correspond to the rest-frame UV. Our data corroborate well-known features that have been seen in other SN Ia samples. Specifically, hosts with active star formation produce brighter and slower SNe Ia on average, and hosts with luminosity-weighted ages older than 1 Gyr produce on average more faint, fast, and fewer bright, slow SNe Ia than younger hosts. New results include that in our sample, the faintest and fastest SNe Ia occur only in galaxies exceeding a stellar mass threshold of approx10{sup 10} M{sub sun}, leading us to conclude that their progenitors must arise in populations that are older and/or more metal rich than the general SN Ia population. A low host extinction subsample hints at a residual trend in peak luminosity with host age, after correcting for light-curve shape, giving the appearance that older hosts produce less-extincted SNe Ia on average. This has implications for cosmological fitting of SNe Ia, and suggests that host age could be useful as a parameter in the fitting. Converting host mass to metallicity and computing {sup 56}Ni mass from the supernova light curves, we find that our local sample is consistent with a model that predicts a shallow trend between stellar metallicity and the {sup 56}Ni mass that powers the explosion, but we cannot rule out the absence of a trend. We measure a correlation between {sup 56}Ni mass and host age in the local universe that is shallower and not as significant as that seen at higher redshifts. The details of the age-{sup 56}Ni mass correlations at low and higher redshift imply a luminosity-weighted age threshold of approx3 Gyr for SN Ia hosts, above which they are less likely to produce SNe Ia with {sup 56}Ni masses above approx0.5 M{sub sun}.

Neill, James D.; Martin, D. Christopher; Barlow, Tom A.; Foster, Karl; Friedman, Peter G.; Morrissey, Patrick; Wyder, Ted K. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Sullivan, Mark [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Howell, D. Andrew [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117 (United States); Conley, Alex [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ONM5S3H8 (Canada); Seibert, Mark; Madore, Barry F. [The Observatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA, 91101 (United States); Neff, Susan G. [Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Bianchi, Luciana [Center for Astrophysical Sciences, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Donas, Jose; Milliard, Bruno [Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France); Heckman, Timothy M. [Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Lee, Young-Wook [Center for Space Astrophysics, Yonsei University, Seoul 120-749 (Korea, Republic of); Rich, R. Michael [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2009-12-20T23:59:59.000Z

78

D-braneworld cosmology  

Science Journals Connector (OSTI)

We discuss D-braneworld cosmology; that is, the brane is described by the Born-Infeld action. Compared with the usual Randall-Sundrum braneworld cosmology where the brane action is the Nambu-Goto one, we can see some drastic changes in the very early universe: (i) the universe may experience a rapidly accelerating phase; (ii) the closed universe may avoid the initial singularity. We also briefly address the dynamics of the cosmology in the open string metric, which might be more favored than the induced metric from the viewpoint of the D-brane.

Tetsuya Shiromizu; Takashi Torii; Tomoko Uesugi

2003-06-26T23:59:59.000Z

79

Cosmology and New Physics  

E-Print Network (OSTI)

A comparison of the standard models in particle physics and in cosmology demonstrates that they are not compatible, though both are well established. Basics of modern cosmology are briefly reviewed. It is argued that the measurements of the main cosmological parameters are achieved through many independent physical phenomena and this minimizes possible interpretation errors. It is shown that astronomy demands new physics beyond the frameworks of the (minimal) standard model in particle physics. More revolutionary modifications of the basic principles of the theory are also discussed.

A. D. Dolgov

2006-06-21T23:59:59.000Z

80

Reconstructing Dark Energy : A Comparison of Cosmological Parameters  

E-Print Network (OSTI)

A large number of cosmological parameters have been suggested for obtaining information on the nature of dark energy. In this work, we study the efficacy of these different parameters in discriminating theoretical models of dark energy, using both currently available supernova (SNe) data, and simulations of future observations. We find that the current data does not put strong constraints on the nature of dark energy, irrespective of the cosmological parameter used. For future data, we find that the although deceleration parameter can accurately reconstruct some dark energy models, it is unable to discriminate between different models of dark energy, therefore limiting its usefulness. Physical parameters such as the equation of state of dark energy, or the dark energy density do a good job of both reconstruction and discrimination if the matter density is known to high accuracy. However, uncertainty in matter density reduces the efficacy of these parameters. A recently proposed parameter, Om(z), constructed f...

Pan, Alexander V

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Signatures of A Companion Star in Type Ia Supernovae  

E-Print Network (OSTI)

While type Ia Supernovae (SNe Ia) have been used as precise cosmological distance indicators, their progenitor systems remain unresolved. One of the key questions is if there is a non-degenerate companion star at the time of a thermonuclear explosion of a white dwarf (WD). In this paper, we investigate if an interaction between the SN ejecta and the companion star may result in observable footprints around the maximum brightness and thereafter, by performing multi-dimensional radiation transfer simulations based on hydrodynamic simulations of the interaction. We find that such systems result in variations in various observational characteristics due to different viewing directions, while the predicted behaviors (redder and fainter for the companion direction) are opposite to what were suggested by the previous study. The variations are generally modest and within observed scatters. However, the model predicts trends between some observables different from observationally derived, thus a large sample of SNe Ia...

Maeda, Keiichi; Shigeyama, Toshikazu

2014-01-01T23:59:59.000Z

82

What We Know About Dark Energy From Supernovae  

ScienceCinema (OSTI)

The measured distances of type Ia (white dwarf) supernovae as a function of redshift (z) have shown that the expansion of the Universe is currently accelerating, probably due to the presence of dark energy (X) having a negative pressure. Combining all of the data with existing results from large-scale structure surveys, we find a best fit for Omega M and Omega X of 0.28 and 0.72 (respectively), in excellent agreement with the values derived independently from WMAP measurements of the cosmic microwave background radiation. Thus far, the best-fit value for the dark energy equation-of-state parameter is -1, and its first derivative is consistent with zero, suggesting that the dark energy may indeed be Einstein's cosmological constant.

Alex Filippenko

2010-01-08T23:59:59.000Z

83

Cosmological Ontology and Epistemology  

E-Print Network (OSTI)

In cosmology, we would like to explain our observations and predict future observations from theories of the entire universe. Such cosmological theories make ontological assumptions of what entities exist and what their properties and relationships are. One must also make epistemological assumptions or metatheories of how one can test cosmological theories. Here I shall propose a Bayesian analysis in which the likelihood of a complete theory is given by the normalized measure it assigns to the observation used to test the theory. In this context, a discussion is given of the trade-off between prior probabilities and likelihoods, of the measure problem of cosmology, of the death of Born's rule, of the Boltzmann brain problem, of whether there is a better principle for prior probabilities than mathematical simplicity, and of an Optimal Argument for the Existence of God.

Don N. Page

2014-12-23T23:59:59.000Z

84

Multiverses and physical cosmology  

Science Journals Connector (OSTI)

......Cosmological Data and the Values of the Fundamental Parameters, to appear. ASP Publications, San Francisco(. Sciama D. , 1993, inIs the universe unique Die Kosmologie der Gegenwart. Serie Piper. Smolin L. , 1999, The Life of the Universe. Oxford Univ......

G. F. R. Ellis; U. Kirchner; W. R. Stoeger

2004-01-21T23:59:59.000Z

85

Massive neutrinos and cosmology  

E-Print Network (OSTI)

The present experimental results on neutrino flavour oscillations provide evidence for non-zero neutrino masses, but give no hint on their absolute mass scale, which is the target of beta decay and neutrinoless double-beta decay experiments. Crucial complementary information on neutrino masses can be obtained from the analysis of data on cosmological observables, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure. In this review we describe in detail how free-streaming massive neutrinos affect the evolution of cosmological perturbations. We summarize the current bounds on the sum of neutrino masses that can be derived from various combinations of cosmological data, including the most recent analysis by the WMAP team. We also discuss how future cosmological experiments are expected to be sensitive to neutrino masses well into the sub-eV range.

Julien Lesgourgues; Sergio Pastor

2006-05-29T23:59:59.000Z

86

IONIZED ABSORBERS AS EVIDENCE FOR SUPERNOVA-DRIVEN COOLING OF THE LOWER GALACTIC CORONA  

SciTech Connect

We show that the ultraviolet absorption features, newly discovered in Hubble Space Telescope spectra, are consistent with being formed in a layer that extends a few kpc above the disk of the Milky Way. In this interface between the disk and the Galactic corona, high-metallicity gas ejected from the disk by supernova feedback can mix efficiently with the virial-temperature coronal material. The mixing process triggers the cooling of the lower corona down to temperatures encompassing the characteristic range of the observed absorption features, producing a net supernova-driven gas accretion onto the disk at a rate of a few M{sub Sun} yr{sup -1}. We speculate that this mechanism explains how the hot mode of cosmological accretion feeds star formation in galactic disks.

Fraternali, Filippo; Marasco, Antonino [Department of Physics and Astronomy, University of Bologna, via Berti Pichat 6/2, I-40127 Bologna (Italy); Marinacci, Federico [Heidelberger Institut fuer Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Binney, James, E-mail: filippo.fraternali@unibo.it [Rudolf Peierls Centre for Theoretical Physics, Keble Road, OX1 3NP Oxford (United Kingdom)

2013-02-20T23:59:59.000Z

87

Massive Stars and their Supernovae  

E-Print Network (OSTI)

Massive stars and their supernovae are prominent sources of radioactive isotopes, the observations of which thus can help to improve our astrophysical models of those. Our understanding of stellar evolution and the final explosive endpoints such as supernovae or hypernovae or gamma-ray bursts relies on the combination of magneto-hydrodynamics, energy generation due to nuclear reactions accompanying composition changes, radiation transport, and thermodynamic properties (such as the equation of state of stellar matter). Nuclear energy production includes all nuclear reactions triggered during stellar evolution and explosive end stages, also among unstable isotopes produced on the way. Radiation transport covers atomic physics (e.g. opacities) for photon transport, but also nuclear physics and neutrino nucleon/nucleus interactions in late phases and core collapse. Here we want to focus on the astrophysical aspects, i.e. a description of the evolution of massive stars and their endpoints, with a special emphasis ...

Thielemann, Friedrich-Karl; Liebendörfer, Matthias; Diehl, Roland; 10.1007/978-3-642-12698-7_4

2010-01-01T23:59:59.000Z

88

SU(2) cosmological solitons  

Science Journals Connector (OSTI)

We present a class of numerical solutions to the SU(2) nonlinear ? model coupled to the Einstein equations with a cosmological constant ?>~0 in spherical symmetry. These solutions are characterized by the presence of a regular static region which includes a center of symmetry. They are parametrized by a dimensionless “coupling constant” ?, the sign of the cosmological constant, and an integer “excitation number” n. The phenomenology we find is compared to the corresponding solutions found for the Einstein-Yang-Mills (EYM) equations with a positive ? (EYM?). If we choose ? positive and fix n, we find a family of static spacetimes with a Killing horizon for 0<~?cosmological context, we apply the concept of a trapping horizon as formulated by Hayward. For small values of ? an asymptotically de Sitter dynamic region contains the static region within a Killing horizon of cosmological type. For strong coupling the static region contains an “eternal cosmological black hole.”

C. Lechner; S. Husa; P. C. Aichelburg

2000-07-27T23:59:59.000Z

89

A Massive Stellar Burst Before the Supernova  

NLE Websites -- All DOE Office Websites (Extended Search)

massive stars shed huge amounts of material in a "penultimate outburst" before final detonation as supernovae. A focused search for Type IIn SN precursor bursts, conducted by Eran...

90

Supernova Recognition using Support Vector Machines  

E-Print Network (OSTI)

tion Using Support Vector Machines and Neural Networks.using Support Vector Machines Raquel A. Romano Cecilia R.nding supernovae do not employ machine learning techniques.

Romano, Raquel A.; Aragon, Cecilia R.; Ding, Chris

2006-01-01T23:59:59.000Z

91

The late emission of thermonuclear supernovae  

E-Print Network (OSTI)

The subject of late-time emission of Type Ia supernovae and its implications for the understanding of the explosions of C+O WDs is reviewed.

Pilar Ruiz-Lapuente

1996-04-16T23:59:59.000Z

92

A LUMINOUS AND FAST-EXPANDING TYPE Ib SUPERNOVA SN 2012au  

SciTech Connect

We present a set of photometric and spectroscopic observations of a bright Type Ib supernova SN 2012au from -6 days until {approx} + 150 days after maximum. The shape of its early R-band light curve is similar to that of an average Type Ib/c supernova. The peak absolute magnitude is M{sub R} = -18.7 {+-} 0.2 mag, which suggests that this supernova belongs to a very luminous group among Type Ib supernovae. The line velocity of He I {lambda}5876 is about 15,000 km s{sup -1} around maximum, which is much faster than that in a typical Type Ib supernova. From the quasi-bolometric peak luminosity of (6.7 {+-} 1.3) Multiplication-Sign 10{sup 42} erg s{sup -1}, we estimate the {sup 56}Ni mass produced during the explosion as {approx}0.30 M{sub Sun }. We also give a rough constraint to the ejecta mass 5-7 M{sub Sun} and the kinetic energy (7-18) Multiplication-Sign 10{sup 51} erg. We find a weak correlation between the peak absolute magnitude and He I velocity among Type Ib SNe. The similarities to SN 1998bw in the density structure inferred from the light-curve model as well as the large peak bolometric luminosity suggest that SN 2012au had properties similar to energetic Type Ic supernovae.

Takaki, Katsutoshi; Fukazawa, Yasushi; Itoh, Ryosuke; Ueno, Issei; Ui, Takahiro; Urano, Takeshi [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Kawabata, Koji S.; Akitaya, Hiroshi; Moritani, Yuki; Ohsugi, Takashi; Uemura, Makoto; Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Yamanaka, Masayuki [Kwasan Observatory, Kyoto University, Ohmine-cho Kita Kazan, Yamashina-ku, Kyoto 607-8471 (Japan); Maeda, Keiichi; Nomoto, Ken'ichi [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Tanaka, Masaomi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Kinugasa, Kenzo [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, 462-2 Nobeyama, Minamimaki, Nagano 384-1305 (Japan); Sasada, Mahito, E-mail: takaki@hep01.hepl.hiroshima-u.ac.jp [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)

2013-08-01T23:59:59.000Z

93

Nuclear physics and cosmology  

SciTech Connect

There are important aspects of Cosmology, the scientific study of the large scale properties of the universe as a whole, for which nuclear physics can provide insights. Here, we will focus on Standard Big-Bang Nucleosynthesis and we refer to the previous edition of the School [1] for the aspects concerning the variations of constants in nuclear cosmo-physics.

Coc, Alain [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), CNRS/IN2P3, Université Paris Sud 11, UMR 8609, Bâtiment 104, F-91405 Orsay Campus (France)

2014-05-09T23:59:59.000Z

94

Cosmology with Coupled Gravity and Dark Energy  

E-Print Network (OSTI)

Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way that dark energy and gravity are introduced into the cosmological field equation in parallel with each other from the beginning. The DEMC universe possesses a composite symmetry from global Galileo invariance and local Lorentz invariance. The observed evolution of the universe expansion rate at redshift z>1 is in tension with the standard LCDM model, but can be well predicted by the DEMC model from measurements of only nearby epochs. The so far most precise measured expansion rate at high z is quite a bit slower than the expectations from LCDM, but remarkably consistent with that from DEMC. It is hoped that the DEMC scenario can also help to solve other existing challenges to cosmology: large scale anomalies in CMB maps and large structures up to about 10^3 Mpc of a quasar group. The DEMC universe is a well defined mechanical system. From measurements we can quantitatively evaluate its total rest energy, present absolute radius and expanding speed.

Ti-Pei Li

2015-01-13T23:59:59.000Z

95

Cosmology with Coupled Gravity and Dark Energy  

E-Print Network (OSTI)

Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way that dark energy and gravity are introduced into the cosmological field equation in parallel with each other from the beginning. The DEMC universe possesses a composite symmetry from global Galileo invariance and local Lorentz invariance. The observed evolution of the universe expansion rate at redshift z>1 is in tension with the standard LCDM model, but can be well predicted by the DEMC model from measurements of only nearby epochs. The so far most precise measured expansion rate at high z is quite a bit slower than the expectations from LCDM, but remarkably consistent with that from DEMC. It is hoped that the DEMC scenario can also help to solve other existing challenges to cosmology: large scale anomalies in CMB maps and large structures up to about 10^3 Mpc of a quasar group. The DEMC universe is a well defined mechanical system. From measurements we can quantitatively evaluate its total rest energy, present absolute radius and expanding speed.

Ti-Pei Li

2014-09-01T23:59:59.000Z

96

Models for Type I supernovae  

SciTech Connect

Two rather disjoint scenarios for Type I supernovae are presented. One is based upon mass accretion by a white dwarf in a binary system. The second involves a star having some 8 to 10 times the mass of the sun which may or may not be a solitary star. Despite the apparent dissimilarities in the models it may be that each occurs to some extent in nature for they both share the possibility of producing substantial quantities of /sup 56/Ni and explosions in stars devoid of hydrogen envelopes. These are believed to be two properties that must be shared by any viable Type I model.

Woosley, S.E.; Weaver, T.A.; Taam, R.E.

1980-06-17T23:59:59.000Z

97

Cosmological implications of baryon acoustic oscillation (BAO) measurements  

E-Print Network (OSTI)

We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) and Type Ia supernova (SN) data. We take advantage of high-precision BAO measurements from galaxy clustering and the Ly-alpha forest (LyaF) in the BOSS survey of SDSS-III. BAO data alone yield a high confidence detection of dark energy, and in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Combining BAO and SN data into an "inverse distance ladder" yields a 1.7% measurement of $H_0=67.3 \\pm1.1$ km/s/Mpc. This measurement assumes standard pre-recombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat LCDM cosmology is an important corroboration of this minimal cosmological model. For open LCDM, our BAO+SN+CMB combination yields $\\Omega_m=0.301 \\pm 0.008$ and curvature $\\Omega_k=-0.003 \\pm ...

Aubourg, Éric; Bautista, Julian E; Beutler, Florian; Bhardwaj, Vaishali; Bizyaev, Dmitry; Blanton, Michael; Blomqvist, Michael; Bolton, Adam S; Bovy, Jo; Brewington, Howard; Brinkmann, J; Brownstein, Joel R; Burden, Angela; Busca, Nicolás G; Carithers, William; Chuang, Chia-Hsun; Comparat, Johan; Cuesta, Antonio J; Dawson, Kyle S; Delubac, Timothée; Eisenstein, Daniel J; Font-Ribera, Andreu; Ge, Jian; Goff, J -M Le; Gontcho, Satya Gontcho A; Gott, J Richard; Gunn, James E; Guo, Hong; Guy, Julien; Hamilton, Jean-Christophe; Ho, Shirley; Honscheid, Klaus; Howlett, Cullan; Kirkby, David; Kitaura, Francisco S; Kneib, Jean-Paul; Lee, Khee-Gan; Long, Dan; Lupton, Robert H; Magaña, Mariana Vargas; Malanushenko, Viktor; Malanushenko, Elena; Manera, Marc; Maraston, Claudia; Margala, Daniel; McBride, Cameron K; Miralda-Escudé, Jordi; Myers, Adam D; Nichol, Robert C; Noterdaeme, Pasquier; Nuza, Sebastián E; Olmstead, Matthew D; Oravetz, Daniel; Pâris, Isabelle; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J; Petitjean, Patrick; Pieri, Matthew M; Prada, Francisco; Reid, Beth; Roe, Natalie A; Ross, Ashley J; Ross, Nicholas P; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Sánchez, Ariel G; Samushia, Lado; Santos, Ricardo Tanausú Génova; Scóccola, Claudia G; Schlegel, David J; Schneider, Donald P; Seo, Hee-Jong; Sheldon, Erin; Simmons, Audrey; Skibba, Ramin A; Slosar, Anže; Strauss, Michael A; Thomas, Daniel; Tinker, Jeremy L; Tojeiro, Rita; Vazquez, Jose Alberto; Viel, Matteo; Wake, David A; Weaver, Benjamin A; Weinberg, David H; Wood-Vasey, W M; Yèche, Christophe; Zehavi, Idit; Zhao, Gong-Bo

2014-01-01T23:59:59.000Z

98

E-Print Network 3.0 - atypical thermonuclear supernovae Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

thermonuclear supernovae Search Powered by Explorit Topic List Advanced Search Sample search results for: atypical thermonuclear supernovae Page: << < 1 2 3 4 5 > >> 1 Supernova...

99

Quantum cosmology: a review  

E-Print Network (OSTI)

In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity: De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting "microscopic" degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.

Bojowald, Martin

2015-01-01T23:59:59.000Z

100

Cosmology with Doppler Lensing  

E-Print Network (OSTI)

Doppler lensing is the apparent change in object size and magnitude due to peculiar velocities. Objects falling into an overdensity appear larger on its near side, and smaller on its far side, than typical objects at the same redshifts. This effect dominates over the usual gravitational lensing magnification at low redshift. Doppler lensing is a promising new probe of cosmology, and we explore in detail how to utilize the effect with forthcoming surveys. We present cosmological simulations of the Doppler and gravitational lensing effects based on the Millennium simulation. We show that Doppler lensing can be detected around stacked voids or unvirialised over-densities. New power spectra and correlation functions are proposed which are designed to be sensitive to Doppler lensing. We consider the impact of gravitational lensing and intrinsic size correlations on these quantities. We compute the correlation functions and forecast the errors for realistic forthcoming surveys, providing predictions for constraints...

Bacon, David J; Clarkson, Chris; Bolejko, Krzysztof; Maartens, Roy

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
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101

Observational constraints to a unified cosmological model  

E-Print Network (OSTI)

We propose a phenomenological unified model for dark matter and dark energy based on an equation of state parameter $w$ that scales with the $\\arctan$ of the redshift. The free parameters of the model are three constants: $\\Omega_{b0}$, $\\alpha$ and $\\beta$. Parameter $\\alpha$ dictates the transition rate between the matter dominated era and the accelerated expansion period. The ratio $\\beta / \\alpha$ gives the redshift of the equivalence between both regimes. Cosmological parameters are fixed by observational data from Primordial Nucleosynthesis (PN), Supernovae of the type Ia (SNIa), Gamma-Ray Bursts (GRB) and Baryon Acoustic Oscillations (BAO). The calibration of the 138 GRBs events is performed using the 580 SNIa of the Union2.1 data set and a new set of 79 high-redshift GRBs is obtained. The various sets of data are used in different combinations to constraint the parameters through statistical analysis. The unified model is compared to the $\\Lambda$CDM model and their differences are emphasized.

Cuzinatto, R R; de Morais, E M

2014-01-01T23:59:59.000Z

102

Cosmology with running parameters  

E-Print Network (OSTI)

The experimental evidence that the equation of state (EOS) of the dark energy (DE) could be evolving with time/redshift (including the possibility that it might behave phantom-like near our time) suggests that there might be dynamical DE fields that could explain this behavior. We propose, instead, that a variable cosmological term (including perhaps a variable Newton's gravitational coupling too) may account in a natural way for all these features.

Joan Sola

2005-12-05T23:59:59.000Z

103

Standard cosmology delayed  

SciTech Connect

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Choudhury, Debajyoti [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Ghoshal, Debashis [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Sen, Anjan Ananda, E-mail: debajyoti.choudhury@gmail.com, E-mail: dghoshal@mail.jnu.ac.in, E-mail: anjan.ctp@jmi.ac.in [Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi 110025 (India)

2012-02-01T23:59:59.000Z

104

Standard Cosmology Delayed  

E-Print Network (OSTI)

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Debajyoti Choudhury; Debashis Ghoshal; Anjan Ananda Sen

2012-02-06T23:59:59.000Z

105

Standard Cosmology Delayed  

E-Print Network (OSTI)

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Choudhury, Debajyoti; Sen, Anjan Ananda

2011-01-01T23:59:59.000Z

106

Detonating Failed Deflagration Model of Thermonuclear Supernovae I. Explosion Dynamics  

E-Print Network (OSTI)

We present a detonating failed deflagration model of Type Ia supernovae. In this model, the thermonuclear explosion of a massive white dwarf follows an off-center deflagration. We conduct a survey of asymmetric ignition configurations initiated at various distances from the stellar center. In all cases studied, we find that only a small amount of stellar fuel is consumed during deflagration phase, no explosion is obtained, and the released energy is mostly wasted on expanding the progenitor. Products of the failed deflagration quickly reach the stellar surface, polluting and strongly disturbing it. These disturbances eventually evolve into small and isolated shock-dominated regions which are rich in fuel. We consider these regions as seeds capable of forming self-sustained detonations that, ultimately, result in the thermonuclear supernova explosion. Preliminary nucleosynthesis results indicate the model supernova ejecta are typically composed of about 0.1-0.25 Msun of silicon group elements, 0.9-1.2 Msun of iron group elements, and are essentially carbon-free. The ejecta have a composite morphology, are chemically stratified, and display a modest amount of intrinsic asymmetry. The innermost layers are slightly egg-shaped with the axis ratio ~1.2-1.3 and dominated by the products of silicon burning. This central region is surrounded by a shell of silicon-group elements. The outermost layers of ejecta are highly inhomogeneous and contain products of incomplete oxygen burning with only small admixture of unburned stellar material. The explosion energies are ~1.3-1.5 10^51 erg.

Tomasz Plewa

2006-11-24T23:59:59.000Z

107

Cosmological shock waves  

E-Print Network (OSTI)

Large-scale structure formation, accretion and merging processes, AGN activity produce cosmological gas shocks. The shocks convert a fraction of the energy of gravitationally accelerated flows to internal energy of the gas. Being the main gas-heating agent, cosmological shocks could amplify magnetic fields and accelerate energetic particles via the multi-fluid plasma relaxation processes. We first discuss the basic properties of standard single-fluid shocks. Cosmological plasma shocks are expected to be collisionless. We then review the plasma processes responsible for the microscopic structure of collisionless shocks. A tiny fraction of the particles crossing the shock is injected into the non-thermal energetic component that could get a substantial part of the ram pressure power dissipated at the shock. The energetic particles penetrate deep into the shock upstream producing an extended shock precursor. Scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are discussed. We show that the multi-fluid nature of collisionless shocks results in excessive gas compression, energetic particle acceleration, precursor gas heating, magnetic field amplification and non-thermal emission. Multi-fluid shocks provide a reduced gas entropy production and could also modify the observable thermodynamic scaling relations for clusters of galaxies.

A. M. Bykov; K. Dolag; F. Durret

2008-01-07T23:59:59.000Z

108

Chasing the phantom: A closer look at type Ia supernovae and the dark energy equation of state  

Science Journals Connector (OSTI)

Some recent observations provide >2? evidence for phantom dark energy—a value of the dark energy equation of state less than the cosmological-constant value of ?1. We focus on constraining the equation of state by combining current data from the most mature geometrical probes of dark energy: type Ia supernovae (SNe Ia) from the Supernova Legacy Survey (SNLS3), the Supernova Cosmology Project (Union2.1), and the Pan-STARRS1 survey (PS1); cosmic microwave background measurements from Planck and WMAP9; and a combination of measurements of baryon acoustic oscillations. The combined data are consistent with w=?1 for the Union2.1 sample, though they present moderate (?1.9?) evidence for a phantom value when either the SNLS3 or PS1 sample is used instead. We study the dependence of the constraints on the redshift, stretch, color, and host galaxy stellar mass of SNe, but we find no unusual trends. In contrast, the constraints strongly depend on any external H0 prior: a higher adopted value for the direct measurement of the Hubble constant (H0?71??km/s/Mpc) leads to ?2? evidence for phantom dark energy. Given Planck data, we can therefore make the following statement at 2? confidence: either the SNLS3 and PS1 data have systematics that remain unaccounted for or the Hubble constant is below 71??km/s/Mpc; else the dark energy equation of state is indeed phantom.

Daniel L. Shafer and Dragan Huterer

2014-03-06T23:59:59.000Z

109

Inference for the dark energy equation of state using Type IA supernova data  

E-Print Network (OSTI)

The surprising discovery of an accelerating universe led cosmologists to posit the existence of "dark energy"--a mysterious energy field that permeates the universe. Understanding dark energy has become the central problem of modern cosmology. After describing the scientific background in depth, we formulate the task as a nonlinear inverse problem that expresses the comoving distance function in terms of the dark-energy equation of state. We present two classes of methods for making sharp statistical inferences about the equation of state from observations of Type Ia Supernovae (SNe). First, we derive a technique for testing hypotheses about the equation of state that requires no assumptions about its form and can distinguish among competing theories. Second, we present a framework for computing parametric and nonparametric estimators of the equation of state, with an associated assessment of uncertainty. Using our approach, we evaluate the strength of statistical evidence for various competing models of dark energy. Consistent with current studies, we find that with the available Type Ia SNe data, it is not possible to distinguish statistically among popular dark-energy models, and that, in particular, there is no support in the data for rejecting a cosmological constant. With much more supernova data likely to be available in coming years (e.g., from the DOE/NASA Joint Dark Energy Mission), we address the more interesting question of whether future data sets will have sufficient resolution to distinguish among competing theories.

Christopher Genovese; Peter Freeman; Larry Wasserman; Robert Nichol; Christopher Miller

2008-05-27T23:59:59.000Z

110

Supernova observations for neutrino mixing parameters  

SciTech Connect

The neutrino spectra from a future galactic core collapse supernova could reveal information on the neutrino mixing pattern, especially on {theta}{sub 13} and the mass hierarchy. I briefly outline our current understanding of neutrino flavor conversions inside a supernova, and point out possible signatures of various neutrino mixing scenarios that the neutrino detectors should look for. Supernova neutrinos provide a probe for {theta}{sub 13} and mass hierarchy that is complementary to, and sometimes even better than, the current and proposed terrestrial neutrino oscillation experiments.

Dighe, Amol [Department of Theoretical Physics, Tata Institute of Fundamental Research, 1, Homi Bhabha Road, Colaba, Mumbai 400005 (India)

2011-10-06T23:59:59.000Z

111

Cosmology for high energy physicists  

SciTech Connect

The standard big bang model of cosmology is presented. Although not perfect, its many successes make it a good starting point for most discussions of cosmology. Places are indicated where well understood laboratory physics is incorporated into the big bang, leading to successful predictions. Much less established aspects of high energy physics and some of the new ideas they have introduced into the field of cosmology are discussed, such as string theory, inflation and monopoles. 49 refs., 5 figs.

Albrecht, A.

1987-11-01T23:59:59.000Z

112

Uncorrelated Measurements of the Cosmic Expansion History and Dark Energy from Supernovae  

E-Print Network (OSTI)

We present a method for measuring the cosmic expansion history H(z) in uncorrelated redshift bins, and apply it to current and simulated type Ia supernova data assuming spatial flatness. If the matter density parameter Omega_m can be accurately measured from other data, then the dark energy density history X(z)=rho_X(z)/rho_X(0) can trivially be derived from this expansion history H(z). In contrast to customary ``black box'' parameter fitting, our method is transparent and easy to interpret: the measurement of H(z)^{-1} in a redshift bin is simply a linear combination of the measured comoving distances for supernovae in that bin, making it obvious how systematic errors propagate from input to output. We find the Riess et al. (2004) ``gold'' sample to be consistent with the ``vanilla'' concordance model where the dark energy is a cosmological constant. We compare two mission concepts for the NASA/DOE Joint Dark Energy Mission (JDEM), the Joint Efficient Dark-energy Investigation (JEDI), and the Supernova Accelaration Probe (SNAP), using simulated data including the effect of weak lensing (based on numerical simulations) and a systematic bias from K-corrections. Estimating H(z) in seven uncorrelated redshift bins, we find that both provide dramatic improvements over current data: JEDI can measure H(z) to about 10% accuracy and SNAP to 30-40% accuracy.

Yun Wang; Max Tegmark

2005-01-18T23:59:59.000Z

113

Timescale stretch parameterization of Type Ia supernova B-band light curves  

SciTech Connect

R-band intensity measurements along the light curve of Type Ia supernovae discovered by the Cosmology Project (SCP) are fitted in brightness to templates allowing a free parameter the time-axis width factor w identically equal to s times (1+z). The data points are then individually aligned in the time-axis, normalized and K-corrected back to the rest frame, after which the nearly 1300 normalized intensity measurements are found to lie on a well-determined common rest-frame B-band curve which we call the ''composite curve.'' The same procedure is applied to 18 low-redshift Calan/Tololo SNe with Z < 0.11; these nearly 300 B-band photometry points are found to lie on the composite curve equally well. The SCP search technique produces several measurements before maximum light for each supernova. We demonstrate that the linear stretch factor, s, which parameterizes the light-curve timescale appears independent of z, and applies equally well to the declining and rising parts of the light curve. In fact, the B band template that best fits this composite curve fits the individual supernova photometry data when stretched by a factor s with chi 2/DoF {approx} 1, thus as well as any parameterization can, given the current data sets. The measurement of the data of explosion, however, is model dependent and not tightly constrained by the current data. We also demonstrate the 1 + z light-cure time-axis broadening expected from cosmological expansion. This argues strongly against alternative explanations, such as tired light, for the redshift of distant objects.

Goldhaber, G.; Groom, D.E.; Kim, A.; Aldering, G.; Astier, P.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fruchter, A.S.; Goobar, A.; Hook, I.; Irwin, M.; Kim, M.; Knop, R.A.; Lidman, C.; McMahon, R.; Nugent, P.E.; Pain, R.; Panagia, N.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente, P.; Schaefer, B.; Walton, N.A.; York, T.

2001-04-01T23:59:59.000Z

114

Hydrogen in Type Ic Supernovae?  

E-Print Network (OSTI)

By definition, a Type Ic supernova (SN Ic) does not have conspicuous lines of hydrogen or helium in its optical spectrum. SNe Ic usually are modelled in terms of the gravitational collapse of bare carbon-oxygen cores. We consider the possibility that the spectra of ordinary (SN 1994I-like) SNe Ic have been misinterpreted, and that SNe Ic eject hydrogen. An absorption feature usually attributed to a blend of Si II 6355 and C II 6580 may be produced by H-alpha. If SN 1994I-like SNe Ic eject hydrogen, the possibility that hypernova (SN 1998bw-like) SNe Ic, some of which are associated with gamma-ray bursts, also eject hydrogen should be considered. The implications of hydrogen for SN Ic progenitors and explosion models are briefly discussed.

David Branch; David J. Jeffery; Timothy R. Young; E. Baron

2006-05-09T23:59:59.000Z

115

String Landscape and Supernovae Ia  

E-Print Network (OSTI)

We present a model for the triggering of Supernovae Ia (SN Ia) by a phase transition to exact supersymmetry (susy) in the core of a white dwarf star. The model, which accomodates the data on SN Ia and avoids the problems of the standard astrophysical accretion based picture, is based on string landscape ideas and assumes that the decay of the false broken susy vacuum is enhanced at high density. In a slowly expanding susy bubble, the conversion of pairs of fermions to pairs of degenerate scalars releases a significant amount of energy which induces fusion in the surrounding normal matter shell. After cooling, the absence of degeneracy pressure causes the susy bubble to collapse to a black hole of about 0.1 solar mass or to some other stable susy object.

L. Clavelli

2011-10-09T23:59:59.000Z

116

Supercomputing and the search for supernovae  

ScienceCinema (OSTI)

Berkeley Lab's Peter Nugent discusses "Supercomputing and the search for supernovae" in this Oct. 28, 2013 talk, which is part of a Science at the Theater event entitled Eight Big Ideas.

Nugent, Peter

2014-06-23T23:59:59.000Z

117

How to See a Recently Discovered Supernova  

ScienceCinema (OSTI)

Berkeley Lab scientist Peter Nugent discusses a recently discovered supernova that is closer to Earth ? approximately 21 million light-years away ? than any other of its kind in a generation. Astronomers believe they caught the supernova within hours of its explosion, a rare feat made possible with a specialized survey telescope and state-of-the-art computational tools. The finding of such a supernova so early and so close has energized the astronomical community as they are scrambling to observe it with as many telescopes as possible, including the Hubble Space Telescope. More info on how to see it: http://newscenter.lbl.gov/feature-stories/2011/08/31/glimpse-cosmic-explosion/ News release: http://newscenter.lbl.gov/feature-stories/2011/08/25/supernova/

Nugent, Peter

2013-05-29T23:59:59.000Z

118

Supercomputing and the search for supernovae  

SciTech Connect

Berkeley Lab's Peter Nugent discusses "Supercomputing and the search for supernovae" in this Oct. 28, 2013 talk, which is part of a Science at the Theater event entitled Eight Big Ideas.

Nugent, Peter

2013-10-31T23:59:59.000Z

119

UV Light Curves of Thermonuclear Supernovae  

E-Print Network (OSTI)

Ultraviolet light curves are calculated for several thermonuclear supernova models using a multifrequency radiation hydrodynamic code. It is found that Chandrasekhar-mass models produce very similar light curves both for detonation and deflagration. Sub-Chandrasekhar-mass models essentially differ from ``normal'' Chandrasekhar ones regarding behaviour of their UV fluxes. Differences in absolute brightness and in shape of light curves of thermonuclear supernovae could be detectable up to 300 Mpc with modern UV space telescopes.

S. I. Blinnikov; E. I. Sorokina

2000-03-17T23:59:59.000Z

120

Inflationary Axion Cosmology  

DOE R&D Accomplishments (OSTI)

If Peccei-Quinn (PQ) symmetry is broken after inflation, the initial axion angle is a random variable on cosmological scales; based on this fact, estimates of the relic-axion mass density give too large a value if the axion mass is less than about 10-6 eV. This bound can be evaded if the Universe underwent inflation after PQ symmetry breaking and if the observable Universe happens to be a region where the initial axion angle was atypically small, .1 . (ma/10-6eV)0.59. We show consideration of fluctuations induced during inflation severely constrains the latter alternative.

Wilczek, Frank; Turner, Michael S.

1990-09-00T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Cosmological models with isotropic singularities  

E-Print Network (OSTI)

In 1985 Goode and Wainwright devised the concept of an isotropic singularity. Since that time, numerous authors have explored the interesting consequences, in mathematical cosmology, of assuming the existence of this type of singularity. In this paper, we collate all examples of cosmological models which are known to admit an isotropic singularity, and make a number of observations regarding their general characteristics.

Susan M. Scott; Geoffery Ericksson

1998-12-07T23:59:59.000Z

122

Dust time in quantum cosmology  

E-Print Network (OSTI)

We give a formulation of quantum cosmology with a pressureless dust and arbitrary additional matter fields. The dust provides a natural time gauge corresponding to a cosmic time, yielding a physical time independent Hamiltonian. The approach simplifies the analysis of both Wheeler-deWitt and loop quantum cosmology models, broadening the applicability of the latter.

Husain, Viqar

2013-01-01T23:59:59.000Z

123

White dwarf mergers,White dwarf mergers, thermonuclear supernovae,thermonuclear supernovae,  

E-Print Network (OSTI)

White dwarf mergers,White dwarf mergers, thermonuclear supernovae,thermonuclear supernovae fusion is ignited. Degenerate, hence runaway. #12;CO white dwarf accretes, either from companion, or from disk after merger. As it approaches maximum mass, C fusion is ignited. Degenerate, hence runaway. SN Ia

Hinton, Jim

124

Synoptic Sky Surveys and the Diffuse Supernova Neutrino Background: Removing Astrophysical Uncertainties and Revealing Invisible Supernovae  

E-Print Network (OSTI)

The cumulative (anti)neutrino production from all core-collapse supernovae within our cosmic horizon gives rise to the diffuse supernova neutrino background (DSNB), which is on the verge of detectability. The observed flux depends on supernova physics, but also on the cosmic history of supernova explosions; currently, the cosmic supernova rate introduces a substantial (+/-40%) uncertainty, largely through its absolute normalization. However, a new class of wide-field, repeated-scan (synoptic) optical sky surveys is coming online, and will map the sky in the time domain with unprecedented depth, completeness, and dynamic range. We show that these surveys will obtain the cosmic supernova rate by direct counting, in an unbiased way and with high statistics, and thus will allow for precise predictions of the DSNB. Upcoming sky surveys will substantially reduce the uncertainties in the DSNB source history to an anticipated +/-5% that is dominated by systematics, so that the observed high-energy flux thus will test supernova neutrino physics. The portion of the universe (z invisible supernovae, which may be unseen either due to unexpected large dust obscuration in host galaxies, or because some core-collapse events proceed directly to black hole formation and fail to give an optical outburst.

Amy Lien; Brian D. Fields; John F. Beacom

2010-01-20T23:59:59.000Z

125

The Standard Cosmological Model  

E-Print Network (OSTI)

The Standard Model of Particle Physics (SMPP) is an enormously successful description of high energy physics, driving ever more precise measurements to find "physics beyond the standard model", as well as providing motivation for developing more fundamental ideas that might explain the values of its parameters. Simultaneously, a description of the entire 3-dimensional structure of the present-day Universe is being built up painstakingly. Most of the structure is stochastic in nature, being merely the result of the particular realisation of the "initial conditions" within our observable Universe patch. However, governing this structure is the Standard Model of Cosmology (SMC), which appears to require only about a dozen parameters. Cosmologists are now determining the values of these quantities with increasing precision in order to search for "physics beyond the standard model", as well as trying to develop an understanding of the more fundamental ideas which might explain the values of its parameters. Although it is natural to see analogies between the two Standard Models, some intrinsic differences also exist, which are discussed here. Nevertheless, a truly fundamental theory will have to explain both the SMPP and SMC, and this must include an appreciation of which elements are deterministic and which are accidental. Considering different levels of stochasticity within cosmology may make it easier to accept that physical parameters in general might have a non-deterministic aspect.

Douglas Scott

2005-10-26T23:59:59.000Z

126

Distance measurements from supernovae and dark energy constraints  

Science Journals Connector (OSTI)

Constraints on dark energy from current observational data are sensitive to how distances are measured from Type Ia supernova (SN Ia) data. We find that flux averaging of SNe Ia can be used to test the presence of unknown systematic uncertainties, and yield more robust distance measurements from SNe Ia. We have applied this approach to the nearby+SDSS+ESSENCE+SNLS+HST set of 288 SNe Ia, and the “Constitution” set of 397 SNe Ia. Combining the SN Ia data with cosmic microwave background anisotropy data from Wilkinson Microwave Anisotropy Probe 5 yr observations, the Sloan Digital Sky Survey baryon acoustic oscillation measurements, the data of 69 gamma-ray bursts (GRBs) , and the Hubble constant measurement from the Hubble Space Telescope project SHOES, we measure the dark energy density function X(z)??X(z)/?X(0) as a free function of redshift (assumed to be a constant at z>1 or z>1.5). Without the flux averaging of SNe Ia, the combined data using the Constitution set of SNe Ia seem to indicate a deviation from a cosmological constant at ?95% confidence level at 0?z?0.8; they are consistent with a cosmological constant at ?68% confidence level when SNe Ia are flux averaged. The combined data using the nearby+SDSS+ESSENCE+SNLS+HST data set of SNe Ia are consistent with a cosmological constant at 68% confidence level with or without flux averaging of SNe Ia, and give dark energy constraints that are significantly more stringent than that using the Constitution set of SNe Ia. Assuming a flat Universe, dark energy is detected at >98% confidence level for z?0.75 using the combined data with 288 SNe Ia from nearby+SDSS+ESSENCE+SNLS+HST, independent of the assumptions about X(z?1). We quantify dark energy constraints without assuming a flat Universe using the dark energy figure of merit for both X(z) and a dark energy equation-of-state linear in the cosmic scale factor.

