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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

Measuring Cosmology with Supernovae  

E-Print Network (OSTI)

Over the past decade, supernovae have emerged as some of the most powerful tools for measuring extragalactic distances. A well developed physical understanding of type II supernovae allow them to be used to measure distances independent of the extragalactic distance scale. Type Ia supernovae are empirical tools whose precision and intrinsic brightness make them sensitive probes of the cosmological expansion. Both types of supernovae are consistent with a Hubble Constant within ~10% of H_0 = 70 km/s/Mpc. Two teams have used type Ia supernovae to trace the expansion of the Universe to a look-back time more than 60% of the age of the Universe. These observations show an accelerating Universe which is currently best explained by a cosmological constant or other form of dark energy with an equation of state near w = p/rho = -1. While there are many possible remaining systematic effects, none appears large enough to challenge these current results. Future experiments are planned to better characterize the equation of state of the dark energy leading to the observed acceleration by observing hundreds or even thousands of objects. These experiments will need to carefully control systematic errors to ensure future conclusions are not dominated by effects unrelated to cosmology.

Saul Perlmutter; Brian P. Schmidt

2003-03-18T23:59:59.000Z

3

Supernova Cosmology Project  

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

& Additional Info The Hubble Space Telescope Cluster Supernova Survey: V. Improving the Dark Energy Constraints Above z>1 and Building an Early-Type-Hosted Supernova Sample N....

4

Supernova Cosmology Project  

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

at AAS Meetings IAU circulars Collaboration Papers Spectra and HST Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation R. Amanullah, et al., ApJ...

5

Supernovae and Cosmology Bruno Leibundgut  

E-Print Network (OSTI)

distances they have become critical probes to further explore astrophysical e#ects, like dust properties a secondary bias into the observations of the distant supernovae, which needs to be carefully evaluated of the universe, and the accelerated cosmic expansion directly inferred from the apparent faintness of the distant

Leibundgut, Bruno

6

Evolution of Dust Extinction and Supernova Cosmology  

E-Print Network (OSTI)

We have made a quantitative calculation for the systematic evolution of average extinction by interstellar dust in host galaxies of high-redshift Type Ia supernovae, by using a realistic model of photometric and chemical evolution of galaxies and supernova rate histories in various galaxy types. We find that average B band extinction at z \\sim 0.5 is typically 0.1-0.2 mag larger than present, under a natural assumption that dust optical depth is proportional to gas column density and gas metallicity. This systematic evolution causes average reddening with E(B-V) \\sim 0.025-0.05 mag with the standard extinction curve, and this is comparable with the observational uncertainty of the reddening of high-redshift supernovae. Therefore, our result does not contradict the observations showing no significant reddening in high-z supernovae. However, the difference in apparent magnitude between an open universe and a \\Lambda-dominated flat universe is only \\sim 0.2 mag at z \\sim 0.5, and hence this systematic evolution of extinction should be taken into account in a reliable measurement of cosmological parameters. Considering this uncertainty, we show that it is difficult to discriminate between an open and \\Lambda-dominated flat cosmologies from the current data.

Tomonori Totani; Chiaki Kobayashi

1999-10-04T23:59:59.000Z

7

A Critique of Supernova Data Analysis in Cosmology  

E-Print Network (OSTI)

Observational astronomy has shown significant growth over the last decade and made important contributions to cosmology. A major paradigm shift in cosmology was brought about by the observations of Type Ia supernovae. The notion that the universe is accelerating has led to several theoretical challenges. Unfortunately, although the supernovae data-sets of high quality are being produced, their statistical analysis leaves much to be desired. Instead of using the data to test the model directly, several studies seem to concentrate on assuming the model to be correct and limiting themselves to estimating model parameters and internal errors. As shown here, the important purpose of testing a cosmological theory is thereby vitiated.