Yun Wang

2009-12-21T23:59:59.000Z

127

The Nuclear Equation of State and Supernovae James M. Lattimer  

E-Print Network (OSTI)

type of supernova is powered by thermonuclear energy. This type of event involves the end product will be devoted to them. We will point out, however, that because thermonuclear supernovae occur from a quite

Lattimer, James M.

128

Stellar core collapse and supernova  

SciTech Connect

Massive stars that end their stable evolution as their iron cores collapse to a neutron star or black hole long been considered good candidates for producing Type II supernovae. For many years the outward propagation of the shock wave produced by the bounce of these iron cores has been studied as a possible mechanism for the explosion. For the most part, the results of these studies have not been particularly encouraging, except, perhaps, in the case of very low mass iron cores or very soft nuclear equations of state. The shock stalls, overwhelmed by photodisintegration and neutrino losses, and the star does not explode. More recently, slow late time heating of the envelope of the incipient neutron star has been found to be capable of rejuvenating the stalled shock and producing an explosion after all. The present paper discusses this late time heating and presents results from numerical calculations of the evolution, core collapse, and subsequent explosion of a number of recent stellar models. For the first time they all, except perhaps the most massive, explode with reasonable choices of input physics. 39 refs., 17 figs., 1 tab.

Wilson, J.R.; Mayle, R.; Woosley, S.E.; Weaver, T.

1985-04-01T23:59:59.000Z

129

The Effect of Supercritical String Cosmology on the Relic Density of Dark Matter  

E-Print Network (OSTI)

. 3 As various type Ia supernovae projects [4,5] and the WMAP data [1,2] have continually confirmed the existence of dark energy, the cause of universe expansion, Supercritical String Cosmology (SSC) [6,7] arises as a model attempting to formulate... imply that exotic matter has negative pressure, acting like a dark energy term. Also, notice that the factor R increases as ?? decreases. When ?? = 0, ???? = 3.8 ? 1014. Such high enhancement factor is obviously ruled out by observational data, so...

Truong, Phuongmai N

2009-06-09T23:59:59.000Z

130

Effects of the interaction between dark energy and dark matter on cosmological parameters  

E-Print Network (OSTI)

We examine the effects of possible phenomenological interactions between dark energy and dark matter on cosmological parameters and their efficiency in solving the coincidence problem. We work with two simple parameterizations of the dynamical dark energy equation of state and the constant dark energy equation of state. Using observational data coming from the new 182 Gold type Ia supernova samples, the shift parameter of the Cosmic Microwave Background given by the three-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey, we perform a statistical joint analysis of different forms of phenomenological interactions between dark energy and dark matter.

Jian-Hua He; Bin Wang

2008-01-28T23:59:59.000Z

131

Effects of the interaction between dark energy and dark matter on cosmological parameters  

SciTech Connect

We examine the effects of possible phenomenological interactions between dark energy and dark matter on cosmological parameters and their efficiency in solving the coincidence problem. We work with two simple parameterizations of the dynamical dark energy equation of state and the constant dark energy equation of state. Using observational data coming from the new 182 Gold type Ia supernova samples, the shift parameter of the Cosmic Microwave Background given by the three-year Wilkinson Microwave Anisotropy Probe observations and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey, we perform a statistical joint analysis of different forms of phenomenological interaction between dark energy and dark matter.

He, Jian-Hua; Wang, Bin, E-mail: 062019010@fudan.edu.cn, E-mail: wangb@fudan.edu.cn [Department of Physics, Fudan University, Shanghai 200433 (China)] [Department of Physics, Fudan University, Shanghai 200433 (China)

2008-06-15T23:59:59.000Z

132

Protein folding and cosmology  

E-Print Network (OSTI)

Protein denaturing induced by supercooling is interpreted as a process where some or all internal symmetries of the native protein are spontaneously broken. Hence, the free-energy potential corresponding to a folding-funnel landscape becomes temperature-dependent and describes a phase transition. The idea that deformed vortices could be produced in the transition induced by temperature quenching, from native proteins to unfolded conformations is discussed in terms of the Zurek mechanism that implements the analogy between vortices, created in the laboratory at low energy, and the cosmic strings which are thought to have been left after symmetry breaking phase transitions in the early universe. An experiment is proposed to test the above idea which generalizes the cosmological analogy to also encompass biological systems and push a step ahead the view that protein folding is a biological equivalent of the big bang.

González-Diáz, P F

1997-01-01T23:59:59.000Z

133

Protein folding and cosmology  

E-Print Network (OSTI)

Protein denaturing induced by supercooling is interpreted as a process where some or all internal symmetries of the native protein are spontaneously broken. Hence, the free-energy potential corresponding to a folding-funnel landscape becomes temperature-dependent and describes a phase transition. The idea that deformed vortices could be produced in the transition induced by temperature quenching, from native proteins to unfolded conformations is discussed in terms of the Zurek mechanism that implements the analogy between vortices, created in the laboratory at low energy, and the cosmic strings which are thought to have been left after symmetry breaking phase transitions in the early universe. An experiment is proposed to test the above idea which generalizes the cosmological analogy to also encompass biological systems and push a step ahead the view that protein folding is a biological equivalent of the big bang.

P. F. Gonzalez-Diaz; C. L. Siguenza

1997-06-04T23:59:59.000Z

134

Turnaround in Cyclic Cosmology  

SciTech Connect

It is speculated how dark energy in a brane world can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model is described, in which dark energy with w<-1 equation of state leads to a turnaround at a time, extremely shortly before the would-be big rip, at which both volume and entropy of our Universe decrease by a gigantic factor, while very many independent similarly small contracting universes are spawned. The entropy of our model decreases almost to zero at turnaround but increases for the remainder of the cycle by a vanishingly small amount during contraction, empty of matter, then by a large factor during inflationary expansion.

Baum, Lauris; Frampton, Paul H. [University of North Carolina, Chapel Hill, North Carolina 27599-3255 (United States)

2007-02-16T23:59:59.000Z

135

LHC Physics and Cosmology  

E-Print Network (OSTI)

In these Lectures I review possible constraints on particle physics models, obtained by means of combining the results of collider measurements with astrophysical data. I emphasize the theoretical-model dependence of these results. I discuss supersymmetric dark matter constraints at colliders (mainly LHC) in various theoretical contexts: the standard Cosmological-Constant-Cold-Dark-Matter (Lambda-CDM) model, (super)string-inspired ones and non-equilibrium relaxation dark energy models. I then investigate the capability of LHC measurements in asserting whether supersymmetric matter (if discovered) constitutes part, or all, of the astrophysical dark matter. I also discuss prospects for improving the constraints in future precision facilities, such as the International Linear Collider.

Nikolaos E. Mavromatos

2007-08-01T23:59:59.000Z

136

Investigations of supernovae and supernova remnants in the era of SKA  

E-Print Network (OSTI)

Two main physical mechanisms are used to explain supernova explosions: thermonuclear explosion of a white dwarf(Type Ia) and core collapse of a massive star (Type II and Type Ib/Ic). Type Ia supernovae serve as distance indicators that led to the discovery of the accelerating expansion of the Universe. The exact nature of their progenitor systems however remain unclear. Radio emission from the interaction between the explosion shock front and its surrounding CSM or ISM provides an important probe into the progenitor star's last evolutionary stage. No radio emission has yet been detected from Type Ia supernovae by current telescopes. The SKA will hopefully detect radio emission from Type Ia supernovae due to its much better sensitivity and resolution. There is a 'supernovae rate problem' for the core collapse supernovae because the optically dim ones are missed due to being intrinsically faint and/or due to dust obscuration. A number of dust-enshrouded optically hidden supernovae should be discovered via SKA1-...

Wang, Lingzhi; Zhu, Hui; Tian, Wenwu; Wang, Xiaofeng

2015-01-01T23:59:59.000Z

137

Plasma Astrophysics - Cosmology and the Growth of Cosmic Structure  

SciTech Connect

I will present some of the ways that x-ray spectroscopy can be utilized to determine cosmological parameters focusing on 5 methods: the gas fraction in clusters, the use of the Sunyaev-Zeldovich effect, the detection of resonance scattering in clusters, the use of resonance absorption and emission in background sources and the growth of structure. All of these techniques except the S-Z effect rely heavily on high resolution x-ray spectroscopy and require the next generation of x-ray spectroscopic missions such as Constellation-X. The promise of these techniques is great and they have the potential for precision cosmology with errors similar to those of other precision techniques such as type Ia supernova. If time permits I will also talk about how we can learn about how active galaxies strongly influence the growth of cosmic structure and how broad band high resolution x-ray spectra are necessary to measure the effects of AGN and how much energy they input into the universe and the role of new atomic physics calculations in interpreting these results. A related discussion can be found in a previously published manuscript.

Mushotzky, Richard [National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, 20771 (United States)

2007-08-02T23:59:59.000Z

138

Plasma Astrophysics — Cosmology and the Growth of Cosmic Structure  

Science Journals Connector (OSTI)

I will present some of the ways that x?ray spectroscopy can be utilized to determine cosmological parameters focusing on 5 methods : the gas fraction in clusters the use of the Sunyaev?Zeldovich effect the detection of resonance scattering in clusters the use of resonance absorption and emission in background sources and the growth of structure. All of these techniques except the S?Z effect rely heavily on high resolution x?ray spectroscopy and require the next generation of x?ray spectroscopic missions such as Constellation?X. The promise of these techniques is great and they have the potential for precision cosmology with errors similar to those of other precision techniques such as type Ia supernova. If time permits I will also talk about how we can learn about how active galaxies strongly influence the growth of cosmic structure and how broad band high resolution x?ray spectra are necessary to measure the effects of AGN and how much energy they input into the universe and the role of new atomic physics calculations in interpreting these results. A related discussion can be found in a previously published manuscript.

Richard Mushotzky

2007-01-01T23:59:59.000Z

139

Radioactive Probes of the Supernova-Contaminated Solar Nebula: Evidence that the Sun was Born in a Cluster  

E-Print Network (OSTI)

We construct a simple model for radioisotopic enrichment of the protosolar nebula by injection from a nearby supernova, based on the inverse square law for ejecta dispersion. We find that the presolar radioisotopes abundances (i.e., in solar masses) demand a nearby supernova: its distance can be no larger than 66 times the size of the protosolar nebula, at a 90% confidence level, assuming 1 solar mass of protosolar material. The relevant size of the nebula depends on its state of evolution at the time of radioactivity injection. In one scenario, a collection of low-mass stars, including our sun, formed in a group or cluster with an intermediate- to high-mass star that ended its life as a supernova while our sun was still a protostar, a starless core, or perhaps a diffuse cloud. Using recent observations of protostars to estimate the size of the protosolar nebula constrains the distance of the supernova at 0.02 to 1.6 pc. The supernova distance limit is consistent with the scales of low-mass stars formation around one or more massive stars, but it is closer than expected were the sun formed in an isolated, solitary state. Consequently, if any presolar radioactivities originated via supernova injection, we must conclude that our sun was a member of such a group or cluster that has since dispersed, and thus that solar system formation should be understood in this context. In addition, we show that the timescale from explosion to the creation of small bodies was on the order of 1.8 Myr (formal 90% confidence range of 0 to 2.2 Myr), and thus the temporal choreography from supernova ejecta to meteorites is important. Finally, we can not distinguish between progenitor masses from 15 to 25 solar masses in the nucleosynthesis models; however, the 20 solar mass model is somewhat preferred.

Leslie W. Looney; John J. Tobin; Brian D. Fields

2006-08-19T23:59:59.000Z

140

Visualizing Type Ia Supernova Explosions at NERSC  

NLE Websites -- All DOE Office Websites (Extended Search)

Supernova Explosions Supernova Explosions Visualizing Type Ia Supernova Explosions Childs1a-Supernovasm.png Deep inside a dying star in a galaxy far, far away, a carbon fusion flame ignites. Ignition may happen in the middle or displaced slightly to one side, but this simulation explores the consequences of central ignition. In a localized hot spot, represented here by a deformed sphere with an average radius of 100 km, carbon is assumed to have already fused to iron, producing hot ash (~10 billion K) with a density about 20% less than its surroundings. As the burning progresses, this hot buoyant ash rises up and interacts with cold fuel. Rayleigh-Taylor fingers give rise to shear and turbulence, which interacts with the flame, causing it to move faster. In about 2 seconds, the energy released blows the entire white dwarf star up,

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Visual Observability of the Cassiopeia A Supernova  

E-Print Network (OSTI)

It is generally believed that the explosion which gave birth to the Cassiopeia A supernova remmant resulted from core collapse of a hydrogen-deficient star. A progenitor that has lost all its hydrogen envelope and part of its helium envelope would lead to an explosion with the optical properties of a Type Ic supernova. There is evidence, if not general agreement, that Flamsteed observed the Cas A supernova as a sixth magnitude object in August, 1680. If an explosion with a typical SNIc light curve at the position and distance of Cas A attained maximum luminosity during the winter of 1679-1680, it would at that time have been poorly situated for visual observation, as its upper culmination would have taken place during daylight, while in August, between 170-200 days after peak luminosity, it would have been a sixth magnitude star.

J. A. Morgan

2007-10-11T23:59:59.000Z

142

Tidally-induced thermonuclear Supernovae  

E-Print Network (OSTI)

We discuss the results of 3D simulations of tidal disruptions of white dwarfs by moderate-mass black holes as they may exist in the cores of globular clusters or dwarf galaxies. Our simulations follow self-consistently the hydrodynamic and nuclear evolution from the initial parabolic orbit over the disruption to the build-up of an accretion disk around the black hole. For strong enough encounters (pericentre distances smaller than about 1/3 of the tidal radius) the tidal compression is reversed by a shock and finally results in a thermonuclear explosion. These explosions are not restricted to progenitor masses close to the Chandrasekhar limit, we find exploding examples throughout the whole white dwarf mass range. There is, however, a restriction on the masses of the involved black holes: black holes more massive than $2\\times 10^5$ M$_\\odot$ swallow a typical 0.6 M$_\\odot$ dwarf before their tidal forces can overwhelm the star's self-gravity. Therefore, this mechanism is characteristic for black holes of moderate masses. The material that remains bound to the black hole settles into an accretion disk and produces an X-ray flare close to the Eddington limit of $L_{\\rm Edd} \\simeq 10^{41} {\\rm erg/s} M_{\\rm bh}/1000 M$_\\odot$), typically lasting for a few months. The combination of a peculiar thermonuclear supernova together with an X-ray flare thus whistle-blows the existence of such moderate-mass black holes. The next generation of wide field space-based instruments should be able to detect such events.

S. Rosswog; E. Ramirez-Ruiz; W. R. Hix

2008-11-13T23:59:59.000Z

143

Cosmology with the SKA -- overview  

E-Print Network (OSTI)

The new frontier of cosmology will be led by three-dimensional surveys of the large-scale structure of the Universe. Based on its all-sky surveys and redshift depth, the SKA is destined to revolutionize cosmology, in combination with future optical/ infrared surveys such as Euclid and LSST. Furthermore, we will not have to wait for the full deployment of the SKA in order to see transformational science. In the first phase of deployment (SKA1), all-sky HI intensity mapping surveys and all-sky continuum surveys are forecast to be at the forefront on the major questions of cosmology. We give a broad overview of the major contributions predicted for the SKA. The SKA will not only deliver precision cosmology -- it will also probe the foundations of the standard model and open the door to new discoveries on large-scale features of the Universe.

Maartens, Roy; Jarvis, Matt; Santos, Mario G

2015-01-01T23:59:59.000Z

144

Inflationary Cosmology: Theory and Phenomenology  

E-Print Network (OSTI)

This article gives a brief overview of some of the theory behind the inflationary cosmology, and discusses prospects for constraining inflation using observations. Particular care is given to the question of falsifiability of inflation or of subsets of inflationary models.

Andrew R Liddle

2001-10-18T23:59:59.000Z

145

Thermodynamics in Loop Quantum Cosmology  

E-Print Network (OSTI)

Loop quantum cosmology (LQC) is very powerful to deal with the behavior of early universe. And the effective loop quantum cosmology gives a successful description of the universe in the semiclassical region. We consider the apparent horizon of the Friedmann-Robertson-Walker universe as a thermodynamical system and investigate the thermodynamics of LQC in the semiclassical region. The effective density and effective pressure in the modified Friedmann equation from LQC not only determine the evolution of the universe in LQC scenario but are actually also found to be the thermodynamic quantities. This result comes from the energy definition in cosmology (the Misner-Sharp gravitational energy) and is consistent with thermodynamic laws. We prove that within the framework of loop quantum cosmology, the elementary equation of equilibrium thermodynamics is still valid.

Li-Fang Li; Jian-Yang Zhu

2008-12-18T23:59:59.000Z

146

Precision Cosmology and the Landscape  

E-Print Network (OSTI)

After reviewing the cosmological constant problem - why is Lambda not huge? - I outline the two basic approaches that had emerged by the late 1980s, and note that each made a clear prediction. Precision cosmological experiments now indicate that the cosmological constant is nonzero. This result strongly favors the environmental approach, in which vacuum energy can vary discretely among widely separated regions in the universe. The need to explain this variation from first principles constitutes an observational constraint on fundamental theory. I review arguments that string theory satisfies this constraint, as it contains a dense discretuum of metastable vacua. The enormous landscape of vacua calls for novel, statistical methods of deriving predictions, and it prompts us to reexamine our description of spacetime on the largest scales. I discuss the effects of cosmological dynamics, and I speculate that weighting vacua by their entropy production may allow for prior-free predictions that do not resort to explicitly anthropic arguments.

Raphael Bousso

2006-11-03T23:59:59.000Z

147

Planck Scale Cosmology and Asymptotic Safety in Resummed Quantum Gravity  

E-Print Network (OSTI)

In Weinberg's asymptotic safety approach, a finite dimensional critical surface for a UV stable fixed point generates a theory of quantum gravity with a finite number of physical parameters. We argue that, in an extension of Feynman's original formulation of the theory, we recover this fixed-point UV behavior from an exact re-arrangement of the respective perturbative series. Our results are consistent with the exact field space Wilsonian renormalization group results of Reuter {\\it et al.} and with recent Hopf- algebraic Dyson-Schwinger renormalization theory results of Kreimer. We obtain the first "first principles" predictions of the dimensionless gravitational and cosmological constants and our results support the Planck scale cosmology of Bonanno and Reuter. We conclude with an estimate for the currently observed value of the cosmological constant.

B. F. L. Ward

2010-12-13T23:59:59.000Z

148

Hydrogen issue in Core Collapse Supernovae  

E-Print Network (OSTI)

We discuss results of analyzing a time series of selected photospheric-optical spectra of core collapse supernovae (CCSNe). This is accomplished by means of the parameterized supernovae synthetic spectrum (SSp) code ``SYNOW''. Special attention is addressed to traces of hydrogen at early phases, especially for the stripped-envelope SNe (i.e. SNe Ib-c). A thin low mass hydrogen layer extending to very high ejection velocities above the helium shell, is found to be the most likely scenario for Type Ib SNe.

A. Elmhamdi; I. J. Danziger; D. Branch; B. Leibundgut

2006-11-06T23:59:59.000Z

149

Supernova remnants in the Magellanic Clouds. III  

SciTech Connect

As part of a continuing study of supernova remnants in the Magellanic Clouds, narrow-band optical images were obtained of seven SNR candidates in the LMC selected on the basis of radio and/or X-ray observations. Four of the candidates are confirmed as new SNRs. The object 0536-692 appears to be a superbubble resulting from one or more supernovae and the stellar winds from the large OB stellar association, NGC 2044, within its interior. The latest results bring the total number of SNRs with optical identifications in the Large Magellanic Cloud to 32. 16 references.

Mathewson, D.S.; Ford, V.L.; Tuohy, I.R.; Mills, B.Y.; Turtle, A.J.; Helfand, D.J.

1985-06-01T23:59:59.000Z

150

Deflagrations and Detonations in Thermonuclear Supernovae  

E-Print Network (OSTI)

We study a type Ia supernova explosion using three-dimensional numerical simulations based on reactive fluid dynamics. We consider a delayed-detonation model that assumes a deflagration-to-detonation transition. In contrast to the pure deflagration model, the delayed-detonation model releases enough energy to account for a healthy explosion, and does not leave carbon, oxygen, and intermediate-mass elements in central parts of a white dwarf. This removes the key disagreement between simulations and observations, and makes a delayed detonation the mostly likely mechanism for type Ia supernovae.

Vadim N. Gamezo; Alexei M. Khokhlov; Elaine S. Oran

2004-06-03T23:59:59.000Z

151

Cosmological implications of baryon acoustic oscillation (BAO) measurements  

E-Print Network (OSTI)

We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) and Type Ia supernova (SN) data. We take advantage of high-precision BAO measurements from galaxy clustering and the Ly-alpha forest (LyaF) in the BOSS survey of SDSS-III. BAO data alone yield a high confidence detection of dark energy, and in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Combining BAO and SN data into an "inverse distance ladder" yields a 1.7% measurement of $H_0=67.3 \\pm1.1$ km/s/Mpc. This measurement assumes standard pre-recombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat LCDM cosmology is an important corroboration of this minimal cosmological model. For open LCDM, our BAO+SN+CMB combination yields $\\Omega_m=0.301 \\pm 0.008$ and curvature $\\Omega_k=-0.003 \\pm 0.003$. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints remain consistent with flat LCDM. While the overall $\\chi^2$ of model fits is satisfactory, the LyaF BAO measurements are in moderate (2-2.5 sigma) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshifts remain consistent with our constraints, but models where dark matter decays into radiation are sharply limited. Expansion history alone yields an upper limit of 0.56 eV on the summed mass of neutrino species, improving to 0.26 eV if we include Planck CMB lensing. Standard dark energy models constrained by our data predict a level of matter clustering that is high compared to most, but not all, observational estimates. (Abridged)

Éric Aubourg; Stephen Bailey; Julian E. Bautista; Florian Beutler; Vaishali Bhardwaj; Dmitry Bizyaev; Michael Blanton; Michael Blomqvist; Adam S. Bolton; Jo Bovy; Howard Brewington; J. Brinkmann; Joel R. Brownstein; Angela Burden; Nicolás G. Busca; William Carithers; Chia-Hsun Chuang; Johan Comparat; Antonio J. Cuesta; Kyle S. Dawson; Timothée Delubac; Daniel J. Eisenstein; Andreu Font-Ribera; Jian Ge; J. -M. Le Goff; Satya Gontcho A Gontcho; J. Richard Gott III; James E. Gunn; Hong Guo; Julien Guy; Jean-Christophe Hamilton; Shirley Ho; Klaus Honscheid; Cullan Howlett; David Kirkby; Francisco S. Kitaura; Jean-Paul Kneib; Khee-Gan Lee; Dan Long; Robert H. Lupton; Mariana Vargas Magaña; Viktor Malanushenko; Elena Malanushenko; Marc Manera; Claudia Maraston; Daniel Margala; Cameron K. McBride; Jordi Miralda-Escudé; Adam D. Myers; Robert C. Nichol; Pasquier Noterdaeme; Sebastián E. Nuza; Matthew D. Olmstead; Daniel Oravetz; Isabelle Pâris; Nikhil Padmanabhan; Nathalie Palanque-Delabrouille; Kaike Pan; Marcos Pellejero-Ibanez; Will J. Percival; Patrick Petitjean; Matthew M. Pieri; Francisco Prada; Beth Reid; Natalie A. Roe; Ashley J. Ross; Nicholas P. Ross; Graziano Rossi; Jose Alberto Rubiño-Martín; Ariel G. Sánchez; Lado Samushia; Ricardo Tanausú Génova Santos; Claudia G. Scóccola; David J. Schlegel; Donald P. Schneider; Hee-Jong Seo; Erin Sheldon; Audrey Simmons; Ramin A. Skibba; Anže Slosar; Michael A. Strauss; Daniel Thomas; Jeremy L. Tinker; Rita Tojeiro; Jose Alberto Vazquez; Matteo Viel; David A. Wake; Benjamin A. Weaver; David H. Weinberg; W. M. Wood-Vasey; Christophe Yèche; Idit Zehavi; Gong-Bo Zhao

2014-11-18T23:59:59.000Z

152

Cosmological implications of baryon acoustic oscillation (BAO) measurements  

E-Print Network (OSTI)

We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) and Type Ia supernova (SN) data. We take advantage of high-precision BAO measurements from galaxy clustering and the Ly-alpha forest (LyaF) in the BOSS survey of SDSS-III. BAO data alone yield a high confidence detection of dark energy, and in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Combining BAO and SN data into an "inverse distance ladder" yields a 1.7% measurement of $H_0=67.3 \\pm1.1$ km/s/Mpc. This measurement assumes standard pre-recombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat LCDM cosmology is an important corroboration of this minimal cosmological model. For open LCDM, our BAO+SN+CMB combination yields $\\Omega_m=0.301 \\pm 0.008$ and curvature $\\Omega_k=-0.003 \\pm 0.003$. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints remain consistent with flat LCDM. While the overall $\\chi^2$ of model fits is satisfactory, the LyaF BAO measurements are in moderate (2-2.5 sigma) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshifts remain consistent with our constraints, but models where dark matter decays into radiation are sharply limited. Expansion history alone yields an upper limit of 0.56 eV on the summed mass of neutrino species, improving to 0.26 eV if we include Planck CMB lensing. Standard dark energy models constrained by our data predict a level of matter clustering that is high compared to most, but not all, observational estimates. (Abridged)

Éric Aubourg; Stephen Bailey; Julian E. Bautista; Florian Beutler; Vaishali Bhardwaj; Dmitry Bizyaev; Michael Blanton; Michael Blomqvist; Adam S. Bolton; Jo Bovy; Howard Brewington; J. Brinkmann; Joel R. Brownstein; Angela Burden; Nicolás G. Busca; William Carithers; Chia-Hsun Chuang; Johan Comparat; Antonio J. Cuesta; Kyle S. Dawson; Timothée Delubac; Daniel J. Eisenstein; Andreu Font-Ribera; Jian Ge; J. -M. Le Goff; Satya Gontcho A Gontcho; J. Richard Gott III; James E. Gunn; Hong Guo; Julien Guy; Jean-Christophe Hamilton; Shirley Ho; Klaus Honscheid; Cullan Howlett; David Kirkby; Francisco S. Kitaura; Jean-Paul Kneib; Khee-Gan Lee; Dan Long; Robert H. Lupton; Mariana Vargas Magaña; Viktor Malanushenko; Elena Malanushenko; Marc Manera; Claudia Maraston; Daniel Margala; Cameron K. McBride; Jordi Miralda-Escudé; Adam D. Myers; Robert C. Nichol; Pasquier Noterdaeme; Sebastián E. Nuza; Matthew D. Olmstead; Daniel Oravetz; Isabelle Pâris; Nikhil Padmanabhan; Nathalie Palanque-Delabrouille; Kaike Pan; Marcos Pellejero-Ibanez; Will J. Percival; Patrick Petitjean; Matthew M. Pieri; Francisco Prada; Beth Reid; Natalie A. Roe; Ashley J. Ross; Nicholas P. Ross; Graziano Rossi; Jose Alberto Rubiño-Martín; Ariel G. Sánchez; Lado Samushia; Ricardo Tanausú Génova Santos; Claudia G. Scóccola; David J. Schlegel; Donald P. Schneider; Hee-Jong Seo; Erin Sheldon; Audrey Simmons; Ramin A. Skibba; Anže Slosar; Michael A. Strauss; Daniel Thomas; Jeremy L. Tinker; Rita Tojeiro; Jose Alberto Vazquez; Matteo Viel; David A. Wake; Benjamin A. Weaver; David H. Weinberg; W. M. Wood-Vasey; Christophe Yèche; Idit Zehavi; Gong-Bo Zhao

2014-11-04T23:59:59.000Z

153

An inhomogeneous fractal cosmological model  

E-Print Network (OSTI)

We present a cosmological model in which the metric allows for an inhomogeneous Universe with no intrinsic symmetries (Stephani models), providing the ideal features to describe a fractal distribution of matter. Constraints on the metric functions are derived using the expansion and redshift relations and allowing for scaling number counts, as expected in a fractal set. The main characteristics of such a cosmological model are discussed.

Fulvio Pompilio; Marco Montuori

2001-11-28T23:59:59.000Z

154

Noncommutivity and Scalar Field Cosmology  

E-Print Network (OSTI)

In this work we extend and apply a previous proposal to study noncommutative cosmology to the FRW cosmological background coupled to a scalar field, this is done in classical and quantum scenarios. In both cases noncommutativity is introduced in the gravitational field as well as in the scalar field through a deformation of minisuperspace and are able to find exact solutions. Finally, the effects of noncommutativity on the classical evolution are analyzed.

W. Guzmán; M. Sabido; J. Socorro

2007-12-10T23:59:59.000Z

155

Reducing Zero-point Systematics in Dark Energy Supernova Experiments  

SciTech Connect

We study the effect of filter zero-point uncertainties on future supernova dark energy missions. Fitting for calibration parameters using simultaneous analysis of all Type Ia supernova standard candles achieves a significant improvement over more traditional fit methods. This conclusion is robust under diverse experimental configurations (number of observed supernovae, maximum survey redshift, inclusion of additional systematics). This approach to supernova fitting considerably eases otherwise stringent mission cali- bration requirements. As an example we simulate a space-based mission based on the proposed JDEM satellite; however the method and conclusions are general and valid for any future supernova dark energy mission, ground or space-based.

Faccioli, Lorenzo; Kim, Alex G; Miquel, Ramon; Bernstein, Gary; Bonissent, Alain; Brown, Matthew; Carithers, William; Christiansen, Jodi; Connolly, Natalia; Deustua, Susana; Gerdes, David; Gladney, Larry; Kushner, Gary; Linder, Eric; McKee, Shawn; Mostek, Nick; Shukla, Hemant; Stebbins, Albert; Stoughton, Chris; Tucker, David

2011-04-01T23:59:59.000Z

156

Type Ia supernova rate studies from the SDSS-II Supernova Study  

SciTech Connect

The author presents new measurements of the type Ia SN rate from the SDSS-II Supernova Survey. The SDSS-II Supernova Survey was carried out during the Fall months (Sept.-Nov.) of 2005-2007 and discovered {approx} 500 spectroscopically confirmed SNe Ia with densely sampled (once every {approx} 4 days), multi-color light curves. Additionally, the SDSS-II Supernova Survey has discovered several hundred SNe Ia candidates with well-measured light curves, but without spectroscopic confirmation of type. This total, achieved in 9 months of observing, represents {approx} 15-20% of the total SNe Ia discovered worldwide since 1885. The author describes some technical details of the SN Survey observations and SN search algorithms that contributed to the extremely high-yield of discovered SNe and that are important as context for the SDSS-II Supernova Survey SN Ia rate measurements.

Dilday, Benjamin; /Chicago U.

2008-08-01T23:59:59.000Z

157

Cosmology at the millennium  

Science Journals Connector (OSTI)

One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning, to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics—inflation+cold dark matter—holds the promise of extending our understanding to an even more fundamental level and much earlier times, as well as shedding light on the unification of the forces and particles of Nature. As we enter the 21st century, a flood of observations is testing this paradigm.

Michael S. Turner and J. Anthony Tyson

1999-03-01T23:59:59.000Z

158

Cosmology at the millennium  

SciTech Connect

One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning, to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics{emdash}inflation+cold dark matter{emdash}holds the promise of extending our understanding to an even more fundamental level and much earlier times, as well as shedding light on the unification of the forces and particles of Nature. As we enter the 21st century, a flood of observations is testing this paradigm. {copyright} {ital 1999} {ital The American Physical Society}

Turner, M.S. [Department of Astronomy Astrophysics and Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637-1433 (United States)] [Department of Astronomy Astrophysics and Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637-1433 (United States); [NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States); Tyson, J.A. [Bell Labs, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)] [Bell Labs, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)

1999-03-01T23:59:59.000Z

159

Cosmology at the Millennium  

E-Print Network (OSTI)

One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding Universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model, we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics -- inflation + cold dark matter -- holds the promise of extending our understanding to an even more fu...

Turner, M S; Turner, Michael S.

1999-01-01T23:59:59.000Z

160

Cosmology at the Millennium  

E-Print Network (OSTI)

One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding Universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model, we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics -- inflation + cold dark matter -- holds the promise of extending our understanding to an even more fundamental level and much earlier times, as well as shedding light on the unification of the forces and particles of nature. As we enter the 21st century, a flood of observations is testing this paradigm.

Michael S. Turner; J. Anthony Tyson

1999-01-11T23:59:59.000Z

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161

Nonlinear Noise in Cosmology  

E-Print Network (OSTI)

This paper derives and analyzes exact, nonlocal Langevin equations appropriate in a cosmological setting to describe the interaction of some collective degree of freedom with a surrounding ``environment.'' Formally, these equations are much more general, involving as they do a more or less arbitrary ``system,'' characterized by some time-dependent potential, which is coupled via a nonlinear, time-dependent interaction to a ``bath'' of oscillators with time-dependent frequencies. The analysis reveals that, even in a Markov limit, which can often be justified, the time dependences and nonlinearities can induce new and potentially significant effects, such as systematic and stochastic mass renormalizations and state-dependent ``memory'' functions, aside from the standard ``friction'' of a heuristic Langevin description. One specific example is discussed in detail, namely the case of an inflaton field, characterized by a Landau-Ginsburg potential, that is coupled quadratically to a bath of scalar ``radiation.'' The principal conclusion derived from this example is that nonlinearities and time-dependent couplings do {\\em not} preclude the possibility of deriving a fluctuation-dissipation theorem, and do {\\em not} change the form of the late-time steady state solution for the system, but {\\em can} significantly shorten the time scale for the approach towards the steady state.

Salman Habib; Henry E. Kandrup

1992-08-13T23:59:59.000Z

162

A flux calibration device for the SuperNova Integral Field Spectrograph (SNIFS)  

E-Print Network (OSTI)

Observational cosmology employing optical surveys often require precise flux calibration. In this context we present SNIFS Calibration Apparatus (SCALA), a flux calibration system developed for the SuperNova Integral Field Spectrograph (SNIFS), operating at the University of Hawaii 2.2 m telescope. SCALA consists of a hexagonal array of 18 small parabolic mirrors distributed over the face of, and feeding parallel light to, the telescope entrance pupil. The mirrors are illuminated by integrating spheres and a wavelength-tunable (from UV to IR) light source, generating light beams with opening angles of 1 degree. These nearly parallel beams are flat and flux-calibrated at a subpercent level, enabling us to calibrate our "telescope + SNIFS system" at the required precision.

Lombardo, Simona; Hoffmann, Akos; Kowalski, Marek; Kuesters, Daniel; Reif, Klaus; Rigault, Mickael

2014-01-01T23:59:59.000Z

163

Merging white dwarfs and thermonuclear supernovae  

Science Journals Connector (OSTI)

...across the Universe . Thermonuclear supernovae result when...companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic...adiabatically, until carbon fusion becomes faster than...time scales and the thermonuclear runaway starts (along...

2013-01-01T23:59:59.000Z

164

GRAVITATIONAL FIELD SHIELDING AND SUPERNOVA EXPLOSIONS  

SciTech Connect

A new mechanism for supernova explosions called gravitational field shielding is proposed, in accord with a five-dimensional fully covariant Kaluza-Klein theory with a scalar field that unifies the four-dimensional Einsteinian general relativity and Maxwellian electromagnetic theory. It is shown that a dense compact collapsing core of a star will suddenly turn off or completely shield its gravitational field when the core collapses to a critical density, which is inversely proportional to the square of mass of the core. As the core suddenly turns off its gravity, the extremely large pressure immediately stops the core collapse and pushes the mantle material of supernova moving outward. The work done by the pressure in the expansion can be the order of energy released in a supernova explosion. The gravity will resume and stop the core from a further expansion when the core density becomes less than the critical density. Therefore, the gravitational field shielding leads a supernova to impulsively explode and form a compact object such as a neutron star as a remnant. It works such that a compressed spring will shoot the oscillator out when the compressed force is suddenly removed.

Zhang, T. X. [Physics Department, Alabama A and M University, Normal, AL 35762 (United States)

2010-12-20T23:59:59.000Z

165

Composite dark energy: cosmon models with running cosmological term and gravitational coupling  

E-Print Network (OSTI)

In the recent literature on dark energy (DE) model building we have learnt that cosmologies with variable cosmological parameters can mimic more traditional DE pictures exclusively based on scalar fields (e.g. quintessence and phantom). In a previous work we have illustrated this situation within the context of a renormalization group running cosmological term, Lambda. Here we analyze the possibility that both the cosmological term and the gravitational coupling, G, are running parameters within a more general framework (a variant of the so-called ``LXCDM models'') in which the DE fluid can be a mixture of a running Lambda and another dynamical entity X (the ``cosmon'') which may behave quintessence-like or phantom-like. We compute the effective EOS parameter, w, of this composite fluid and show that the LXCDM can mimic to a large extent the standard LCDM model while retaining features hinting at its potential composite nature (such as the smooth crossing of the cosmological constant boundary w=-1). We further argue that the LXCDM models can cure the cosmological coincidence problem. All in all we suggest that future experimental studies on precision cosmology should take seriously the possibility that the DE fluid can be a composite medium whose dynamical features are partially caused and renormalized by the quantum running of the cosmological parameters.

Javier Grande; Joan Sola; Hrvoje Stefancic

2006-12-16T23:59:59.000Z

166

Probing thermonuclear supernova explosions with neutrinos  

E-Print Network (OSTI)

Aims: We present neutrino light curves and energy spectra for two representative type Ia supernova explosion models: a pure deflagration and a delayed detonation. Methods: We calculate the neutrino flux from $\\beta$ processes using nuclear statistical equilibrium abundances convoluted with approximate neutrino spectra of the individual nuclei and the thermal neutrino spectrum (pair+plasma). Results: Although the two considered thermonuclear supernova explosion scenarios are expected to produce almost identical electromagnetic output, their neutrino signatures appear vastly different, which allow an unambiguous identification of the explosion mechanism: a pure deflagration produces a single peak in the neutrino light curve, while the addition of the second maximum characterizes a delayed-detonation. We identified the following main contributors to the neutrino signal: (1) weak electron neutrino emission from electron captures (in particular on the protons Co55 and Ni56) and numerous beta-active nuclei produced by the thermonuclear flame and/or detonation front, (2) electron antineutrinos from positron captures on neutrons, and (3) the thermal emission from pair annihilation. We estimate that a pure deflagration supernova explosion at a distance of 1 kpc would trigger about 14 events in the future 50 kt liquid scintillator detector and some 19 events in a 0.5 Mt water Cherenkov-type detector. Conclusions: While in contrast to core-collapse supernovae neutrinos carry only a very small fraction of the energy produced in the thermonuclear supernova explosion, the SN Ia neutrino signal provides information that allows us to unambiguously distinguish between different possible explosion scenarios. These studies will become feasible with the next generation of proposed neutrino observatories.

A. Odrzywolek; T. Plewa

2011-03-27T23:59:59.000Z

167

Cosmological Tests of Coupled Galileons  

E-Print Network (OSTI)

We investigate the cosmological properties of Galileon models with positive kinetic terms. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distortions of the Cosmic Microwave Background spectrum which are known to be very small. The conformal coupling to baryons leads to a variation of particle masses since Big Bang Nucleosynthesis which is also tightly constrained. We consider the background cosmology of Galileon models coupled to Cold Dark Matter (CDM), photons and baryons and impose that the speed of light and particle masses respect the observational bounds on cosmological time scales. We find that requiring that the equation of state for the Galileon models must be close to -1 now restricts severely their parameter space and can only be achieved with a combination of the conformal and disformal couplings. This leads to large variations of particle masses and the speed of light which are not compatible with observations. As a result, we find that cosmological Galileon models are viable dark energy theories coupled to dark matter but their couplings, both disformal and conformal, to baryons and photons must be heavily suppressed making them only sensitive to CDM.

Philippe Brax; Clare Burrage; Anne-Christine Davis; Giulia Gubitosi

2014-11-27T23:59:59.000Z

168

Improving Type Ia Supernova Standard Candle Cosmology Measurements Using Observations of Early-Type Host Galaxies  

E-Print Network (OSTI)

surveys (e.g. The Dark Energy Survey 4 or the Large Synopticsurveys such as the Dark Energy Survey, Hyper-Suprime Cam,dark energy but face sev- eral hurdles for their continued success in future large surveys.

Meyers, Joshua Evan

2012-01-01T23:59:59.000Z

169

Conformal transformations and accelerated cosmologies  

Science Journals Connector (OSTI)

A cosmological theory that predicts a late-time accelerated attractor with a constant dark matter to dark energy ratio can be said to solve the coincidence problem. Such cosmologies are naturally generated in the context of nonstandard gravity theories under conformal transformation because of the resulting couplings between scalar fields and matter. The present work examines four classes of these transformed theories and finds that only a small subset-those with a single scalar field-are capable of solving the coincidence problem.

James L. Crooks and Paul H. Frampton

2006-06-09T23:59:59.000Z

170

Noncommutative models in patch cosmology  

SciTech Connect

We consider several classes of noncommutative inflationary models within an extended version of patch cosmological braneworlds, starting from a maximally invariant generalization of the action for scalar and tensor perturbations to a noncommutative brane embedded in a commutative bulk. Slow-roll expressions and consistency relations for the cosmological observables are provided, both in the UV and IR region of the spectrum; the inflaton field is assumed to be either an ordinary scalar field or a Born-Infeld tachyon. The effects of noncommutativity are then analyzed in a number of ways and energy regimes.

Calcagni, Gianluca [Dipartimento di Fisica, Universita di Parma, Parco Area delle Scienze 7/A, I-43100 Parma (Italy) and INFN-Gruppo Collegato di Parma, Parco Area delle Scienze 7/A, I-43100 Parma (Italy)

2004-11-15T23:59:59.000Z

171

THE CARNEGIE SUPERNOVA PROJECT: FIRST NEAR-INFRARED HUBBLE DIAGRAM TO z approx 0.7  

SciTech Connect

The Carnegie Supernova Project (CSP) is designed to measure the luminosity distance for Type Ia supernovae (SNe Ia) as a function of redshift, and to set observational constraints on the dark energy contribution to the total energy content of the universe. The CSP differs from other projects to date in its goal of providing an I-band rest-frame Hubble diagram. Here, we present the first results from near-infrared observations obtained using the Magellan Baade telescope for SNe Ia with 0.1 supernova cosmology programs. Finally, we conclude that either the dust affecting the luminosities of SNe Ia has a different extinction law (R{sub V} = 1.8) than that in the Milky Way (where R{sub V} = 3.1), or that there is an additional intrinsic color term with luminosity for SNe Ia, independent of the decline rate. Understanding and disentangling these effects is critical for minimizing the systematic uncertainties in future SN Ia cosmology studies.

Freedman, Wendy L.; Burns, Christopher R.; Wyatt, Pamela; Persson, S. E.; Madore, Barry F.; Kelson, Daniel D.; Murphy, D. C.; Sturch, Laura [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Phillips, M. M.; Contreras, Carlos; Folatelli, Gaston; Gonzalez, E. Sergio; Morrell, Nidia; Roth, Miguel; Stritzinger, Maximilian [Carnegie Institution of Washington, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile); Hamuy, Mario [Universidad de Chile, Departmento de Astronomia, Casilla 36-D, Santiago (Chile); Hsiao, Eric [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Stn CSC, Victoria, BC V8W 3P6 (Canada); Suntzeff, Nick B. [Physics Department, Texas A and M University, College Station, TX 77843 (United States); Astier, P.; Balland, C. [LPNHE, CNRS-IN2P3 and Universites Paris VI and VII, 4 place Jussieu, 75252 Paris Cedex 05 (France)

2009-10-20T23:59:59.000Z

172

THE DISCOVERY OF THE MOST DISTANT KNOWN TYPE Ia SUPERNOVA AT REDSHIFT 1.914  

SciTech Connect

We present the discovery of a Type Ia supernova (SN) at redshift z = 1.914 from the CANDELS multi-cycle treasury program on the Hubble Space Telescope (HST). This SN was discovered in the infrared using the Wide-Field Camera 3, and it is the highest-redshift Type Ia SN yet observed. We classify this object as a SN Ia by comparing its light curve and spectrum with those of a large sample of Type Ia and core-collapse SNe. Its apparent magnitude is consistent with that expected from the {Lambda}CDM concordance cosmology. We discuss the use of spectral evidence for classification of z > 1.5 SNe Ia using HST grism simulations, finding that spectral data alone can frequently rule out SNe II, but distinguishing between SNe Ia and SNe Ib/c can require prohibitively long exposures. In such cases, a quantitative analysis of the light curve may be necessary for classification. Our photometric and spectroscopic classification methods can aid the determination of SN rates and cosmological parameters from the full high-redshift CANDELS SN sample.

Jones, David O.; Rodney, Steven A.; Riess, Adam G. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Dahlen, Tomas; Casertano, Stefano; Koekemoer, Anton [Space Telescope Science Institute, Baltimore, MD 21218 (United States); McCully, Curtis; Keeton, Charles R.; Patel, Brandon [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States); Frederiksen, Teddy F.; Hjorth, Jens [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Strolger, Louis-Gregory [Department of Physics, Western Kentucky University, Bowling Green, KY 42101 (United States); Wiklind, Tommy G. [Joint ALMA Observatory, ESO, Santiago (Chile); Challis, Peter [Harvard/Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Graur, Or [School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel); Hayden, Brian; Garnavich, Peter [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Weiner, Benjamin J. [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); and others

2013-05-10T23:59:59.000Z

173

Towards simulating star formation in turbulent high-z galaxies with mechanical supernova feedback  

E-Print Network (OSTI)

Feedback from supernovae is essential to understanding the self-regulation of star formation in galaxies. However, the efficacy of the process in a cosmological context remains unclear due to excessive radiative losses during the shock propagation. To better understand the impact of SN explosions on the evolution of galaxies, we perform a suite of high-resolution (12 pc), zoom-in cosmological simulations of a Milky Way-like galaxy at z=3 with adaptive mesh refinement. We find that SN explosions can efficiently regulate star formation, leading to the stellar mass and metallicity consistent with the observed mass-metallicity relation and stellar mass-halo mass relation at z~3. This is achieved by making three important changes to the classical feedback scheme: i) the different phases of SN blast waves are modelled directly by injecting radial momentum expected at each stage, ii) the realistic time delay of SNe, commencing at as early as 3 Myr, is required to disperse very dense gas before a runaway collapse set...

Kimm, Taysun; Devriendt, Julien; Dubois, Yohan; Slyz, Adrianne

2015-01-01T23:59:59.000Z

174

Ejection of Supernova-Enriched Gas From Dwarf Disk Galaxies  

E-Print Network (OSTI)

We examine the efficiency with which supernova-enriched gas may be ejected from dwarf disk galaxies, using a methodology previously employed to study the self-enrichment efficiency of dwarf spheroidal systems. Unlike previous studies that focused on highly concentrated starbursts, in the current work we consider discrete supernova events spread throughout various fractions of the disk. We model disk systems having gas masses of 10^8 and 10^9 solar masses with supernova rates of 30, 300, and 3000 per Myr. The supernova events are confined to the midplane of the disk, but distributed over radii of 0, 30, and 80% of the disk radius, consistent with expectations for Type II supernovae. In agreement with earlier studies, we find that the enriched material from supernovae is largely lost when the supernovae are concentrated near the nucleus, as expected for a starburst event. In contrast, however, we find the loss of enriched material to be much less efficient when the supernovae occur over even a relatively small fraction of the disk. The difference is due to the ability of the system to relax following supernova events that occur over more extended regions. Larger physical separations also reduce the likelihood of supernovae going off within low-density "chimneys" swept out by previous supernovae. We also find that, for the most distributed systems, significant metal loss is more likely to be accompanied by significant mass loss. A comparison with theoretical predications indicates that, when undergoing self-regulated star formation, galaxies in the mass range considered shall efficiently retain the products of Type II supernovae.

P. Chris Fragile; Stephen D. Murray; Douglas N. C. Lin

2004-08-24T23:59:59.000Z

175

Merging White Dwarfs and Thermonuclear Supernovae  

E-Print Network (OSTI)

Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure, and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and our suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar mass remnants. I then turn to possible observational tests, in particular those that test the absence or presence of electron captures during the burning.

van Kerkwijk, Marten H

2012-01-01T23:59:59.000Z

176

Dynamical Collective Calculation of Supernova Neutrino Signals  

SciTech Connect

We present the first calculations with three flavors of collective and shock wave effects for neutrino propagation in core-collapse supernovae using hydrodynamical density profiles and the S matrix formalism. We explore the interplay between the neutrino-neutrino interaction and the effects of multiple resonances upon the time signal of positrons in supernova observatories. A specific signature is found for the inverted hierarchy and a large third neutrino mixing angle and we predict, in this case, a dearth of lower energy positrons in Cherenkov detectors midway through the neutrino signal and the simultaneous revelation of valuable information about the original fluxes. We show that this feature is also observable with current generation neutrino detectors at the level of several sigmas.

Gava, Jerome; Kneller, James; Volpe, Cristina; McLaughlin, G. C. [Institut de Physique Nucleaire, F-91406 Orsay cedex, CNRS/IN2P3 and University of Paris-XI (France); Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 (United States)

2009-08-14T23:59:59.000Z

177

Nucleosynthesis in O-Ne-Mg Supernovae  

SciTech Connect

We have studied detailed nucleosynthesis in the shocked surface layers of an oxygen-neon-magnesium core collapse supernova with an eye to determining whether the conditions are suitable for r-process nucleosynthesis. We find no such conditions in an unmodified model, but do find overproduction of N=50 nuclei (previously seen in early neutron-rich neutrino winds) in amounts that, if ejected, would pose serious problems for Galactic chemical evolution.

Hoffman, R D; Janka, H; Muller, B

2007-12-18T23:59:59.000Z

178

Earth Matter Effects in Detection of Supernova Neutrinos  

E-Print Network (OSTI)

We calculated the matter effect, including both the Earth and supernova, on the detection of neutrinos from type II supernovae at the proposed Daya Bay reactor neutrino experiment. It is found that apart from the dependence on the flip probability P_H inside the supernova and the mass hierarchy of neutrinos, the amount of the Earth matter effect depends on the direction of the incoming supernova neutrinos, and reaches the biggest value when the incident angle of neutrinos is around 93^\\circ. In the reaction channel \\bar{\

X. -H. Guo; Bing-Lin Young

2006-05-11T23:59:59.000Z

179

Asymmetric cyclic evolution in polymerised cosmology  

SciTech Connect

The dynamical systems methods are used to study evolution of the polymerised scalar field cosmologies with the cosmological constant. We have found all evolutional paths admissible for all initial conditions on the two-dimensional phase space. We have shown that the cyclic solutions are generic. The exact solution for polymerised cosmology is also obtained. Two basic cases are investigated, the polymerised scalar field and the polymerised gravitational and scalar field part. In the former the division on the cyclic and non-cyclic behaviour is established following the sign of the cosmological constant. The value of the cosmological constant is upper bounded purely from the dynamical setting.

Hrycyna, Orest [Department of Theoretical Physics, Faculty of Philosophy, The John Paul II Catholic University of Lublin, Al. Rac?awickie 14, 20-950 Lublin (Poland); Mielczarek, Jakub; Szyd?owski, Marek, E-mail: hrycyna@kul.lublin.pl, E-mail: jakub.mielczarek@uj.edu.pl, E-mail: uoszydlo@cyf-kr.edu.pl [Astronomical Observatory, Jagiellonian University, Orla 171, 30-244 Kraków (Poland)

2009-12-01T23:59:59.000Z

180

Chi-Variable-Speed-of-Light Cosmologies  

E-Print Network (OSTI)

Variable-Speed-of-Light (VSL) cosmologies are currently attracting much interest as a possible alternative to cosmological inflation. We discuss the fundamental geometrodynamic aspects of VSL cosmologies, and provide several alternative implementations. These implementations provide a large class of VSL cosmologies that pass the zeroth-order consistency tests of being compatible with both classical Einstein gravity and low-energy particle physics. While they solve the ``kinematic'' puzzles as well as inflation does, VSL cosmologies typically do not solve the flatness problem since in their purest form no violation of the strong energy condition occurs. Nevertheless, these models are easy to unify with inflation.

Stefano Liberati; Bruce A. Bassett; Carmen Molina-Paris; Matt Visser

2000-01-27T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Electric Time in Quantum Cosmology  

E-Print Network (OSTI)

Effective quantum cosmology is formulated with a realistic global internal time given by the electric vector potential. New possibilities for the quantum behavior of space-time are found, and the high-density regime is shown to be very sensitive to the specific form of state realized.

Stephon Alexander; Martin Bojowald; Antonino Marciano; David Simpson

2012-12-10T23:59:59.000Z

182

The Higgs boson and cosmology  

Science Journals Connector (OSTI)

...and beyond the discovery of the Higgs boson. organised and edited by John...Tejinder Virdee and David Charlton The Higgs boson and cosmology Mikhail Shaposhnikov...and beyond the discovery of the Higgs boson . I will discuss how the Higgs...

2015-01-01T23:59:59.000Z

183

Climbing the cosmological distance ladder  

Science Journals Connector (OSTI)

......knowledge of cosmological distance - towards redshift 1000! Humankind's efforts to measure the distances of the planets, stars...the epoch when matter and radiation finally decoupled at the end of the hot Big Bang phase. Apparently we have reached a precision......

Michael Rowan-Robinson

2008-06-01T23:59:59.000Z

184

Cosmological models with variable constants  

E-Print Network (OSTI)

The behavior of the constants, G,c,h,a,e,m and Lambda, considering them as variable, in the framework of a flat cosmological model with FRW symmetries described by a bulk viscous fluid and considering mechanisms of adiabatic matter creation are investigated. Within two models; one with radiation predominance and another of matter predominance, this behavior are studied.

J. A. Belinchon

1999-07-01T23:59:59.000Z

185

Towards Noncommutative Supersymmetric Quantum Cosmology  

SciTech Connect

In this work a construction of supersymmetric noncommutative cosmology is presented. We start with a ''noncommutative'' deformation of the minisuperspace variables, and by using the time reparametrization invariance of the noncommutative bosonic model we proceed to construct a super field description of the model.

Sabido, M.; Socorro, J. [Physics Department of the Division of Science and Engineering of the University of Guanajuato, Campus Leon P.O. Box E-143, 37150 Leon Gto. (Mexico); Guzman, W. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil)

2010-12-07T23:59:59.000Z

186

E-Print Network 3.0 - aspherical core-collapse supernovae Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

supernovae: New challenges and perspectives 12;Outline Introduction... Gamma-ray bursts Nucleosynthesis, etc.. Up to now only SN1987A TAMA300 Core-collapse Supernovae...

187

Supernova Simulations with Boltzmann Neutrino Transport: A Comparison of Methods  

E-Print Network (OSTI)

Accurate neutrino transport has been built into spherically symmetric simulations of stellar core collapse and postbounce evolution. The results of such simulations agree that spherically symmetric models with standard microphysical input fail to explode by the delayed, neutrino-driven mechanism. Independent groups implemented fundamentally different numerical methods to tackle the Boltzmann neutrino transport equation. Here we present a direct and detailed comparison of such neutrino radiation-hydrodynamical simulations for two codes, Agile-Boltztran of the Oak Ridge-Basel group and Vertex of the Garching group. The former solves the Boltzmann equation directly by an implicit, general relativistic discrete angle method on the adaptive grid of a conservative implicit hydrodynamics code with second-order TVD advection. In contrast, the latter couples a variable Eddington factor technique with an explicit, moving-grid, conservative high-order Riemann solver with important relativistic effects treated by an effective gravitational potential. The presented study is meant to test both neutrino radiation-hydrodynamics implementations and to provide a data basis for comparisons and verifications of supernova codes to be developed in the future. Results are discussed for simulations of the core collapse and post-bounce evolution of a 13 solar mass star with Newtonian gravity and a 15 solar mass star with relativistic gravity.

M. Liebendoerfer; M. Rampp; H. -Th. Janka; A. Mezzacappa

2003-10-22T23:59:59.000Z

188

Real time cosmology - A direct measure of the expansion rate of the Universe  

E-Print Network (OSTI)

In recent years cosmology has undergone a revolution, with precise measurements of the microwave background radiation, large galaxy redshift surveys, and the discovery of the recent accelerated expansion of the Universe using observations of distant supernovae. In this light, the SKA enables us to do an ultimate test in cosmology by measuring the expansion rate of the Universe in real time. This can be done by a rather simple experiment of observing the neutral hydrogen (HI) signal of galaxies at two different epochs. The signal will encounter a change in frequency imprinted as the Universe expands over time and thus monitoring the drift in frequencies will provide a real time measure of the cosmic acceleration. Over a period of 12 years one would expected a frequency shift of the order of 0.1 Hz assuming a standard Lambda-CDM cosmology. Based on the sensitivity estimates of the SKA and the number counts of the expected HI galaxies, it is shown that the number counts are sufficiently high to compensate for th...

Klöckner, H -R; Martins, C; Raccanelli, A; Champion, D; Roy, A; Lobanov, A; Wagner, J; Keller, R

2015-01-01T23:59:59.000Z

189

Cosmographic bounds on the cosmological deceleration-acceleration transition redshift in $f(\\mathcal{R})$ gravity  

E-Print Network (OSTI)

We examine the observational viability of a class of $f(\\mathcal{R})$ gravity cosmological models. Particular attention is devoted to constraints from the recent observational determination of the redshift of the cosmological deceleration-acceleration transition. Making use of the fact that the Ricci scalar is a function of redshift $z$ in these models, $\\mathcal {R=R}(z)$, and so is $f(z)$, we use cosmography to relate a $f(z)$ test function evaluated at higher $z$ to late-time cosmographic bounds. First, we consider a model independent procedure to build up a numerical $f(z)$ by requiring that at $z=0$ the corresponding cosmological model reduces to standard $\\Lambda$CDM. We then infer late-time observational constraints on $f(z)$ in terms of bounds on the Taylor expansion cosmographic coefficients. In doing so we parameterize possible departures from the standard $\\Lambda$CDM model in terms of a two-parameter logarithmic correction. The physical meaning of the two parameters is also discussed in terms of the post Newtonian approximation. Second, we provide numerical estimates of the cosmographic series terms by using Type Ia supernova apparent magnitude data and Hubble parameter measurements. Finally, we use these estimates to bound the two parameters of the logarithmic correction. We find that the deceleration parameter in our model changes sign at a redshift consistent with what is observed.

Salvatore Capozziello; Omer Farooq; Orlando Luongo; Bharat Ratra

2014-03-06T23:59:59.000Z

190

Snapping Supernovae at z>1.7  

E-Print Network (OSTI)

dark energy to higher redshift, the improvement of the ideal z = 3 depth surveysurveys at z > 1.7 o?er little cosmological leverage on dark energy.survey is seen to be close to optimal for determination of the dark energy

Aldering, Greg

2009-01-01T23:59:59.000Z

191

Sensitivity study of explosive nucleosynthesis in type Ia supernovae: Modification of individual thermonuclear reaction rates  

Science Journals Connector (OSTI)

Background: Type Ia supernovae contribute significantly to the nucleosynthesis of many Fe-group and intermediate-mass elements. However, the robustness of nucleosynthesis obtained via models of this class of explosions has not been studied in depth until now.Purpose: We explore the sensitivity of the nucleosynthesis resulting from thermonuclear explosions of massive white dwarfs with respect to uncertainties in nuclear reaction rates. We put particular emphasis on indentifying the individual reactions rates that most strongly affect the isotopic products of these supernovae.Method: We have adopted a standard one-dimensional delayed detonation model of the explosion of a Chandrasekhar-mass white dwarf and have postprocessed the thermodynamic trajectories of every mass shell with a nucleosynthetic code to obtain the chemical composition of the ejected matter. We have considered increases (decreases) by a factor of 10 on the rates of 1196 nuclear reactions (simultaneously with their inverse reactions), repeating the nucleosynthesis calculations after modification of each reaction rate pair. We have computed as well hydrodynamic models for different rates of the fusion reactions of 12C and of 16O. From the calculations we have selected the reactions that have the largest impact on the supernova yields, and we have computed again the nucleosynthesis using two or three alternative prescriptions for their rates, taken from the JINA REACLIB database. For the three reactions with the largest sensitivity we have analyzed as well the temperature ranges where a modification of their rates has the strongest effect on nucleosynthesis.Results: The nucleosynthesis resulting from the type Ia supernova models is quite robust with respect to variations of nuclear reaction rates, with the exception of the reaction of fusion of two 12C nuclei. The energy of the explosion changes by less than ?4% when the rates of the reactions 12C+12C or 16O+16O are multiplied by a factor of ×10 or ×0.1. The changes in the nucleosynthesis owing to the modification of the rates of these fusion reactions are also quite modest; for instance, no species with a mass fraction larger than 0.02 experiences a variation of its yield larger than a factor of 2. We provide the sensitivity of the yields of the most abundant species with respect to the rates of the most intense reactions with protons, neutrons, and ?. In general, the yields of Fe-group nuclei are more robust than the yields of intermediate-mass elements. Among the species with yields larger than 10?8M?, 35S has the largest sensitivity to the nuclear reaction rates. It is remarkable that the reactions involving elements with Z>22 have a tiny influence on the supernova nucleosynthesis. Among the charged-particle reactions, the most influential on supernova nucleosynthesis are 30Si+p?31P+?, 20Ne+??24Mg+?, and 24Mg+??27Al+p. The temperatures at which a modification of their rate has a larger impact are in the range 2?T?4 GK.Conclusions: The explosion model (i.e., the assumed conditions and propagation of the flame) chiefly determines the element production of type Ia supernovae and derived quantities such as their luminosity, while the nuclear reaction rates used in the simulations have a small influence on the kinetic energy and final chemical composition of the ejecta. Our results show that the uncertainty in individual thermonuclear reaction rates cannot account for discrepancies of a factor of 2 between isotopic ratios in type Ia supernovae and those in the solar system, especially within the Fe group.

Eduardo Bravo and Gabriel Martínez-Pinedo

2012-05-18T23:59:59.000Z

192

Rates of superluminous supernovae at z 0.2  

Science Journals Connector (OSTI)

......research-article Article Rates of superluminous supernovae...ACT 2611, Australia 3 Physics Department, University...calculate the volumetric rate of superluminous supernovae...in our unfiltered band pass and may suggest an even...we measure the SLSN-I rate to be about (32 )Gpcyrh......

Robert M. Quimby; Fang Yuan; Carl Akerlof; J. Craig Wheeler

2013-01-01T23:59:59.000Z

193

Synthetic Spectrum Methods for Three-Dimensional Supernova Models  

E-Print Network (OSTI)

Current observations stimulate the production of fully three-dimensional explosion models, which in turn motivates three-dimensional spectrum synthesis for supernova atmospheres. We briefly discuss techniques adapted to address the latter problem, and consider some fundamentals of line formation in supernovae without recourse to spherical symmetry. Direct and detailed extensions of the technique are discussed, and future work is outlined.

R. C. Thomas

2003-10-21T23:59:59.000Z

194

Thermodynamics of decaying vacuum cosmologies  

Science Journals Connector (OSTI)

The thermodynamic behavior of decaying vacuum cosmologies is investigated within a manifestly covariant formulation. Such a process corresponds to a continuous, irreversible energy flow from the vacuum component to the created matter constituents. It is shown that if the specific entropy per particle remains constant during the process, the equilibrium relations are preserved. In particular, if the vacuum decays into photons, the energy density ? and average number density of photons n scale with the temperature as ??T4 and n?T3. The temperature law is determined and a generalized Planckian-type form of the spectrum, which is preserved in the course of the evolution, is also proposed. Some consequences of these results for decaying vacuum FRW-type cosmologies as well as for models with "adiabatic" photon creation are discussed.

J. A. S. Lima

1996-08-15T23:59:59.000Z

195

Inflationary nonsingular quantum cosmological model  

SciTech Connect

A stiff matter-dominated universe modeled by a free massless scalar field minimally coupled to gravity in a Friedmann-Lemaitre-Robertson-Walker (FLRW) geometry is quantized. Generalized complex-width Gaussian superpositions of the solutions of the Wheeler-DeWitt equation are constructed and the Bohm-de Broglie interpretation of quantum cosmology is applied. A planar dynamical system is found in which a diversity of quantum Bohmian trajectories are obtained and discussed. One class of solutions represents nonsingular inflationary models starting at infinity past from flat space-time with Planckian size spacelike hypersurfaces, which inflates without inflaton but due to a quantum cosmological effect, until it makes an analytical graceful exit from this inflationary epoch to a decelerated classical stiff matter expansion phase.

Falciano, Felipe T.; Pinto-Neto, Nelson; Santini, E. Sergio [Instituto de Cosmologia Relatividade e Astrofisica ICRA-CBPF, Rua Xavier Sigaud, 150, Urca, 22290-180, Rio de Janeiro (Brazil); Instituto de Cosmologia Relatividade e Astrofisica ICRA-CBPF, Rua Xavier Sigaud, 150, Urca, 22290-180, Rio de Janeiro, Brazil and ComisSao Nacional de Energia Nuclear, Rua General Severiano 90, Botafogo 22290-901, Rio de Janeiro (Brazil)

2007-10-15T23:59:59.000Z

196

Effective perfect fluids in cosmology  

SciTech Connect

We describe the cosmological dynamics of perfect fluids within the framework of effective field theories. The effective action is a derivative expansion whose terms are selected by the symmetry requirements on the relevant long-distance degrees of freedom, which are identified with comoving coordinates. The perfect fluid is defined by requiring invariance of the action under internal volume-preserving diffeomorphisms and general covariance. At lowest order in derivatives, the dynamics is encoded in a single function of the entropy density that characterizes the properties of the fluid, such as the equation of state and the speed of sound. This framework allows a neat simultaneous description of fluid and metric perturbations. Longitudinal fluid perturbations are closely related to the adiabatic modes, while the transverse modes mix with vector metric perturbations as a consequence of vorticity conservation. This formalism features a large flexibility which can be of practical use for higher order perturbation theory and cosmological parameter estimation.

Ballesteros, Guillermo [Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, I-00184 Rome (Italy); Bellazzini, Brando, E-mail: guillermo.ballesteros@unige.ch, E-mail: brando.bellazzini@pd.infn.it [Dipartimento di Fisica, Università di Padova and INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy)

2013-04-01T23:59:59.000Z

197

Complex Lagrangians and phantom cosmology  

E-Print Network (OSTI)

Motivated by the generalization of quantum theory for the case of non-Hermitian Hamiltonians with PT symmetry, we show how a classical cosmological model describes a smooth transition from ordinary dark energy to the phantom one. The model is based on a classical complex Lagrangian of a scalar field. Specific symmetry properties analogous to PT in non-Hermitian quantum mechanics lead to purely real equation of motion.

A. A. Andrianov; F. Cannata; A. Y. Kamenshchik

2006-04-28T23:59:59.000Z

198

Complex Lagrangians and phantom cosmology  

E-Print Network (OSTI)

Motivated by the generalization of quantum theory for the case of non-Hermitian Hamiltonians with PT symmetry, we show how a classical cosmological model describes a smooth transition from ordinary dark energy to the phantom one. The model is based on a classical complex Lagrangian of a scalar field. Specific symmetry properties analogous to PT in non-Hermitian quantum mechanics lead to purely real equation of motion.

Andrianov, A A; Kamenshchik, A Yu

2006-01-01T23:59:59.000Z

199

Cosmology, Thermodynamics and Matter Creation  

E-Print Network (OSTI)

Several approaches to the matter creation problem in the context of cosmological models are summarily reviewed. A covariant formulation of the general relativistic imperfect simple fluid endowed with a process of matter creation is presented. By considering the standard big bang model, it is shown how the recent results of Prigogine et alii \\cite{1} can be recovered and, at the same time their limits of validity are explicited.

J. A. S. Lima; M. O. Calvao; I. Waga

2007-08-24T23:59:59.000Z

200

Pair-Production Supernovae: Theory and Observation  

E-Print Network (OSTI)

I review the physical properties of pair-production supernovae (PPSNe) as well as the prospects for them to be constrained observationally. In very massive (140-260 solar mass) stars, much of the pressure support comes from the radiation field, meaning that they are loosely bound, with an adiabatic coefficient that is close to the minimum stable value. Near the end of C/O burning, the central temperature increases to the point that photons begin to be converted into electron-positron pairs, softening gamma below this critical value. The result is a runaway collapse, followed by explosive burning that completely obliterates the star. While these explosions can be up to 100 times more energetic that core collapse and Type Ia supernovae, their peak luminosities are only slightly greater. However, due both to copious Ni-56 production and hydrogen recombination, they are brighter much longer, and remain observable for ~ 1 year. Since metal enrichment is a local process, PPSNe should occur in pockets of metal-free gas over a broad range of redshifts, greatly enhancing their detectability, and distributing their nucleosyntehtic products about the Milky Way. This means that measurements of the abundances of metal-free stars should be thought of as directly constraining these objects. It also means that ongoing supernova searches, already provide weak constraints for PPSN models. A survey with the NIRCam instrument on JWST, on the other hand, would be able to extend these limits to z ~ 10. Observing a 0.3 deg^2 patch of sky for one week per year for three consecutive years, such a program would either detect or rule out the existence of these remarkable objects.

Evan Scannapieco

2006-09-07T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Flavor Changing Supersymmetry Interactions in a Supernova  

E-Print Network (OSTI)

We consider for the first time R-parity violating interactions of the Minimal Standard Supersymmetric Model involving neutrinos and quarks (``flavor changing neutral currents'', FCNC's) in the infall stage of stellar collapse. Our considerations extend to other kinds of flavor changing neutrino reactions as well. We examine non-forward neutrino scattering processes on heavy nuclei and free nucleons in the supernova core. This investigation has led to four principal original discoveries/products: (1) first calculation of neutrino flavor changing cross sections for spin one half (e.g. free nucleon) and spin zero nuclear targets; (2) discovery of nuclear mass number squared (A squared) coherent amplification of neutrino-quark FCNC's; (3) analysis of FCNC-induced alteration of electron capture and weak/nuclear equilibrium in the collapsing core; and (4) generalization of the calculated cross sections (mentioned in 1) for the case of hot heavy nuclei to be used in collapse/supernova and neutrino transport simulations. The scattering processes that we consider allow electron neutrinos to change flavor during core collapse, thereby opening holes in the electron neutrino sea, which allows electron capture to proceed and results in a lower core electron fraction. A lower electron fraction implies a lower homologous core mass, a lower shock energy, and a greater nuclear photo-disintegration burden for the shock. In addition, unlike the standard supernova model, the core now could have net muon and/or tau lepton numbers. These effects could be significant even for supersymmetric couplings below current experimental bounds.

Philip S. Amanik; George M. Fuller; Benjamin Grinstein

2005-10-14T23:59:59.000Z

202

Multiverse understanding of cosmological coincidences  

SciTech Connect

There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.

Bousso, Raphael; Hall, Lawrence J.; Nomura, Yasunori [Center for Theoretical Physics, Department of Physics, University of California, Berkeley, California 94720-7300 (United States) and Lawrence Berkeley National Laboratory, Berkeley, California 94720-8162 (United States)

2009-09-15T23:59:59.000Z

203

Disformal transformation of cosmological perturbations  

E-Print Network (OSTI)

We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar-tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar-tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (non)conservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame.

Masato Minamitsuji

2014-09-04T23:59:59.000Z

204

Supernova neutrinos, giant resonances, and nucleosynthesis  

SciTech Connect

Almost all of the 3{center dot}10{sup 53} ergs liberated in a core collapse supernova is radiated as neutrinos by the cooling neutron star. The neutrinos can excite nuclei in the mantle of the star by their neutral and charged current reactions. I argue that the resulting spallation reactions are an important nucleosynthesis mechanism that may be responsible for the galactic abundances of {sup 7}Li, {sup 11}B, {sup 19}F, {sup 138}La, {sup 180}Ta, and approximately a dozen other light nuclei. 18 refs., 1 fig., 1 tab.

Haxton, W.

1990-01-01T23:59:59.000Z

205

Emergent cosmological constant from colliding electromagnetic waves  

E-Print Network (OSTI)

In this study we advocate the view that the cosmological constant is of electromagnetic (em) origin, which can be generated from the collision of em shock waves coupled with gravitational shock waves. The wave profiles that participate in the collision have different amplitudes. It is shown that, circular polarization with equal amplitude waves does not generate cosmological constant. We also prove that the generation of the cosmological constant is related to the linear polarization. The addition of cross polarization generates no cosmological constant. Depending on the value of the wave amplitudes, the generated cosmological constant can be positive or negative. We show additionally that, the collision of nonlinear em waves in a particular class of Born-Infeld theory also yields a cosmological constant.

M. Halilsoy; S. Habib Mazharimousavi; O. Gurtug

2014-10-15T23:59:59.000Z

206

String Gas Cosmology and Non-Gaussianities  

E-Print Network (OSTI)

Recently it has been shown that string gas cosmology, an alternative model of the very early universe which does not involve a period of cosmological inflation, can give rise to an almost scale invariant spectrum of metric perturbations. Here we calculate the non-Gaussianities of the spectrum of cosmological fluctuations in string gas cosmology, and find that these non-Gaussianities depend linearly on the wave number and that their amplitude depends sensitively on the string scale. If the string scale is at the TeV scale, string gas cosmology could lead to observable non-Gaussianities, if it is close to the Planck scale, then the non-Gaussianities on current cosmological scales are negligible.

Bin Chen; Yi Wang; Wei Xue; Robert Brandenberger

2008-03-05T23:59:59.000Z

207

Accelerating cosmological expansion from shear viscosity  

E-Print Network (OSTI)

The dissipation of energy from local velocity perturbations in the cosmological fluid affects the time evolution of spatially averaged fluid dynamic fields and the cosmological solution of Einstein's field equations. We show how this backreaction effect depends on shear viscosity and other material properties of the dark sector, as well as the spectrum of perturbations. If sufficiently large, this effect could account for the acceleration of the cosmological expansion.

Floerchinger, Stefan; Wiedemann, Urs Achim

2014-01-01T23:59:59.000Z

208

Cosmological Constant and Axions in String Theory  

SciTech Connect

String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. In this paper, we study conditions on the string compactifications under which axion quintessence can happen. For sufficiently large number of axions, cosmological constant can be accounted for as the potential energy of axions that have not yet relaxed to their minima. In compactifications that incorporate unified models of particle physics, the height of the axion potential can naturally fall close to the observed value of cosmological constant.

Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC

2006-08-18T23:59:59.000Z

209

Landscape Predictions from Cosmological Vacuum Selection  

E-Print Network (OSTI)

In BP models with hundreds of fluxes, we compute the effects of cosmological dynamics on the probability distribution of landscape vacua. Starting from generic initial conditions, we find that most fluxes are dynamically driven into a different and much narrower range of values than expected from landscape statistics alone. Hence, cosmological evolution will access only a tiny fraction of the vacua with small cosmological constant. This leads to a host of sharp predictions. Unlike other approaches to eternal inflation, the holographic measure employed here does not lead to "staggering", an excessive spread of probabilities that would doom the string landscape as a solution to the cosmological constant problem.

Raphael Bousso; I-Sheng Yang

2007-05-09T23:59:59.000Z

210

JLF User Group  

NLE Websites -- All DOE Office Websites (Extended Search)

or a radiative shocks in a supernova remnants. She has lead experiments at the Omega Laser Facility and National Ignition Facility and participated in experiments at the...

211

Discovering the Nature of Dark Energy: Towards Better Distances from Type Ia Supernovae -- Final Technical Report  

SciTech Connect

Type Ia supernovae (SNe Ia; exploding white-dwarf stars) were the key to the Nobel-worthy 1998 discovery and subsequent verification that the expansion of the Universe is accelerating, driven by the effects of dark energy. Understanding the nature of this mysterious, yet dominant, component of the Universe is at the forefront of research in cosmology and fundamental physics. SNe Ia will continue to play a leading role in this enterprise, providing precise cosmological distances that improve constraints on the nature of dark energy. However, for this effort to succeed, we need to more thoroughly understand relatively nearby SNe Ia, because our conclusions come only from comparisons between them and distant (high-redshift) SNe Ia. Thus, detailed studies of relatively nearby SNe Ia are the focus of this research program. Many interesting results were obtained during the course of this project; these were published in 32 refereed research papers that acknowledged the grant. A major accomplishment was the publication of supernova (SN) rates derived from about a decade of operation of the Lick Observatory Supernova Search (LOSS) with the 0.76-meter Katzman Automatic Imaging Telescope (KAIT). We have determined the most accurate rates for SNe of different types in large, nearby galaxies in the present-day Universe, and these can be compared with SN rates far away (and hence long ago in the past) to set constraints on the types of stars that explode. Another major accomplishment was the publication of the light curves (brightness vs. time) of 165 SNe Ia, along with optical spectroscopy of many of these SNe as well as other SNe Ia, providing an extensive, homogeneous database for detailed studies. We have conducted intensive investigations of a number of individual SNe Ia, including quite unusual examples that allow us to probe the entire range of SN explosions and provide unique insights into these objects and the stars before they explode. My team's studies have also led to the identification of subsamples of SNe Ia that can be used to provide the most reliable cosmological distances, and we developed ways to deal with the dust that makes SNe Ia appear fainter than they really are. Using the KAIT/LOSS sample, we produced an excellent Hubble diagram (galaxy recession speed vs. distance), accurately showing the expansion of the Universe. Even smaller scatter was achieved when spectroscopic characteristics were taken into account. Another high-quality Hubble diagram was constructed with SNe Ia from the Sloan Digital Sky Survey (SDSS). These Hubble diagrams provide useful new constraints on the nature of the dark energy that is accelerating the expansion of the Universe. As an added bonus of our research, we also studied core-collapse SNe, which differ fundamentally from SNe Ia.

Filippenko, Alexei Vladimir [Univ. California, Berkeley

2014-05-09T23:59:59.000Z

212

Systematic Effects in Type-1a Supernovae Surveys from Host Galaxy Spectra  

SciTech Connect

The physical relation between the properties of Type Ia supernovae and their host galaxies is investigated. Such supernovae are used to constrain the properties of dark energy, making it crucial to understand their physical properties and to check for systematic effects relating to the stellar populations of the progenitor stars from which these supernovae arose. This grant found strong evidence for two distinct populations of supernovae, and correlations between the progenitor stellar populations and the nature of the supernova light curves.

Strauss, Michael A. [Princeton University

2013-08-23T23:59:59.000Z

213

Incompatibility of a comoving Ly-alpha forest with supernova-Ia luminosity distances  

E-Print Network (OSTI)

Recently Perlmutter et al. suggested a positive value of Einstein's cosmological constant Lambda on the basis of luminosity distances from type-Ia supernovae. However, Lambda world models had earlier been proposed by Hoell & Priester and Liebscher et al. on the basis of quasar absorption-line data. Employing more general repulsive fluids ("dark energy") encompassing the Lambda component we quantitatively compare both approaches with each other. Fitting the SN-data by a minimum-component model consisting of dark energy + dust yields a closed universe with a large amount of dust exceeding the baryonic content constrained by big-bang nucleosynthesis. The nature of the dark energy is hardly constrained. Only when enforcing a flat universe there is a clear tendency to a dark-energy Lambda fluid and the `canonical' value Omega_M = 0.3 for dust. Conversely, fitting the quasar-data by a minimum-component model yields a sharply defined, slightly closed model with a low dust density ruling out significant pressureless dark matter. The dark-energy component obtains an equation-of-state P = -0.96 epsilon close to that of a Lambda-fluid. Omega_M = 0.3 or a precisely flat spatial geometry are inconsistent with minimum-component models. It is found that quasar and supernova data sets cannot be reconciled with each other via (repulsive ideal fluid+dust+radiation)-world models. Compatibility could be reached by drastic expansion of the parameter space with at least two exotic fluids added to dust and radiation as world constituents. If considering such solutions as far-fetched one has to conclude that the quasar absorption line and the SN-Ia constraints are incompatible.

Jens Thomas; Hartmut Schulz

2001-03-18T23:59:59.000Z

214

Cosmological constraints on dark energy  

E-Print Network (OSTI)

It has been only ~15 years since the discovery of dark energy (although some may argue there were strong indications even earlier). In the short time since measurements of type Ia supernovae indicated an accelerating universe, many other techniques have now confirmed the acceleration is real. The variety of ways in which dark energy has been confirmed is one of the reasons we are so confident in the statement that most of the energy in the universe is in a form we can not see except through its gravitational influence. This review aims to summarise briefly the many varied ways we now have measured dark energy. The fact that these different techniques all indicate that the simplest model remains the best -- that dark energy contributes a constant background acceleration -- is remarkable, since each of these different types of measurements represented opportunities for this simplest model to fail. Although we currently lack a compelling theoretical explanation for this acceleration, any explanation will have to...

Davis, Tamara M

2014-01-01T23:59:59.000Z

215

Distance-Redshift in Inhomogeneous $Omega_0=1$ Friedmann-Lemaitre-Robertson-Walker Cosmology  

E-Print Network (OSTI)

Distance--redshift relations are given in terms of associated Legendre functions for partially filled beam observations inspatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies. These models are dynamically pressure-free, flat FLRW on large scales but, due to mass inhomogeneities, differ in their optical properties. The partially filled beam area-redshift equation is a Lame$^{\\prime}$ equation for arbitrary FLRW and is shown to simplify to the associated Legendre equation for the spatially flat, i.e. $\\Omega_0=1$ case. We fit these new analytic Hubble curves to recent supernovae (SNe) data in an attempt to determine both the mass parameter $\\Omega_m$ and the beam filling parameter $\

R. Kantowski; R. C. Thomas

2001-06-18T23:59:59.000Z

216

Mapping the Heavens: Probing Cosmology with the Sloan Digital Sky Survey  

SciTech Connect

This talk will provide an overview of results from the on-going Sloan Digital Sky Survey (SDSS), the most ambitious mapping of the Universe yet undertaken, focusing on those with implications for cosmology. It will include a virtual fly-through of the survey that reveals the 3-dimensional large-scale structure of the galaxy distribution. Recent measurements of this large-scale structure, in combination with observations of the cosmic microwave background, have provided independent evidence for a Universe dominated by dark matter and dark energy as well as insights into how galaxies and larger-scale structures formed. I will also describe early results from the SDSS Supernova Survey, which aims to provide more precise constraints on the nature of dark energy. Future planned surveys from the ground and from space will build on these foundations to probe the history of the cosmic expansion--and thereby the dark energy--with even greater precision.

Professor Josh Frieman

2006-12-04T23:59:59.000Z

217

Thermonuclear supernova explosions and their remnants: the case of Tycho  

E-Print Network (OSTI)

We propose to use the thermal X-ray emission from young supernova remnants (SNRs) originated in Type Ia supernovae (SNe) to extract relevant information concerning the explosion mechanism. We focus on the differences between numerical 1D and 3D explosion calculations, and the impact that these differences could have on young SNRs. We use the remnant of the Tycho supernova (SN 1572) as a test case to compare with our predictions, discussing the observational features that allow to accept or discard a given model.

Carles Badenes; Eduardo Bravo; Kazimierz J. Borkowski

2003-09-03T23:59:59.000Z

218

A Time-dependent Cosmological Constant Phenomenology  

E-Print Network (OSTI)

We construct a cosmological toy model in which a step-function ``cosmological constant'' is taken into consideration beside ordinary matter. We assume that $\\Lambda$ takes two values depending on the epoch, and matter goes from a radiation dominated era to a dust dominated era. The model is exactly solvable and it can be compared with recent observations.

Salvatore Capozziello; Ruggiero de Ritis; Alma Angela Marino

1996-05-29T23:59:59.000Z

219

Planck Scale Cosmology in Resummed Quantum Gravity  

E-Print Network (OSTI)

We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

B. F. L. Ward

2008-08-23T23:59:59.000Z

220

Planck Scale Cosmology and Resummed Quantum Gravity  

E-Print Network (OSTI)

We show that, by using amplitude-based resummation techniques for Feynman's formulation of Einstein's theory, we get quantum field theoretic 'first principles' predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

B. F. L. Ward

2009-10-13T23:59:59.000Z

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221

Cosmological rolling solutions of nonlocal theories  

E-Print Network (OSTI)

We find nonperturbative solutions of a nonlocal scalar field equation, with cubic or exponential potential on a cosmological background. The former case corresponds to the lowest level effective tachyon action of cubic string field theory. While the well known Minkowski solution is wildly oscillating, due to Hubble friction its cosmological counterpart describes smooth rolling towards the local minimum of the potential.