Vishwakarma, Ram Gopal

2010-01-01T23:59:59.000Z

8

A Critique of Supernova Data Analysis in Cosmology  

E-Print Network (OSTI)

Observational astronomy has shown significant growth over the last decade and has made important contributions to cosmology. A major paradigm shift in cosmology was brought about by observations of Type Ia supernovae. The notion that the universe is accelerating has led to several theoretical challenges. Unfortunately, although high quality supernovae data-sets are being produced, their statistical analysis leaves much to be desired. Instead of using the data to directly test the model, several studies seem to concentrate on assuming the model to be correct and limiting themselves to estimating model parameters and internal errors. As shown here, the important purpose of testing a cosmological theory is thereby vitiated.

Ram Gopal Vishwakarma; Jayant V. Narlikar

2010-10-25T23:59:59.000Z

9

Tachyon cosmology, supernovae data, and the big brake singularity  

SciTech Connect

We compare the existing observational data on type Ia supernovae with the evolutions of the Universe predicted by a one-parameter family of tachyon models which we have introduced recently [Phys. Rev. D 69, 123512 (2004)]. Among the set of the trajectories of the model which are compatible with the data there is a consistent subset for which the Universe ends up in a new type of soft cosmological singularity dubbed big brake. This opens up yet another scenario for the future history of the Universe besides the one predicted by the standard {lambda}CDM model.

Keresztes, Z.; Gergely, L. A.; Gorini, V.; Moschella, U.; Kamenshchik, A. Yu. [Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Department of Experimental Physics, University of Szeged, Dom Ter 9, Szeged 6720 (Hungary); Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Department of Experimental Physics, University of Szeged, Dom Ter 9, Szeged 6720 (Hungary); Department of Applied Science, London South Bank University, 103 Borough Road, London SE1 OAA (United Kingdom); Dipartimento di Scienze Fisiche e Mathematiche, Universita dell'Insubria, Via Valleggio 11, 22100 Como (Italy); INFN, sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Dipartimento di Fisica and INFN, via Irnerio 46, 40126 Bologna (Italy); L. D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, Kosygin street 2, 119334 Moscow (Russian Federation)

2009-04-15T23:59:59.000Z

10

PHOTOMETRIC SUPERNOVA COSMOLOGY WITH BEAMS AND SDSS-II  

SciTech Connect

Supernova (SN) cosmology without spectroscopic confirmation is an exciting new frontier, which we address here with the Bayesian Estimation Applied to Multiple Species (BEAMS) algorithm and the full three years of data from the Sloan Digital Sky Survey II Supernova Survey (SDSS-II SN). BEAMS is a Bayesian framework for using data from multiple species in statistical inference when one has the probability that each data point belongs to a given species, corresponding in this context to different types of SNe with their probabilities derived from their multi-band light curves. We run the BEAMS algorithm on both Gaussian and more realistic SNANA simulations with of order 10{sup 4} SNe, testing the algorithm against various pitfalls one might expect in the new and somewhat uncharted territory of photometric SN cosmology. We compare the performance of BEAMS to that of both mock spectroscopic surveys and photometric samples that have been cut using typical selection criteria. The latter typically either are biased due to contamination or have significantly larger contours in the cosmological parameters due to small data sets. We then apply BEAMS to the 792 SDSS-II photometric SNe with host spectroscopic redshifts. In this case, BEAMS reduces the area of the {Omega}{sub m}, {Omega}{sub {Lambda}} contours by a factor of three relative to the case where only spectroscopically confirmed data are used (297 SNe). In the case of flatness, the constraints obtained on the matter density applying BEAMS to the photometric SDSS-II data are {Omega}{sup BEAMS}{sub m} = 0.194 {+-} 0.07. This illustrates the potential power of BEAMS for future large photometric SN surveys such as Large Synoptic Survey Telescope.