Gianluca Calcagni; Giuseppe Nardelli

2009-04-27T23:59:59.000Z

222

COSMOLOGICAL SIMULATIONS OF INTERGALACTIC MEDIUM EVOLUTION. I. TEST OF THE SUBGRID CHEMICAL ENRICHMENT MODEL  

SciTech Connect

We present a one-zone galactic chemical enrichment model that takes into account the contribution of stellar winds from massive stars under the effect of rotation, Type II supernovae, hypernovae, stellar winds from low- and intermediate-mass stars, and Type Ia supernovae. This enrichment model will be implemented in a galactic model designed to be used as a subgrid treatment for galaxy evolution and outflow generation in large-scale cosmological simulations, in order to study the evolution of the intergalactic medium. We test our enrichment prescription by comparing its predictions with the metallicity distribution function and the abundance patterns of 14 chemical elements observed in the Milky Way stars. To do so, we combine the effect of many stellar populations created from the star formation history of the Galaxy in the solar neighborhood. For each stellar population, we keep track of its specific mass, initial metallicity, and age. We follow the time evolution of every population in order to respect the time delay between the various stellar phases. Our model is able to reproduce the observed abundances of C, O, Na, Mg, Al, S, and Ca. For Si, Cr, Mn, Ni, Cu, and Zn, the fits are still reasonable, but improvements are needed. We marginally reproduce the nitrogen abundance in very low metallicity stars. Overall, our results are consistent with the predicted abundance ratios seen in previous studies of the enrichment history of the Milky Way. We have demonstrated that our semi-analytic one-zone model, which cannot deal with spatial information such as the metallicity gradient, can nevertheless successfully reproduce the global Galactic enrichment evolution obtained by more complex models, at a fraction of the computational cost. This model is therefore suitable for a subgrid treatment of chemical enrichment in large-scale cosmological simulations.

Côté, Benoit; Martel, Hugo; Drissen, Laurent [Département de physique, de Génie Physique et d'Optique, Université Laval, Québec, QC G1V 0A6 (Canada)

2013-11-10T23:59:59.000Z

223

INTERPLAY OF NEUTRINO OPACITIES IN CORE-COLLAPSE SUPERNOVA SIMULATIONS  

SciTech Connect

We have conducted a series of numerical experiments using spherically symmetric, general relativistic, neutrino radiation hydrodynamics with the code Agile-BOLTZTRAN to examine the effects of modern neutrino opacities on the development of supernova simulations. We test the effects of opacities by removing opacities or by undoing opacity improvements for individual opacities and groups of opacities. We find that improvements to electron capture (EC) on nuclei, namely EC on an ensemble of nuclei using modern nuclear structure models rather than the simpler independent-particle approximation (IPA) for EC on a mean nucleus, plays the most important role during core collapse of all tested neutrino opacities. Low-energy neutrinos emitted by modern nuclear EC preferentially escape during collapse without the energy downscattering on electrons required to enhance neutrino escape and deleptonization for the models with IPA nuclear EC. During shock breakout the primary influence on the emergent neutrinos arises from non-isoenergetic scattering (NIS) on electrons. For the accretion phase, NIS on free nucleons and pair emission by e {sup +} e {sup -} annihilation have the largest impact on the neutrino emission and shock evolution. Other opacities evaluated, including nucleon-nucleon bremsstrahlung and especially neutrino-positron scattering, have little measurable impact on neutrino emission or shock dynamics. Modern treatments of nuclear EC, e {sup +} e {sup -}-annihilation pair emission, and NIS on electrons and free nucleons are critical elements of core-collapse simulations of all dimensionality.

Lentz, Eric J. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Mezzacappa, Anthony; Hix, W. Raphael [Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6354 (United States); Messer, O. E. Bronson [National Center for Computational Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Bruenn, Stephen W., E-mail: elentz@utk.edu [Department of Physics, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991 (United States)

2012-11-20T23:59:59.000Z

224

Interplay of Neutrino Opacities in Core-collapse Supernova Simulations  

SciTech Connect

We have conducted a series of numerical experiments using spherically symmetric, general relativistic, neutrino radiation hydrodynamics with the code Agile-BOLTZTRAN to examine the effects of including, and improving, the calculation of neutrino opacities on the development of supernova simulations by removing, or replacing, each opacity individually, or removing opacities in groups. We find that during core collapse improvements to electron capture (EC) on nuclei, namely EC on an ensemble of nuclei based on the hybrid model, relative to the simpler independent-particle approximation (IPA) for a mean nucleus, plays the most important role of all tested neutrino opacities. Low-energy neutrinos emitted by nuclear EC preferentially escape during collapse leading to larger deleptonization of the collapsing core, without the energy downscattering via non-isoenergetic scattering (NIS) on electrons required for the models with IPA nuclear EC. During shock breakout the primary influence on the emergent neutrinos arises from NIS on electrons. For the accretion phase NIS on free nucleons and pair emission by $e^+e^-$-annihilation have the largest impact on the neutrino emission and shock evolution. Other opacities evaluated including nucleon-nucleon bremsstrahlung and especially neutrino-positron scattering have little measurable impact on neutrino emission or shock dynamics. Modern treatments of nuclear electron capture, $e^+e^-$-annihilation pair emission, and non-isoenergetic scattering on electrons and free nucleons are critical elements of core-collapse simulations of all dimensionality.

Lentz, Eric J [ORNL; Mezzacappa, Anthony [ORNL; Messer, Bronson [ORNL; Hix, William Raphael [ORNL; Bruenn, S. W. [Florida Atlantic University

2012-01-01T23:59:59.000Z

225

Vacuum energy and cosmological evolution  

E-Print Network (OSTI)

An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature $R$ as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect $\\delta\\Lambda\\sim R\\sim H^2$. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological data, and conveniently extended can account for the complete cosmic evolution from the inflationary epoch till the present days. These models are very close to the $\\Lambda$CDM model for the late universe, but very different from it at the early times. Traces of the inherent vacuum dynamics could be detectable in our recent past.

Joan Sola

2014-03-03T23:59:59.000Z

226

Relaxing a large cosmological constant  

E-Print Network (OSTI)

The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter is presently so close to the CC density. However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of the CC at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could solve the big CC problem and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the LCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments.

Florian Bauer; Joan Sola; Hrvoje Stefancic

2009-07-23T23:59:59.000Z

227

Supernovae of the Same Brightness, Cut From Vastly Different...  

NLE Websites -- All DOE Office Websites (Extended Search)

that the progenitor system of a Type 1a supernova, called PTF 11kx, contains a red giant star. They also show that the system previously underwent at least one much...

228

Neutrino signatures of the supernova - gamma ray burst relationship  

E-Print Network (OSTI)

We calculate the TeV-PeV neutrino fluxes of gamma-ray bursts associated with supernovae, based on the observed association between GRB 030329 and supernova SN 2003dh. The neutrino spectral flux distributions can test for possible delays between the supernova and the gamma-ray burst events down to much shorter timescales than what can be resolved with photons. As an illustrative example, we calculate the probability of neutrino induced muon and electron cascade events in a km scale under-ice detector at the South Pole, from the GRB 030329. Our calculations demonstrate that km scale neutrino telescopes are expected to detect signals that will allow to constrain supernova-GRB models.

Soebur Razzaque; Peter Meszaros; Eli Waxman

2003-08-13T23:59:59.000Z

229

A Critique of Core--Collapse Supernova Theory Circa 1997  

E-Print Network (OSTI)

There has been a new infusion of ideas in the study of the mechanism and early character of core--collapse supernovae. However, despite recent conceptual and computational progress, fundamental questions remain. Some are summarize herein.

Adam Burrows

1997-03-02T23:59:59.000Z

230

A Critique of Core-Collapse Supernova Theory Circa 1997  

E-Print Network (OSTI)

There has been a new infusion of ideas in the study of the mechanism and early character of core--collapse supernovae. However, despite recent conceptual and computational progress, fundamental questions remain. Some are summarize herein.

Burrows, A

1998-01-01T23:59:59.000Z

231

BORON SYNTHESIS IN TYPE Ic SUPERNOVAE  

SciTech Connect

We investigate the {nu}-process in an energetic Type Ic supernova (SN Ic) and the resultant productions of the light elements including boron and its stable isotopes. SN Ic is a very unique boron source because it can produce boron not only through spallation reactions as discussed in Nakamura and Shigeyama but also the {nu}-process. The {nu}-process is considered to occur in core-collapse supernovae and previous studies were limited to SNe II. Although the progenitor star of an SN Ic does not posses an He envelope so that {sup 7}Li production via the {nu}-process is unlikely, {sup 11}B can be produced in the C-rich layers. We demonstrate a hydrodynamic simulation of a SN Ic explosion and estimate the amounts of the light elements produced via the {nu}-process for the first time, and also the subsequent spallation reactions between the outermost layers of the compact SN Ic progenitor and the ambient medium. We find that the {nu}-process in the current SN Ic model produces a significant amount of {sup 11}B, which is diluted by {sup 10}B from spallation reactions to get closer to B isotopic ratios observed in meteorites. We also confirm that high-temperature {mu} and {tau} neutrinos and their anti-neutrinos, reasonably suggested from the compact structure of SN Ic progenitors, enhance the light-element production through the neutral current reactions, which may imply an important role of SNe Ic in the Galactic chemical evolution.

Nakamura, Ko; Kajino, Toshitaka [National Astronomical Observatory of Japan, Mitaka, Tokyo (Japan); Yoshida, Takashi; Shigeyama, Toshikazu [Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo (Japan)

2010-08-01T23:59:59.000Z

232

Gamma Ray Bursts with (and without) Supernova Fireworks  

Science Journals Connector (OSTI)

We review the observational status of the Supernova/Gamma?Ray Burst connection. Observations of long duration Gamma?ray bursts suggest that they are associated with bright SNe?Ic. However recent observations of GRB 060614 puzzle this scenario pointing out the existence of long?duration Gamma?ray Burst not accompanied by a bright supernova. Current estimates of the SN and GRB rates yield a ratio GRB/SNe?Ibc in the range ?0.4%–3%.

Massimo Della Valle

2008-01-01T23:59:59.000Z

233

Global Anisotropies in Supernova Explosions and Pulsar Recoil  

E-Print Network (OSTI)

We show by two-dimensional and first three-dimensional simulations of neutrino-driven supernova explosions that low (l=1,2) modes can dominate the flow pattern in the convective postshock region on timescales of hundreds of milliseconds after core bounce. This can lead to large global anisotropy of the supernova explosion and pulsar kicks in excess of 500 km/s.

L. Scheck; T. Plewa; K. Kifonidis; H. -Th. Janka; E. Müller

2004-05-17T23:59:59.000Z

234

A Newly Recognized Very Young Supernova Remnant in M83  

E-Print Network (OSTI)

As part of a spectroscopic survey of supernova remnant candidates in M83 using the Gemini-South telescope and GMOS, we have discovered one object whose spectrum shows very broad lines at H$\\alpha$, [O~I] 6300,6363, and [O~III] 4959,5007, similar to those from other objects classified as `late time supernovae.' Although six historical supernovae have been observed in M83 since 1923, none were seen at the location of this object. Hubble Space Telescope Wide Field Camera 3 images show a nearly unresolved emission source, while Chandra and ATCA data reveal a bright X-ray source and nonthermal radio source at the position. Objects in other galaxies showing similar spectra are only decades post-supernova, which raises the possibility that the supernova that created this object occurred during the last century but was missed. Using photometry of nearby stars from the HST data, we suggest the precursor was at least 17 $\\rm M_{sun}$, and the presence of broad H$\\alpha$ in the spectrum makes a type II supernova likely....

Blair, William P; Long, Knox S; Whitmore, Bradley C; Kim, Hwihyun; Soria, Roberto; Kuntz, K D; Plucinsky, Paul P; Dopita, Michael A; Stockdale, Christopher

2015-01-01T23:59:59.000Z

235

Regional averaging and scaling in relativistic cosmology  

E-Print Network (OSTI)

Averaged inhomogeneous cosmologies lie at the forefront of interest, since cosmological parameters like the rate of expansion or the mass density are to be considered as volume-averaged quantities and only these can be compared with observations. For this reason the relevant parameters are intrinsically scale-dependent and one wishes to control this dependence without restricting the cosmological model by unphysical assumptions. In the latter respect we contrast our way to approach the averaging problem in relativistic cosmology with shortcomings of averaged Newtonian models. Explicitly, we investigate the scale-dependence of Eulerian volume averages of scalar functions on Riemannian three-manifolds. We propose a complementary view of a Lagrangian smoothing of (tensorial) variables as opposed to their Eulerian averaging on spatial domains. This program is realized with the help of a global Ricci deformation flow for the metric. We explain rigorously the origin of the Ricci flow which, on heuristic grounds, has already been suggested as a possible candidate for smoothing the initial data set for cosmological spacetimes. The smoothing of geometry implies a renormalization of averaged spatial variables. We discuss the results in terms of effective cosmological parameters that would be assigned to the smoothed cosmological spacetime.

Thomas Buchert; Mauro Carfora

2002-10-11T23:59:59.000Z

236

Constraining the dark energy and smoothness parameter with type Ia supernovae and gamma-ray bursts  

Science Journals Connector (OSTI)

The existence of inhomogeneities in the observed Universe modifies the distance-redshift relations thereby affecting the results of cosmological tests in comparison to the ones derived assuming spatially uniform models. By modeling the inhomogeneities through a Zeldovich-Kantowski-Dyer-Roeder approach which is phenomenologically characterized by a smoothness parameter ?, we rediscuss the constraints on the cosmic parameters based on type Ia supernovae (SNe Ia) and gamma-ray bursts (GRBs) data. The present analysis is restricted to a flat ?CDM model with the reasonable assumption that ? does not clump. A ?2 analysis using 557 SNe Ia data from the Union2 compilation data (R. Amanullah et al., Astrophys. J. 716, 712 (2010).) constrains the pair of parameters (?m, ?) to ?m=0.27-0.03+0.08 (2?) and ??0.25. A similar analysis based only on 59 Hymnium GRBs (H. Wei, J. Cosmol. Astropart. Phys. 08 (2010) 020.) constrains the matter density parameter to be ?m=0.35-0.24+0.62 (2?) while all values for the smoothness parameter are allowed. By performing a joint analysis, it is found that ?m=0.27-0.03+0.06 and ??0.52. As a general result, although considering that current GRB data alone cannot constrain the smoothness ? parameter, our analysis provides an interesting cosmological probe for dark energy even in the presence of inhomogeneities.

V. C. Busti; R. C. Santos; J. A. S. Lima

2012-05-07T23:59:59.000Z

237

Ultraviolet divergences in cosmological correlations  

SciTech Connect

A method is developed for dealing with ultraviolet divergences in calculations of cosmological correlations, which does not depend on dimensional regularization. An extended version of the WKB approximation is used to analyze the divergences in these calculations, and these divergences are controlled by the introduction of Pauli-Villars regulator fields. This approach is illustrated in the theory of a scalar field with arbitrary self-interactions in a fixed flat-space Robertson-Walker metric with arbitrary scale factor a(t). Explicit formulas are given for the counterterms needed to cancel all dependence on the regulator properties, and an explicit prescription is given for calculating finite regulator-independent correlation functions. The possibility of infrared divergences in this theory is briefly considered.

Weinberg, Steven [Theory Group, Department of Physics, University of Texas Austin, Texas, 78712 (United States)

2011-03-15T23:59:59.000Z

238

Gravitational wave astronomy and cosmology  

E-Print Network (OSTI)

The first direct observation of gravitational waves' action upon matter has recently been reported by the BICEP2 experiment. Advanced ground-based gravitational-wave detectors are being installed. They will soon be commissioned, and then begin searches for high-frequency gravitational waves at a sensitivity level that is widely expected to reach events involving compact objects like stellar mass black holes and neutron stars. Pulsar timing arrays continue to improve the bounds on gravitational waves at nanohertz frequencies, and may detect a signal on roughly the same timescale as ground-based detectors. The science case for space-based interferometers targeting millihertz sources is very strong. The decade of gravitational-wave discovery is poised to begin. In this writeup of a talk given at the 2013 TAUP conference, we will briefly review the physics of gravitational waves and gravitational-wave detectors, and then discuss the promise of these measurements for making cosmological measurements in the near future.

Scott A. Hughes

2014-05-02T23:59:59.000Z

239

Island Cosmology in the Landscape  

E-Print Network (OSTI)

In the eternally inflationary background driven by the metastable vacua of the landscape, it is possible that some local quantum fluctuations with the null energy condition violation can be large enough to stride over the barriers among different vacua, so that create some islands full of radiation in new vacua, and then these emergently thermalized islands will enter into the evolution of standard big bang cosmology. In this paper, we calculate the spectrum of curvature perturbation generated during the emergence of island. We find that generally the spectrum obtained is nearly scale invariant, which can be well related to that of slow roll inflation by a simple duality. This in some sense suggests a degeneracy between their scalar spectra. In addition, we also simply estimate the non-Gaussianity of perturbation, which is naturally large, yet, can lie well in the observational bound. The results shown here indicate that the island emergently thermalized in the landscape can be consistent with our observable universe.

Yun-Song Piao

2008-06-11T23:59:59.000Z

240

Cosmological Solutions of Emergent Noncommutative Gravity  

SciTech Connect

Matrix models of the Yang-Mills type lead to an emergent gravity theory, which does not require fine-tuning of a cosmological constant. We find cosmological solutions of the Friedmann-Robertson-Walker type. They generically have a big bounce, and an early inflationlike phase with graceful exit. The mechanism is purely geometrical; no ad hoc scalar fields are introduced. The solutions are stabilized through vacuum fluctuations and are thus compatible with quantum mechanics. This leads to a Milne-like universe after inflation, which appears to be in remarkably good agreement with observation and may provide an alternative to standard cosmology.

Klammer, Daniela; Steinacker, Harold [Fakultaet fuer Physik, Universitaet Wien, A-1090 Wien (Austria)

2009-06-05T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Confronting the relaxation mechanism for a large cosmological constant with observations  

E-Print Network (OSTI)

In order to deal with a large cosmological constant a relaxation mechanism based on modified gravity has been proposed recently. By virtue of this mechanism the effect of the vacuum energy density of a given quantum field/string theory (no matter how big is its initial value in the early universe) can be neutralized dynamically, i.e. without fine tuning, and hence a Big Bang-like evolution of the cosmos becomes possible. Remarkably, a large class F^n_m of models of this kind, namely capable of dynamically adjusting the vacuum energy irrespective of its value and size, has been identified. In this paper, we carefully put them to the experimental test. By performing a joint likelihood analysis we confront these models with the most recent observational data on type Ia supernovae (SNIa), the Cosmic Microwave Background (CMB), the Baryonic Acoustic Oscillations (BAO) and the high redshift data on the expansion rate, so as to determine which ones are the most favored by observations. We compare the optimal relaxation models F^n_m found by this method with the standard or concordance LambdaCDM model, and find that some of these models may appear as almost indistinguishable from it. Interestingly enough, this shows that it is possible to construct viable solutions to the tough cosmological fine tuning problem with models that display the same basic phenomenological features as the concordance model.

Spyros Basilakos; Florian Bauer; Joan Sola

2012-01-03T23:59:59.000Z

242

Testing the Distance–Duality Relation with Galaxy Clusters and Type Ia Supernovae  

Science Journals Connector (OSTI)

In this Letter, we propose a new and model-independent cosmological test for the distance-duality (DD) relation, ? = DL (z)(1 + z)–2/DA (z) = 1, where DL and DA are, respectively, the luminosity and angular diameter distances. For DL we consider two sub-samples of Type Ia supernovae (SNe Ia) taken from Constitution data whereas DA distances are provided by two samples of galaxy clusters compiled by De Filippis et al. and Bonamente et al. by combining Sunyaev-Zeldovich effect and X-ray surface brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to coincide with the ones of the associated galaxy cluster sample (?z DA (z) ? DL (z), we have tested the DD relation by assuming that ? is a function of the redshift parameterized by two different expressions: ?(z) = 1 + ?0 z and ?(z) = 1 + ?0 z/(1 + z), where ?0 is a constant parameter quantifying a possible departure from the strict validity of the reciprocity relation (?0 = 0). In the best scenario (linear parameterization), we obtain ?0 = –0.28+0.44 –0.44 (2?, statistical + systematic errors) for the De Filippis et al. sample (elliptical geometry), a result only marginally compatible with the DD relation. However, for the Bonamente et al. sample (spherical geometry) the constraint is ?0 = –0.42+0.34 –0.34 (3?, statistical + systematic errors), which is clearly incompatible with the duality-distance relation.

R. F. L. Holanda; J. A. S. Lima; M. B. Ribeiro

2010-01-01T23:59:59.000Z

243

Phenomenology for Supernova Ia Data Based on a New Cosmic Time  

E-Print Network (OSTI)

A new phenomenological theory for the expansion of our universe is presented. Because fundamental supporting theory is still in development, its discussion is not presented in this paper. The theory is based on a new algebraic expression for cosmic time G Rho t^2=3/32Pi, which correctly predicts the WMAP measured cosmological constants and the fundamental Hubble parameter H(t) for the expansion of the universe. A replacement for dark matter, called here "dark mass", is proposed which scales as with the expansion and incorporated. It does not react with ordinary matter, except gravitationally, and produces flat rotational curves for spiral galaxies. Also a new expression for the approaching velocity of radiation in a closed 3-sphere expanding universe is given that accounts for the early degrading negative approach of radiation for z > 1.7. The expression is v = Hr-c. Combining these three elements produces a luminosity distance dL that successfully predicts the apparent magnitude of exploding supernova Ia stars and even the new gamma ray bursts with no need for dark energy or acceleration of the expansion of the universe.

Charles B. Leffert

2007-07-26T23:59:59.000Z

244

Supernovae and Gamma-Ray Bursts Powered by Hot Neutrino-Cooled Coronae  

E-Print Network (OSTI)

Cosmological explosions such as core-collapse supernovae (SNe) and gamma-ray bursts (GRBs) are thought to be powered by the rapid conversion of roughly a solar mass' worth of gravitational binding energy into a comparatively small amount of outgoing observable kinetic energy. A fractional absorption of the emitted neutrinos, the particles which carry away the binding energy, by the expelled matter is a widely discussed mechanism for powering such explosions. Previous work addressing neutrino emission from core-collapse like environments assumes that the outgoing neutrino spectrum closely resembles a black body whose effective temperature is determined by both the rate of energy release and the surface area of the entire body. Unfortunately, this assumption minimizes the net efficiency for both neutrino-driven explosion mechanisms. Motivated by this fact, we qualitatively outline a scenario where a hot corona deforms the neutrino spectrum away from that of a cool thermal emitter. Our primary result is that in principle, a coronal-driven explosion mechanism can enhance the net efficiency of neutrino-driven SNe and GRBs by more than an order of magnitude.

Enrico Ramirez-Ruiz; Aristotle Socrates

2005-04-11T23:59:59.000Z

245

Probing the anisotropic expansion from supernovae and GRBs in a model-independent way  

E-Print Network (OSTI)

In this paper, we study the anisotropic expansion of the universe using type Ia supernovae Union 2.1 sample and 116 long gamma-ray bursts. The luminosity distance is expanded with model-independent cosmographic parameters as a function of $z/(1+z)$ directly. Thus the results are independent of cosmology model. We find a dipolar anisotropy in the direction ($l=309.2^\\circ \\pm 15.8^\\circ$, $b=-8.6^\\circ \\pm 10.5^\\circ$) in galactic coordinates with a significant evidence $97.29\\%$ (more than $2~\\sigma$). The magnitude is $(1.37\\pm 0.57) \\times 10^{-3}$ for the dipole, and $(2.6\\pm 2.1)\\times 10^{-4}$ for the monopole, respectively. This dipolar anisotropy is more significant at low redshift from the redshift tomography analysis. We also test whether this preferred direction is caused by bulk flow motion or dark energy dipolar scalar perturbation. We find that the direction and the amplitude of the bulk flow in our results are approximately consistent with the bulk flow surveys. Therefore, bulk flow motion may b...

Wang, J S

2014-01-01T23:59:59.000Z

246

eLISA: Astrophysics and cosmology in the millihertz regime  

E-Print Network (OSTI)

This document introduces the exciting and fundamentally new science and astronomy that the European New Gravitational Wave Observatory (NGO) mission (derived from the previous LISA proposal) will deliver. The mission (which we will refer to by its informal name "eLISA") will survey for the first time the low-frequency gravitational wave band (about 0.1 mHz to 1 Hz), with sufficient sensitivity to detect interesting individual astrophysical sources out to z = 15. The eLISA mission will discover and study a variety of cosmic events and systems with high sensitivity: coalescences of massive black holes binaries, brought together by galaxy mergers; mergers of earlier, less-massive black holes during the epoch of hierarchical galaxy and black-hole growth; stellar-mass black holes and compact stars in orbits just skimming the horizons of massive black holes in galactic nuclei of the present era; extremely compact white dwarf binaries in our Galaxy, a rich source of information about binary evolution and about future Type Ia supernovae; and possibly most interesting of all, the uncertain and unpredicted sources, for example relics of inflation and of the symmetry-breaking epoch directly after the Big Bang. eLISA's measurements will allow detailed studies of these signals with high signal-to-noise ratio, addressing most of the key scientific questions raised by ESA's Cosmic Vision programme in the areas of astrophysics and cosmology. They will also provide stringent tests of general relativity in the strong-field dynamical regime, which cannot be probed in any other way. This document not only describes the science but also gives an overview on the mission design and orbits.

Pau Amaro-Seoane; Sofiane Aoudia; Stanislav Babak; Pierre Binétruy; Emanuele Berti; Alejandro Bohé; Chiara Caprini; Monica Colpi; Neil J. Cornish; Karsten Danzmann; Jean-François Dufaux; Jonathan Gair; Oliver Jennrich; Philippe Jetzer; Antoine Klein; Ryan N. Lang; Alberto Lobo; Tyson Littenberg; Sean T. McWilliams; Gijs Nelemans; Antoine Petiteau; Edward K. Porter; Bernard F. Schutz; Alberto Sesana; Robin Stebbins; Tim Sumner; Michele Vallisneri; Stefano Vitale; Marta Volonteri; Henry Ward

2012-01-17T23:59:59.000Z

247

SNLS3: Constraints on Dark Energy Combining the Supernova Legacy Survey Three-year Data with Other Probes  

Science Journals Connector (OSTI)

We present observational constraints on the nature of dark energy using the Supernova Legacy Survey three-year sample (SNLS3) of Guy et al. and Conley et al. We use the 472 Type Ia supernovae (SNe Ia) in this sample, accounting for recently discovered correlations between SN Ia luminosity and host galaxy properties, and include the effects of all identified systematic uncertainties directly in the cosmological fits. Combining the SNLS3 data with the full WMAP7 power spectrum, the Sloan Digital Sky Survey luminous red galaxy power spectrum, and a prior on the Hubble constant H 0 from SHOES, in a flat universe we find ? m = 0.269 ± 0.015 and w = –1.061+0.069 – 0.068 (where the uncertainties include all statistical and SN Ia systematic errors)—a 6.5% measure of the dark energy equation-of-state parameter w. The statistical and systematic uncertainties are approximately equal, with the systematic uncertainties dominated by the photometric calibration of the SN Ia fluxes—without these calibration effects, systematics contribute only a ~2% error in w. When relaxing the assumption of flatness, we find ? m = 0.271 ± 0.015, ? k = –0.002 ± 0.006, and w = –1.069+0.091 – 0.092. Parameterizing the time evolution of w as w(a) = w 0 + wa (1 – a) gives w 0 = –0.905 ± 0.196, wa = –0.984+1.094 – 1.097 in a flat universe. All of our results are consistent with a flat, w = –1 universe. The size of the SNLS3 sample allows various tests to be performed with the SNe segregated according to their light curve and host galaxy properties. We find that the cosmological constraints derived from these different subsamples are consistent. There is evidence that the coefficient, ?, relating SN Ia luminosity and color, varies with host parameters at >4? significance (in addition to the known SN luminosity-host relation); however, this has only a small effect on the cosmological results and is currently a subdominant systematic.

M. Sullivan; J. Guy; A. Conley; N. Regnault; P. Astier; C. Balland; S. Basa; R. G. Carlberg; D. Fouchez; D. Hardin; I. M. Hook; D. A. Howell; R. Pain; N. Palanque-Delabrouille; K. M. Perrett; C. J. Pritchet; J. Rich; V. Ruhlmann-Kleider; D. Balam; S. Baumont; R. S. Ellis; S. Fabbro; H. K. Fakhouri; N. Fourmanoit; S. González-Gaitán; M. L. Graham; M. J. Hudson; E. Hsiao; T. Kronborg; C. Lidman; A. M. Mourao; J. D. Neill; S. Perlmutter; P. Ripoche; N. Suzuki; E. S. Walker

2011-01-01T23:59:59.000Z

248

Nuclear & Particle Physics, Astrophysics & Cosmology, Group T-2 Group Leader: Joseph A. Carlson (7-6245)  

E-Print Network (OSTI)

Arthur N. Cox 013664 anc@lanl.gov Off-site Off-site Off-site Huiayu Duan 179390 duan@unm.edu Off-site Off-site Off-site James L. Friar 080393 friar@lanl.gov 7-6184 123 129 Alexander Friedland 187483 friedland@restmass.com Off-site Off-site Off-site Nicolas Jarrett 2055914 njarret@lanl.gov 123 173 Gerard Jungman 121969

249

Magnetism Group  

Science Journals Connector (OSTI)

... of the Institute of Physics and the Physical Society has announced the establishment of a Magnetism Group. The aim of the new Group is to further interest in ... Group. The aim of the new Group is to further interest in magnetism by holding regular discussion meetings and in other ways. It is intended that these ...

1965-09-04T23:59:59.000Z

250

TASI Lectures on the cosmological constant  

E-Print Network (OSTI)

discovery in tones of wonder and stupefaction, as a “mysterious dark energy”,dark energy. 5.3 The real second problem By sharpening the cosmological constant problem, the discovery

Bousso, Raphael

2008-01-01T23:59:59.000Z

251

Cosmology of hidden sector with Higgs portal  

E-Print Network (OSTI)

In this thesis, we are investigating cosmological implications of hidden sector models which involve scalar fields that do not interact with the Standard Model gauge interactions, but couple directly to the Higgs field. ...

Cabi, Serkan

2009-01-01T23:59:59.000Z

252

Self Creation Cosmology - An Alternative Gravitational Theory  

E-Print Network (OSTI)

The premature acceptance of the standard cosmological model, the 'LambdaCDM' paradigm, is questioned; Self Creation Cosmology is offered as an alternative and shown to be as equally concordant with observed cosmological constraints and local observations including the EEP. The Brans Dicke theory is modified to enable the creation of matter and energy out of the self contained gravitational and scalar fields constrained by the local conservation of energy so that rest masses vary whereas the observed Newtonian Gravitation 'constant' does not. There is a conformal equivalence between self-creation and General Relativity in vacuo, which results in the predictions of the two theories being equal in the standard tests. In self-creation test particles in vacuo follow the geodesics of General Relativity. Nevertheless there are three types of experiment, including the LIGO apparatus, which are able to distinguish between the two theories. Self-creation is as consistent with cosmological constraints in the distant sup...

Barber, G A

2004-01-01T23:59:59.000Z

253

Cosmology at the Beach Lecture: Anne Green  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.  

Ann Green

2010-01-08T23:59:59.000Z

254

Cosmology at the Beach Lecture: David Hughes  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

David Hughes

2010-01-08T23:59:59.000Z

255

Cosmology at the Beach Lecture: Simon White  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Simon White

2010-01-08T23:59:59.000Z

256

Cosmology on the Beach: Kendrick Smith  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

George Smoot

2010-01-08T23:59:59.000Z

257

Cosmology on the Beach - George Smoot  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

George Smoot

2010-01-08T23:59:59.000Z

258

An Inertial Reaction to Cosmological Accelerations  

E-Print Network (OSTI)

Mach's "fixed stars" are actually not fixed at all. The distant clusters of galaxies are not only receding from each observer but they are also accelerating since the rate of cosmological expansion is not constant. If the distant cosmic masses in someway constitute the frame of inertial reference then an additional force should be generated among local bodies in reaction to the apparent cosmological accelerations of the distant galaxies.

Scott Funkhouser

2005-05-17T23:59:59.000Z

259

Patch dualities and remarks on nonstandard cosmologies  

SciTech Connect

In this paper we establish dualities between inflationary, cyclic/ekpyrotic, and phantom cosmologies within the patch formalism approximating high-energy effects in scenarios with extra dimensions. The exact dualities relating the four-dimensional spectra are broken in favor of their braneworld counterparts; the dual solutions display new interesting features because of the modification of the effective Friedmann equation on the brane. We then address some qualitative issues about phantomlike cosmologies without phantom matter.

Calcagni, Gianluca [Dipartimento di Fisica, Universita di Parma, Parma (Italy) and INFN-Gruppo Collegato di Parma, Parco Area delle Scienze 7/A, I-43100 Parma (Italy)

2005-01-15T23:59:59.000Z

260

Mass Spectrum, Actons and Cosmological Landscape  

E-Print Network (OSTI)

It is suggested that the properties of the mass spectrum of elementary particles could be related with cosmology. Solutions of the Klein-Gordon equation on the Friedmann type manifold with the finite action are constructed. These solutions (actons) have a discrete mass spectrum. We suggest that such solutions could select a universe from cosmological landscape. In particular the solutions with the finite action on de Sitter space are investigated.

V. V. Kozlov; I. V. Volovich

2006-12-13T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Cosmological acceleration from a gas of strings  

Science Journals Connector (OSTI)

In string gas cosmology, the extra dimensions of the underlying theory are kept at a microscopic scale by a gas of strings. In the matter-dominated era, however, dust pressure can lead to oscillations of the extra dimensions and to acceleration in the three visible dimensions, even with a vanishing cosmological term. We review the resulting oscillating expansion history, that provides an acceptable fit to the observed accelerated expansion of the Universe.

Francesc Ferrer

2009-01-01T23:59:59.000Z

262

Cosmological acceleration from a gas of strings  

E-Print Network (OSTI)

In string gas cosmology, the extra dimensions of the underlying theory are kept at a microscopic scale by a gas of strings. In the matter-dominated era, however, dust pressure can lead to oscillations of the extra dimensions and to acceleration in the three visible dimensions, even with a vanishing cosmological term. We review the resulting oscillating expansion history, that provides an acceptable fit to the observed accelerated expansion of the Universe.

Francesc Ferrer

2009-07-08T23:59:59.000Z

263

CONSTRAINING EXPLOSION TYPE OF YOUNG SUPERNOVA REMNANTS USING 24 ?m EMISSION MORPHOLOGY  

E-Print Network (OSTI)

Determination of the explosion type of supernova remnants (SNRs) can be challenging, as SNRs are hundreds to thousands of years old and supernovae are classified based on spectral properties days after explosion. Previous ...

Peters, Charee L.

264

Oxygen emission in remnants of thermonuclear supernovae as a probe for their progenitor system  

E-Print Network (OSTI)

Recent progress in numerical simulations of thermonuclear supernova explosions brings up a unique opportunity in studying the progenitors of Type Ia supernovae. Coupling state-of-the-art explosion models with detailed hydrodynamical simulations of the supernova remnant evolution and the most up-to-date atomic data for X-ray emission calculations makes it possible to create realistic synthetic X-ray spectra for the supernova remnant phase. Comparing such spectra with high quality observations of supernova remnants could allow to constrain the explosion mechanism and the progenitor of the supernova. The present study focuses in particular on the oxygen emission line properties in young supernova remnants, since different explosion scenarios predict a different amount and distribution of this element. Analysis of the soft X-ray spectra from supernova remnants in the Large Magellanic Cloud and confrontation with remnant models for different explosion scenarios suggests that SNR 0509-67.5 could originate from a de...

Kosenko, D; Kromer, M; Blinnikov, S I; Pakmor, R; Kaastra, J S

2014-01-01T23:59:59.000Z

265

EVOLUTION OF PROGENITORS FOR ELECTRON CAPTURE SUPERNOVAE  

SciTech Connect

We provide progenitor models for electron capture supernovae (ECSNe) with detailed evolutionary calculation. We include minor electron capture nuclei using a large nuclear reaction network with updated reaction rates. For electron capture, the Coulomb correction of rates is treated and the contribution from neutron-rich isotopes is taken into account in each nuclear statistical equilibrium (NSE) composition. We calculate the evolution of the most massive super asymptotic giant branch stars and show that these stars undergo off-center carbon burning and form ONe cores at the center. These cores become heavier up to the critical mass of 1.367 M{sub Sun} and keep contracting even after the initiation of O+Ne deflagration. Inclusion of minor electron capture nuclei causes convective URCA cooling during the contraction phase, but the effect on the progenitor evolution is small. On the other hand, electron capture by neutron-rich isotopes in the NSE region has a more significant effect. We discuss the uniqueness of the critical core mass for ECSNe and the effect of wind mass loss on the plausibility of our models for ECSN progenitors.

Takahashi, Koh; Umeda, Hideyuki [Department of Astronomy, University of Tokyo, Tokyo 113-0033 (Japan); Yoshida, Takashi, E-mail: ktakahashi@astron.s.u-tokyo.ac.jp, E-mail: umeda@astron.s.u-tokyo.ac.jp, E-mail: yoshida@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2013-07-01T23:59:59.000Z

266

Surface detonation in type Ia supernova explosions?  

E-Print Network (OSTI)

We explore the evolution of thermonuclear supernova explosions when the progenitor white dwarf star ignites asymmetrically off-center. Several numerical simulations are carried out in two and three dimensions to test the consequences of different initial flame configurations such as spherical bubbles displaced from the center, more complex deformed configurations, and teardrop-shaped ignitions. The burning bubbles float towards the surface while releasing energy due to the nuclear reactions. If the energy release is too small to gravitationally unbind the star, the ash sweeps around it, once the burning bubble approaches the surface. Collisions in the fuel on the opposite side increase its temperature and density and may -- in some cases -- initiate a detonation wave which will then propagate inward burning the core of the star and leading to a strong explosion. However, for initial setups in two dimensions that seem realistic from pre-ignition evolution, as well as for all three-dimensional simulations the collimation of the surface material is found to be too weak to trigger a detonation.

F. K. Roepke; S. E. Woosley

2006-09-25T23:59:59.000Z

267

EARLY EMISSION FROM TYPE Ia SUPERNOVAE  

SciTech Connect

A unique feature of deflagration-to-detonation (DDT) white dwarf explosion models of supernovae of type Ia is the presence of a strong shock wave propagating through the outer envelope. We consider the early emission expected in such models, which is produced by the expanding shock-heated outer part of the ejecta and precedes the emission driven by radioactive decay. We expand on earlier analyses by considering the modification of the pre-detonation density profile by the weak shocks generated during the deflagration phase, the time evolution of the opacity, and the deviation of the post-shock equation of state from that obtained for radiation pressure domination. A simple analytic model is presented and shown to provide an acceptable approximation to the results of one-dimensional numerical DDT simulations. Our analysis predicts a {approx}10{sup 3} s long UV/optical flash with a luminosity of {approx}1 to {approx}3 Multiplication-Sign 10{sup 39} erg s{sup -1}. Lower luminosity corresponds to faster (turbulent) deflagration velocity. The luminosity of the UV flash is predicted to be strongly suppressed at t > t{sub drop} {approx} 1 hr due to the deviation from pure radiation domination.

Rabinak, Itay; Waxman, Eli [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Livne, Eli, E-mail: itay.rabinak@weizmann.ac.il [Racah Institute of Physics, Hebrew University, Jerusalem (Israel)

2012-09-20T23:59:59.000Z

268

Supernovae Driven Turbulence In The Interstellar Medium  

E-Print Network (OSTI)

I model the multi-phase interstellar medium (ISM) randomly heated and shocked by supernovae, with gravity, differential rotation and other parameters we understand to be typical of the solar neighbourhood. The simulations are 3D extending horizontally 1 x 1 kpc squared and vertically 2 kpc, symmetric about the galactic mid-plane. They routinely span gas number densities 1/10000 to 100 per cubic cm, temperatures 100 to 100 MK, speeds up to 10000 km/s and Mach number up to 25. Radiative cooling is applied from two widely adopted parameterizations, and compared directly to assess the sensitivity of the results to cooling. There is strong evidence to describe the ISM as comprising well defined cold, warm and hot regions, which are statistically close to thermal and total pressure equilibrium. This result is not sensitive to the choice of parameters considered here. The distribution of the gas density within each can be robustly modelled as lognormal. Appropriate distinction is required between the properties of t...

Gent, Frederick

2014-01-01T23:59:59.000Z

269

Supernova Explosions and Neutron Star Formation  

E-Print Network (OSTI)

The current picture of the collapse and explosion of massive stars and the formation of neutron stars is reviewed. According to the favored scenario, however by no means proven and undisputed, neutrinos deposit the energy of the explosion in the stellar medium which surrounds the nascent neutron star. Observations, in particular of Supernova~1987A, suggest that mixing processes play an important role in the expanding star, and multi-dimensional simulations show that these are linked to convective instabilities in the immediate vicinity of the neutron star. Convectively enhanced energy transport inside the neutron star can have important consequences for the neutrino emission and thus the neutrino-heating mechanism. This also holds for a suppression of the neutrino interactions at nuclear densities. Multi-dimensional hydrodynamics, general relativity, and a better understanding of the neutrino interactions in neutron star matter may be crucial to resolve the problem that state-of-the-art spherical models do not yield explosions even with a very accurate treatment of neutrino transport by solving the Boltzmann equation.

H. -Th. Janka; K. Kifonidis; M. Rampp

2001-03-01T23:59:59.000Z

270

Supernova Remnant Progenitor Masses in M31  

E-Print Network (OSTI)

Using HST photometry, we age-date 59 supernova remnants (SNRs) in the spiral galaxy M31 and use these ages to estimate zero-age main sequence masses (MZAMS) for their progenitors. To accomplish this, we create color-magnitude diagrams (CMDs) and use CMD fitting to measure the recent star formation history (SFH) of the regions surrounding cataloged SNR sites. We identify any young coeval population that likely produced the progenitor star and assign an age and uncertainty to that population. Application of stellar evolution models allows us to infer the MZAMS from this age. Because our technique is not contingent on precise location of the progenitor star, it can be applied to the location of any known SNR. We identify significant young SF around 53 of the 59 SNRs and assign progenitor masses to these, representing a factor of 2 increase over currently measured progenitor masses. We consider the remaining 6 SNRs as either probable Type Ia candidates or the result of core-collapse progenitors that have escaped ...

Jennings, Zachary G; Murphy, Jeremiah W; Dalcanton, Julianne J; Gilbert, Karoline M; Dolphin, Andrew E; Fouesneau, Morgan; Weisz, Daniel R

2012-01-01T23:59:59.000Z

271

Sensitivity study of explosive nucleosynthesis in Type Ia supernovae: I. Modification of individual thermonuclear reaction rates  

E-Print Network (OSTI)

We explore the sensitivity of the nucleosynthesis due to type Ia supernovae with respect to uncertainties in nuclear reaction rates. We have adopted a standard one-dimensional delayed detonation model of the explosion of a Chandrasekhar-mass white dwarf, and have post-processed the thermodynamic trajectories of every mass-shell with a nucleosynthetic code, with increases (decreases) by a factor of ten on the rates of 1196 nuclear reactions. We have computed as well hydrodynamic models for different rates of the fusion reactions of 12C and of 16O. For selected reactions, we have recomputed the nucleosynthesis with alternative prescriptions for their rates taken from the JINA REACLIB database, and have analyzed the temperature ranges where modifications of their rates have the strongest effect on nucleosynthesis. The nucleosynthesis resulting from the Type Ia supernova models is quite robust with respect to variations of nuclear reaction rates, with the exception of the reaction of fusion of 12C nuclei. The energy of the explosion changes by less than \\sim4%. The changes in the nucleosynthesis due to the modification of the rates of fusion reactions are as well quite modest, for instance no species with a mass fraction larger than 0.02 experiences a variation of its yield larger than a factor of two. We provide the sensitivity of the yields of the most abundant species with respect to the rates of the most intense reactions with protons, neutrons, and alphas. In general, the yields of Fe-group nuclei are more robust than the yields of intermediate-mass elements. Among the charged particle reactions, the most influential on supernova nucleosynthesis are 30Si + p \\rightleftarrows 31P + {\\gamma}, 20Ne + {\\alpha} \\rightleftarrows 24Mg + {\\gamma}, and 24Mg + {\\alpha} \\rightleftarrows 27Al + p. The temperatures at which a modification of their rate has a larger impact are in the range 2 < T < 4 GK. (abridged)

Eduardo Bravo; Gabriel Martínez-Pinedo

2012-04-09T23:59:59.000Z

272

Cosmological Acceleration: Dark Energy or Modified Gravity?  

E-Print Network (OSTI)

We review the evidence for recently accelerating cosmological expansion or "dark energy", either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any Dark Energy constituent. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of "dark energy" cannot be derived from the homogeneous expansion alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, with nearly static Dark Energy, or with gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish static "dark energy" from dynamic "dark energy" with equation of state $w(z)$ either changing rapidly or tracking the background matter. But to cosmologically distinguish $\\Lambda$CDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati modifications of Einstein gravity may also be detected in refined bservations in the solar system or at the intermediate Vainstein scale. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence ("Why now?") without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity.

Sidney Bludman

2006-05-08T23:59:59.000Z

273

THE CARNEGIE SUPERNOVA PROJECT: SECOND PHOTOMETRY DATA RELEASE OF LOW-REDSHIFT TYPE Ia SUPERNOVAE  

SciTech Connect

The Carnegie Supernova Project (CSP) was a five-year observational survey conducted at Las Campanas Observatory that obtained, among other things, high-quality light curves of {approx}100 low-redshift Type Ia supernovae (SNe Ia). Presented here is the second data release of nearby SN Ia photometry consisting of 50 objects, with a subset of 45 having near-infrared follow-up observations. Thirty-three objects have optical pre-maximum coverage with a subset of 15 beginning at least five days before maximum light. In the near-infrared, 27 objects have coverage beginning before the epoch of B-band maximum, with a subset of 13 beginning at least five days before maximum. In addition, we present results of a photometric calibration program to measure the CSP optical (uBgVri) bandpasses with an accuracy of {approx}1%. Finally, we report the discovery of a second SN Ia, SN 2006ot, similar in its characteristics to the peculiar SN 2006bt.

Stritzinger, Maximilian D. [The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm (Sweden); Phillips, M. M.; Campillay, Abdo; Morrell, Nidia; Krzeminski, Wojtek; Roth, Miguel [Carnegie Observatories, Las Campanas Observatory, La Serena (Chile); Boldt, Luis N. [Argelander Institut fuer Astronomie, Universitaet Bonn, D-53111 Bonn (Germany); Burns, Chris; Freedman, Wendy L.; Madore, Barry F.; Persson, Sven E. [Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States); Contreras, Carlos [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Victoria 3122 (Australia); Gonzalez, Sergio [Atacama Large Millimeter/Submillimeter Array, European Southern Observatory (Chile); Folatelli, Gaston [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Salgado, Francisco [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); DePoy, D. L.; Marshall, J. L.; Rheault, Jean-Philippe; Suntzeff, Nicholas B. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Hamuy, Mario, E-mail: max.stritzinger@astro.su.se, E-mail: max@dark-cosmology.dk, E-mail: mstritzinger@lco.cl [Departamento de Astronomia, Universidad de Chile, Santiago (Chile)

2011-11-15T23:59:59.000Z

274

Principal components of dark energy with Supernova Legacy Survey supernovae: The effects of systematic errors  

Science Journals Connector (OSTI)

We study the effects of systematic errors in Type Ia supernova (SN Ia) measurements on dark energy (DE) constraints using current data from the Supernova Legacy Survey. We consider how SN systematic errors affect constraints from combined SN Ia, baryon acoustic oscillations, and cosmic microwave background data, given that SNe Ia still provide the strongest constraints on DE but are arguably subject to more significant systematics than the latter two probes. We focus our attention on the temporal evolution of DE described in terms of principal components (PCs) of the equation of state, though we examine a few of the more common, simpler parametrizations as well. We find that the SN Ia systematics degrade the total generalized figure of merit, which characterizes constraints in multidimensional DE parameter space, by a factor of 3 to 4. Nevertheless, overall constraints obtained on roughly five PCs are very good even with current data and systematics. We further show that current constraints are robust to allowing for the finite detection significance of the baryon acoustic oscillations feature in galaxy surveys.

Eduardo J. Ruiz; Daniel L. Shafer; Dragan Huterer; Alexander Conley

2012-11-06T23:59:59.000Z

275

Supernova Neutrino Spectra and Applications to Flavor Oscillations  

E-Print Network (OSTI)

We study the flavor-dependent neutrino spectra formation in the core of a supernova (SN) by means of Monte Carlo simulations. A high-statistics neutrino signal from a galactic SN may contain information that severely constrains the parameter space for neutrino oscillations. Therefore, reliable predictions for flavor-dependent fluxes and spectra are urgently needed. In all traditional hydrodynamic simulations the nu_mu,tau and nu_mu,tau-bar interactions commonly included are rather schematic. With our Monte Carlo simulations we find that the most relevant sources for nu_mu,tau and nu_mu,tau-bar are traditionally not included. In comparing our numerical results for all flavors we find the standard hierarchy of mean energies nu_e < nu_e-bar < nu_mu,tau, with, however, very similar values for nu_mu,tau and nu_e-bar. The luminosities of nu_mu,tau and nu_mu,tau-bar can differ by up to a factor of 2 from L_nue-bar and L_nue, the latter two are very similar. The Garching Group obtains similar results from their self-consistent simulation with the full set of interactions. These results are almost orthogonal to the previous standard picture of exactly equal luminosities of all flavors and differences in mean energies of up to a factor of 2. Existing concepts for identifying oscillation effects in a SN neutrino signal need to be revised. We present two methods for detecting the earth-matter effect that are rather independent of predictions from SN simulations.

Mathias Th. Keil

2003-08-13T23:59:59.000Z

276

Group X  

SciTech Connect

This project is currently under contract for research through the Department of Homeland Security until 2011. The group I was responsible for studying has to remain confidential so as not to affect the current project. All dates, reference links and authors, and other distinguishing characteristics of the original group have been removed from this report. All references to the name of this group or the individual splinter groups has been changed to 'Group X'. I have been collecting texts from a variety of sources intended for the use of recruiting and radicalizing members for Group X splinter groups for the purpose of researching the motivation and intent of leaders of those groups and their influence over the likelihood of group radicalization. This work included visiting many Group X websites to find information on splinter group leaders and finding their statements to new and old members. This proved difficult because the splinter groups of Group X are united in beliefs, but differ in public opinion. They are eager to tear each other down, prove their superiority, and yet remain anonymous. After a few weeks of intense searching, a list of eight recruiting texts and eight radicalizing texts from a variety of Group X leaders were compiled.

Fields, Susannah

2007-08-16T23:59:59.000Z

277

Progress Report on the Berkeley/Anglo-Australian Observatory High-redshift Supernova Search  

DOE R&D Accomplishments (OSTI)

There are two main efforts related to supernovae in progress at Berkeley. The first is an automated supernova search for nearby supernovae, which was already discussed by Carl Pennypacker at this conference. The second is a search for distant supernovae, in the z = 0.3 to 0.5 region, aimed at measuring {Omega}. It is the latter that I want to discuss in this paper.

Goldhaber, G.; Perlmutter, S.; Pennypacker, C.; Marvin, H.; Muller, R. A.; Couch, W.; Boyle, B.

1990-11-00T23:59:59.000Z

278

Neutrino oscillation signatures of oxygen-neon-magnesium supernovae  

E-Print Network (OSTI)

We discuss the flavor conversion of neutrinos from core collapse supernovae that have oxygen-neon-magnesium (ONeMg) cores. Using the numerically calculated evolution of the star up to 650 ms post bounce, we find that, for the normal mass hierarchy, the electron neutrino flux in a detector shows signatures of two typical features of an ONeMg-core supernova: a sharp step in the density profile at the base of the He shell and a faster shock wave propagation compared to iron core supernovae. Before the shock hits the density step (t ~ 150 ms), the survival probability of electron neutrinos is about 0.68, in contrast to values of 0.32 or less for an iron core supernova. The passage of the shock through the step and its subsequent propagation cause a decrease of the survival probability and a decrease of the amplitude of oscillations in the Earth, reflecting the transition to a more adiabatic propagation inside the star. These changes affect the lower energy neutrinos first; they are faster and more sizable for larger theta_13. They are unique of ONeMg-core supernovae, and give the possibility to test the speed of the shock wave. The time modulation of the Earth effect and its negative sign at the neutronization peak are the most robust signatures in a detector.

C. Lunardini; B. Mueller; H. -Th. Janka

2007-12-18T23:59:59.000Z

279

Simulations of Turbulent Thermonuclear Burning in Type Ia Supernovae  

E-Print Network (OSTI)

Type Ia supernovae have recently received considerable attention because it appears that they can be used as "standard candles" to measure cosmic distances out to billions of light years away from us. Observations of type Ia supernovae seem to indicate that we are living in a universe that started to accelerate its expansion when it was about half its present age. These conclusions rest primarily on phenomenological models which, however, lack proper theoretical understanding, mainly because the explosion process, initiated by thermonuclear fusion of carbon and oxygen into heavier elements, is difficult to simulate even on supercomputers. Here, we investigate a new way of modeling turbulent thermonuclear deflagration fronts in white dwarfs undergoing a type Ia supernova explosion. Our approach is based on a level set method which treats the front as a mathematical discontinuity and allows for full coupling between the front geometry and the flow field. New results of the method applied to the problem of type Ia supernovae are obtained. It is shown that in 2-D with high spatial resolution and a physically motivated subgrid scale model for the nuclear flames numerically "converged" results can be obtained, but for most initial conditions the stars do not explode. In contrast, simulations in 3-D, do give the desired explosions and many of their properties, such as the explosion energies, lightcurves and nucleosynthesis products, are in very good agreement with observed type Ia supernovae.

W. Hillebrandt; M. Reinecke; W. Schmidt; F. K. Roepke; C. Travaglio; J. C. Niemeyer

2004-05-11T23:59:59.000Z

280

Understanding Supernova Neutrino Physics using Low-Energy Beta-Beams  

E-Print Network (OSTI)

We show that fitting linear combinations of low-energy beta-beam spectra to supernova-neutrino energy-distributions reconstructs the response of a nuclear target to a supernova flux in a very accurate way. This allows one to make direct predictions about the supernova-neutrino signal in a terrestrial neutrino detector.

N. Jachowicz; G. C. McLaughlin

2005-11-24T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
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281

Magnetic Bianchi type II string cosmological model in loop quantum cosmology  

E-Print Network (OSTI)

The loop quantum cosmology of the Bianchi type II string cosmological model in the presence of a homogeneous magnetic field is studied. We present the effective equations which provide modifications to the classical equations of motion due to quantum effects. The numerical simulations confirm that the big bang singularity is resolved by quantum gravity effects.

Victor Rikhvitsky; Bijan Saha; Mihai Visinescu

2013-12-09T23:59:59.000Z

282

Cosmological Consequences of String Axions  

SciTech Connect

Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the consequences of a measurement of these fluctuations for two additional string axions. We do so independent of any cosmological assumptions except for the axions being massless during inflation. The first axion has been shown to solve the strong CP problem for most compactifications of the heterotic string while the second axion, which does not solve the strong CP problem, obeys a mass formula which is independent of the axion scale. We find that if gravitational waves interpreted as arising from inflation are observed by the PLANCK polarimetry experiment with a Hubble constant during inflation of H{sub inf} {approx}> 10{sup 13} GeV the existence of the first axion is ruled out and the second axion cannot obey the scale independent mass formula. In an appendix we quantitatively justify the often held assumption that temperature corrections to the zero temperature QCD axion mass may be ignored for temperatures T {approx}< {Lambda}{sub QCD}.

Kain, Ben

2005-12-15T23:59:59.000Z

283

Friction forces in cosmological models  

E-Print Network (OSTI)

We investigate the dynamics of test particles undergoing friction forces in a Friedmann-Robertson-Walker (FRW) spacetime. The interaction with the background fluid is modeled by introducing a Poynting-Robertson-like friction force in the equations of motion, leading to measurable (at least in principle) deviations of the particle trajectories from geodesic motion. The effect on the peculiar velocities of the particles is investigated for various equations of state of the background fluid and different standard cosmological models. The friction force is found to have major effects on particle motion in closed FRW universes, where it turns the time-asymptotic value (approaching the recollapse) of the peculiar particle velocity from ultra-relativistic (close to light speed) to a co-moving one, i.e., zero peculiar speed. On the other hand, for open or flat universes the effect of the friction is not so significant, because the time-asymptotic peculiar particle speed is largely non-relativistic also in the geodesi...

Bini, Donato; Gregoris, Daniele; Succi, Sauro

2014-01-01T23:59:59.000Z

284

Friction forces in cosmological models  

E-Print Network (OSTI)

We investigate the dynamics of test particles undergoing friction forces in a Friedmann-Robertson-Walker (FRW) spacetime. The interaction with the background fluid is modeled by introducing a Poynting-Robertson-like friction force in the equations of motion, leading to measurable (at least in principle) deviations of the particle trajectories from geodesic motion. The effect on the peculiar velocities of the particles is investigated for various equations of state of the background fluid and different standard cosmological models. The friction force is found to have major effects on particle motion in closed FRW universes, where it turns the time-asymptotic value (approaching the recollapse) of the peculiar particle velocity from ultra-relativistic (close to light speed) to a co-moving one, i.e., zero peculiar speed. On the other hand, for open or flat universes the effect of the friction is not so significant, because the time-asymptotic peculiar particle speed is largely non-relativistic also in the geodesic case.

Donato Bini; Andrea Geralico; Daniele Gregoris; Sauro Succi

2014-08-23T23:59:59.000Z

285

THE LOS ALAMOS SUPERNOVA LIGHT-CURVE PROJECT: COMPUTATIONAL METHODS  

SciTech Connect

We have entered the era of explosive transient astronomy, in which current and upcoming real-time surveys such as the Large Synoptic Survey Telescope, the Palomar Transient Factory, and the Panoramic Survey Telescope and Rapid Response System will detect supernovae in unprecedented numbers. Future telescopes such as the James Webb Space Telescope may discover supernovae from the earliest stars in the universe and reveal their masses. The observational signatures of these astrophysical transients are the key to unveiling their central engines, the environments in which they occur, and to what precision they will pinpoint cosmic acceleration and the nature of dark energy. We present a new method for modeling supernova light curves and spectra with the radiation hydrodynamics code RAGE coupled with detailed monochromatic opacities in the SPECTRUM code. We include a suite of tests that demonstrate how the improved physics and opacities are indispensable to modeling shock breakout and light curves when radiation and matter are tightly coupled.

Frey, Lucille H. [Department of Computer Science, University of New Mexico, Albuquerque, NM 87131 (United States); Even, Wesley; Hungerford, Aimee L. [XTD-6, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Whalen, Daniel J. [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Fryer, Chris L. [CCS-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fontes, Christopher J. [XCP-5, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colgan, James [T-1, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2013-02-15T23:59:59.000Z

286

THE EXTREME HOSTS OF EXTREME SUPERNOVAE  

SciTech Connect

We use GALEX ultraviolet (UV) and optical integrated photometry of the hosts of 17 luminous supernovae (LSNe, having peak M{sub V} < -21) and compare them to a sample of 26, 000 galaxies from a cross-match between the SDSS DR4 spectral catalog and GALEX interim release 1.1. We place the LSN hosts on the galaxy NUV - r versus M{sub r} color-magnitude diagram (CMD) with the larger sample to illustrate how extreme they are. The LSN hosts appear to favor low-density regions of the galaxy CMD falling on the blue edge of the blue cloud toward the low-luminosity end. From the UV-optical photometry, we estimate the star formation history of the LSN hosts. The hosts have moderately low star formation rates (SFRs) and low stellar masses (M{sub *}) resulting in high specific star formation rates (sSFR). Compared with the larger sample, the LSN hosts occupy low-density regions of a diagram plotting sSFR versus M{sub *} in the area having higher sSFR and lower M{sub *}. This preference for low M{sub *}, high sSFR hosts implies that the LSNe are produced by an effect having to do with their local environment. The correlation of mass with metallicity suggests that perhaps wind-driven mass loss is the factor that prevents LSNe from arising in higher-mass, higher-metallicity hosts. The massive progenitors of the LSNe (>100 M{sub sun}), by appearing in low-SFR hosts, are potential tests for theories of the initial mass function that limit the maximum mass of a star based on the SFR.

Neill, James D.; Quimby, Robert; Ofek, Eran; Wyder, Ted K.; Martin, D. Christopher; Barlow, Tom A.; Foster, Karl; Friedman, Peter G.; Morrissey, Patrick [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Sullivan, Mark [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Gal-Yam, Avishay [Department of Particle Physics and Astrophysics, Faculty of Physics, Weizmann Institute of Science, 76100 Rehovot (Israel); Howell, D. Andrew [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117 (United States); Nugent, Peter [Lawrence Berkeley National Laboratory, MS 50F-1650, 1 Cyclotron Road, Berkeley, CA 94720-8139 (United States); Seibert, Mark [The Observatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Overzier, Roderik [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Neff, Susan G. [Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Bianchi, Luciana [Center for Astrophysical Sciences, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Donas, Jose [Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France); Heckman, Timothy M. [Department of Physics and Astronomy, The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States)

2011-01-20T23:59:59.000Z

287

Supernova Remnants, Cosmic Rays, and GLAST  

SciTech Connect

The shock waves of supernova remnants (SNRs) are the traditional sources of Galactic cosmic rays, at least up to about 3000 TeV (the 'knee' energy in the cosmic-ray spectrum). In the last decade or so, X-ray observations have confirmed in a few SNRs the presence of synchrotron-X-ray-emitting electrons with energies of order 100 TeV. TeV photons from SNRs have been observed with ground-based air Cerenkov telescopes as well, but it is still unclear whether they are due to hadronic processes (inelastic p-p scattering of cosmic-ray protons from thermal gas, with secondary neutral pions decaying to gamma rays), or to leptonic processes (inverse-Compton upscattering of cosmic microwave background photons, or bremsstrahlung). The spatial structure of synchrotron X-rays as observed with the Chandra X-ray Observatory suggests the remarkable possibility that magnetic fields are amplified by orders of magnitude in strong shock waves. The electron spectra inferred from X-rays reach 100 TeV, but at that energy are cutting off steeply, well below the 'knee' energy. Are the cutoff processes due only to radiative losses so that ion spectra might continue unsteepened? Can we confirm the presence of energetic ions in SNRs at all? Are typical SNRs capable of supplying the pool of Galactic cosmic rays? Is strong magnetic-field amplification a property of strong astrophysical shocks in general? These major questions require the next generation of observational tools. I shall outline the theoretical and observational framework of particle acceleration to high energies in SNRs, and shall describe how GLAST will advance this field.

Reynolds, Steve (North Carolina State University) [North Carolina State University

2006-02-13T23:59:59.000Z

288

Silicon carbide grains of type C provide evidence for the production of the unstable isotope $^{32}$Si in supernovae  

E-Print Network (OSTI)

Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae, within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotpic signatures of explosive supernova nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from supernovae. They show peculiar abundance signatures for Si and S, isotopically heavy Si and isotopically light S, which appear to to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme $^{32}$S enrichments observed in C grains may be explained by the presence of short-lived $^{32}$Si ($\\tau$$_{1/2}$ = 153 years) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to mole...

Pignatari, M; Bertolli, M G; Trappitsch, R; Hoppe, P; Rauscher, T; Fryer, C; Herwig, F; Hirschi, R; Timmes, F X; Thielemann, F -K

2013-01-01T23:59:59.000Z

289

A luminous, blue progenitor system for a type-Iax supernova  

E-Print Network (OSTI)

Type-Iax supernovae (SN Iax) are stellar explosions that are spectroscopically similar to some type-Ia supernovae (SN Ia) at maximum light, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from other SN, but their composition (dominated by iron-group and intermediate-mass elements) suggests a physical connection to normal SN Ia. These are not rare; SN Iax occur at a rate between 5 and 30% of the normal SN Ia rate. The leading models for SN Iax are thermonuclear explosions of accreting carbon-oxygen white dwarfs that do not completely unbind the star, implying they are "less successful" cousins of normal SN Ia, where complete disruption is observed. Here we report the detection of the luminous, blue progenitor system of the type-Iax SN 2012Z in deep pre-explosion imaging. Its luminosity, colors, environment, and similarity to the progenitor of the Galactic helium nova V445 Puppis, suggest that SN 2012Z was the explosio...

McCully, Curtis; Foley, Ryan J; Bildsten, Lars; Fong, Wen-fai; Kirshner, Robert P; Marion, G H; Riess, Adam G; Stritzinger, Maximilian D

2014-01-01T23:59:59.000Z

290

Double degenerates and progenitors of supernovae type Ia  

E-Print Network (OSTI)

We report on systematic radial velocity surveys for white dwarf - white dwarf binaries (double degenerates - DDs) including SPY (ESO Supernovae Ia progenitor survey) recently carried out at the VLT. A large sample of DD will allow us to put strong constrains on the phases of close binary evolution of the progenitor systems and to perform an observational test of the DD scenario for supernovae of type Ia. We explain how parameters of the binaries can be derived from various methods. Results for a sample of DDs are presented and discussed.

R. Napiwotzki; L. Yungelson; G. Nelemans; T. R. Marsh; B. Leibundgut; A. Renzini; D. Homaier; D. Koester; S. Moehler; N. Christlieb; D. Reimers; H. Drechsel; U. Heber; C. Karl; E. -M. Pauli

2004-03-25T23:59:59.000Z

291

ASTRO-H White Paper - Young Supernova Remnants  

E-Print Network (OSTI)

Thanks to the unprecedented spectral resolution and sensitivity of the Soft X-ray Spectrometer (SXS) to soft thermal X-ray emission, ASTRO-H will open a new discovery window for understanding young, ejecta-dominated, supernova remnants (SNRs). In particular we study how ASTRO-H observations will address, comprehensively, three key topics in SNR research: (1) using abundance measurements to unveil SNR progenitors, (2) using spatial and velocity distribution of the ejecta to understand supernova explosion mechanisms, (3) revealing the link between the thermal plasma state of SNRs and the efficiency of their particle acceleration.

Hughes, J P; Bamba, A; Katsuda, S; Leutenegger, M; Long, K S; Maeda, Y; Mori, K; Nakajima, H; Sawada, M; Tanaka, T; Uchida, H; Yamaguchi, H; Aharonian, F; Funk, S; Hiraga, J; Ishida, M; Koyama, K; Matsumoto, H; Nobukawa, M; Ozaki, M; Tamagawa, T; Tsunemi, H; Tomida, H; Uchiyama, Y; Uno, S

2014-01-01T23:59:59.000Z

292

MIXING OF CLUMPY SUPERNOVA EJECTA INTO MOLECULAR CLOUDS  

SciTech Connect

Several lines of evidence, from isotopic analyses of meteorites to studies of the Sun's elemental and isotopic composition, indicate that the solar system was contaminated early in its evolution by ejecta from a nearby supernova. Previous models have invoked supernova material being injected into an extant protoplanetary disk, or isotropically expanding ejecta sweeping over a distant (>10 pc) cloud core, simultaneously enriching it and triggering its collapse. Here, we consider a new astrophysical setting: the injection of clumpy supernova ejecta, as observed in the Cassiopeia A supernova remnant, into the molecular gas at the periphery of an H II region created by the supernova's progenitor star. To track these interactions, we have conducted a suite of high-resolution (1500{sup 3} effective) three-dimensional numerical hydrodynamic simulations that follow the evolution of individual clumps as they move into molecular gas. Even at these high resolutions, our simulations do not quite achieve numerical convergence, due to the challenge of properly resolving the small-scale mixing of ejecta and molecular gas, although they do allow some robust conclusions to be drawn. Isotropically exploding ejecta do not penetrate into the molecular cloud or mix with it, but, if cooling is properly accounted for, clumpy ejecta penetrate to distances {approx}10{sup 18} cm and mix effectively with large regions of star-forming molecular gas. In fact, the {approx}2 M{sub Sun} of high-metallicity ejecta from a single core-collapse supernova is likely to mix with {approx}2 Multiplication-Sign 10{sup 4} M{sub Sun} of molecular gas material as it is collapsing. Thus, all stars forming late ( Almost-Equal-To 5 Myr) in the evolution of an H II region may be contaminated by supernova ejecta at the level {approx}10{sup -4}. This level of contamination is consistent with the abundances of short-lived radionuclides and possibly some stable isotopic shifts in the early solar system and is potentially consistent with the observed variability in stellar elemental abundances. Supernova contamination of forming planetary systems may be a common, universal process.

Pan Liubin; Desch, Steven J.; Scannapieco, Evan; Timmes, F. X. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)

2012-09-01T23:59:59.000Z

293

Beyond the Cosmological Standard Model  

E-Print Network (OSTI)

After a decade and a half of research motivated by the accelerating universe, theory and experiment have a reached a certain level of maturity. The development of theoretical models beyond \\Lambda, or smooth dark energy, often called modified gravity, has led to broader insights into a path forward, and a host of observational and experimental tests have been developed. In this review we present the current state of the field and describe a framework for anticipating developments in the next decade. We identify the guiding principles for rigorous and consistent modifications of the standard model, and discuss the prospects for empirical tests. We begin by reviewing attempts to consistently modify Einstein gravity in the infrared, focusing on the notion that additional degrees of freedom introduced by the modification must screen themselves from local tests of gravity. We categorize screening mechanisms into three broad classes: mechanisms which become active in regions of high Newtonian potential, those in which first derivatives become important, and those for which second derivatives are important. Examples of the first class, such as f(R) gravity, employ the familiar chameleon or symmetron mechanisms, whereas examples of the last class are galileon and massive gravity theories, employing the Vainshtein mechanism. In each case, we describe the theories as effective theories. We describe experimental tests, summarizing laboratory and solar system tests and describing in some detail astrophysical and cosmological tests. We discuss future tests which will be sensitive to different signatures of new physics in the gravitational sector. Parts that are more relevant to theorists vs. observers/experimentalists are clearly indicated, in the hope that this will serve as a useful reference for both audiences, as well as helping those interested in bridging the gap between them.

Austin Joyce; Bhuvnesh Jain; Justin Khoury; Mark Trodden

2014-12-15T23:59:59.000Z

294

Supernovae of the Same Brightness, Cut From Vastly Different Cosmic Cloth  

NLE Websites -- All DOE Office Websites (Extended Search)

Supernovae of the Supernovae of the Same Brightness, Cut From Vastly Different Cosmic Cloth Supernovae of the Same Brightness, Cut From Vastly Different Cosmic Cloth Berkeley Lab researchers make historic observation of rare Type 1a Supernova August 23, 2012 | Tags: Astrophysics Linda Vu, lvu@lbl.gov, +1 510 495 2402 ptf11kx.png The supernova PTF 11kx can be seen as the blue dot on the galaxy. The image was taken when the supernova was near maximum brightness by the Faulkes Telescope North. The system is located approximately 600 million light years away in the constellation Lynx. Image Credit: BJ Fulton (Las Cumbres Observatory Global Telescope Network) Exploding stars called Type 1a supernova are ideal for measuring cosmic distance because they are bright enough to spot across the Universe and

295

Light right-handed neutrinos: + an incursion in cosmology  

E-Print Network (OSTI)

Light right-handed neutrinos: why not? + an incursion in cosmology R. Barbieri "Neutrinos in Venice? " The typical lifetime of a new trend in high energy physics and cosmology nowadays is about 5 to 10 years

Abbondandolo, Alberto

296

Some Implications of the Cosmological Constant to Fundamental Physics  

E-Print Network (OSTI)

In the presence of a cosmological constant, ordinary Poincare' special relativity is no longer valid and must be replaced by a de Sitter special relativity, in which Minkowski space is replaced by a de Sitter spacetime. In consequence, the ordinary notions of energy and momentum change, and will satisfy a different kinematic relation. Such a theory is a different kind of a doubly special relativity. Since the only difference between the Poincare' and the de Sitter groups is the replacement of translations by certain linear combinations of translations and proper conformal transformations, the net result of this change is ultimately the breakdown of ordinary translational invariance. From the experimental point of view, therefore, a de Sitter special relativity might be probed by looking for possible violations of translational invariance. If we assume the existence of a connection between the energy scale of an experiment and the local value of the cosmological constant, there would be changes in the kinematics of massive particles which could hopefully be detected in high-energy experiments. Furthermore, due to the presence of a horizon, the usual causal structure of spacetime would be significantly modified at the Planck scale.

R. Aldrovandi; J. P. Beltran Almeida; J. G. Pereira

2007-02-12T23:59:59.000Z

297

The Universe Adventure - The Cosmological Principle  

NLE Websites -- All DOE Office Websites (Extended Search)

Cosmological Principle Cosmological Principle The distribution of matter across the universe is approximately even. The distribution of matter across the Universe is approximately even, homogeneous, when considered at large scales. Albert Einstein's theory of General Relativity permits many possible types of universes. In applying the theory to describe the dynamics of our Universe, Einstein made a central empirical assumption to limit the number of possible solutions to the equations. He assumed that on very large scales the distribution of matter in the Universe is constant, making the Universe appear smooth. This idea is a form of the modern cosmological principle. This principle is not exact since much of the Universe's matter is found clustered together in planets, stars, and galaxies, but when considered at

298

Cosmological perturbations in mimetic matter model  

E-Print Network (OSTI)

We investigate the cosmological evolution of mimetic matter model with arbitrary scalar potential. The cosmological reconstruction is explicitly done for different choices of potential. The cases that mimetic matter model shows the evolution as Cold Dark Matter(CDM), wCDM model, dark matter and dark energy with dynamical $Om(z)$ or phantom dark energy with phantom-non-phantom crossing are presented in detail. The cosmological perturbations for such evolution are studied in mimetic matter model. For instance, the evolution behavior of the matter density contrast which is different from usual one, i.e. $\\ddot \\delta + 2 H \\dot \\delta - \\kappa ^2 \\rho \\delta /2 = 0$ is investigated. The possibility of peculiar evolution of $\\delta$ in the model under consideration is shown. Special attention is paid to the behavior of matter density contrast near to future singularity where decay of perturbations may occur much earlier the singularity.

Matsumoto, Jiro; Sushkov, Sergey V

2015-01-01T23:59:59.000Z

299

Cosmological and Astrophysical Probes of Vacuum Energy  

E-Print Network (OSTI)

Vacuum energy changes during cosmological phase transitions and becomes relatively important at epochs just before phase transitions. For a viable cosmology the vacuum energy just after a phase transition must be set by the critical temperature of the next phase transition, which exposes the cosmological constant problem from a different angle. Here we propose to experimentally test the properties of vacuum energy under circumstances different from our current vacuum. One promising avenue is to consider the effect of high density phases of QCD in neutron stars. Such phases have different vacuum expectation values and a different vacuum energy from the normal phase, which can contribute an order one fraction to the mass of neutron stars. Precise observations of the mass of neutron stars can potentially yield information about the gravitational properties of vacuum energy, which can significantly affect their mass-radius relation. A more direct test of cosmic evolution of vacuum energy could be inferred from a ...

Bellazzini, Brando; Hubisz, Jay; Serra, Javi; Terning, John

2015-01-01T23:59:59.000Z

300

Local Conformal Symmetry in Physics and Cosmology  

E-Print Network (OSTI)

We show how to lift a generic non-scale invariant action in Einstein frame into a locally conformally-invariant (or Weyl-invariant) theory and present a new general form for Lagrangians consistent with Weyl symmetry. Advantages of such a conformally invariant formulation of particle physics and gravity include the possibility of constructing geodesically complete cosmologies. We present a conformal-invariant version of the standard model coupled to gravity, and show how Weyl symmetry may be used to obtain unprecedented analytic control over its cosmological solutions. Within this new framework, generic FRW cosmologies are geodesically complete through a series of big crunch - big bang transitions. We discuss a new scenario of cosmic evolution driven by the Higgs field in a \\textquotedblleft minimal\\textquotedblright% \\ conformal standard model, in which there is no new physics beyond the standard model at low energies, and the current Higgs vacuum is metastable as indicated by the latest LHC data.

Itzhak Bars; Paul Steinhardt; Neil Turok

2013-07-07T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Accelerating Cosmologies with Extended Product Spaces  

E-Print Network (OSTI)

Accelerating cosmologies in extra dimensional spaces have been studied. These extra dimensional spaces are products of many spaces. The physical behaviors of accelerating cosmologies are investigated from Einstein's field equation in higher dimensional Friedmann-Robertson-Walker (FRW) universe and superstring/M theory points of view. It is found that if some assumptions of flatness are made for sector of the FRW universe, the remaining sector needs to be hyperbolic. These properties are in parallel with those found in the model of superstring/M theory. The extended product made for the superstring model did not show any more new features other than those already found. A similar accelerating phase of this product space cosmology was found with difference in numerical values of the accelerating period.

Han Siong Ch'ng

2008-10-15T23:59:59.000Z

302

Quantum Exclusion of Positive Cosmological Constant?  

E-Print Network (OSTI)

We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state because of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources.

Gia Dvali; Cesar Gomez

2014-12-27T23:59:59.000Z

303

Cosmological birefringence constraints from CMB and astrophysical polarization data  

E-Print Network (OSTI)

Cosmological birefringence is a rotation of the polarization plane of photons coming from sources of astrophysical and cosmological origin. The rotation can also depend on the energy of the photons and not only on the distance of the source and on the cosmological evolution of the underlying theoretical model. In this work, we constrain few selected models for cosmological birefringence, combining CMB and astrophysical data at radio, optical, X and gamma wavelengths, taking into account the specific energy and distance dependences.

Galaverni, M; Paci, F; Finelli, F

2014-01-01T23:59:59.000Z

304

Effects of a time-varying color-luminosity parameter $?$ on the cosmological constraints of modified gravity models  

E-Print Network (OSTI)

It has been found that, for the Supernova Legacy Survey three-year (SNLS3) data, there is strong evidence for the redshift-evolution of color-luminosity parameter $\\beta$. In previous studies, only dark energy (DE) models are used to explore the effects of a time-varying $\\beta$ on parameter estimation. In this paper, we extend the discussions to the case of modified gravity (MG), by considering Dvali-Gabadadze-Porrati (DGP) model, power-law type $f(T)$ model and exponential type $f(T)$ model. In addition to the SNLS3 data, we also use the latest Planck distance priors data, the galaxy clustering (GC) data extracted from Sloan Digital Sky Survey (SDSS) data release 7 (DR7) and Baryon Oscillation Spectroscopic Survey (BOSS), as well as the direct measurement of Hubble constant $H_0$ from the Hubble Space Telescope (HST) observation. We find that, for both cases of using the supernova (SN) data alone and using the combination of all data, adding a parameter of $\\beta$ can reduce $\\chi^2$ by $\\sim$ 36 for all the MG models, showing that a constant $\\beta$ is ruled out at 6$\\sigma$ confidence level (CL). Moreover, we find that a time-varying $\\beta$ always yields a larger fractional matter density $\\Omega_{m0}$ and a smaller reduced Hubble constant $h$; in addition, it significantly changes the shapes of 1$\\sigma$ and 2$\\sigma$ confidence regions of various MG models, and thus corrects systematic bias for the parameter estimation. These conclusions are consistent with the results of DE models, showing that $\\beta$'s evolution is completely independent of the cosmological models in the background. Therefore, our work highlights the importance of considering the evolution of $\\beta$ in the cosmology-fits.

Shuang Wang; Yong-Zhen Wang; Xin Zhang

2014-07-28T23:59:59.000Z

305

Cosmology with Type Ia The Sloan Digital Sky Survey  

E-Print Network (OSTI)

- Present) - Cosmic Microwave Background - Supernovae and Dark Energy - Galaxy Clustering SDSS Supernova% of recollapse density · Favors Dark Energy #12;M51: June 2005 M51: July 2005 #12;#12;· Easy to identify · Geometry is flat · ~70% Dark Energy · ~30% Matter · There was a Big Bang · There will be a Big Chill #12

Cinabro, David

306

Rates, progenitors and cosmic mix of Type Ia supernovae  

Science Journals Connector (OSTI)

......2004) from the supernova survey spin-off of the GOODS project (Giavalisco et al. 2004). The mentioned Gaussian DDT is...fig. 13 in Greggio (2005). For this reason, we take the liberty of re-discussing here the Della Valle et al. interpretation......

Laura Greggio; Alvio Renzini; Emanuele Daddi

2008-08-01T23:59:59.000Z

307

Treating Unresolvable Flame Physics in Simulations of Thermonuclear Supernovae  

Science Journals Connector (OSTI)

Due to the small width of the subsonic burning front (flame) in thermonuclear supernovae, micrometers to centimeters, and the influence of turbulence, which adds structure to this front on a broad range of scales, it won't be possible in the foreseeable ... Keywords: Computational astrophysics, combustion, turbulence

Dean M. Townsley

2009-03-01T23:59:59.000Z

308

Perspectives of Core-Collapse Supernovae beyond SN 1987A  

E-Print Network (OSTI)

The observation of neutrinos from Supernova 1987A has confirmed the theoretical conjecture that these particles play a crucial role during the collapse of the core of a massive star. Only one per cent of the energy they carry away from the newly formed neutron star may account for all the kinetic and electromagnetic energy responsible for the spectacular display of the supernova explosion. However, the neutrinos emitted from the collapsed stellar core at the center of the explosion couple so weakly to the surrounding matter that convective processes behind the supernova shock and/or inside the nascent neutron star might be required to increase the efficiency of the energy transfer to the stellar mantle and envelope. The conditions for a successful explosion by the neutrino-heating mechanism and the possible importance of convection in and around the neutron star are shortly discussed. Neutrino-driven explosions turn out to be very sensitive to the parameters describing the neutrino emission of the proto-neutron star and to the details of the dynamical processes in the collapsed stellar core. Therefore uniform explosions with a well defined energy seem unlikely and type-II supernova explosions do not offer promising perspectives for being useful as standard candles.

H. -Th. Janka; W. Keil

1997-09-02T23:59:59.000Z

309

Cosmology with X-ray Cluster Baryons  

SciTech Connect

X-ray cluster measurements interpreted with a universal baryon/gas mass fraction can theoretically serve as a cosmological distance probe. We examine issues of cosmological sensitivity for current (e.g., Chandra X-ray Observatory, XMM-Newton) and next generation (e.g., Con-X, XEUS) observations, along with systematic uncertainties and biases. To give competitive next generation constraints on dark energy, we find that systematics will need to be controlled to better than 1percent and any evolution in f_gas (and other cluster gas properties) must be calibrated so the residual uncertainty is weaker than (1+z)0.03.

Linder, Eric V.

2007-04-10T23:59:59.000Z

310

Role of ? in the Cosmological Lens Equation  

Science Journals Connector (OSTI)

The cosmological constant ? affects cosmological gravitational lensing. Effects due to ? can be studied in the framework of the Schwarzschild–de Sitter spacetime. Two novel contributions, which cannot be accounted for by a proper use of angular diameter distances, are derived. First, a term ??^?=2mb?/3 has to be added to the bending angle, where m is the lens mass and b the impact parameter. Second, ? brings about a difference in the redshifts of multiple images. Both effects are quite small for real astrophysical systems, ??^??1?arcsec and ?zs?10-7.

Mauro Sereno

2009-01-14T23:59:59.000Z

311

Future Singularities and Completeness in Cosmology  

E-Print Network (OSTI)

We review recent work on the existence and nature of cosmological singularities that can be formed during the evolution of generic as well as specific cosmological spacetimes in general relativity. We first discuss necessary and sufficient conditions for the existence of geodesically incomplete spacetimes based on a tensorial analysis of the geodesic equations. We then classify the possible singularities of isotropic globally hyperbolic universes using the Bel-Robinson slice energy that closely monitors the asymptotic properties of fields near the singularity. This classification includes all known forms of spacetime singularities in isotropic universes and also predicts new types.

Spiros Cotsakis

2006-06-04T23:59:59.000Z

312

Non-standard loop quantum cosmology  

E-Print Network (OSTI)

We present results concerning the nature of the cosmological big bounce(BB) transition within the loop geometry underlying loop quantum cosmology (LQC). Our canonical quantization method is an alternative to the standard LQC. An evolution parameter we use has clear interpretation both at classical and quantum levels. The physical volume operator has discrete spectrum which is bounded from below. The minimum gap in the spectrum defines a quantum of the volume. The spectra of operators are parametrized by a free parameter to be determined.

Wlodzimierz Piechocki

2010-01-19T23:59:59.000Z

313

Asymptotic safety and the cosmological constant  

E-Print Network (OSTI)

We study the non-perturbative renormalisation of quantum gravity in four dimensions. Taking care to disentangle physical degrees of freedom, we observe the topological nature of conformal fluctuations arising from the functional measure. The resulting beta functions possess an asymptotically safe fixed point with a global phase structure leading to classical general relativity for positive, negative or vanishing cosmological constant. If only the conformal fluctuations are quantised we find an asymptotically safe fixed point predicting a vanishing cosmological constant on all scales. At this fixed point we reproduce the critical exponent, $\

Kevin Falls

2014-08-01T23:59:59.000Z

314

Constraining supersymmetric SO(10) models through cosmology  

Science Journals Connector (OSTI)

We study the impact of the symmetry-breaking patterns from supersymmetric SO(10) down to the standard model on the standard big-bang cosmology through the formation of topological defects. None of the models is consistent with the standard cosmology without invoking any mechanism to solve the monopole problem. For this purpose, we use a hybrid false vacuum inflationary scenario. Only two symmetry-breaking patterns are consistent with these topological considerations and with the actual data on the proton lifetime. © 1995 The American Physical Society.