Hlozek, Renee [Oxford Astrophysics, Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH (United Kingdom); Kunz, Martin [Department de physique theorique, Universite de Geneve, 30, quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland); Bassett, Bruce; Smith, Mat; Newling, James [African Institute for Mathematical Sciences, 68 Melrose Road, Muizenberg 7945 (South Africa); Varughese, Melvin [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, Cape Town, 7700 (South Africa); Kessler, Rick; Frieman, Joshua [The Kavli Institute for Cosmological Physics, The University of Chicago, 933 East 56th Street, Chicago, IL 60637 (United States); Bernstein, Joseph P.; Kuhlmann, Steve; Marriner, John [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Campbell, Heather; Lampeitl, Hubert; Nichol, Robert C. [Institute of Cosmology and Gravitation, Dennis Sciama Building Burnaby Road Portsmouth PO1 3FX (United Kingdom); Dilday, Ben [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Falck, Bridget; Riess, Adam G. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Sako, Masao [Department of Physics and Astronomy, University of Pennsylvania, 203 South 33rd Street, Philadelphia, PA 19104 (United States); Schneider, Donald P., E-mail: rhlozek@astro.princeton.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

2012-06-20T23:59:59.000Z

11

Just What is a Supernova?  

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

Matter transfer in a binary system Distances to Type Ia Supernovae Slide 8 Supernova "CAT Scan" Type Ia Supernova lightcurves Type Ia Supernovae and Cosmology Type Ia Supernovae...

12

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."

13

Particle Data Group - Astrophysics and Cosmology  

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

Astrophysical Constants and Parameters Experimental tests of gravitational theory Big-Bang cosmology Big-Bang nucleosynthesis Cosmological parameters Dark matter Cosmic...

14

Notes on the compatibility of type Ia supernovae data and varying--$G$ cosmology  

E-Print Network (OSTI)

Observational data for type Ia supernovae, shows that the expansion of the universe is accelerated. This accelerated expansion can be described by a cosmological constant or by dark energy models like quintessence. An interesting question may be raised here. Is it possible to describe the accelerated expansion of universe using varying--$G$ cosmological models? Here we shall show that the price for having accelerated expansion in slow--varying--$G$ models (in which the dynamical terms of $G$ are ignored) is to have highly non--conserved matter and also that it is in contradiction with other data.

Shojai, F

2013-01-01T23:59:59.000Z

15

The discovery of high-redshift supernovae and their cosmological implications  

SciTech Connect

In this thesis the author discusses the methodology for doing photometry: from procedure of extracting supernova counts from images that contain combined supernova plus galaxy flux, to standard star calibration, to additional instrumental corrections that arise due to the multiple telescopes used for observations. He discusses the different sources of photometric error and their correlations, and the construction of the covariance matrix for all the points in the light curve. He then describes the K corrections which account for the redshifting of spectra that are necessary to compare the photometry of the high-redshift data with those from nearby (z < 0.1) supernovae. Finally, he uses the first seven of the supernovae to test the hypothesis that they live in an under-dense bubble where the locally measured Hubble constant differs significantly from the true Hubble constant. He also uses the data to place limits on the value of the Hubble constant. Discussions of several other important aspects of the data analysis are or will be included in other papers. These topics include a description of how the covariance matrix is used to generate light-curve fits, a discussion of non-photometric systematic errors that also effect the measurements, and a discussion of the application of the supernovae to address other scientific/cosmological problems.

Kim, A.G. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States). Physics Div.

1997-09-01T23:59:59.000Z

16

Absence of Black Holes Information Paradox in Group Field Cosmology  

E-Print Network (OSTI)

In this paper we will analyse the black hole information paradox in group field cosmology. We will first construct a group field cosmology with third quantized gauge symmetry. Then we will argue that that in this group field cosmology the process that change the topology of spacetime are unitarity process. Thus, the information paradox from this perspective appears only because we are using a second quantized formalism to explain a third quantized process. A similar paradox would also occur if we analyse a second quantized process in first quantized formalism. Hence, we will demonstrated that in reality there is no information paradox but only a breakdown of the second quantized formalism.