Rachel Jeannerot and Anne-Christine Davis

1995-12-15T23:59:59.000Z

315

Thermodynamics of Ideal Gas in Cosmology  

E-Print Network (OSTI)

The equation of state and the state functions for the gravitational source are necessary conditions for solving cosmological model and stellar structure. The usual treatments are directly based on the laws of thermodynamics, and the physical meanings of some concepts are obscure. This letter show that, we can actually derive all explicit fundamental state functions for the ideal gas in the context of cosmology via rigorous dynamical and statistical calculation. These relations have clear physical meanings, and are valid in both non-relativistic and ultra-relativistic cases. Some features of the equation of state are important for a stable structure of a star with huge mass.

Ying-Qiu Gu

2007-08-22T23:59:59.000Z

316

Cosmology and gravity in the brane world  

E-Print Network (OSTI)

, and cosmological problems such as the origin and nature of dark energy and dark matter as well as inflation are not explained. Supersymmetry (SUSY) (see [2] for a review of global and local supersymmetry) is an extension of the SM that can seemingly ameliorate some... unresolved questions such as the origin and nature of both inflation and dark energy (the cosmological constant problem), the number of generations, why would the universe use certain SUSY GUTs as opposed to others, and why is spacetime 3+1 dimensional. Over...

Dent, James Blackman

2005-11-01T23:59:59.000Z

317

Cosmology as Science?: From Inflation to Eternity  

ScienceCinema (OSTI)

The last decade or two have represented the golden age of observational cosmology, producing a revolution in our picture of the Universe on its largest scales, and perhaps also its smallest ones. I will argue that these recent development bring to the forefront some vexing questions about whether various fundamental assumptions about the universe are in fact falsifiable. I will focus on 3 issues: (1) "Proving" Inflation, (2) Dark Energy and Anthropic Arguments, and (3) Cosmology of the far future.Interview with Lawrence M. Krauss

None

2011-10-06T23:59:59.000Z

318

INJECTION OF SUPERNOVA DUST IN NEARBY PROTOPLANETARY DISKS  

SciTech Connect

The early solar system contained a number of short-lived radionuclides (SLRs) such as {sup 26}Al with half-lives <15 Myr. The one-time presence of {sup 60}Fe strongly suggests that the source of these radionuclides was a nearby supernova. In this paper, we investigate the 'aerogel' model, which hypothesizes that the solar system's SLRs were injected directly into the solar system's protoplanetary disk from a supernova within the same star-forming region. Previous work has shown that disks generally survive the impact of supernova ejecta, but also that little gaseous ejecta can be injected into the disk. The aerogel model hypothesizes that radionuclides in the ejecta condensed into micron-sized dust grains that were injected directly into the solar nebula disk. Here, we discuss the density structure of supernova ejecta and the observational support for dust condensation in the ejecta. We argue that supernova ejecta are clumpy and describe a model to quantify this clumpiness. We also argue that infrared observations may be underestimating the fraction of material that condenses into dust. Building on calculations of how supernova ejecta interact with protoplanetary disks, we calculate the efficiency with which dust grains in the ejecta are injected into a disk. We find that about 70% of material in grains roughly 0.4 {mu}m in diameter can be injected into disks. If ejecta are clumpy, the solar nebula was struck by a clump with higher-than-average {sup 26}Al and {sup 60}Fe, and these elements condensed efficiently into large grains, then the abundances of SLRs in the early solar system can be explained, even if the disk lies 2 pc from the supernova explosion. The probability that all these factors are met is low, perhaps {approx}10{sup -3}-10{sup -2}, and receiving as much {sup 26}Al and {sup 60}Fe as the solar system did may be a rare event. Still, the aerogel model remains a viable explanation for the origins of the radionuclides in the early solar system, and may be the most plausible one.

Ouellette, N. [Department of Physics, Arizona State University, P.O. Box 871504, Tempe, AZ 85287-1504 (United States); Desch, S. J.; Hester, J. J. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)

2010-03-10T23:59:59.000Z

319

Automata groups  

E-Print Network (OSTI)

-presentation. We also find the L-presentation for several other groups generated by three-state automata, and we describe the defining relations in the Grigorchuk groups G_w. In case when the sequence w is almost periodic these relations provide an L...

Muntyan, Yevgen

2010-01-16T23:59:59.000Z

320

Impacts of different SNLS3 light-curve fitters on cosmological consequences of interacting dark energy models  

E-Print Network (OSTI)

Aims: We explore the cosmological consequences of interacting dark energy (IDE) models using the Supernova Legacy Survey three-year (SNLS3) data sets. In particular, we focus on the impacts of different SNLS3 light-curve fitters (LCF) (corresponding to the "SALT2", the "SiFTO", and the "Combined" supernova sample). Methods: Firstly, making use of the three SNLS3 data sets, as well as the observational data from the cosmic microwave background (CMB), the galaxy clustering (GC) and the direct measurement of Hubble constant $H_0$, we constrain the parameter spaces of three IDE models. Then, we plot the cosmic evolutions of Hubble diagram $H(z)$, deceleration diagram $q(z)$ and statefinder hierarchy $\\{S^{(1)}_3, S^{(1)}_4\\}$, and check whether or not these dark energy (DE) diagnosis can distinguish the differences among the results of different LCF. At last, we perform high-redshift cosmic age test using three old high redshift objects (OHRO), and explore the fate of the Universe. Results: For all the IDE models...

Hu, Yazhou; Li, Nan; Wang, Shuang

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Excited-state OH Masers and Supernova Remnants  

E-Print Network (OSTI)

The collisionally pumped, ground-state 1720 MHz maser line of OH is widely recognized as a tracer for shocked regions and observed in star forming regions and supernova remnants. Whereas some lines of excited states of OH have been detected and studied in star forming regions, the subject of excited-state OH in supernova remnants -- where high collision rates are to be expected -- is only recently being addressed. Modeling of collisional excitation of OH demonstrates that 1720, 4765 and 6049 MHz masers can occur under similar conditions in regions of shocked gas. In particular, the 6049 and 4765 MHz masers become more significant at increased OH column densities where the 1720 MHz masers begin to be quenched. In supernova remnants, the detection of excited-state OH line maser emission could therefore serve as a probe of regions of higher column densities. Using the Very Large Array, we searched for excited-state OH in the 4.7, 7.8, 8.2 and 23.8 GHz lines in four well studied supernova remnants with strong 1720 MHz maser emission (SgrAEast, W28, W44 and IC443). No detections were made, at typical detection limits of around 10 mJy/beam. The search for the 6 GHz lines were done using Effelsberg since the VLA receivers did not cover those frequencies, and are reported on in an accompanying letter (Fish, Sjouwerman & Pihlstrom 2007). We also cross-correlated the positions of known supernova remnants with the positions of 1612 MHz maser emission obtained from blind surveys. No probable associations were found, perhaps except in the SgrAEast region. The lack of detections of excited-state OH indicates that the OH column densities suffice for 1720 MHz inversion but not for inversion of excited-state transitions, consistent with the expected results for C-type shocks.

Ylva M. Pihlström; Vincent L. Fish; Loránt O. Sjouwerman; Laura K. Zschaechner; Philip B. Lockett; Moshe Elitzur

2007-12-29T23:59:59.000Z

322

Generalized quantum gravity condensates for homogeneous geometries and cosmology  

E-Print Network (OSTI)

We construct a generalized class of quantum gravity condensate states, that allows the description of continuum homogeneous quantum geometries within the full theory. They are based on similar ideas already applied to extract effective cosmological dynamics from the group field theory formalism, and thus also from loop quantum gravity. However, they represent an improvement over the simplest condensates used in the literature, in that they are defined by an infinite superposition of graph-based states encoding in a precise way the topology of the spatial manifold. The construction is based on the definition of refinement operators on spin network states, written in a second quantized language. The construction lends itself easily to be applied also to the case of spherically symmetric quantum geometries.

Daniele Oriti; Daniele Pranzetti; James P. Ryan; Lorenzo Sindoni

2015-01-05T23:59:59.000Z

323

Cosmology with SKA Radio Continuum Surveys  

E-Print Network (OSTI)

Radio continuum surveys have, in the past, been of restricted use in cosmology. Most studies have concentrated on cross-correlations with the cosmic microwave background to detect the integrated Sachs-Wolfe effect, due to the large sky areas that can be surveyed. As we move into the SKA era, radio continuum surveys will have sufficient source density and sky area to play a major role in cosmology on the largest scales. In this chapter we summarise the experiments that can be carried out with the SKA as it is built up through the coming decade. We show that the SKA can play a unique role in constraining the non-Gaussianity parameter to \\sigma(f_NL) ~ 1, and provide a unique handle on the systematics that inhibit weak lensing surveys. The SKA will also provide the necessary data to test the isotropy of the Universe at redshifts of order unity and thus evaluate the robustness of the cosmological principle.Thus, SKA continuum surveys will turn radio observations into a central probe of cosmological research in th...

Jarvis, Matt J; Blake, Chris; Brown, Michael L; Lindsay, Sam N; Raccanelli, Alvise; Santos, Mario; Schwarz, Dominik

2015-01-01T23:59:59.000Z

324

Surface Tension and the Cosmological Constant  

E-Print Network (OSTI)

The astronomically observed value of the cosmological constant is small but non-zero. This raises two questions together known as the cosmological constant problem a) why is lambda so nearly zero? b) why is lambda not EXACTLY zero? Sorkin has proposed that b) can be naturally explained as a one by square root N fluctuation by invoking discreteness of spacetime at the Planck scale due to quantum gravity. In this paper we shed light on these questions by developing an analogy between the cosmological constant and the surface tension of membranes. The ``cosmological constant problem'' has a natural analogue in the membrane context: the vanishingly small surface tension of fluid membranes provides an example where question a) above arises and is answered. We go on to find a direct analogue of Sorkin's proposal for answering question b) in the membrane context, where the discreteness of spacetime translates into the molecular structure of matter. We propose analogue experiments to probe a small and fluctuating surface tension in fluid membranes. A counterpart of dimensional reduction a la Kaluza-Klein and large extra dimensions also appears in the physics of fluid membranes.

Joseph Samuel; Supurna Sinha

2006-04-18T23:59:59.000Z

325

ccsd00000531 Early Cosmology and Fundamental Physics  

E-Print Network (OSTI)

, open problems and future perspectives in connection with dark energy and string theory are overviewed. Contents I. The history of the universe 1 II. Fundamental Physics 2 III. Essentials of Cosmology 3 IV and Outlook 13 References 14 I. THE HISTORY OF THE UNIVERSE The history of the universe is a history

326

Gamma-ray bursts and cosmology  

Science Journals Connector (OSTI)

...research-article Discussion Meeting Issue Gamma-ray bursts organized by Alan Wells, Ralph...J. Wijers and Martin Rees Gamma-ray bursts and cosmology D.Q Lamb...current status of the use of gamma-ray bursts (GRBs) as probes of the early...

2007-01-01T23:59:59.000Z

327

Observed Cosmological Redshifts Support Contracting Accelerating Universe  

E-Print Network (OSTI)

The main argument that Universe is currently expanding is observed redshift increase by distance. However, this conclusion may not be correct, because cosmological redshift depends only on the scaling factors, the change in the size of the universe during the time of light propagation and is not related to the speed of observer or speed of the object emitting the light. An observer in expanding universe will measure the same redshift as observer in contracting universe with the same scaling. This was not taken into account in analysing the SN Ia data related to the universe acceleration. Possibility that universe may contract, but that the observed light is cosmologically redshifted allows for completely different set of cosmological parameters $\\Omega_M, \\Omega_{\\Lambda}$, including the solution $\\Omega_M=1, \\Omega_{\\Lambda}=0$. The contracting and in the same time accelerating universe explains observed deceleration and acceleration in SN Ia data, but also gives significantly larger value for the age of the universe, $t_0 = 24$ Gyr. This allows to reconsider classical cosmological models with $\\Lambda =0$. The contracting stage also may explain the observed association of high redshifted quasars to low redshifted galaxies.

Branislav Vlahovic

2012-07-02T23:59:59.000Z

328

Cosmologies with a time dependent vacuum  

E-Print Network (OSTI)

The idea that the cosmological term, Lambda, should be a time dependent quantity in cosmology is a most natural one. It is difficult to conceive an expanding universe with a strictly constant vacuum energy density, namely one that has remained immutable since the origin of time. A smoothly evolving vacuum energy density that inherits its time-dependence from cosmological functions, such as the Hubble rate or the scale factor, is not only a qualitatively more plausible and intuitive idea, but is also suggested by fundamental physics, in particular by quantum field theory (QFT) in curved space-time. To implement this notion, is not strictly necessary to resort to ad hoc scalar fields, as usually done in the literature (e.g. in quintessence formulations and the like). A "running" Lambda term can be expected on very similar grounds as one expects (and observes) the running of couplings and masses with a physical energy scale in QFT. Furthermore, the experimental evidence that the equation of state of the dark energy could be evolving with time/redshift (including the possibility that it might currently behave phantom-like) suggests that a time-variable Lambda term (possibly accompanied by a variable Newton's gravitational coupling G=G(t)) could account in a natural way for all these features. Remarkably enough, a class of these models (the "new cosmon") could even be the clue for solving the old cosmological constant problem, including the coincidence problem.

Joan Sola

2011-02-09T23:59:59.000Z

329

Cosmology at the Beach Lecture: Wayne Hu  

ScienceCinema (OSTI)

Wayne Hu lectures on Secondary Anisotropy in the CMB. The lecture is the first in a series of 3 he delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Wayne Hu

2010-01-08T23:59:59.000Z

330

Scalar potentials out of canonical quantum cosmology  

E-Print Network (OSTI)

Using canonical quantization of a flat FRW cosmological model containing a real scalar field $\\phi$ endowed with a scalar potential $V(\\phi)$, we are able to obtain exact and semiclassical solutions of the so called Wheeler-DeWitt equation for a particular family of scalar potentials. Some features of the solutions and their classical limit are discussed.

W. Guzman; M. Sabido; J. Socorro; L. Arturo Urena-Lopez

2005-06-06T23:59:59.000Z

331

The Cosmological Constant and the String Landscape  

E-Print Network (OSTI)

Theories of the cosmological constant fall into two classes, those in which the vacuum energy is fixed by the fundamental theory and those in which it is adjustable in some way. For each class we discuss key challenges. The string theory landscape is an example of an adjustment mechanism. We discuss the status of this idea, and future directions.

Joseph Polchinski

2006-04-21T23:59:59.000Z

332

SUPERNOVAE AND AGN DRIVEN GALACTIC OUTFLOWS  

SciTech Connect

We present analytical solutions for winds from galaxies with a Navarro-Frank-White (NFW) dark matter halo. We consider winds driven by energy and mass injection from multiple supernovae (SNe), as well as momentum injection due to radiation from a central black hole. We find that the wind dynamics depends on three velocity scales: (1) v{sub *}{approx}( E-dot / 2 M-dot ){sup 1/2} describes the effect of starburst activity, with E-dot and M-dot as energy and mass injection rate in a central region of radius R; (2) v {sub .} {approx} (GM {sub .}/2R){sup 1/2} for the effect of a central black hole of mass M {sub .} on gas at distance R; and (3) v{sub s}=(GM{sub h} / 2Cr{sub s}){sup 1/2}, which is closely related to the circular speed (v{sub c} ) for an NFW halo, where r{sub s} is the halo scale radius and C is a function of the halo concentration parameter. Our generalized formalism, in which we treat both energy and momentum injection from starbursts and radiation from the central active galactic nucleus (AGN), allows us to estimate the wind terminal speed to be (4v {sup 2} {sub *} + 6({Gamma} - 1)v {sub .} {sup 2} - 4v {sup 2} {sub s}){sup 1/2}, where {Gamma} is the ratio of force due to radiation pressure to gravity of the central black hole. Our dynamical model also predicts the following: (1) winds from quiescent star-forming galaxies cannot escape from 10{sup 11.5} M {sub Sun} {<=} M{sub h} {<=} 10{sup 12.5} M {sub Sun} galaxies; (2) circumgalactic gas at large distances from galaxies should be present for galaxies in this mass range; (3) for an escaping wind, the wind speed in low- to intermediate-mass galaxies is {approx}400-1000 km s{sup -1}, consistent with observed X-ray temperatures; and (4) winds from massive galaxies with AGNs at Eddington limit have speeds {approx}> 1000 km s{sup -1}. We also find that the ratio [2v {sup 2} {sub *} - (1 - {Gamma})v {sub .} {sup 2}]/v {sup 2} {sub c} dictates the amount of gas lost through winds. Used in conjunction with an appropriate relation between M {sub .} and M{sub h} and an appropriate opacity of dust grains in infrared (K band), this ratio has the attractive property of being minimum at a certain halo mass scale (M{sub h} {approx} 10{sup 12}-10{sup 12.5} M {sub Sun }) that signifies the crossover of AGN domination in outflow properties from starburst activity at lower masses. We find that stellar mass for massive galaxies scales as M {sub *}{proportional_to}M {sup 0.26} {sub h}, and for low-mass galaxies, M {sub *}{proportional_to}M {sup 5/3} {sub h}.

Sharma, Mahavir; Nath, Biman B., E-mail: mahavir@rri.res.in, E-mail: biman@rri.res.in [Raman Research Institute, Sadashiva Nagar, Bangalore 560080 (India)

2013-01-20T23:59:59.000Z

333

Cosmological perturbations and structure formation in nonlocal infrared modifications of general relativity  

E-Print Network (OSTI)

We study the cosmological consequences of a recently proposed nonlocal modification of general relativity, obtained by adding a term $m^2R\\,\\Box^{-2}R$ to the Einstein-Hilbert action. The model has the same number of parameters as $\\Lambda$CDM, with $m$ replacing $\\Omega_{\\Lambda}$, and is very predictive. At the background level, after fixing $m$ so as to reproduce the observed value of $\\Omega_M$, we get a pure prediction for the equation of state of dark energy as a function of redshift, $w_{\\rm DE}(z)$, with $w_{\\rm DE}(0)$ in the range $[-1.165,-1.135]$ as $\\Omega_M$ varies over the broad range $\\Omega_M\\in [0.20,0.36]$. We find that the cosmological perturbations are well-behaved, and the model fully fixes the dark energy perturbations as a function of redshift $z$ and wavenumber $k$. The nonlocal model provides a good fit to supernova data and predicts deviations from General Relativity in structure formation and in weak lensing at the level of 3-4%, therefore consistent with existing data but readily detectable by future surveys. For the logarithmic growth factor we obtain $\\gamma\\simeq 0.53$, to be compared with $\\gamma\\simeq 0.55$ in $\\Lambda$CDM. For the Newtonian potential on subhorizon scales our results are well fitted by $\\Psi(a;k)=[1+\\mu_s a^s]\\Psi_{\\rm GR}(a;k)$ with a scale-independent $\\mu_s\\simeq 0.09$ and $s\\simeq 2$, while the anisotropic stress is negligibly small.

Yves Dirian; Stefano Foffa; Nima Khosravi; Martin Kunz; Michele Maggiore

2014-03-24T23:59:59.000Z

334

Dynamics and constraints of the massive graviton dark matter flat cosmologies  

SciTech Connect

We discuss the dynamics of the Universe within the framework of the massive graviton cold dark matter scenario (MGCDM) in which gravitons are geometrically treated as massive particles. In this modified gravity theory, the main effect of the gravitons is to alter the density evolution of the cold dark matter component in such a way that the Universe evolves to an accelerating expanding regime, as presently observed. Tight constraints on the main cosmological parameters of the MGCDM model are derived by performing a joint likelihood analysis involving the recent supernovae type Ia data, the cosmic microwave background shift parameter, and the baryonic acoustic oscillations as traced by the Sloan Digital Sky Survey red luminous galaxies. The linear evolution of small density fluctuations is also analyzed in detail. It is found that the growth factor of the MGCDM model is slightly different ({approx}1-4%) from the one provided by the conventional flat {Lambda}CDM cosmology. The growth rate of clustering predicted by MGCDM and {Lambda}CDM models are confronted to the observations and the corresponding best fit values of the growth index ({gamma}) are also determined. By using the expectations of realistic future x-ray and Sunyaev-Zeldovich cluster surveys we derive the dark matter halo mass function and the corresponding redshift distribution of cluster-size halos for the MGCDM model. Finally, we also show that the Hubble flow differences between the MGCDM and the {Lambda}CDM models provide a halo redshift distribution departing significantly from the those predicted by other dark energy models. These results suggest that the MGCDM model can observationally be distinguished from {Lambda}CDM and also from a large number of dark energy models recently proposed in the literature.

Basilakos, S.; Plionis, M.; Alves, M. E. S.; Lima, J. A. S. [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, 11527, Athens (Greece); Institute of Astronomy and Astrophysics, National Observatory of Athens, Thessio 11810, Athens, Greece, and Instituto Nacional de Astrofisica, Optica y Electronica, 72000 Puebla (Mexico); Instituto de Ciencias Exatas, Universidade Federal de Itajuba, Av. BPS, 1303, 37500-903, Itajuba, MG (Brazil); Departamento de Astronomia (IAGUSP), Universidade de Sao Paulo, Rua do Matao, 1226, 05508-900, Sao Paulo (Brazil)

2011-05-15T23:59:59.000Z

335

How to See the Supernova Berkeley Lab Just Discovered | Department of  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

How to See the Supernova Berkeley Lab Just Discovered How to See the Supernova Berkeley Lab Just Discovered How to See the Supernova Berkeley Lab Just Discovered September 1, 2011 - 10:12am Addthis Berkeley Lab scientist Peter Nugent discusses a recently discovered supernova that is closer to Earth - approximately 21 million light-years away - than any other of its kind in a generation. Linda Vu Skywatchers -- grab your binoculars and telescopes, and head for some clear dark skies. A new supernova has been discovered near the Big Dipper. Scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley caught the supernova just hours after its explosion, a rare feat made possible with a specialized survey telescope and state-of-the-art computational tools. The researchers note

336

A Precision Photometric Comparison between SDSS-II and CSP Type Ia Supernova Data  

E-Print Network (OSTI)

Consistency between Carnegie Supernova Project (CSP) and SDSS-II supernova (SN) survey ugri measurements has been evaluated by comparing SDSS and CSP photometry for nine spectroscopically confirmed Type Ia supernova observed contemporaneously by both programs. The CSP data were transformed into the SDSS photometric system. Sources of systematic uncertainty have been identified, quantified, and shown to be at or below the 0.023 magnitude level in all bands. When all photometry for a given band is combined, we find average magnitude differences of equal to or less than 0.011 magnitudes in ugri, with rms scatter ranging from 0.043 to 0.077 magnitudes. The u band agreement is promising, with the caveat that only four of the nine supernovae are well-observed in u and these four exhibit an 0.038 magnitude supernova-to-supernova scatter in this filter.

Mosher, J; Corlies, L; Folatelli, G; Frieman, J; Holtzman, J; Jha, S W; Kessler, R; Marriner, J; Phillips, M M; Stritzinger, M; Morrell, N; Schneider, D P

2012-01-01T23:59:59.000Z

337

A PRECISION PHOTOMETRIC COMPARISON BETWEEN SDSS-II AND CSP TYPE Ia SUPERNOVA DATA  

SciTech Connect

Consistency between Carnegie Supernova Project (CSP) and SDSS-II Supernova Survey ugri measurements has been evaluated by comparing Sloan Digital Sky Survey (SDSS) and CSP photometry for nine spectroscopically confirmed Type Ia supernova observed contemporaneously by both programs. The CSP data were transformed into the SDSS photometric system. Sources of systematic uncertainty have been identified, quantified, and shown to be at or below the 0.023 mag level in all bands. When all photometry for a given band is combined, we find average magnitude differences of equal to or less than 0.011 mag in ugri, with rms scatter ranging from 0.043 to 0.077 mag. The u-band agreement is promising, with the caveat that only four of the nine supernovae are well observed in u and these four exhibit an 0.038 mag supernova-to-supernova scatter in this filter.

Mosher, J.; Sako, M.; Corlies, L. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Folatelli, G. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Frieman, J.; Kessler, R. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Holtzman, J. [Department of Astronomy, MSC 4500, New Mexico State University, P.O. Box 30001, Las Cruces, NM 88003 (United States); Jha, S. W. [Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Marriner, J. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Phillips, M. M.; Morrell, N. [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile); Stritzinger, M. [Oskar Klein Centre for Cosmo Particle Physics, AlbaNova University Center, 106 91 Stockholm (Sweden); Schneider, D. P., E-mail: jmosher@sas.upenn.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

2012-07-15T23:59:59.000Z

338

A Precision Photometric Comparison between SDSS-II and CSP Type Ia Supernova Data  

SciTech Connect

Consistency between Carnegie Supernova Project (CSP) and SDSS-II Supernova Survey ugri measurements has been evaluated by comparing Sloan Digital Sky Survey (SDSS) and CSP photometry for nine spectroscopically confirmed Type Ia supernova observed contemporaneously by both programs. The CSP data were transformed into the SDSS photometric system. Sources of systematic uncertainty have been identified, quantified, and shown to be at or below the 0.023 mag level in all bands. When all photometry for a given band is combined, we find average magnitude differences of equal to or less than 0.011 mag in ugri, with rms scatter ranging from 0.043 to 0.077 mag. The u-band agreement is promising, with the caveat that only four of the nine supernovae are well observed in u and these four exhibit an 0.038 mag supernova-to-supernova scatter in this filter.

Mosher, J.; /Pennsylvania U.; Sako, M.; /Pennsylvania U.; Corlies, L.; /Pennsylvania U. /Columbia U.; Folatelli, G.; /Tokyo U. /Carnegie Inst. Observ.; Frieman, J.; /Chicago U., KICP /Chicago U., Astron. Astrophys. Ctr.; Holtzman, J.; /New Mexico State U.; Jha, S.W.; /Rutgers U., Piscataway; Kessler, R.; /Chicago U., Astron. Astrophys. Ctr. /Chicago U., KICP; Marriner, J.; /Fermilab; Phillips, M.M.; /Carnegie Inst. Observ.; Stritzinger, M.; /Aarhus U. /Stockholm U., OKC /Bohr Inst. /Carnegie Inst. Observ.

2012-06-01T23:59:59.000Z

339

How to See the Supernova Berkeley Lab Just Discovered | Department of  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

How to See the Supernova Berkeley Lab Just Discovered How to See the Supernova Berkeley Lab Just Discovered How to See the Supernova Berkeley Lab Just Discovered September 1, 2011 - 10:12am Addthis Berkeley Lab scientist Peter Nugent discusses a recently discovered supernova that is closer to Earth - approximately 21 million light-years away - than any other of its kind in a generation. Linda Vu Skywatchers -- grab your binoculars and telescopes, and head for some clear dark skies. A new supernova has been discovered near the Big Dipper. Scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley caught the supernova just hours after its explosion, a rare feat made possible with a specialized survey telescope and state-of-the-art computational tools. The researchers note

340

Theoretical models for Type I and Type II supernova  

SciTech Connect

Recent theoretical progress in understanding the origin and nature of Type I and Type II supernovae is discussed. New Type II presupernova models characterized by a variety of iron core masses at the time of collapse are presented and the sensitivity to the reaction rate /sup 12/C(..cap alpha..,..gamma..)/sup 16/O explained. Stars heavier than about 20 M/sub solar/ must explode by a ''delayed'' mechanism not directly related to the hydrodynamical core bounce and a subset is likely to leave black hole remnants. The isotopic nucleosynthesis expected from these massive stellar explosions is in striking agreement with the sun. Type I supernovae result when an accreting white dwarf undergoes a thermonuclear explosion. The critical role of the velocity of the deflagration front in determining the light curve, spectrum, and, especially, isotopic nucleosynthesis in these models is explored. 76 refs., 8 figs.

Woosley, S.E.; Weaver, T.A.

1985-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
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341

The onset of the bipolar flavor conversion of supernova neutrinos  

E-Print Network (OSTI)

The study of supernova neutrinos result an interesting non-linear phenomenon, consisting of three phases: synchronized oscillation phase, bipolar flavor conversion phase and the phase of spectral split. In the collective oscillation of supernova neutrino the self energy is not a constant but varies adiabatically, which is responsible to have such different phases. In this article the transition point from synchronized oscillation to bipolar phase is studied numerically as well as analytically. The numerical results yielding different graphs depending on different values of possible small but non-vanishing mixing angles show the onset of the bipolar phase from the synchronized phase varies as the mixing angle. But the analytical study in terms of a spinning top model results a unique onset condition, which is independent of the choice of mixing angle. Such discrepancy between numerical results and analytical results is explained properly.

Bhattacharyya, Indranath

2014-01-01T23:59:59.000Z

342

Emission angle distribution and flavor transformation of supernova neutrinos  

E-Print Network (OSTI)

Using moment equations we analyze collective flavor transformation of supernova neutrinos. We study the convergence of moment equations and find that numerical results using a few moment converge quite fast. We study effects of emission angle distribution of neutrinos on neutrino sphere. We study scaling law of the amplitude of neutrino self-interaction Hamiltonian and find that it depends on model of emission angle distribution of neutrinos. Dependence of neutrino oscillation on different models of emission angle distribution is studied.

Wei Liao

2009-06-28T23:59:59.000Z

343

The Supernovae Associated with Gamma-Ray Bursts  

E-Print Network (OSTI)

Supernovae (SNe) were long suspected as possible progenitors of gamma-ray bursts (GRBs). The arguments relied on circumstantial evidence. Several recent GRBs, notably GRB 030329, have provided direct, spectroscopic evidence that SNe and GRBs are related. The SNe associated with GRBs are all of Type Ic, implying a compact progenitor, which has implications for GRB models. Other peculiar Type Ic SNe may help to expand understanding of the mechanisms involved.

Thomas Matheson

2004-10-27T23:59:59.000Z

344

E-Print Network 3.0 - automated supernova search Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

and analysis Summary: : Search Contact information Astrophysics Grand Challenge: Dark Energy The Nearby Supernova Factory... the four components (Search, Workflow Status...

345

Search for Correlations Between Batse Gamma-Ray Bursts and Supernovae  

Science Journals Connector (OSTI)

We report on our statistical research of space-time correlated supernovae and CGRO-BATSE gamma-ray bursts (GRBs). There exists a significantly higher...

Ji?í Polcar; Martin Topinka; Graziella Pizzichini…

2005-01-01T23:59:59.000Z

346

Stellar Evolution/Supernova Research Data Archives from the SciDAC Computational Astrophysics Consortium  

DOE Data Explorer (OSTI)

Theoretical high-energy astrophysics studies the most violent explosions in the universe - supernovae (the massive explosions of dying stars) and gamma ray bursts (mysterious blasts of intense radiation). The evolution of massive stars and their explosion as supernovae and/or gamma ray bursts describes how the "heavy" elements needed for life, such as oxygen and iron, are forged (nucleosynthesis) and ejected to later form new stars and planets. The Computational Astrophysics Consortium's project includes a Science Application Partnership on Adaptive Algorithms that develops software involved. The principal science topics are - in order of priority - 1) models for Type Ia supernovae, 2) radiation transport, spectrum formation, and nucleosynthesis in model supernovae of all types; 3) the observational implications of these results for experiments in which DOE has an interest, especially the Joint Dark Energy Mission, Supernova/Acceleration Probe (SNAP) satellite observatory, the Large Synoptic Survey Telescope (LSST), and ground based supernova searches; 4) core collapse supernovae; 5) gamma-ray bursts; 6) hypernovae from Population III stars; and 7) x-ray bursts. Models of these phenomena share a common need for nuclear reactions and radiation transport coupled to multi-dimensional fluid flow. The team has developed and used supernovae simulation codes to study Type 1A and core-collapse supernovae. (Taken from http://www.scidac.gov/physics/grb.html) The Stellar Evolution Data Archives contains more than 225 Pre-SN models that can be freely accessed.

Woosley, Stan (University of California, Santa Cruz)

347

On the Stability of Thermonuclear Burning Fronts in Type Ia Supernovae  

Science Journals Connector (OSTI)

The propagation of cellularly stabilized thermonuclear flames is investigated by means of numerical ... fuel flows. Our simulations indicate that in thermonuclear supernova explosions stable cellular flames devel...

F.K. Röpke; W. Hillebrandt

2005-01-01T23:59:59.000Z

348

High Energy Neutrinos from Gamma-Ray Bursts with Precursor Supernovae  

E-Print Network (OSTI)

The high energy neutrino signature from proton-proton and photo-meson interactions in a supernova remnant shell ejected prior to a gamma-ray burst provides a test for the precursor supernova, or supranova, model of gamma-ray bursts. Protons in the supernova remnant shell, and photons entrapped from a supernova explosion or a pulsar wind from a fast-rotating neutron star remnant provide ample targets for protons escaping the internal shocks of the gamma-ray burst to interact and produce high energy neutrinos. We calculate the expected neutrino fluxes, which can be detected by current and future experiments.

Soebur Razzaque; Peter Meszaros; Eli Waxman

2002-12-24T23:59:59.000Z

349

Extended supernova shock breakout signals from inflated stellar envelopes  

E-Print Network (OSTI)

Stars close to the Eddington luminosity can have large low-density inflated envelopes. We show that the rise times of shock breakout signals from supernovae can be extended significantly if supernova progenitors have an inflated stellar envelope. If the shock breakout occurs in such inflated envelopes, the shock breakout signals diffuse in them, and their rise time can be significantly extended. Then, the rise times of the shock breakout signals are dominated by the diffusion time in the inflated envelope rather than the light-crossing time of the progenitors. We show that our inflated Wolf-Rayet star models whose radii are of the order of the solar radius can have shock breakout signals which are longer than ~100 sec. The existence of inflated envelopes in Wolf-Rayet supernova progenitors may be related to the mysterious long shock breakout signal observed in Type Ib SN 2008D. Extended shock breakout signals may provide evidence for the existence of inflated stellar envelopes and can be used to constrain the...

Moriya, Takashi J; Langer, Norbert

2015-01-01T23:59:59.000Z

350

Ion Heating in Collisionless Shocks in Supernovae and the Heliosphere  

E-Print Network (OSTI)

Collisionless shocks play a role in many astrophysical phenomena, from coronal mass ejections (CMEs) in the heliosphere to supernova remnants. Their role in heating and accelerating particles is well accepted yet the exact mechanism for ion heating is not well understood. Two systems, CMEs and supernova remnants, were examined to determine the heating of heavy ions as they pass through collisionless shocks thus providing a seed population for cosmic ray acceleration processes. Three parameters are examined, the plasma beta, the Mach number of the shock and the magnetic angle of the shock. CMEs heat heavy ions preferentially. This is in contrast to the supernova data which shows less than mass proportional heating. In addition to these studies, heating in astrophysical systems involves neutral atoms. A Monte Carlo model simulated neutral particles as they pass through the shock. Neutrals can create a precursor to the shock additionally heating the plasma. This work uses in situ data from the heliosphere to study astronomical systems because of common shock properties is a unique way to study magnetic components of shocks remotely.

K. E. Korreck

2005-06-14T23:59:59.000Z

351

Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries  

Science Journals Connector (OSTI)

Helium that accretes onto a carbon/oxygen white dwarf in double white dwarf AM Canum Venaticorum (AM CVn) binaries undergoes unstable thermonuclear flashes when the orbital period is in the 3.5-25 minute range. At the shortest orbital periods (and highest accretion rates, > 10-7 M? yr-1), the flashes are weak and likely lead to the helium equivalent of classical nova outbursts. However, as the orbit widens and drops, the mass required for the unstable ignition increases, leading to progressively more violent flashes up to a final flash with helium shell mass ?0.02-0.1 M?. The high pressures of these last flashes allow the burning to produce the radioactive elements 48Cr, 52Fe, and 56Ni that power a faint (MV = -15 to -18) and rapidly rising (few days) thermonuclear supernova. Current galactic AM CVn space densities imply one such explosion every 5,000-15,000 years in 1011 M? of old stars (?2%-6% of the Type Ia rate in E/SO galaxies). These ".Ia" supernovae (one-tenth as bright for one-tenth the time as a Type Ia supernovae) are excellent targets for deep (e.g., V = 24) searches with nightly cadences, potentially yielding an all-sky rate of 1000 per year.

Lars Bildsten; Ken J. Shen; Nevin N. Weinberg; Gijs Nelemans

2007-01-01T23:59:59.000Z

352

Cutting-edge issues of core-collapse supernova theory  

SciTech Connect

Based on multi-dimensional neutrino-radiation hydrodynamic simulations, we report several cutting-edge issues about the long-veiled explosion mechanism of core-collapse supernovae (CCSNe). In this contribution, we pay particular attention to whether three-dimensional (3D) hydrodynamics and/or general relativity (GR) would or would not help the onset of explosions. By performing 3D simulations with spectral neutrino transport, we show that it is more difficult to obtain an explosion in 3D than in 2D. In addition, our results from the first generation of full general relativistic 3D simulations including approximate neutrino transport indicate that GR can foster the onset of neutrino-driven explosions. Based on our recent parametric studies using a light-bulb scheme, we discuss impacts of nuclear energy deposition behind the supernova shock and stellar rotation on the neutrino-driven mechanism, both of which have yet to be included in the self-consistent 3D supernova models. Finally we give an outlook with a summary of the most urgent tasks to extract the information about the explosion mechanisms from multi-messenger CCSN observables.

Kotake, Kei [Department of Applied Physics, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180 (Japan); Nakamura, Ko [Faculty of Science and Engineering, Waseda University, Ohkubo 3-4-1, Shinjuku, Tokyo, 169-8555 (Japan); Kuroda, Takami [Department Physik, Universität Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Takiwaki, Tomoya [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 (Japan)

2014-05-02T23:59:59.000Z

353

Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries  

E-Print Network (OSTI)

Helium that accretes onto a Carbon/Oxygen white dwarf in the double white dwarf AM Canum Venaticorum (AM CVn) binaries undergoes unstable thermonuclear flashes when the orbital period is in the 3.5-25 minute range. At the shortest orbital periods (and highest accretion rates, Mdot > 10^-7 Msol/yr), the flashes are weak and likely lead to the Helium equivalent of classical nova outbursts. However, as the orbit widens and Mdot drops, the mass required for the unstable ignition increases, leading to progressively more violent flashes up to a final flash with Helium shell mass ~ 0.02-0.1 Msol. The high pressures of these last flashes allow the burning to produce the radioactive elements 48Cr, 52Fe, and 56Ni that power a faint (M_V in the range of -15 to -18) and rapidly rising (few days) thermonuclear supernova. Current galactic AM CVn space densities imply one such explosion every 5,000-15,000 years in 10^11 Msol of old stars (~ 2-6% of the Type Ia rate in E/SO galaxies). These ".Ia" supernovae (one-tenth as bright for one-tenth the time as a Type Ia supernovae) are excellent targets for deep (e.g. V=24) searches with nightly cadences, potentially yielding an all-sky rate of 1,000 per year.

Lars Bildsten; Ken J. Shen; Nevin N. Weinberg; Gijs Nelemans

2007-05-06T23:59:59.000Z

354

Cosmological perturbations in f(T) gravity  

SciTech Connect

We investigate the cosmological perturbations in f(T) gravity. Examining the pure gravitational perturbations in the scalar sector using a diagonal vierbein, we extract the corresponding dispersion relation, which provides a constraint on the f(T) Ansaetze that lead to a theory free of instabilities. Additionally, upon inclusion of the matter perturbations, we derive the fully perturbed equations of motion, and we study the growth of matter overdensities. We show that f(T) gravity with f(T) constant coincides with General Relativity, both at the background as well as at the first-order perturbation level. Applying our formalism to the power-law model we find that on large subhorizon scales (O(100 Mpc) or larger), the evolution of matter overdensity will differ from {Lambda}CDM cosmology. Finally, examining the linear perturbations of the vector and tensor sectors, we find that (for the standard choice of vierbein) f(T) gravity is free of massive gravitons.

Chen, Shih-Hung; Dent, James B. [Department of Physics and School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404 (United States); Dutta, Sourish [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Saridakis, Emmanuel N. [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)

2011-01-15T23:59:59.000Z

355

A Cosmological Model of Thermodynamic Open Universe  

E-Print Network (OSTI)

In this paper we have given a generalisation of the earlier work by Prigogine et al. who have constructed a phenomenological model of entropy production via particle creation in the very early universe generated out of the vacuum rather than from a singularity, by including radiation also as the energy source and tried to develop an alternative cosmological model in which particle creation prevents the big bang. We developed Radiation dominated model of the universe which shows a general tendency that (i) it originates from instability of vacuum rather than from a singularity. (ii) Up to a characteristic time cosmological quantities like density, pressure, Hubble constant and expansion parameter vary rapidly with time. (iii) After the characteristic time these quantities settles down and the models are turned into de-sitter type model with uniform matter, radiation, creation densities and Hubble's constant H. The de-sitter regime survives during a decay time then connects continuously to a usual adiabatic mat...

Goswami, G K

2012-01-01T23:59:59.000Z

356

A Spinor Model for Quantum Cosmology  

E-Print Network (OSTI)

The question of the interpretation of Wheeler-DeWitt solutions in the context of cosmological models is addressed by implementing the Hamiltonian constraint as a spinor wave equation in minisuperspace. We offer a relative probability interpretation based on a non-closed vector current in this space and a prescription for a parametrisation of classical solutions in terms of classical time. Such a prescription can accommodate classically degenerate metrics describing manifolds with signature change. The relative probability density, defined in terms of a Killing vector of the Dewitt metric on minisuperspace, should permit one to identify classical loci corresponding to geometries for a classical manifold. This interpretation is illustrated in the context of a quantum cosmology model for two-dimensional dilaton gravity.

T Dereli; M Onder; R W Tucker

1994-03-02T23:59:59.000Z

357

Cosmology of a Lorentz violating Galileon theory  

E-Print Network (OSTI)

We modify the scalar Einstein-aether theory by breaking the Lorentz invariance of a gravitational theory coupled to a Galileon type scalar field. This is done by introducing a Lagrange multiplier term into the action, thus ensuring that the gradient of the scalar field is time-like, with unit norm. The resulting theory is then generally invariant at the level of action, breaking the Lorentz invariance at the level of equations of motion. The theory can also be considered as an extension to the mimetic dark matter theory, by adding some derivative self interactions to the action, which keeps the equations of motion at most second order in time derivatives. The cosmological implications of the model are discussed in detail. In particular, we show that a matter dominated (dust) universe experiences a late time acceleration. The cosmological implications of a special coupling between the scalar field and the trace of the energy-momentum tensor are also explored.

Haghani, Zahra; Sepangi, Hamid Reza; Shahidi, Shahab

2015-01-01T23:59:59.000Z

358

Genesis of Dark Energy: Dark Energy as a Consequence of Cosmological Nuclear Energy  

E-Print Network (OSTI)

Recent observations on Type-Ia supernovae and low density measurement of matter (including dark matter) suggest that the present day universe consists mainly of repulsive-gravity type exotic-matter with negative-pressure often referred as dark-energy. But the mystery is about the nature of dark-energy and its puzzling questions such as why, how, where & when about the dark- energy are intriguing. In the present paper the author attempts to answer these questions while making an effort to reveal the genesis of dark-energy, and suggests that the cosmological nuclear-binding-energy liberated during primordial nucleo-synthesis remains trapped for long time and then is released free which manifests itself as dark-energy in the universe. It is also explained why for dark energy the parameter w = -2/3. Noting that w=+1for stiff matter and w=+1/3 for radiation; w = - 2/3 is for dark energy, because -1 is due to deficiency of stiff-nuclear-matter and that this binding energy is ultimately released as radiation contributing +1/3, making w = -1 + 1/3 = -2/3. This thus almost solves the dark-energy mystery of negative-pressure & repulsive-gravity. It is concluded that dark-energy is a consequence of released-free nuclear-energy of cosmos. The proposed theory makes several estimates / predictions, which agree reasonably well with the astrophysical constraints & observations.

R. C. Gupta

2004-12-07T23:59:59.000Z

359

Gamma Ray Bursts as cosmological tools  

E-Print Network (OSTI)

The use of Gamma Ray Bursts as ``standard candles'' has been made possible by the recent discovery of a very tight correlation between their rest frame intrinsic properties. This correlation relates the GRB prompt emission peak spectral energy E_peak to the energy E_gamma corrected for the collimation angle theta_jet of these sources. The possibility to use GRBs to constrain the cosmological parameters and to study the nature of Dark Energy are very promising.

G. Ghirlanda; G. Ghisellini; L. Nava; C. Firmani

2005-12-30T23:59:59.000Z

360

Gamma Ray Bursts as Cosmological Tools  

Science Journals Connector (OSTI)

The use of Gamma Ray Bursts as “standard candles” has been made possible by the recent discovery of a very tight correlation between their rest frame intrinsic properties. This correlation relates the GRB prompt emission peak spectral energy E peak to the energy E ? corrected for the collimation angle ?jet of these sources. The possibility to use GRBs to constrain the cosmological parameters and to study the nature of Dark Energy are very promising.

G. Ghirlanda; G. Ghisellini; L. Nava; C. Firmani

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Simple Cosmological Model with Relativistic Gas  

E-Print Network (OSTI)

We construct simple and useful approximation for the relativistic gas of massive particles. The equation of state is given by an elementary function and admits analytic solution of the Friedmann equation, including more complex cases when the relativistic gas of massive particles is considered together with radiation or with dominating cosmological constant. The model of relativistic gas may be interesting for the description of primordial Universe, especially as a candidate for the role of a Dark Matter.

Guilherme de Berredo-Peixoto; Ilya L. Shapiro; Flavia Sobreira

2005-06-16T23:59:59.000Z

362

Cosmological parameter estimation: impact of CMB aberration  

SciTech Connect

The peculiar motion of an observer with respect to the CMB rest frame induces an apparent deflection of the observed CMB photons, i.e. aberration, and a shift in their frequency, i.e. Doppler effect. Both effects distort the temperature multipoles a{sub lm}'s via a mixing matrix at any l. The common lore when performing a CMB based cosmological parameter estimation is to consider that Doppler affects only the l = 1 multipole, and neglect any other corrections. In this paper we reconsider the validity of this assumption, showing that it is actually not robust when sky cuts are included to model CMB foreground contaminations. Assuming a simple fiducial cosmological model with five parameters, we simulated CMB temperature maps of the sky in a WMAP-like and in a Planck-like experiment and added aberration and Doppler effects to the maps. We then analyzed with a MCMC in a Bayesian framework the maps with and without aberration and Doppler effects in order to assess the ability of reconstructing the parameters of the fiducial model. We find that, depending on the specific realization of the simulated data, the parameters can be biased up to one standard deviation for WMAP and almost two standard deviations for Planck. Therefore we conclude that in general it is not a solid assumption to neglect aberration in a CMB based cosmological parameter estimation.

Catena, Riccardo [Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Notari, Alessio, E-mail: riccardo.catena@theorie.physik.uni-goettingen.de, E-mail: notari@ffn.ub.es [Departament de Física Fondamental i Institut de Ciéncies del Cosmos, Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona (Spain)

2013-04-01T23:59:59.000Z

363

Cosmological supersymmetric model of dark energy  

Science Journals Connector (OSTI)

Recently, a supersymmetric model of dark energy coupled to cold dark matter, the supersymmetron, has been proposed. In the absence of cold dark matter, the supersymmetron field converges to a supersymmetric minimum with a vanishing cosmological constant. When cold dark matter is present, the supersymmetron evolves to a matter-dependent minimum where its energy density does not vanish and could lead to the present acceleration of the Universe. The supersymmetron generates a short-ranged fifth force which evades gravitational tests. It could lead to observable signatures on structure formation due to a very strong coupling to dark matter. We investigate the cosmological evolution of the field, focusing on the linear perturbations and the spherical collapse and find that observable modifications in structure formation can indeed exist. Unfortunately, we find that when the growth rate of perturbations is in agreement with observations, an additional cosmological constant is required to account for dark energy. In this case, effects on large-scale structures are still present at the nonlinear level which are investigated using the spherical collapse approach.

Philippe Brax; Anne-Christine Davis; Hans A. Winther

2012-04-18T23:59:59.000Z

364

Bianchi type II brane-world cosmologies (U>~0)  

Science Journals Connector (OSTI)

The asymptotic properties of the Bianchi type II cosmological model in the brane-world scenario are investigated. The matter content is assumed to be a combination of a perfect fluid and a minimally coupled scalar field that is restricted to the brane. The isotropic brane-world solution is determined to represent the initial singularity in all brane-world cosmologies. Additionally, it is shown that it is the kinetic energy of the scalar field which dominates the initial dynamics in these brane-world cosmologies. It is important to note that the dynamics of these brane-world cosmologies is not necessarily asymptotic to general relativistic cosmologies to the future in the case of a zero four-dimensional cosmological constant.

R. J. van den Hoogen and J. Ibañez

2003-04-24T23:59:59.000Z

365

Brane World Cosmologies with Varying Speed of Light  

E-Print Network (OSTI)

We study cosmologies in the Randall-Sundrum models, incorporating the possibility of time-varying speed of light and Newton's constant. The cosmologies with varying speed of light (VSL) were proposed by Moffat and by Albrecht and Magueijo as an alternative to inflation for solving the cosmological problems. We consider the case in which the speed of light varies with time after the radion or the scale of the extra dimension has been stabilized. We elaborate on the conditions under which the flatness problem and the cosmological constant problem can be resolved. We find that the RS models are more restrictive about possible desirable VSL cosmological models than the standard general relativity. Particularly, the VSL cosmologies may provide with a possible mechanism for bringing the quantum corrections to the fine-tuned brane tensions after the SUSY breaking under control.

Donam Youm

2001-01-31T23:59:59.000Z

366

Isotropic singularities in shear-free perfect fluid cosmologies  

E-Print Network (OSTI)

We investigate barotropic perfect fluid cosmologies which admit an isotropic singularity. From the General Vorticity Result of Scott, it is known that these cosmologies must be irrotational. In this paper we prove, using two different methods, that if we make the additional assumption that the perfect fluid is shear-free, then the fluid flow must be geodesic. This then implies that the only shear-free, barotropic, perfect fluid cosmologies which admit an isotropic singularity are the FRW models.

Geoffery Ericksson; Susan M. Scott

2001-08-02T23:59:59.000Z

367

Cosmological Evolution of Fundamental Constants: From Theory to Experiment  

E-Print Network (OSTI)

In this paper we discuss a possible cosmological time evolution of fundamental constants from the theoretical and experimental point of views. On the theoretical side, we explain that such a cosmological time evolution is actually something very natural which can be described by mechanisms similar to those used to explain cosmic inflation. We then discuss implications for grand unified theories, showing that the unification condition of the gauge coupling could evolve with cosmological time. Measurements of the electron-to-proton mass ratio can test grand unified theories using low energy data. Following the theoretical discussion, we review the current status of precision measurements of fundamental constants and their potential cosmological time dependence.

Xavier Calmet; Matthias Keller

2014-12-05T23:59:59.000Z

368

Constraining gravitational and cosmological parameters with astrophysical data  

E-Print Network (OSTI)

We use astrophysical data to shed light on fundamental physics by constraining parametrized theoretical cosmological and gravitational models. Gravitational parameters are those constants that parametrize possible departures ...

Mao, Yi, Ph. D. Massachusetts Institute of Technology

2008-01-01T23:59:59.000Z

369

Thermodynamic Stability of a Multi-Bubble Cosmological Model  

E-Print Network (OSTI)

Multibubble solutions for a cosmological model which lead to thermal inflationary states due to a semi-classical tunneling of gravity are calculated.

G. Horwitz; O. Fonarev

1994-10-20T23:59:59.000Z

370

Phenomenology and cosmology of weakly coupled string theory  

E-Print Network (OSTI)

ph/9805320 May 1998 Phenomenology and cosmology of weaklyThe important point for phenomenology is the decomposition2]. Implications for phenomenology and open questions The

Gaillard, Mary K.

1998-01-01T23:59:59.000Z

371

Flames in Type Ia Supernova: Deflagration-Detonation Transition in the Oxygen Burning Flame  

E-Print Network (OSTI)

Flames in Type Ia Supernova: Deflagration-Detonation Transition in the Oxygen Burning Flame S. E of these regions can be supersonic and could initiate a detonation. Subject headings: supernovae: general a late time transition of the thermonuclear burning to a detonation wave (e.g., Hoflich et al. 1995

372

IS THE SUPERNOVA OF A.D. 185 RECORDED IN ANCIENT ROMAN LITERATURE?  

E-Print Network (OSTI)

443 IS THE SUPERNOVA OF A.D. 185 RECORDED IN ANCIENT ROMAN LITERATURE? By Richard Stothers* Records. R. Stephenson, "A Revised Catalogue of Pre-Telescopic Galactic No- vae and Supernovae," Quarterly.11). The Roman poet Claudian (Panegyricus de quarto con- The-ancient Chinese astronomers, un- like their Western

Fridlind, Ann

373

Abelian groups  

E-Print Network (OSTI)

s a 1-1 mapping. Also (na + ma)c' [(n + m)a]c ge (n + m)b ra nb + mb gt (na)c + (ma)o. Thus a is a homomorphism, and th1s together with the above tells us that a is an isomorphism. Hence (2) is proved, and thus the theorem, Definition 2 e6 If a...t o e. d ix elexext x oi s dross G is ~dvdsdt s by' n if there exists y such that ny rx x, As sn example of divisibility we note that the element 0 is divisible by every integer. Also, in the additive group of' xational numbers, we note every...

Bolen, James Cordell

2012-06-07T23:59:59.000Z

374

Cosmic Rays from Supernovae Proven to Hit Earth | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Cosmic Rays from Supernovae Proven to Hit Earth Cosmic Rays from Supernovae Proven to Hit Earth Cosmic Rays from Supernovae Proven to Hit Earth March 5, 2013 - 4:40pm Addthis When stars explode, the supernovas send off shock waves like the one shown in this artist's rendition, which accelerate protons to cosmic-ray energies through a process known as Fermi acceleration. Andy Freeberg SLAC National Accelerator Laboratory Did you know? Protons make up 90 percent of the cosmic rays that hit Earth's atmosphere, triggering showers of particles that reach the ground and creating radiation for air travelers. The energies of these protons as they leave the supernovae are far beyond what the most powerful particle colliders on Earth can produce. Cosmic rays, energetic particles that pelt Earth, are born in the violent

375

E-Print Network 3.0 - accelerated cosmological lattice Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

, and the accelerating expansion of the universe. VUW Matt Visser Cosmology: Dark energy, dark matter, and all that... : Accelerating expansion Matt Visser Cosmology: Dark...

376

Precision cosmology in muddy waters: cosmological constraints and N-body codes  

Science Journals Connector (OSTI)

......have performed a box-car smoothing of the correlation...constitutes a plausible alternative to various other ad hoc...matrix has been box-car smoothed by a square...addition, when exploring alternative cosmological models...parameters are: dark energy EOS parameters w 0......

Robert E. Smith; Darren S. Reed; Doug Potter; Laura Marian; Martin Crocce; Ben Moore

2014-01-01T23:59:59.000Z

377

Turbulence-Flame Interactions in Type Ia Supernovae  

E-Print Network (OSTI)

The large range of time and length scales involved in type Ia supernovae (SN Ia) requires the use of flame models. As a prelude to exploring various options for flame models, we consider, in this paper, high-resolution three-dimensional simulations of the small-scale dynamics of nuclear flames in the supernova environment in which the details of the flame structure are fully resolved. The range of densities examined, 1 to $8 \\times 10^7$ g cm$^{-3}$, spans the transition from the laminar flamelet regime to the distributed burning regime where small scale turbulence disrupts the flame. The use of a low Mach number algorithm facilitates the accurate resolution of the thermal structure of the flame and the inviscid turbulent kinetic energy cascade, while implicitly incorporating kinetic energy dissipation at the grid-scale cutoff. For an assumed background of isotropic Kolmogorov turbulence with an energy characteristic of SN Ia, we find a transition density between 1 and $3 \\times 10^7$ g cm$^{-3}$ where the nature of the burning changes qualitatively. By $1 \\times 10^7$ g cm$^{-3}$, energy diffusion by conduction and radiation is exceeded, on the flame scale, by turbulent advection. As a result, the effective Lewis Number approaches unity. That is, the flame resembles a laminar flame, but is turbulently broadened with an effective diffusion coefficient, $D_T \\sim u' l$, where $u'$ is the turbulent intensity and $l$ is the integral scale. For the larger integral scales characteristic of a real supernova, the flame structure is predicted to become complex and unsteady. Implications for a possible transition to detonation are discussed.

A. J. Aspden; J. B. Bell; M. S. Day; S. E. Woosley; M. Zingale

2008-11-17T23:59:59.000Z

378

Type Ia Supernova Hubble Residuals and Host-Galaxy Properties  

SciTech Connect

Kim et al. (2013) [K13] introduced a new methodology for determining peak- brightness absolute magnitudes of type Ia supernovae from multi-band light curves. We examine the relation between their parameterization of light curves and Hubble residuals, based on photometry synthesized from the Nearby Supernova Factory spec- trophotometric time series, with global host-galaxy properties. The K13 Hubble residual step with host mass is 0.013 ? 0.031 mag for a supernova subsample with data coverage corresponding to the K13 training; at ? 1?, the step is not significant and lower than previous measurements. Relaxing the data coverage requirement the Hubble residual step with host mass is 0.045 ? 0.026 mag for the larger sample; a calculation using the modes of the distributions, less sensitive to outliers, yields a step of 0.019 mag. The analysis of this article uses K13 inferred luminosities, as distinguished from previous works that use magnitude corrections as a function of SALT2 color and stretch param- eters: Steps at> 2? significance are found in SALT2 Hubble residuals in samples split by the values of their K13 x(1) and x(2) light-curve parameters. x(1) affects the light- curve width and color around peak (similar to the?m15 and stretch parameters), and x(2) affects colors, the near-UV light-curve width, and the light-curve decline 20 to 30 days after peak brightness. The novel light-curve analysis, increased parameter set, and magnitude corrections of K13 may be capturing features of SN Ia diversity arising from progenitor stellar evolution.

Nearby Supernova Factory; Kim, A. G.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Cellier-Holzem, F.; Childress, M.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Feindt, U.; Fleury, M.; Gangler, E.; Greskovic, P.; Guy, J.; Kowalski, M.; Lombardo, S.; Nordin, J.; Nugent, P.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigault, M.; Runge, K.; Saunders, C.; Scalzo, R.; Smadja, G.; Tao, C.; Thomas, R. C.; Weaver, B. A.

2014-01-17T23:59:59.000Z

379

The Recurrent Nova U Scorpii - A Type Ia Supernova Progenitor  

E-Print Network (OSTI)

We derive the mass of the white dwarf in the eclipsing recurrent nova U Sco from the radial velocity semi-amplitudes of the primary and secondary stars. Our results give a high white dwarf mass of M_1 = 1.55 \\pm 0.24M_\\odot, consistent with the thermonuclear runaway model of recurrent nova outbursts. We confirm that U Sco is the best Type Ia supernova progenitor known, and predict that the time to explosion is within ~700,000 years.

T. D. Thoroughgood; V. S. Dhillon; S. P. Littlefair; T. R. Marsh; D. A. Smith

2001-09-28T23:59:59.000Z

380

Measuring dark energy spatial inhomogeneity with supernova data  

E-Print Network (OSTI)

The gravitational lensing distortion of distant sources by the large-scale distribution of matter in the Universe has been extensively studied. In contrast, very little is known about the effects due to the large-scale distribution of dark energy. We discuss the use of Type Ia supernovae as probes of the spatial inhomogeneity and anisotropy of dark energy. We show that a shallow, almost all-sky survey can limit rms dark energy fluctuations at the horizon scale down to a fractional energy density of ~10^-4

Asantha Cooray; Daniel E. Holz; Robert Caldwell

2008-12-01T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Neutrino-induced nucleosynthesis in core-collapse supernovae  

SciTech Connect

Almost all of the 3{center dot}10{sup 53} ergs liberated in a core collapse supernova is radiated as neutrinos by the cooling neutron star. The neutrinos can excite nuclei in the mantle of the star by their neutral and charged current reactions. The resulting spallation reactions are an important nuleosynthesis mechanism that may be responsible for the galactic abundances of {sup 7}Li, {sup 11}B, {sup 19}F, {sup 138}La, {sup 180}Ta, and number of other nuclei. 10 refs., 1 fig., 1 tab.

Hartmann, D.H. (Lawrence Livermore National Lab., CA (USA)); Haxton, W.C. (Washington Univ., Seattle, WA (USA). Dept. of Physics); Hoffman, R.D. (California Univ., Santa Cruz, CA (USA). Board of Studies in Astronomy and Astrophysics); Woosley, S.E. (Lawrence Livermore National Lab., CA (USA) California Univ., Santa Cruz, CA (USA). Board of Studies in Astronomy and Astrophysics)

1990-01-01T23:59:59.000Z

382

Tension in the Recent Type Ia Supernovae Datasets  

E-Print Network (OSTI)

In the present work, we investigate the tension in the recent Type Ia supernovae (SNIa) datasets Constitution and Union. We show that they are in tension not only with the observations of the cosmic microwave background (CMB) anisotropy and the baryon acoustic oscillations (BAO), but also with other SNIa datasets such as Davis and SNLS. Then, we find the main sources responsible for the tension. Further, we make this more robust by employing the method of random truncation. Based on the results of this work, we suggest two truncated versions of the Union and Constitution datasets, namely the UnionT and ConstitutionT SNIa samples, whose behaviors are more regular.

Hao Wei

2010-04-07T23:59:59.000Z

383

Thermonuclear Supernovae: Simulations of the Deflagration Stage and Their Implications  

E-Print Network (OSTI)

Large-scale three-dimensional numerical simulations of the deflagration stage of a thermonuclear supernova explosion show the formation and evolution of a highly convoluted turbulent flame in a gravitational field of an expanding carbon-oxygen white dwarf. The flame dynamics is dominated by the gravity-induced Rayleigh-Taylor instability that controls the burning rate. The thermonuclear deflagration releases enough energy to produce a healthy explosion. The turbulent flame, however, leaves large amounts of unburnt and partially burnt material near the star center, whereas observations imply these materials only in outer layers. This disagreement could be resolved if the deflagration triggers a detonation.

V. N. Gamezo; A. M. Khokhlov; E. S. Oran; A. Y. Chtchelkanova; R. O. Rosenberg

2002-12-03T23:59:59.000Z

384

Measuring dark energy spatial inhomogeneity with supernova data  

SciTech Connect

The gravitational lensing distortion of distant sources by the matter in the Universe has been extensively studied. In contrast, very little is known about the effects due to the large-scale distribution of dark energy. We discuss the use of Type Ia supernovae as probes of the spatial inhomogeneity and anisotropy of dark energy. We show that a shallow, almost all-sky survey can limit rms dark energy fluctuations at the horizon scale down to ? 10{sup ?3} of the energy density.

Cooray, Asantha [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Holz, Daniel E. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Caldwell, Robert, E-mail: acooray@uci.edu, E-mail: abc@lanl.gov, E-mail: robert.r.caldwell@dartmouth.edu [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)

2010-11-01T23:59:59.000Z

385

First detection of $^{56}$Co gamma-ray lines from type Ia supernova (SN2014J) with INTEGRAL  

E-Print Network (OSTI)

We report the first ever detection of $^{56}$Co lines at 847 and 1237 keV and a continuum in the 200-400 keV band from the Type Ia supernova SN2014J in M82 with INTEGRAL observatory. The data were taken between 50th and 100th day since the SN2014J outburst. The line fluxes suggest that $0.62\\pm0.13~M\\odot$ of radioactive $^{56}$Ni were synthesized during the explosion. Line broadening gives a characteristic ejecta expansion velocity $V_e\\sim 2100\\pm 500~{\\rm km~s^{-1}}$. The flux at lower energies (200-400 keV) flux is consistent with the three-photon positronium annihilation, Compton downscattering and absorption in the $\\sim~1.4~M\\odot$ ejecta composed from equal fractions of iron-group and intermediate-mass elements and a kinetic energy $E_k\\sim 1.4~10^{51}~{\\rm erg}$. All these parameters are in broad agreement with a "canonical" model of an explosion of a Chandrasekhar-mass White Dwarf (WD), providing an unambiguous proof of the nature of Type Ia supernovae as a thermonuclear explosion of a solar mass co...

Churazov, E; Isern, J; Knödlseder, J; Jean, P; Lebrun, F; Chugai, N; Grebenev, S; Bravo, E; Sazonov, S; Renaud, M

2014-01-01T23:59:59.000Z

386

The Spin Holonomy Group In General Relativity  

E-Print Network (OSTI)

It has recently been shown by Goldberg et al that the holonomy group of the chiral spin-connection is preserved under time evolution in vacuum general relativity. Here, the underlying reason for the time-independence of the holonomy group is traced to the self-duality of the curvature 2-form for an Einstein space. This observation reveals that the holonomy group is time-independent not only in vacuum, but also in the presence of a cosmological constant. It also shows that once matter is coupled to gravity, the "conservation of holonomy" is lost. When the fundamental group of space is non-trivial, the holonomy group need not be connected. For each homotopy class of loops, the holonomies comprise a coset of the full holonomy group modulo its connected component. These cosets are also time-independent. All possible holonomy groups that can arise are classified, and examples are given of connections with these holonomy groups. The classification of local and global solutions with given holonomy groups is discussed.

Ted Jacobson; Joseph D. Romano

1992-07-23T23:59:59.000Z

387

Cosmological evolution and hierarchical galaxy formation  

E-Print Network (OSTI)

We provide a new multi-waveband compilation of the data describing the cosmological evolution of quasars, and discuss a model that attributes the evolution to variation in the rate of merging between dark halos in a hierarchical universe. We present a new Press-Schechter calculation of the expected merger rate and show that this can reproduce the principal features of the evolution. We also show that the evolution in the star-formation history of the universe is well-described by this model.

L. Miller; W. J. Percival

1998-09-24T23:59:59.000Z

388

A New Approach to Cosmological Bulk Viscosity  

E-Print Network (OSTI)

We examine the cosmological consequences of an alternative to the standard expression for bulk viscosity, one which was proposed to avoid the propagation of superluminal signals without the necessity of extending the space of variables of the theory. The Friedmann equation is derived for this case, along with an expression for the effective pressure. We find solutions for the evolution of the density of a viscous component, which differs markedly from the case of conventional Eckart theory; our model evolves toward late-time phantom-like behavior with a future singularity. Entropy production is addressed, and some similarities and differences to approaches based on the Mueller-Israel-Stewart theory are discussed.

Disconzi, Marcelo M; Scherrer, Robert J

2014-01-01T23:59:59.000Z

389

Cosmological Evolution of Pilgrim Dark Energy  

E-Print Network (OSTI)

We study pilgrim dark energy model by taking IR cut-offs as particle and event horizons as well as conformal age of the universe. We derive evolution equations for fractional energy density and equation of state parameters for pilgrim dark energy. The phantom cosmic evolution is established in these scenarios which is well supported by the cosmological parameters such as deceleration parameter, statefinder parameters and phase space of $\\omega_\\vartheta$ and $\\omega'_\\vartheta$. We conclude that the consistent value of parameter $\\mu$ is $\\mu<0$ in accordance with the current Planck and WMAP$9$ results.

Sharif, M

2015-01-01T23:59:59.000Z

390

Scalar field collapse with negative cosmological constant  

E-Print Network (OSTI)

The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter, which determines the equation of state and decides the fate of the spacetime. Without fine tuning the value of this parameter the collapse ends in a generic formation of a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

R. Baier; Hiromichi Nishimura; S. A. Stricker

2014-10-13T23:59:59.000Z

391

Scalar field collapse with negative cosmological constant  

E-Print Network (OSTI)

The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter which determines the equation of state and decides the fate of the spacetime. Depending on the value of this parameter the collapse ends in a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

Baier, R; Stricker, S A

2014-01-01T23:59:59.000Z

392

Non-Gaussian signatures of tachyacoustic cosmology  

SciTech Connect

I investigate non-Gaussian signatures in the context of tachyacoustic cosmology, that is, a noninflationary model with superluminal speed of sound. I calculate the full non-Gaussian amplitude A, its size f{sub NL}, and corresponding shapes for a red-tilted spectrum of primordial scalar perturbations. Specifically, for cuscuton-like models I show that f{sub NL} ? O(1), and the shape of its non-Gaussian amplitude peaks for both equilateral and local configurations, the latter being dominant. These results, albeit similar, are quantitatively distinct from the corresponding ones obtained by Magueijo et al. in the context of superluminal bimetric models.

Bessada, Dennis, E-mail: dennis.bessada@unifesp.br [UNIFESP — Universidade Federal de São Paulo, Laboratório de Física Teórica e Computação Científica, Rua São Nicolau, 210, 09913-030, Diadema, SP (Brazil)

2012-09-01T23:59:59.000Z

393

Singularities of varying light speed cosmologies  

E-Print Network (OSTI)

We study the possible singularities of isotropic cosmological models that have a varying speed of light as well as a varying gravitational constant. The field equations typically reduce to two dimensional systems which are then analyzed both by dynamical systems techniques in phase space and by applying the method of asymptotic splittings. In the general case we find initially expanding closed models which recollapse to a future singularity and open universes that are eternally expanding towards the future. The precise nature of the singularities is also discussed.

John Miritzis; Spiros Cotsakis

2006-09-21T23:59:59.000Z

394

Cosmological Constant and the Speed of Light  

E-Print Network (OSTI)

By exploring the relationship between the propagation of electromagnetic waves in a gravitational field and the light propagation in a refractive medium, it is shown that, in the presence of a positive cosmological constant, the velocity of light will be smaller than its special relativity value. Then, restricting again to the domain of validity of geometrical optics, the same result is obtained in the context of wave optics. It is argued that this phenomenon and the anisotropy in the velocity of light in a gravitational field are produced by the same mechanism.

W. R. Esposito Miguel; J. G. Pereira

2000-06-28T23:59:59.000Z

395

The Atacama Cosmology Telescope Project: A Progress Report  

E-Print Network (OSTI)

The Atacama Cosmology Telescope is a project to map the microwave background radiation at arcminute angular resolution and high sensitivity in three frequency bands over substantial sky areas. Cosmological signals driving such an experiment are reviewed, and current progress in hardware construction is summarized. Complementary astronomical observations in other wavebands are also discussed.

Arthur Kosowsky; for the ACT Collaboration

2006-08-25T23:59:59.000Z

396

ON PROVING FUTURE STABILITY OF COSMOLOGICAL SOLUTIONS WITH ACCELERATED EXPANSION  

E-Print Network (OSTI)

ON PROVING FUTURE STABILITY OF COSMOLOGICAL SOLUTIONS WITH ACCELERATED EXPANSION HANS RINGSTR at an accelerated rate. As a consequence, it is of interest to prove that cosmological solutions to Ein- stein's equations with accelerated expansion are future stable. That is the topic of the present contribution

Ringström, Hans

397

Cosmology as Science: From Inflation to the Future  

ScienceCinema (OSTI)

Recent developments in cosmology bring to the forefront fundamental questions about our ability to falsify various fundamental assumptions about the universe.  I will discuss three issues that reflect different aspects of these questions:  (1) "Proving" Inflation (2) Anthropic "Explanations" (3) Cosmology of the far future.

Lawrence Krauss

2010-01-08T23:59:59.000Z

398

BUILDING COSMOLOGICAL MODELS VIA NONCOMMUTATIVE GEOMETRY MATILDE MARCOLLI  

E-Print Network (OSTI)

of theoretical high energy physics models that are capable of producing a range of predictions, bothBUILDING COSMOLOGICAL MODELS VIA NONCOMMUTATIVE GEOMETRY MATILDE MARCOLLI and cosmology to formulate testable predictions that can be confronted with the data. While model building

Marcolli, Matilde

399

Radioactive Decay Energy Deposition in Supernovae and the Exponential/Quasi-Exponential Behavior of Late-Time Supernova Light Curves  

E-Print Network (OSTI)

The radioactive decay energy (RDE) deposition in supernovae from the decay chain Ni56-Co56-Fe56 usually directly powers the UV/optical/IR (UVOIR) bolometric luminosity of supernovae in their quasi-steady state phase until very late times. The result for this phase is exponential/quasi-exponential UVOIR bolometric light curves and often exponential/quasi-exponential broad band light curves. A presentation is given of a simple, approximate, analytic treatment of RDE deposition that provides a straightforward understanding of the exponential/quasi-exponential behavior of the UVOIR bolometric luminosity and a partial understanding of the exponential/quasi-exponential behavior of the broad band light curves. The treatment reduces to using a normalized deposition function N_{Ni}^{*}(t) as an analysis tool. The one free parameter of N_{Ni}^{*}(t) is a fiducial time t_{0} which governs time-varying gamma-ray optical depth behavior of a supernova. The N_{Ni}^{*}(t) function is used to analyze the preliminary UVOIR bolometric light curve of SN Ic 1998bw (the possible cause of gamma-ray burst GRB980425). The SN 1998bw t_{0} is found to be 134.42 days and a prediction is made for the evolution of the SN 1998bw RDE deposition curve and quasi-steady state UVOIR bolometric light curve out to day 1000 after the explosion. A very crude estimate of the SN 1998bw mass obtained from the light curve analysis is 4.26 M_{Sun}. As further examples of the simple analytic treatment, the RDE deposition and luminosity evolution of SN Ia 1992A and SN II 1987A have also been examined. The simple analytic treatment of RDE deposition has actually existed for 20 years at least without, apparently, being discussed at length. The main value of this paper is the explicit, detailed, general presentation of this analytic treatment.

David J. Jeffery

1999-07-01T23:59:59.000Z

400

Cosmological evolution of a D-brane  

Science Journals Connector (OSTI)

We study the cosmological evolution of a single BPS D-brane coupled to gravity in the absence of potential. When such a D-brane moves in the bulk with nonvanishing velocity, it tends to slow down to zero velocity via mechanisms like gravitational wave leakage to the bulk, losing its kinetic energy to fuel the expansion of the Universe on the D-brane. If the initial velocity of the D-brane is high enough, the Universe on the D-brane undergoes a dustlike stage at early times and an acceleration stage at late times, realizing the original Chaplygin gas model. When the D-brane velocity is initially zero, the D-brane will always remain fixed at some position in the bulk, with the brane tension over the Plank mass squared as a cosmological constant. It is further shown that this kind of fixed brane universe can arise as defects from tachyon inflation on a non-Bogomol’nyi-Prasad-Sommerfeld D-brane with one dimension higher.

Huiquan Li

2011-03-01T23:59:59.000Z

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401

Planck 2015 results. XIII. Cosmological parameters  

E-Print Network (OSTI)

We present results based on full-mission Planck observations of temperature and polarization anisotropies of the CMB. These data are consistent with the six-parameter inflationary LCDM cosmology. From the Planck temperature and lensing data, for this cosmology we find a Hubble constant, H0= (67.8 +/- 0.9) km/s/Mpc, a matter density parameter Omega_m = 0.308 +/- 0.012 and a scalar spectral index with n_s = 0.968 +/- 0.006. (We quote 68% errors on measured parameters and 95% limits on other parameters.) Combined with Planck temperature and lensing data, Planck LFI polarization measurements lead to a reionization optical depth of tau = 0.066 +/- 0.016. Combining Planck with other astrophysical data we find N_ eff = 3.15 +/- 0.23 for the effective number of relativistic degrees of freedom and the sum of neutrino masses is constrained to Spatial curvature is found to be |Omega_K| < 0.005. For LCDM we find a limit on the tensor-to-scalar ratio of r <0.11 consistent with the B-mode constraints fr...

,

2015-01-01T23:59:59.000Z

402

Holographic Dark Energy with Cosmological Constant  

E-Print Network (OSTI)

Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the $\\Lambda$HDE model. By studying the $\\Lambda$HDE model theoretically, we find that the parameters $c$ and $\\Omega_{hde}$ are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the $\\Lambda$HDE model by using the recent observational data. We find the model yields $\\chi^2_{\\rm min}=426.27$ when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant $\\Lambda$CDM model (431.35). At 68.3\\% CL, we obtain $-0.07<\\Omega_{\\Lambda0}<0.68$ and correspondingly $0.04<\\Omega_{hde0}<0.79$, implying at present there is considerable degeneracy bet...

Hu, Yazhou; Li, Nan; Zhang, Zhenhui

2015-01-01T23:59:59.000Z

403

Dynamical dark energy or variable cosmological parameters?  

E-Print Network (OSTI)

One of the main aims in the next generation of precision cosmology experiments will be an accurate determination of the equation of state (EOS) for the dark energy (DE). If the latter is dynamical, the resulting barotropic index \\omega should exhibit a non-trivial evolution with the redshift. Usually this is interpreted as a sign that the mechanism responsible for the DE is related to some dynamical scalar field, and in some cases this field may behave non-canonically (phantom field). Present observations seem to favor an evolving DE with a potential phantom phase near our time. In the literature there is a plethora of dynamical models trying to describe this behavior. Here we show that the simplest option, namely a model with a variable cosmological term, \\Lambda=\\Lambda(t), leads in general to a non-trivial effective EOS, with index \\omega_e, which may naturally account for these data features. We prove that in this case there is always a ``crossing'' of the \\omega_e=-1 barrier near our time. We also show how this effect is modulated (or even completely controled) by a variable Newton's constant G=G(t).

Joan Sola; Hrvoje Stefancic

2005-12-21T23:59:59.000Z

404

Observational Cosmology With Semi-Relativistic Stars  

E-Print Network (OSTI)

Galaxy mergers lead to the formation of massive black hole binaries which can accelerate background stars close to the speed of light. We estimate the comoving density of ejected stars with a peculiar velocity in excess of $0.1c$ or $0.5c$ to be $\\sim 10^{10}$ and $10^5$ Gpc$^{-3}$ respectively, in the present-day Universe. Semi-relativistic giant stars will be detectable with forthcoming telescopes out to a distance of a few Mpc, where their proper motion, radial velocity, and age, can be spectroscopically measured. In difference from traditional cosmological messengers, such as photons, neutrinos, or cosmic-rays, these stars shine and so their trajectories need not be directed at the observer for them to be detected. Tracing the stars to their parent galaxies as a function of speed and age will provide a novel test of the equivalence principle and the standard cosmological parameters. Semi-relativistic stars could also flag black hole binaries as gravitational wave sources for the future eLISA observatory.

Loeb, Abraham

2014-01-01T23:59:59.000Z

405

KPD1930+2752 - a candidate Type Ia supernova progenitor  

E-Print Network (OSTI)

We present spectra of the pulsating sdB star KPD1930+2752 which confirm that this star is a binary. The radial velocities measured from the H-alpha and HeI6678 spectral lines vary sinusoidally with the same period (2h 17m) as the ellipsoidal variability seen by Billeres et al. (2000). The amplitude of the orbital motion (349.3+-2.7 km/s) combined with the canonical mass for sdB stars (0.5 solar masses) implies a total mass for the binary of 1.47+-0.01 solar masses The unseen companion star is almost certainly a white dwarf star. The binary will merge within about 200 million years due to gravitational wave radiation. The accretion of helium and other elements heavier than hydrogen onto the white dwarf which then exceeds the Chandrasekhar mass (1.4 solar masses) is a viable model for the cause of Type Ia supernovae. KPD1930+2752 is the first star to be discovered which is a good candidate for the progenitor of a Type Ia supernova of this type which will merge on an astrophysically interesting timescale.

P. F. L. Maxted; T. R. Marsh; R. C. North

2000-07-18T23:59:59.000Z

406

Double-detonation explosions as progenitors of type Iax supernovae  

E-Print Network (OSTI)

It has recently been proposed that one sub-class of type Ia supernovae (SNe Ia) is sufficiently both distinct and common to be classified separately from the bulk of SNe Ia, with a suggested class name of "type Iax supernovae" (SNe Iax), after SN 2002cx. We show that the population properties of this class can be understood if the events originate from helium double-detonation sub-Chandrasekhar mass explosions, in which a carbon--oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star. We have incorporated detailed binary evolution calculations for the progenitor systems into a binary population synthesis model to obtain birthrates and delay times for such events. The predicted Galactic event rate is $\\sim$$0.6-1.8\\times 10^{-3}\\,{\\rm yr}^{-1}$, in good agreement with the measured rates of SNe Iax. In addition, predicted delay times are $\\sim$70\\,Myr$-$710\\,Myr, consistent with the fact that SNe Iax have so far only been discovered in late-type galaxies. Based on the CO WD mass...

Wang, Bo; Han, Zhanwen

2013-01-01T23:59:59.000Z

407

The Detectability of Pair-Production Supernovae at z < 6  

E-Print Network (OSTI)

Nonrotating, zero metallicity stars with initial masses 140 production supernovae (PPSNe), in which an electron-positron pair-production instability triggers explosive nuclear burning. Interest in such stars has been rekindled by recent theoretical studies that suggest primordial molecular clouds preferentially form stars with these masses. Since metal enrichment is a local process, the resulting PPSNe could occur over a broad range of redshifts, in pockets of metal-free gas. Using the implicit hydrodynamics code KEPLER, we have calculated a set of PPSN light curves that addresses the theoretical uncertainties and allows us to assess observational strategies for finding these objects at intermediate redshifts. The peak luminosities of typical PPSNe are only slightly greater than those of Type Ia, but they remain bright much longer (~ 1 year) and have hydrogen lines. Ongoing supernova searches may soon be able to limit the contribution of these very massive stars to < 1% of the total star formation rate density out to z=2 which already provides useful constraints for theoretical models. The planned Joint Dark Energy Mission satellite will be able to extend these limits out to z=6.

Evan Scannapieco; Piero Madau; Stan Woosley; Alexander Heger; Andrea Ferrara

2005-07-08T23:59:59.000Z

408

Exploring the Outer Solar System with the ESSENCE Supernova Survey  

SciTech Connect

We report the discovery and orbital determination of 14 trans-Neptunian objects (TNOs) from the ESSENCE Supernova Survey difference imaging data set. Two additional objects discovered in a similar search of the SDSS-II Supernova Survey database were recovered in this effort. ESSENCE repeatedly observed fields far from the solar system ecliptic (-21{sup o} < {beta} < -5{sup o}), reaching limiting magnitudes per observation of I {approx} 23.1 and R {approx} 23.7. We examine several of the newly detected objects in detail, including 2003 UC{sub 414}, which orbits entirely between Uranus and Neptune and lies very close to a dynamical region that would make it stable for the lifetime of the solar system. 2003 SS{sub 422} and 2007 TA{sub 418} have high eccentricities and large perihelia, making them candidate members of an outer class of TNOs. We also report a new member of the 'extended' or 'detached' scattered disk, 2004 VN{sub 112}, and verify the stability of its orbit using numerical simulations. This object would have been visible to ESSENCE for only {approx}2% of its orbit, suggesting a vast number of similar objects across the sky. We emphasize that off-ecliptic surveys are optimal for uncovering the diversity of such objects, which in turn will constrain the history of gravitational influences that shaped our early solar system.

Becker, A.C.; /Washington U., Seattle, Astron. Dept.; Arraki, K.; /Washington U., Seattle, Astron. Dept.; Kaib, N.A.; /Washington U., Seattle, Astron. Dept.; Wood-Vasey, W.M.; /Harvard-Smithsonian Ctr. Astrophys.; Aguilera, C.; /Cerro-Tololo InterAmerican Obs.; Blackman, J.W.; /Australian Natl. U., Canberra; Blondin, S.; /Harvard-Smithsonian Ctr. Astrophys.; Challis, P.; /Harvard-Smithsonian Ctr. Astrophys.; Clocchiatti, A.; /Rio de Janeiro, Pont. U. Catol.; Covarrubias, R.; /Kyushu Sangyo U.; Damke, G.; /Cerro-Tololo InterAmerican Obs.; Davis, T.M.; /Bohr Inst. /Queensland U.; Filippenko, A.V.; /UC, Berkeley; Foley, R.J.; /UC, Berkeley; Garg, A.; /Harvard-Smithsonian Ctr. Astrophys. /Harvard U.; Garnavich, P.M.; /Notre Dame U.; Hicken, M.; /Harvard-Smithsonian Ctr. Astrophys. /Harvard U.; Jha, S.; /Harvard U. /SLAC; Kirshner, R.P.; /Harvard-Smithsonian Ctr. Astrophys.; Krisciunas, K.; /Notre Dame U. /Texas A-M; Leibundgut, B.; /Munich, Tech. U. /UC, Berkeley /NOAO, Tucson /Washington U., Seattle, Astron. Dept. /Fermilab /Harvard-Smithsonian Ctr. Astrophys. /Harvard U. /Chile U., Santiago /Ohio State U. /Cerro-Tololo InterAmerican Obs. /Harvard U. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Australian Natl. U., Canberra /Australian Natl. U., Canberra /Cerro-Tololo InterAmerican Obs. /Munich, Tech. U. /Harvard-Smithsonian Ctr. Astrophys. /Harvard U. /Cerro-Tololo InterAmerican Obs. /Texas A-M /Cerro-Tololo InterAmerican Obs.