Mir Faizal

2013-01-02T23:59:59.000Z

17

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

18

Cosmological constraints on Chaplygin gas dark energy from galaxy clusters X-ray and supernova data  

E-Print Network (OSTI)

The recent observational evidences for the present accelerated stage of the Universe have stimulated renewed interest for alternative cosmologies. In general, such models contain an unknown negative-pressure dark component that explains the supernova results and reconciles the inflationary flatness prediction ($Omega_{rm{T}} = 1$) and the cosmic microwave background measurements with the dynamical estimates of the quantity of matter in the Universe ($Omega_{rm{m}} simeq 0.3 pm 0.1$). In this paper we study some observational consequences of a dark energy candidate, the so-called generalized Chaplygin gas which is characterized by an equation of state $p_{C} = -A/rho_{C}^{alpha}$, where $A$ and $alpha$ are positive constants. We investigate the prospects for constraining the equation of state of this dark energy component by combining Chandra observations of the X-ray luminosity of galaxy clusters, independent measurements of the baryonic matter density, the latest measurements of the Hubble parameter as given...

Cunha, J V; Lima, J A S

2004-01-01T23:59:59.000Z

19

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

Science Conference Proceedings (OSTI)

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. /Fermilab /Harvard U. /UC, Berkeley, Astron. Dept. /KIPAC, Menlo Park /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Notre Dame U. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Res. Sch. Astron. Astrophys., Weston Creek /Chile U., Catolica /Toronto U., Astron. Dept. /Bohr Inst. /Stockholm U. /Texas A-M /European Southern Observ. /NOAO, Tucson /Ohio State U., Dept. Astron. /Inst. Astron., Honolulu

2007-01-05T23:59:59.000Z

20

Supernova Simulation Images 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; SciDAC Computational Astrophysics Consortium

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

Towards a Cosmological Hubble Diagram for Type II-P Supernovae  

E-Print Network (OSTI)

Carnegie Supernova Project (CSP) (Freedman 2005), will bebeen observed by the CCCP and CSP both photometrically andresearch by the CCCP and CSP will improve our understanding

2006-01-01T23:59:59.000Z

22

Higgs boson, renormalization group, and naturalness in cosmology  

E-Print Network (OSTI)

We consider the renormalization group improvement in the theory of the Standard Model (SM) Higgs boson playing the role of an inflaton with a strong non-minimal coupling to gravity. At the one-loop level with the running of constants taken into account, it leads to a range of the Higgs mass that is entirely determined by the lower WMAP bound on the cosmic microwave background (CMB) spectral index. We find that the SM phenomenology is sensitive to current cosmological data, which suggests to perform more precise CMB measurements as a SM test complementary to the LHC program. By using the concept of a field-dependent cutoff, we show the naturalness of the gradient and curvature expansion in this model within the conventional perturbation theory range of the SM. We also discuss the relation of these results to two-loop calculations and the limitations of the latter caused by parametrization and gauge dependence problems.

A. O. Barvinsky; A. Yu. Kamenshchik; C. Kiefer; A. A. Starobinsky; C. F. Steinwachs

2009-10-06T23:59:59.000Z

23

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

24

Modern supernova search  

Science Conference Proceedings (OSTI)

Supernovae play a critical role in observational cosmology as well as in astrophysics of stars and galaxies. Recent era has seen dramatic progress in the research of supernovae. Several programs to search systematically supernovae in nearby to distant galaxies have been very successful. Recent progresses in the modern supernova search are reviewed.

Myung Gyoon Lee

2001-01-01T23:59:59.000Z

25

Rates and progenitors of type Ia supernovae  

SciTech Connect

The remarkable uniformity of Type Ia supernovae has allowed astronomers to use them as distance indicators to measure the properties and expansion history of the Universe. However, Type Ia supernovae exhibit intrinsic variation in both their spectra and observed brightness. The brightness variations have been approximately corrected by various methods, but there remain intrinsic variations that limit the statistical power of current and future observations of distant supernovae for cosmological purposes. There may be systematic effects in this residual variation that evolve with redshift and thus limit the cosmological power of SN Ia luminosity-distance experiments. To reduce these systematic uncertainties, we need a deeper understanding of the observed variations in Type Ia supernovae. Toward this end, the Nearby Supernova Factory has been designed to discover hundreds of Type Ia supernovae in a systematic and automated fashion and study them in detail. This project will observe these supernovae spectrophotometrically to provide the homogeneous high-quality data set necessary to improve the understanding and calibration of these vital cosmological yardsticks. From 1998 to 2003, in collaboration with the Near-Earth Asteroid Tracking group at the Jet Propulsion Laboratory, a systematic and automated searching program was conceived and executed using the computing facilities at Lawrence Berkeley National Laboratory and the National Energy Research Supercomputing Center. An automated search had never been attempted on this scale. A number of planned future large supernovae projects are predicated on the ability to find supernovae quickly, reliably, and efficiently in large datasets. A prototype run of the SNfactory search pipeline conducted from 2002 to 2003 discovered 83 SNe at a final rate of 12 SNe/month. A large, homogeneous search of this scale offers an excellent opportunity to measure the rate of Type Ia supernovae. This thesis presents a new method for analyzing the true sensitivity of a multi-epoch supernova search and finds a Type Ia supernova rate from z {approx} 0.01-0.1 of r{sub V} = 4.26{sub -1.93 -0.10}{sup +1.39 +0.10} h{sup 3} x 10{sup -4} SNe Ia/yr/Mpc{sup 3} from a preliminary analysis of a subsample of the SNfactory prototype search. Several unusual supernovae were found in the course of the SNfactory prototype search. One in particular, SN 2002ic, was the first SN Ia to exhibit convincing evidence for a circumstellar medium and offers valuable insight into the progenitors of Type Ia supernovae.

Wood-Vasey, William Michael

2004-08-16T23:59:59.000Z

26

Extended-Lorentz Quantum-Cosmology Symmetry Group  

E-Print Network (OSTI)

Unitarily representable by transformations of Milne quantum-universe (MQU) Hilbert-space vectors is a 9-parameter 'extended-Lorentz' Lie group whose algebra comprises 9 conserved MQU-constituent ('quc') attributes: electric charge, energy, spirality, 3-vector momentum and 3-vector angular momentum. Commutation with the full symmetry algebra by the 3-element Lorentz-extending sub-algebra identifies any quc by its (permanent) trio of charge, spirality and energy integers. Milne's redshift-specifying 'universe age' is invariant under the MQU symmetry group. Also invariant is the (elsewhere specified) universe hamiltonian--a self-adjoint age-dependent Hilbert-space operator (not a symmetry-algebra member) that generates universe evolution with increasing age through a 'Schrodinger' (first-order) differential equation.

Chew, Geoffrey F

2013-01-01T23:59:59.000Z

27

Extended-Lorentz Quantum-Cosmology Symmetry Group  

E-Print Network (OSTI)

Unitarily representable by transformations of Milne quantum-universe (MQU) Hilbert-space vectors is a 9-parameter 'extended-Lorentz' Lie group whose algebra comprises 9 conserved MQU-constituent ('quc') attributes: electric charge, energy, spirality, 3-vector momentum and 3-vector angular momentum. Commutation with the full symmetry algebra by the 3-element Lorentz-extending sub-algebra identifies any quc by its (permanent) trio of charge, spirality and energy integers. Milne's redshift-specifying 'universe age' is invariant under the MQU symmetry group. Also invariant is the (elsewhere specified) universe hamiltonian--a self-adjoint age-dependent Hilbert-space operator (not a symmetry-algebra member) that generates universe evolution with increasing age through a 'Schrodinger' (first-order) differential equation.

Geoffrey F. Chew

2013-08-17T23:59:59.000Z

28

The nearby supernova factory  

SciTech Connect

The Nearby Supernova Factory (SNfactory) is an ambitious project to find and study in detail approximately 300 nearby Type Ia supernovae (SNe Ia) at redshifts 0.03 < z < 0.08. This program will provide an exceptional data set of well-studied SNe in the nearby smooth Hubble flow that can be used as calibration for the current and future programs designed to use SNe to measure the cosmological parameters. The first key ingredient for this program is a reliable supply of Hubble-flow SNe systematically discovered in unprecedented numbers using the same techniques as those used in distant SNe searches. In 2002, 35 SNe were found using our test-bed pipeline for automated SN search and discovery. The pipeline uses images from the asteroid search conducted by the Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction techniques and analysis have allowed us to increase our effective SN discovery rate to {approx}12 SNe/month in 2003.