2011-11-10T23:59:59.000Z

409

Large Late-time Asphericities in Three Type IIP Supernovae  

E-Print Network (OSTI)

Type II-plateau supernovae (SNe IIP) are the result of the explosions of red supergiants and are the most common subclass of core-collapse supernovae. Past observations have shown that the outer layers of the ejecta of SNe IIP are largely spherical, but the degree of asphericity increases toward the core. We present evidence for high degrees of asphericity in the inner cores of three recent SNe IIP (SNe 2006my, 2006ov, and 2007aa), as revealed by late-time optical spectropolarimetry. The three objects were all selected to have very low interstellar polarization (ISP), which minimizes the uncertainties in ISP removal and allows us to use the continuum polarization as a tracer of asphericity. The three objects have intrinsic continuum polarizations in the range of 0.83-1.56% in observations taken after the end of the photometric plateau, with the polarization dropping to almost zero at the wavelengths of strong emission lines. Our observations of SN 2007aa at earlier times, taken on the photometric plateau, sho...

Chornock, Ryan; Li, Weidong; Silverman, Jeffrey M; ;,

2009-01-01T23:59:59.000Z

410

Empirical Solar Abundance Scaling Laws of Supernova {gamma} Process Isotopes  

SciTech Connect

Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p- and s-nuclei with the same atomic number. They are evidence that the 27 p-nuclei are synthesized by the supernova {gamma}-process. The scalings lead to a novel concept of 'universality of {gamma}-process' that the s/p and p/p ratios of nuclei produced by individual {gamma}-processes are almost constant, respectively. We have calculated the ratios of materials produced by the {gamma}-process based on core-collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for individual {gamma}-processes independent of the conditions assumed. The results further suggest an extended universality that the s/p ratios in the {gamma}-process layers are not only constant but also centered on a specific value of 3. With this specific value and the scaling of the s/p ratios, we estimate that the ratios of the s-process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the s-nuclei of A>90 in the solar system.

Hayakawa, Takehito [Kansai Photon Science Institute, Japan Atomic Energy Agency, Kazoo, Kyoto 619-0215 (Japan); Iwamoto, Nobuyuki [Nuclear Data Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kajino, Toshitaka [National Astronomical Observatory, Osawa, Mitaka, Tokyo 181-8588 (Japan); Shizum, Toshiyuki [Kansai Photon Science Institute, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan); Umeda, Hideyuki; Nomoto, Ken'Ichi [Department of Astronomy, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2008-11-11T23:59:59.000Z

411

Destruction of Interstellar Dust in Evolving Supernova Remnant Shock Waves  

E-Print Network (OSTI)

Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities >~ 200 km/s for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction timescales are incre...

Slavin, Jonathan D; Jones, Anthony P

2015-01-01T23:59:59.000Z

412

Collective three-flavor oscillations of supernova neutrinos  

SciTech Connect

Neutrinos and antineutrinos emitted from a core collapse supernova interact among themselves, giving rise to collective flavor conversion effects that are significant near the neutrinosphere. We develop a formalism to analyze these collective effects in the complete three-flavor framework. It naturally generalizes the spin-precession analogy to three flavors and is capable of analytically describing phenomena like vacuum/Mikheyev-Smirnov-Wolfenstein (MSW) oscillations, synchronized oscillations, bipolar oscillations, and spectral split. Using the formalism, we demonstrate that the flavor conversions may be 'factorized' into two-flavor oscillations with hierarchical frequencies. We explicitly show how the three-flavor solution may be constructed by combining two-flavor solutions. For a typical supernova density profile, we identify an approximate separation of regions where distinctly different flavor conversion mechanisms operate, and demonstrate the interplay between collective and MSW effects. We pictorialize our results in terms of the 'e{sub 3}-e{sub 8} triangle' diagram, which is a tool that can be used to visualize three-neutrino flavor conversions in general, and offers insights into the analysis of the collective effects in particular.

Dasgupta, Basudeb; Dighe, Amol [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2008-06-01T23:59:59.000Z

413

ELECTRON-CAPTURE SUPERNOVAE AS ORIGIN OF {sup 48}Ca  

SciTech Connect

We report that electron-capture supernovae (ECSNe), arising from collapsing oxygen-neon-magnesium cores, are a possible source of {sup 48}Ca, whose origin has remained a longstanding puzzle. Our two-dimensional, self-consistent explosion model of an ECSN predicts ejection of neutron-rich matter with electron fractions Y{sub e} Almost-Equal-To 0.40-0.42 and relatively low entropies, s Almost-Equal-To 13-15 k{sub B} per nucleon (k{sub B} is the Boltzmann constant). Post-processing nucleosynthesis calculations result in appreciable production of {sup 48}Ca in such neutron-rich and low-entropy matter during the quasi-nuclear equilibrium and subsequent freezeout phases. The amount of ejected {sup 48}Ca can account for that in the solar inventory when we consider possible uncertainties in the entropies. ECSNe could thus be a site of {sup 48}Ca production in addition to a hypothetical, rare class of high-density Type Ia supernovae.

Wanajo, Shinya [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Janka, Hans-Thomas; Mueller, Bernhard, E-mail: shinya.wanajo@nao.ac.jp [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)

2013-04-20T23:59:59.000Z

414

General Relativistic Instability Supernova of a Supermassive Population III Star  

E-Print Network (OSTI)

The formation of supermassive Population III stars with masses $\\gtrsim$ 10,000 Msun in primeval galaxies in strong UV backgrounds at $z \\sim$ 15 may be the most viable pathway to the formation of supermassive black holes by $z \\sim$ 7. Most of these stars are expected to live for short times and then directly collapse to black holes, with little or no mass loss over their lives. But we have now discovered that non-rotating primordial stars with masses close to 55,000 Msun can instead die as highly energetic thermonuclear supernovae powered by explosive helium burning, releasing up to 10$ ^{55}$ erg, or about 10,000 times the energy of a Type Ia supernova. The explosion is triggered by the general relativistic contribution of thermal photons to gravity in the core of the star, which causes the core to contract and explosively burn. The energy release completely unbinds the star, leaving no compact remnant, and about half of the mass of the star is ejected into the early cosmos in the form of heavy elements. T...

Chen, Ke-Jung; Woosley, Stan; Almgren, Ann; Whalen, Daniel; Johnson, Jarrett

2014-01-01T23:59:59.000Z

415

Galaxy groups in the 2dFGRS: the group-finding algorithm and the 2PIGG catalogue  

E-Print Network (OSTI)

The construction of a catalogue of galaxy groups from the 2-degree Field Galaxy Redshift Survey (2dFGRS) is described. Groups are identified by means of a friends-of-friends percolation algorithm which has been thoroughly tested on mock versions of the 2dFGRS generated from cosmological N-body simulations. The tests suggest that the algorithm groups all galaxies that it should be grouping, with an additional 40% of interlopers. About 55% of the ~190000 galaxies considered are placed into groups containing at least two members of which ~29000 are found. Of these, ~7000 contain at least four galaxies, and these groups have a median redshift of 0.11 and a median velocity dispersion of 260km/s. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue represents the largest available homogeneous sample of galaxy groups. It is publicly available on the WWW.

V. R. Eke; C. M. Baugh; S. Cole; C. S. Frenk; P. Norberg; J. A. Peacock; I. K. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; B. A. Peterson; W. Sutherland; K. Taylor

2004-02-26T23:59:59.000Z

416

SSRL ETS Group  

NLE Websites -- All DOE Office Websites (Extended Search)

STANFORD SYNCHROTRON RADIATION LABORATORY Stanford Linear Accelerator Center Engineering & Technical Services Groups: Mechanical Services Group Mechanical Services Group Sharepoint...

417

Explosions of O-Ne-Mg Cores, the Crab Supernova, and Subluminous Type II-P Supernovae  

E-Print Network (OSTI)

We present results of simulations of stellar collapse and explosions in spherical symmetry for progenitor stars in the 8-10 solar mass range with an O-Ne-Mg core. The simulations were continued until nearly one second after core bounce and were performed with the Prometheus/Vertex code with a variable Eddington factor solver for the neutrino transport, including a state-of-the-art treatment of neutrino-matter interactions. Particular effort was made to implement nuclear burning and electron capture rates with sufficient accuracy to ensure a smooth continuation, without transients, from the progenitor evolution to core collapse. Using two different nuclear equations of state (EoSs), a soft version of the Lattimer & Swesty EoS and the significantly stiffer Wolff & Hillebrandt EoS, we found no prompt explosions, but instead delayed explosions, powered by neutrino heating and the neutrino-driven baryonic wind which sets in about 200 ms after bounce. The models eject little nickel ( 0.46, which suggests a chemical composition that is not in conflict with galactic abundances. No low-entropy matter with Ye << 0.5 is ejected. This excludes such explosions as sites of a low-entropy r-process. The low explosion energy and nucleosynthetic implications are compatible with the observed properties of the Crab supernova, and the small nickel mass supports the possibility that our models explain some subluminous Type II-P supernovae.

F. S. Kitaura; H. -Th. Janka; W. Hillebrandt

2005-12-02T23:59:59.000Z

418

Supernova SN1987A Bound on Neutrino Spectra for R-Process Nucleosynthesis  

E-Print Network (OSTI)

The neutrino driven wind during a core collapse supernova is an attractive site for r-process nucleosynthesis. The electron fraction $Y_e$ in the wind depends on observable neutrino energies and luminosities. The mean antineutrino energy is limited by supernova SN1987A data while lepton number conservation constrains the ratio of antineutrino to neutrino luminosities. If $Y_e$, in the wind, is to be suitable for rapid neutron capture nucleosynthesis, then the mean electron neutrino energy may be significantly lower then that predicted in present supernova simulations, or there may be new neutrino physics such as oscillations to sterile neutrinos.

C. J. Horowitz

2001-08-07T23:59:59.000Z

419

Cosmological Landscape From Nothing: Some Like It Hot  

E-Print Network (OSTI)

We suggest a novel picture of the quantum Universe -- its creation is described by the {\\em density matrix} defined by the Euclidean path integral. This yields an ensemble of universes -- a cosmological landscape -- in a mixed state which is shown to be dynamically more preferable than the pure quantum state of the Hartle-Hawking type. The latter is dynamically suppressed by the infinitely large positive action of its instanton, generated by the conformal anomaly of quantum fields within the cosmological bootstrap (the self-consistent back reaction of hot matter). This bootstrap suggests a solution to the problem of boundedness of the on-shell cosmological action and eliminates the infrared catastrophe of small cosmological constant in Euclidean quantum gravity. The cosmological landscape turns out to be limited to a bounded range of the cosmological constant $\\Lambda_{\\rm min}\\leq \\Lambda \\leq \\Lambda_{\\rm max}$. The domain $\\Lambdalandscape. The dependence of the cosmological constant range on particle phenomenology suggests a possible dynamical selection mechanism for the landscape of string vacua.

A. O. Barvinsky; A. Yu. Kamenshchik

2006-09-13T23:59:59.000Z

420

Quaternionic and Poisson-Lie structures in three-dimensional gravity: The cosmological constant as deformation parameter  

SciTech Connect

Each of the local isometry groups arising in three-dimensional (3d) gravity can be viewed as a group of unit (split) quaternions over a ring which depends on the cosmological constant. In this paper we explain and prove this statement and use it as a unifying framework for studying Poisson structures associated with the local isometry groups. We show that, in all cases except for the case of Euclidean signature with positive cosmological constant, the local isometry groups are equipped with the Poisson-Lie structure of a classical double. We calculate the dressing action of the factor groups on each other and find, among others, a simple and unified description of the symplectic leaves of SU(2) and SL(2,R). We also compute the Poisson structure on the dual Poisson-Lie groups of the local isometry groups and on their Heisenberg doubles; together, they determine the Poisson structure of the phase space of 3d gravity in the so-called combinatorial description.

Meusburger, C. [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Schroers, B. J. [Department of Mathematics and Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2008-08-15T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Genesis of Dark Energy: Dark Energy as Consequence of Release and Two-stage Tracking Cosmological Nuclear Energy  

E-Print Network (OSTI)

Recent observations on Type-Ia supernovae and low density ($\\Omega_{m} = 0.3$) measurement of matter including dark matter suggest that the present-day universe consists mainly of repulsive-gravity type `exotic matter' with negative-pressure often said `dark energy' ($\\Omega_{x} = 0.7$). But the nature of dark energy is mysterious and its puzzling questions, such as why, how, where and when about the dark energy, are intriguing. In the present paper the authors attempt to answer these questions while making an effort to reveal the genesis of dark energy and suggest that `the cosmological nuclear binding energy liberated during primordial nucleo-synthesis remains trapped for a long time and then is released free which manifests itself as dark energy in the universe'. It is also explained why for dark energy the parameter $w = - {2/3}$. Noting that $ w = 1$ for stiff matter and $w = {1/3}$ for radiation; $w = - {2/3}$ is for dark energy because $"-1"$ is due to `deficiency of stiff-nuclear-matter' and that this binding energy is ultimately released as `radiation' contributing $"+ {1/3}"$, making $w = -1 + {1/3} = - {2/3}$. When dark energy is released free at $Z = 80$, $w = -{2/3}$. But as on present day at $Z = 0$ when radiation strength has diminished to $\\delta \\to 0$, $w = -1 + \\delta{1/3} = - 1$. This, thus almost solves the dark-energy mystery of negative pressure and repulsive-gravity. The proposed theory makes several estimates /predictions which agree reasonably well with the astrophysical constraints and observations. Though there are many candidate-theories, the proposed model of this paper presents an entirely new approach (cosmological nuclear energy) as a possible candidate for dark energy.

R. C. Gupta; Anirudh Pradhan

2009-07-28T23:59:59.000Z

422

The Cosmology of Composite Inelastic Dark Matter  

SciTech Connect

Composite dark matter is a natural setting for implementing inelastic dark matter - the O(100 keV) mass splitting arises from spin-spin interactions of constituent fermions. In models where the constituents are charged under an axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark matter scatters inelastically off Standard Model nuclei and can explain the DAMA/LIBRA annual modulation signal. This article describes the early Universe cosmology of a minimal implementation of a composite inelastic dark matter model where the dark matter is a meson composed of a light and a heavy quark. The synthesis of the constituent quarks into dark hadrons results in several qualitatively different configurations of the resulting dark matter composition depending on the relative mass scales in the system.

Spier Moreira Alves, Daniele; Behbahani, Siavosh R.; /SLAC /Stanford U., ITP; Schuster, Philip; Wacker, Jay G.; /SLAC

2011-08-19T23:59:59.000Z

423

Cosmological origin of anomalous radio background  

SciTech Connect

The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate several potential mechanisms and show that injection of relativistic electrons through late decays of a metastable particle can give rise to the observed excess radio spectrum through synchrotron emission. However, constraints from the cosmic microwave background (CMB) anisotropy, on injection of charged particles and on the primordial magnetic field, present a challenge. The simplest scenario is with a ?>9 GeV particle decaying into e{sup +}e{sup ?} at a redshift of z ? 5, in a magnetic field of ? 5?G, which exceeds the CMB B-field constraints, unless the field was generated after decoupling. Decays into exotic millicharged particles can alleviate this tension, if they emit synchroton radiation in conjunction with a sufficiently large background magnetic field of a dark U(1)' gauge field.

Cline, James M. [Department of Physics, McGill University, 3600 Rue University, Montréal, Québec, H3A 2T8 Canada (Canada); Vincent, Aaron C., E-mail: jcline@physics.mcgill.ca, E-mail: vincent@ific.uv.es [Instituto de Física Corpuscular, Universitat de València - CSIC, 46071, Valencia (Spain)

2013-02-01T23:59:59.000Z

424

Large extra dimensions and cosmological problems  

Science Journals Connector (OSTI)

We consider a variant of the brane-world model in which the universe is the direct product of a Friedmann-Robertson-Walker (FRW) space and a compact hyperbolic manifold of dimension d>~2. Cosmology in this space is particularly interesting. The dynamical evolution of the space-time leads to the injection of a large entropy into the observable (FRW) universe. The exponential dependence of surface area on distance in hyperbolic geometry makes this initial entropy very large, even if the CHM has a relatively small diameter (in fundamental units). The very large statistical averaging inherent in the collapse of the initial entropy onto the brane acts to smooth out initial inhomogeneities. This smoothing is then sufficient to account for the current homogeneity of the universe. With only mild fine-tuning, the current flatness of the universe can also then be understood. Finally, recent brane-world approaches to the hierarchy problem can be readily realized within this framework.

Glenn D. Starkman; Dejan Stojkovic; Mark Trodden

2001-04-24T23:59:59.000Z

425

Quantum Rainbow Cosmological Model With Perfect Fluid  

E-Print Network (OSTI)

Isotropic quantum cosmological perfect fluid model is studied in the formalism of Rainbow gravity. It is found that the only surviving matter degree of freedom played the role of cosmic time. With the suitable choice of the Rainbow functions it is possible to find the wave packet naturally from the superposition of the wave functions of the Schr$\\ddot{o}$dinger-Wheeler-deWitt equation. The many-worlds interpretation of quantum mechanics is applied to investigate the behavior of the scale factor and the behavior is found to depend on the operator ordering. It is shown that the model in the Rainbow framework may avoid singularity yielding a bouncing non-singular universe.

Majumder, Barun

2013-01-01T23:59:59.000Z

426

Five-Dimensional Cosmological Scaling Solution  

E-Print Network (OSTI)

A five-dimensional Ricci-flat cosmological solution is studied by assuming that the induced 4D matter contains two components: the usual fluid for dark matter as well as baryons and a scalar field with an exponential potential for dark energy. With use of the phase-plane analysis it is shown that there exist two late-time attractors one of which corresponds to a universe dominated by the scalar field alone and the other is a scaling solution in which the energy density of the scalar field remains proportional to that of the dark matter. It is furthermore shown that for this 5D scaling solution the universe expands with the same rate as in the 4D FRW models and not relies on which 4D hypersurface the universe is located in the 5D manifold.

Baorong Chang; Hongya Liu; Huanying Liu; Lixin Xu

2005-05-08T23:59:59.000Z

427

Two cosmological solutions of Regge calculus  

Science Journals Connector (OSTI)

Two cosmological solutions of Regge calculus are presented which correspond to the flat Friedmann-Robertson-Walker and the Kasner solutions of general relativity. By taking advantage of the symmetries that are present, I am able to show explicitly that a limit of Regge calculus does yield Einstein's equations for these cases. The method of averaging these equations when taking limits is important, especially for the Kasner model. I display the leading error term that arises from keeping the Regge equations in discrete form rather than using their continuum limit. In particular, this work shows that for the "Reggeized" Friedmann model the minimum volume is a velocitydominated singularity as in the continuum Friedmann model. However, unlike the latter, the Regge version has a nonzero minimum volume.

Steve M. Lewis

1982-01-15T23:59:59.000Z

428

Replication Regulates Volume Weighting in Quantum Cosmology  

E-Print Network (OSTI)

Probabilities for observations in cosmology are conditioned both on the universe's quantum state and on local data specifying the observational situation. We show the quantum state defines a measure for prediction through such conditional probabilities that is well behaved for spatially large or infinite universes when the probabilities that our data is replicated are taken into account. In histories where our data are rare volume weighting connects top-down probabilities conditioned on both the data and the quantum state to the bottom-up probabilities conditioned on the quantum state alone. We apply these principles to a calculation of the number of inflationary e-folds in a homogeneous, isotropic minisuperspace model with a single scalar field moving in a quadratic potential. We find that volume weighting is justified and the top-down probabilities favor a large number of e-folds.

James Hartle; Thomas Hertog

2009-05-24T23:59:59.000Z

429

Eternal Higgs inflation and cosmological constant problem  

E-Print Network (OSTI)

We investigate the Higgs potential beyond the Planck scale in the superstring theory, under the assumption that the supersymmetry is broken at the string scale. We identify the Higgs field as a massless state of the string, which is indicated by the fact that the bare Higgs mass can be zero around the string scale. We find that, in the large field region, the Higgs potential is connected to a runaway vacuum with vanishing energy, which corresponds to opening up an extra dimension. We verify that such universal behavior indeed follows from the toroidal compactification of the non-supersymmetric $SO(16)\\times SO(16)$ heterotic string theory. We show that this behavior fits in the picture that the Higgs field is the source of the eternal inflation. The observed small value of the cosmological constant of our universe may be understood as the degeneracy with this runaway vacuum, which has vanishing energy, as is suggested by the multiple point criticality principle.

Hamada, Yuta; Oda, Kin-ya

2015-01-01T23:59:59.000Z

430

Low energy branes, effective theory, and cosmology  

Science Journals Connector (OSTI)

The low energy regime of cosmological BPS-brane configurations with a bulk scalar field is studied. We construct a systematic method to obtain five-dimensional solutions to the full system of equations governing the geometry and dynamics of the bulk. This is done for an arbitrary bulk scalar field potential and taking into account the presence of matter on the branes. The method, valid in the low energy regime, is a linear expansion of the system about the static vacuum solution. Additionally, we develop a four-dimensional effective theory describing the evolution of the system. At the lowest order in the expansion, the effective theory is a biscalar tensor theory of gravity. One of the main features of this theory is that the scalar fields can be stabilized naturally without the introduction of additional mechanisms, allowing satisfactory agreement between the model and current observational constraints. The special case of the Randall-Sundrum model is discussed.

Gonzalo A. Palma and Anne-Christine Davis

2004-09-15T23:59:59.000Z

431

Defrosting in an emergent Galileon cosmology  

Science Journals Connector (OSTI)

We study the transition from an emergent Galileon condensate phase of the early universe to a later expanding radiation phase. This defrosting or preheating transition is a consequence of the excitation of matter fluctuations by the coherent Galileon condensate, in analogy to how preheating in inflationary cosmology occurs via the excitation of matter fluctuations through coupling of matter with the coherent inflaton condensate. We show that the minimal coupling of matter (modeled as a massless scalar field) to the Galileon field introduced by Creminelli, Nicolis, and Trincherini in order to generate a scale-invariant spectrum of matter fluctuations is sufficient to lead to efficient defrosting, provided that the effects of the nonvanishing expansion rate of the universe are taken into account. If we neglect the effects of expansion, an additional coupling of matter to the Galileon condensate is required. We study the efficiency of the defrosting mechanism in both cases.

Laurence Perreault Levasseur; Robert Brandenberger; Anne-Christine Davis

2011-11-09T23:59:59.000Z

432

Probing Quintessence Potential with Future Cosmological Surveys  

E-Print Network (OSTI)

Quintessence, a scalar field model, has been proposed to account for the acceleration of the Universe at present. We discuss how accurately quintessence models are discriminated by future cosmological surveys, which include experiments of CMB, galaxy clustering, weak lensing, and the type Ia SNe surveys, by making use of the conventional parameterized dark energy models. We can see clear differences between the thawing and the freezing quintessence models at more than $1\\sigma$ ($2\\sigma$) confidence level as long as the present equation of state for quintessence is away from $-1$ as $w_X \\gtrsim -0.95 (-0.90)$. However, it is found to be difficult to probe the effective mass squared for the potential in thawing models, whose signs are different between the quadratic and the cosine-type potentials. This fact may require us to invent a new estimator to distinguish quintessence models beyond the thawing and the freezing ones.

Takeuchi, Yoshitaka; Takahashi, Tomo; Yamaguchi, Masahide

2014-01-01T23:59:59.000Z

433

Probing Quintessence Potential with Future Cosmological Surveys  

E-Print Network (OSTI)

Quintessence, a scalar field model, has been proposed to account for the acceleration of the Universe at present. We discuss how accurately quintessence models are discriminated by future cosmological surveys, which include experiments of CMB, galaxy clustering, weak lensing, and the type Ia SNe surveys, by making use of the conventional parameterized dark energy models. We can see clear differences between the thawing and the freezing quintessence models at more than $1\\sigma$ ($2\\sigma$) confidence level as long as the present equation of state for quintessence is away from $-1$ as $w_X \\gtrsim -0.95 (-0.90)$. However, it is found to be difficult to probe the effective mass squared for the potential in thawing models, whose signs are different between the quadratic and the cosine-type potentials. This fact may require us to invent a new estimator to distinguish quintessence models beyond the thawing and the freezing ones.

Yoshitaka Takeuchi; Kiyotomo Ichiki; Tomo Takahashi; Masahide Yamaguchi

2014-01-27T23:59:59.000Z

434

Antisymmetric field in string gas cosmology  

E-Print Network (OSTI)

We study how the introduction of a 2-form field flux modify the dynamics of a T-duality invariant string gas cosmology model of Greene, Kabat and Marnerides. It induces a repulsive potential term in the effective action for the scale factor of the spacial dimensions. Without the 2-form field flux, the universe fails to expand when the pressure due to string modes vanishes. With the presence of a homogeneous 2-form field flux, it propels 3 spacial dimensions to grow into a macroscopic 4 dimensional space-time. We find that it triggers an expansion of a universe away from the oscillating phase around the self-dual radius. We also investigate the effects of a constant 2-form field. We can obtain an expanding 4 dimensional space-time by tuning it at the critical value.

Igmar C. Rosas-López; Yoshihisa Kitazawa

2010-07-09T23:59:59.000Z

435

String spectra near some null cosmological singularities  

E-Print Network (OSTI)

We construct cosmological spacetimes with null Kasner-like singularities as purely gravitational solutions with no other background fields turned on. These can be recast as anisotropic plane-wave spacetimes by coordinate transformations. We analyse string quantization to find the spectrum of string modes in these backgrounds. The classical string modes can be solved for exactly in these time-dependent backgrounds, which enables a detailed study of the near singularity string spectrum, (time-dependent) oscillator masses and wavefunctions. We find that for low lying string modes(finite oscillation number), the classical near-singularity string mode functions are non-divergent for various families of singularities. Furthermore, for any infinitesimal regularization of the vicinity of the singularity, we find a tower of string modes of ultra-high oscillation number which propagate essentially freely in the background. The resulting picture suggests that string interactions are non-negligible near the singularity.

Kallingalthodi Madhu; K. Narayan

2009-04-29T23:59:59.000Z

436

Measuring the speed of cosmological gravitational waves  

E-Print Network (OSTI)

In general relativity gravitational waves propagate at the speed of light, however in alternative theories of gravity that might not be the case. We study the effects of a modified speed of gravity, $c_T^2$, on the B-modes of the Cosmic Microwave Background (CMB) anisotropy in polarisation. We find that a departure from the light speed value would leave a characteristic imprint on the BB spectrum part induced by tensors, manifesting as a shift in the angular scale of its peaks. We derive constraints by using the available {\\it Planck} and BICEP2 datasets showing how $c_T^2$ can be measured, albeit obtaining weak constraints due to the overall poor accuracy of the current BB power spectrum measurements. The present constraint corresponds to $c_T^2 = 1.30 \\pm 0.79$ and $c_T^2measurements, largely due to the absence of degeneracy with other cosmological parameters.

Marco Raveri; Carlo Baccigalupi; Alessandra Silvestri; Shuang-Yong Zhou

2014-05-30T23:59:59.000Z

437

Failed-detonation Supernovae: Subluminous Low-velocity Ia Supernovae and their Kicked Remnant White Dwarfs with Iron-rich Cores  

Science Journals Connector (OSTI)

Type Ia supernovae (SNe Ia) originate from the thermonuclear explosions of carbon-oxygen (C-O) white dwarfs (WDs). The single-degenerate scenario is a well-explored model of SNe Ia where unstable thermonuclear burning initiates in an accreting, Chandrasekhar-mass WD and forms an advancing flame. By several proposed physical processes, the rising, burning material triggers a detonation, which subsequently consumes and unbinds the WD. However, if a detonation is not triggered and the deflagration is too weak to unbind the star, a completely different scenario unfolds. We explore the failure of the gravitationally confined detonation mechanism of SNe Ia, and demonstrate through two-dimensional and three-dimensional simulations the properties of failed-detonation SNe. We show that failed-detonation SNe expel a few 0.1 M ? of burned and partially burned material and that a fraction of the material falls back onto the WD, polluting the remnant WD with intermediate-mass and iron-group elements that likely segregate to the core forming a WD whose core is iron rich. The remaining material is asymmetrically ejected at velocities comparable to the escape velocity from the WD, and in response, the WD is kicked to velocities of a few hundred km s–1. These kicks may unbind the binary and eject a runaway/hypervelocity WD. Although the energy and ejected mass of the failed-detonation SN are a fraction of typical thermonuclear SNe, they are likely to appear as subluminous low-velocity SNe Ia. Such failed detonations might therefore explain or are related to the observed branch of peculiar SNe Ia, such as the family of low-velocity subluminous SNe (SN 2002cx/SN 2008ha-like SNe).

George C. Jordan, IV; Hagai B. Perets; Robert T. Fisher; Daniel R. van Rossum

2012-01-01T23:59:59.000Z

438

FAILED-DETONATION SUPERNOVAE: SUBLUMINOUS LOW-VELOCITY Ia SUPERNOVAE AND THEIR KICKED REMNANT WHITE DWARFS WITH IRON-RICH CORES  

SciTech Connect

Type Ia supernovae (SNe Ia) originate from the thermonuclear explosions of carbon-oxygen (C-O) white dwarfs (WDs). The single-degenerate scenario is a well-explored model of SNe Ia where unstable thermonuclear burning initiates in an accreting, Chandrasekhar-mass WD and forms an advancing flame. By several proposed physical processes, the rising, burning material triggers a detonation, which subsequently consumes and unbinds the WD. However, if a detonation is not triggered and the deflagration is too weak to unbind the star, a completely different scenario unfolds. We explore the failure of the gravitationally confined detonation mechanism of SNe Ia, and demonstrate through two-dimensional and three-dimensional simulations the properties of failed-detonation SNe. We show that failed-detonation SNe expel a few 0.1 M{sub Sun} of burned and partially burned material and that a fraction of the material falls back onto the WD, polluting the remnant WD with intermediate-mass and iron-group elements that likely segregate to the core forming a WD whose core is iron rich. The remaining material is asymmetrically ejected at velocities comparable to the escape velocity from the WD, and in response, the WD is kicked to velocities of a few hundred km s{sup -1}. These kicks may unbind the binary and eject a runaway/hypervelocity WD. Although the energy and ejected mass of the failed-detonation SN are a fraction of typical thermonuclear SNe, they are likely to appear as subluminous low-velocity SNe Ia. Such failed detonations might therefore explain or are related to the observed branch of peculiar SNe Ia, such as the family of low-velocity subluminous SNe (SN 2002cx/SN 2008ha-like SNe).

Jordan, George C. IV; Van Rossum, Daniel R. [Center for Astrophysical Thermonuclear Flashes, University of Chicago, Chicago, IL 60637 (United States); Perets, Hagai B. [Physics Department, Technion, Israel Institute of Technology, Haifa 32000 (Israel); Fisher, Robert T. [Department of Physics, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02740 (United States)

2012-12-20T23:59:59.000Z

439

Quintessence and phantom cosmology with nonminimal derivative coupling  

SciTech Connect

We investigate cosmological scenarios with a nonminimal derivative coupling between the scalar field and the curvature, examining both the quintessence and the phantom cases in zero and constant potentials. In general, we find that the universe transits from one de Sitter solution to another, determined by the coupling parameter. Furthermore, according to the parameter choices and without the need for matter, we can obtain a big bang, an expanding universe with no beginning, a cosmological turnaround, an eternally contracting universe, a big crunch, a big rip avoidance, and a cosmological bounce. This variety of behaviors reveals the capabilities of the present scenario.

Saridakis, Emmanuel N. [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Sushkov, Sergey V. [Department of General Relativity and Gravitation, Kazan State University, Kremlevskaya Street 18, Kazan 420008 (Russian Federation); Department of Mathematics, Tatar State University of Humanities and Education, Tatarstan Street 2, Kazan 420021 (Russian Federation)

2010-04-15T23:59:59.000Z

440

Open Inflation, the Four Form and the Cosmological Constant  

E-Print Network (OSTI)

Fundamental theories of quantum gravity such as supergravity include a four form field strength which contributes to the cosmological constant. The inclusion of such a field into our theory of open inflation (hep-th/9802030) allows an anthropic solution to the cosmological constant problem in which the cosmological constant gives a small but non-negligible contribution to the density of today's universe. We include a discussion of the role of the singularity in our solution and a reply to Vilenkin's recent criticism (hep-th/9803084).

Neil Turok; S. W. Hawking

1998-03-19T23:59:59.000Z

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Non minimally coupled condensate cosmologies: a phase space analysis  

E-Print Network (OSTI)

We present an analysis of the phase space of cosmological models based on a non minimal coupling between the geometry and a fermionic condensate. We obtain that the strong constraint coming from the Dirac equations allows a detailed design of the cosmology of these models and at the same time guarantees an evolution towards a state indistinguishable from General Relativistic cosmological models. In this light, we show how the use of some specific potentials is able to reproduce naturally two de Sitter phases separated by a power law expansion which could be an interesting model for the unification of an inflationary phase and a dark energy era.

Sante Carloni; Stefano Vignolo; Roberto Cianci

2014-03-11T23:59:59.000Z

442

A Modification of the Standard Cosmological Metric  

E-Print Network (OSTI)

In this article we firstly present an explicit dynamical equation satisfying the general principle of relativity under the framework of classical mechanics. In light of this fact, the necessity of Einstein's equivalence principle for the gravity being geometrized should be reexamined. Especially, Einstein's (strong) equivalence principle claims that the inertial force is equivalent to the gravitational force. But in fact the new dynamical equation proves that the essence of the inertial force is the real force exerted on the reference object, which can actually be all kinds of forces such as the gravitational force, electromagnetic force and so on. Therefore, in this context we only retain the numerical equality between the inertial mass and gravitational mass and abandon Einstein's (strong) equivalence principle. Consequently, the candidate for the standard clock should be corrected into the mathematical clock which duplicates the real clock equipped by the observer himself. Then a new physical picture for how to convert the gravitational force into a geometric description on spacetime is presented. On the other hand, we point out that all cosmological observations are made by the observer at present on the earth, instead of any other observers including the comoving observers in the earlier unverse. On this basis, we introduce an extra factor $b(t)$ in $FRW$ cosmological metric to depict the gravitational time dilation effect since the local proper clock may run in a faster and faster rate with the expanding of the universe. In this way, we may obtain a positive value of $\\rho+3p$ and avoid the introduction of dark energy in the current universe.

ChiYi Chen

2004-11-04T23:59:59.000Z

443

Cosmological Constraints on the Higgs Boson Mass  

Science Journals Connector (OSTI)

For a robust interpretation of upcoming observations from PLANCK and Large Hadron Collider experiments it is imperative to understand how the inflationary dynamics of a non-minimally coupled Higgs scalar field with gravity may affect the determination of the inflationary observables. We make a full proper analysis of the Wilkinson Microwave Anisotropy Probe, Type Ia supernova distance-redshift relation, and the baryon acoustic oscillations data sets in a context of the non-minimally coupled Higgs inflation field with gravity. For the central value of the top quark pole mass mT = 171.3 GeV, the fit of the inflation model with a non-minimally coupled Higgs scalar field leads to a Higgs boson mass in the range 143.7 GeV ? mH ? 167 GeV (95% CL). We show that the inflation driven by a non-minimally coupled scalar field to the Einstein gravity leads to significant constraints on the scalar spectral index nS and the tensor-to-scalar ratio R when compared with a tensor with similar constraints to form the standard inflation with a minimally coupled scalar field. We also show that an accurate reconstruction of the Higgs potential in terms of inflationary observables requires an improved accuracy of other parameters of the standard model of particle physics such as the top quark mass and the effective QCD coupling constant.

L. A. Popa; A. Caramete

2010-01-01T23:59:59.000Z

444

Microsystems and Nanotechnology Group  

E-Print Network (OSTI)

Microsystems and Nanotechnology Group Microsystems and Nanotechnology Group 1 Microsystems and Nanotechnology Research Group The University of British Columbia Microsystems and Nanotechnology Research Group The University of British Columbia Annual Report ­ 2008 Microsystems and Nanotechnology Research Group 1 About

Pulfrey, David L.

445

Microsystems and Nanotechnology Group  

E-Print Network (OSTI)

Microsystems and Nanotechnology Group Microsystems and Nanotechnology Group 1 Microsystems and Nanotechnology Research Group The University of British Columbia Microsystems and Nanotechnology Research Group The University of British Columbia Annual Report ­ 2007 Microsystems and Nanotechnology Research Group 1 About

Pulfrey, David L.

446

CIRCUMSTELLAR ABSORPTION IN DOUBLE DETONATION TYPE Ia SUPERNOVAE  

SciTech Connect

Upon formation, degenerate He core white dwarfs are surrounded by a radiative H-rich layer primarily supported by ideal gas pressure. In this Letter, we examine the effect of this H-rich layer on mass transfer in He+C/O double white dwarf binaries that will eventually merge and possibly yield a Type Ia supernova (SN Ia) in the double detonation scenario. Because its thermal profile and equation of state differ from the underlying He core, the H-rich layer is transferred stably onto the C/O white dwarf prior to the He core's tidal disruption. We find that this material is ejected from the binary system and sweeps up the surrounding interstellar medium hundreds to thousands of years before the SN Ia. The close match between the resulting circumstellar medium profiles and values inferred from recent observations of circumstellar absorption in SNe Ia gives further credence to the resurgent double detonation scenario.

Shen, Ken J. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Guillochon, James [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Foley, Ryan J., E-mail: kenshen@astro.berkeley.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-06-20T23:59:59.000Z

447

Type Ia Supernova: Burning and Detonation in the Distributed Regime  

E-Print Network (OSTI)

A simple, semi-analytic representation is developed for nuclear burning in Type Ia supernovae in the special case where turbulent eddies completely disrupt the flame. The speed and width of the ``distributed'' flame front are derived. For the conditions considered, the burning front can be considered as a turbulent flame brush composed of corrugated sheets of well-mixed flames. These flames are assumed to have a quasi-steady-state structure similar to the laminar flame structure, but controlled by turbulent diffusion. Detonations cannot appear in the system as long as distributed flames are still quasi-steady-state, but this condition is violated when the distributed flame width becomes comparable to the size of largest turbulent eddies. When this happens, a transition to detonation may occur. For current best estimates of the turbulent energy, the most likely density for the transition to detonation is in the range 0.5 - 1.5 x 10^7 g cm^{-3}.

S. E. Woosley

2007-09-26T23:59:59.000Z

448

Intermediate-band Photometry of Type Ia Supernovae  

E-Print Network (OSTI)

We present optical light curves of five Type Ia supernovae (2002er, 2002fk, 2003cg, 2003du, 2003fk). The photometric observations were performed in a set of intermediate-band filters. SNe 2002er, 2003du appear to be normal SN Ia events with similar light curve shapes, while SN 2003kf shows the behavior of a brighter SN Ia with slower decline rate after maximum. The light curves of SN 2003cg is unusual; they show a fast rise and dramatic decline near maximum and do not display secondary peak at longer wavelengths during 15-30 days after maximum light. This suggests that SN 2003cg is likely to be an intrinsically subluminous, 91bg-like SN Ia. Exploration of SN Ia feature lines through intermediate-band photometry is briefly discussed.

Wang, X; Zhang, T; Li, Z; Wang, Xiaofeng; Zhou, Xu; Zhang, Tianmeng; Li, Zongwei

2004-01-01T23:59:59.000Z

449

No Collective Neutrino Flavor Conversions during the Supernova Accretion Phase  

SciTech Connect

We perform a dedicated study of the supernova (SN) neutrino flavor evolution during the accretion phase, using results from recent neutrino radiation hydrodynamics simulations. In contrast to what was expected in the presence of only neutrino-neutrino interactions, we find that the multiangle effects associated with the dense ordinary matter suppress collective oscillations. The matter suppression implies that neutrino oscillations will start outside the neutrino decoupling region and therefore will have a negligible impact on the neutrino heating and the explosion dynamics. Furthermore, the possible detection of the next galactic SN neutrino signal from the accretion phase, based on the usual Mikheyev-Smirnov-Wolfenstein effect in the SN mantle and Earth matter effects, can reveal the neutrino mass hierarchy in the case that the mixing angle {theta}{sub 13} is not very small.

Chakraborty, Sovan; Mirizzi, Alessandro; Saviano, Ninetta; Tomas, Ricard [II Institut fuer Theoretische Physik, Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Fischer, Tobias [GSI, Helmholtzzentrum fuer Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt (Germany); Technische Universitaet Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany)

2011-10-07T23:59:59.000Z

450

Influence of light nuclei on neutrino-driven supernova outflows  

E-Print Network (OSTI)

We study the composition of the outer layers of a protoneutron star and show that light nuclei are present in substantial amounts. The composition is dominated by nucleons, deuterons, tritons and alpha particles; 3He is present in smaller amounts. This composition can be studied in laboratory experiments with new neutron-rich radioactive beams that can reproduce similar densities and temperatures. After including the corresponding neutrino interactions, we demonstrate that light nuclei have a small impact on the average energy of the emitted electron neutrinos, but are significant for the average energy of antineutrinos. During the early post-explosion phase, the average energy of electron antineutrinos is slightly increased, while at later times during the protoneutron star cooling it is reduced by about 1 MeV. The consequences of these changes for nucleosynthesis in neutrino-driven supernova outflows are discussed.

A. Arcones; G. Martinez-Pinedo; E. O'Connor; A. Schwenk; H. -Th. Janka; C. J. Horowitz; K. Langanke

2008-05-25T23:59:59.000Z

451

Core Collapse Supernovae --- Theory between Achievements and New Challenges  

E-Print Network (OSTI)

Multi-dimensional hydrodynamic simulations of the post-bounce evolution of collapsed stellar iron cores have demonstrated that convective overturn between the stalled shock and the neutrinosphere can have an important effect on the neutrino-driven explosion mechanism. Whether a model yields a successful explosion or not, however, still depends on the power of neutrino energy deposition behind the stalled shock. The neutrino interaction with the stellar gas in the ``hot bubble'' also determines the duration of the shock stagnation phase, the explosion energy, and the composition of the neutrino-heated supernova ejecta. More accurate models require a more precise calculation of the neutrino luminosities and spectra and of the angular distributions of the neutrinos in the heating region. Therefore it is necessary to improve the numerical treatment of the neutrino transport, to develop a better understanding of the neutrino opacities of the dense nuclear medium, and to take into account convective processes {\\it inside} the newly formed neutron star.

H. -Th. Janka

1998-10-05T23:59:59.000Z

452

Type Ia Supernovae Yielding Distances with 3-4% Precision  

E-Print Network (OSTI)

The luminosities of Type Ia supernovae (SN), the thermonuclear explosions of white dwarf stars, vary systematically with their intrinsic color and light-curve decline rate. These relationships have been used to calibrate their luminosities to within ~0.14-0.20 mag from broadband optical light curves, yielding individual distances accurate to ~7-10%. Here we identify a subset of SN Ia that erupt in environments having high ultraviolet surface brightness and star-formation surface density. When we apply a steep model extinction law, these SN can be calibrated to within ~0.065-0.075 mag, corresponding to ~3-4% in distance -- the best yet with SN Ia by a substantial margin. The small scatter suggests that variations in only one or two progenitor properties account for their light-curve-width/color/luminosity relati