Wood-Vasey, W.M.; Aldering, G.; Lee, B.C.; Loken, S.; Nugent, P.; Perlmutter, S.; Siegrist, J.; Wang, L.; Antilogus, P.; Astier, P.; Hardin, D.; Pain, R.; Copin, Y.; Smadja, G.; Gangler, E.; Castera, A.; Adam, G.; Bacon, R.; Lemonnier, J.-P.; Pecontal, A.; Pecontal, E.; Kessler, R.

2004-01-23T23:59:59.000Z

29

Constraints on cosmological parameters  

E-Print Network (OSTI)

A cosmological model with total density close to critical (and flat geometry), dominated by dark matter and dark energy of unknown nature, and consistent with the basic predictions of the inflationary scenario is a very good fit to a variety of cosmological probes: the anisotropy of the CMB, the large scale distribution of matter, the luminosity distance of high-redshift type Ia supernovae and so on. These high-quality data have established a new standard of precision in the determination of cosmological parameters. CMB and Physics of the Early universe

Amedeo Balbi; Amedeo Balbi

2006-01-01T23:59:59.000Z

30

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

31

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

32

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

33

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

34

Aspherical supernovae  

E-Print Network (OSTI)

be associated w i t h gamma-ray bursts? D r . Peter Nugentinterest: 1. The gamma-ray burst/supernova connection: T h eof supernovae is the gamma-ray bursts ( G R B s ) . T h a t

Kasen, Daniel Nathan

2004-01-01T23:59:59.000Z

35

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

Science Conference Proceedings (OSTI)

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 InterAmerican Obs. /Harvard-Smithsonian Ctr. Astrophys. /Harvard U. /UC, Berkeley, Astron. Dept. /NOAO, Tucson /Inst. Astron., Honolulu /Res. Sch. Astron. Astrophys., Weston Creek /Washington U., Seattle, Astron. Dept. /Bohr Inst. /Notre Dame U. /KIPAC, Menlo Park /Texas A-M /European Southern Observ. /Ohio State U., Dept. Astron. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Stockholm U.

2007-01-08T23:59:59.000Z

36

Distant Supernovae and Cosmic Deceleration  

E-Print Network (OSTI)

Distant supernovae can now be detected routinely. To date 34 supernovae at $z > 0.1$ have been discovered. Among them are 12 Type~Ia supernovae confirmed spectroscopically and suited to measure the cosmic deceleration when appropriately employed as standard candles. However, peak magnitudes have been determined for only two objects so far and a determination of $q_0$ is not yet possible. We describe the current status of the searches and possible pitfalls of the method which rests on few basic assumptions. The importance of sufficient information on the distant events is stressed and the observations of SN~1995K are used as an example of the detailed procedures employed in the analysis. Only spectroscopic classification and light curves in at least two filter bands provide the basis to use correction schemes for the luminosity which have successfully been established in nearby samples. Time dilation has been detected acting on the light curve of SN~1995K at a redshift of 0.478, providing clear evidence of universal expansion. The observations are fully consistent with local Type Ia supernovae in an expanding universe but incompatible with the expectations from a static universe. The contributions of the new, large telescopes to this research area are described. The extension of the observations to even more distant objects will provide a better leverage to distinguish between the possible decelerations and the inclusion of Type II supernovae into the sample add an independent check on the cosmological distances.

B. Leibundgut; J. Spyromilio

1996-08-22T23:59:59.000Z

37

The nearby supernova factory  

Science Conference Proceedings (OSTI)

The Nearby Supernova Factory (SNfactory) is an ambitious project to find and study in detail approximately 300 nearby Type Ia supernovae (SNe Ia) at redshifts 0.03 distant SNe searches. In 2002, 35 SNe were found using our test-bed pipeline for automated SN search and discovery. The pipeline uses images from the asteroid search conducted by the Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction techniques and analysis have allowed us to increase our effective SN discovery rate to {approx}12 SNe/month in 2003.

Wood-Vasey, W.M.; Aldering, G.; Lee, B.C.; Loken, S.; Nugent, P.; Perlmutter, S.; Siegrist, J.; Wang, L.; Antilogus, P.; Astier, P.; Hardin, D.; Pain, R.; Copin, Y.; Smadja, G.; Gangler, E.; Castera, A.; Adam, G.; Bacon, R.; Lemonnier, J.-P.; Pecontal, A.; Pecontal, E.; Kessler, R.

2004-01-23T23:59:59.000Z

38

Late Light Curves of Normally-Luminous Type Ia Supernovae  

E-Print Network (OSTI)

The use of Type Ia supernovae as cosmological tools has reinforced the need to better understand these objects and their light curves. The light curves of Type Ia supernovae are powered by the nuclear decay of $^{56}Ni \\to ^{56}Co \\to ^{56}Fe$. The late time light curves can provide insight into the behavior of the decay products and their effect of the shape of the curves. We present the optical light curves of six "normal" Type Ia supernovae, obtained at late times with template image subtraction, and the fits of these light curves to supernova energy deposition models.

J. C. Lair; M. D. Leising; P. A. Milne; G. G. Williams

2006-01-05T23:59:59.000Z

39

Quantum Cosmology  

E-Print Network (OSTI)

We give an introduction into quantum cosmology with emphasis on its conceptual parts. After a general motivation we review the formalism of canonical quantum gravity on which discussions of quantum cosmology are usually based. We then present the minisuperspace Wheeler--DeWitt equation and elaborate on the problem of time, the imposition of boundary conditions, the semiclassical approximation, the origin of irreversibility, and singularity avoidance. Restriction is made to quantum geometrodynamics; loop quantum gravity and string theory are discussed in other contributions to this volume.

Claus Kiefer; Barbara Sandhoefer

2008-04-04T23:59:59.000Z

40

Type Ia Supernovae Project at NERSC  

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

Type Ia Supernovae Type Ia Supernovae Supernova-1.jpg Update: Recent Berkeley Lab Computing Sciences News about supernovae: read more... Key Challenges: Understanding Type Ia...

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

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

42

Higgs mass determined by cosmological parameters  

E-Print Network (OSTI)

Postulating that all massless elementary fields have conformal scaling symmetry removes a conflict between gravitational theory and the standard model of elementary quantum fields. If the scalar field essential to SU(2) symmetry breaking has conformal symmetry, it must depend explicitly on the Ricci curvature scalar of gravitational theory. This has profound consequences for both cosmology and elementary particle physics, since cosmological data determine scalar field parameters. A modified Friedmann equation is derived and solved numerically. The theory is consistent with all relevant data for supernovae redshifts below $z=1$. The implied value of the cosmological constant implies extremely small Higgs mass, far below current empirical lower bounds. Detection of a Higgs boson with large mass would falsify this argument.

R. K. Nesbet

2008-11-25T23:59:59.000Z

43

Timescape cosmology with radiation fluid  

E-Print Network (OSTI)

The timescape cosmology represents a potentially viable alternative to the standard homogeneous cosmology, without the need for dark energy. Although average cosmic evolution in the timescape scenario only differs substantially from that of Friedmann-Lemaitre model at relatively late epochs when the contribution from the energy density of radiation is negligible, a full solution of the Buchert equations to incorporate radiation is necessary to smoothly match parameters to the epoch of photon decoupling and to obtain constraints from cosmic microwave background data. Here we extend the matter-dominated solution found in earlier work to include radiation, providing series solutions at early times and an efficient numerical integration strategy for generating the complete solution. The numerical solution is used to directly calculate the scale of the sound horizon at decoupling, and at the baryon drag epoch. The constraints on these scales from the Planck satellite data yield bounds on the timescape cosmological parameters, which are found to also agree with the best-fit values from a recent analysis of SDSS-II supernova data, while avoiding the problem of a primordial lithium-7 abundance anomaly.

James A. G. Duley; M. Ahsan Nazer; David L. Wiltshire

2013-06-13T23:59:59.000Z

44

String Gas Cosmology  

E-Print Network (OSTI)

String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the current standard paradigm of cosmology, the inflationary universe scenario. Here, the current status of string gas cosmology is reviewed.

Brandenberger, Robert H

2009-01-01T23:59:59.000Z

45

Constraints on supernovae dimming from photon-pseudo scalar coupling  

E-Print Network (OSTI)

An alternative mechanism that dims high redshift supernovae without cosmic acceleration utilizes an oscillation of photons into a pseudo-scalar particle during transit. Since angular diameter distance measures are immune to the loss of photons, this ambiguity in interpretation can be resolved by combining CMB acoustic peak measurements with the recent baryon oscillation detection in galaxy power spectra. This combination excludes a non-accelerating dark energy species at the 4sigma level regardless of the level of the pseudo-scalar coupling. While solutions still exist with substantial non-cosmological dimming of supernovae, they may be tested with future improvement in baryon oscillation experiments.

Yong-Seon Song; Wayne Hu

2005-07-29T23:59:59.000Z

46

Dark energy constraints from a space-based supernova survey  

E-Print Network (OSTI)

We present a forecast of dark energy constraints that could be obtained from a large sample of distances to Type Ia supernovae detected and measured from space. We simulate the supernova events as they would be observed by a EUCLID-like telescope with its two imagers, assuming those would be equipped with 4 visible and 3 near infrared swappable filters. We account for known systematic uncertainties affecting the cosmological constraints, including those arising through the training of the supernova model used to fit the supernovae light curves. Using conservative assumptions and Planck priors, we find that a 18 month survey would yield constraints on the dark energy equation of state comparable to the cosmic shear approach in EUCLID: a variable two-parameter equation of state can be constrained to ~0.03 at z~0.3. These constraints are derived from distances to about 13,000 supernovae out to z=1.5, observed in two cones of 10 and 50 deg^2. These constraints do not require measuring a nearby supernova sample fr...

Astier, P; Pain, R; Balland, C

2010-01-01T23:59:59.000Z

47

Inflationary Cosmology  

E-Print Network (OSTI)

The big bang model and the history of the early universe according to the grand unified theories are introduced. The shortcomings of big bang are discussed together with their resolution by inflationary cosmology. Inflation, the subsequent oscillation and decay of the inflaton, and the resulting "reheating" of the universe are studied. The density perturbations produced by inflation and the temperature fluctuations of the cosmic background radiation are discussed. The hybrid inflationary model is described. Two "natural" extensions of this model which avoid the disaster encountered in its standard realization from the overproduction of monopoles are presented. Successful "reheating" satisfying the gravitino constraint takes place after the end of inflation in all three versions of hybrid inflation. Adequate baryogenesis via a primordial leptogenesis occurs consistently with the solar and atmospheric neutrino oscillation data. The primordial lepton asymmetry is turned partly into baryon asymmetry via the sphalerons which are summarized.

G. Lazarides

2001-11-26T23:59:59.000Z

48

Cosmology and Astrophysical Constraints of Gauss-Bonnet Dark Energy  

E-Print Network (OSTI)

Cosmological consequences of a string-motivated dark energy scenario featuring a scalar field coupled to the Gauss-Bonnet invariant are investigated. We study the evolution of the universe in such a model, identifying its key properties. The evolution of the homogeneous background and cosmological perturbations, both at large and small scales, are calculated. The impact of the coupling on galaxy distributions and the cosmic microwave background is examined. We find the coupling provides a mechanism to viably onset the late acceleration, to alleviate the coincidence problem, and furthermore to effectively cross the phantom divide at the present while avoiding a Big Rip in the future. We show the model could explain the present cosmological observations, and discuss how various astrophysical and cosmological data, from the Solar system, supernovae Ia, cosmic microwave background radiation and large scale structure constrain it.

Tomi Koivisto; David F. Mota

2006-06-04T23:59:59.000Z

49

Magnetorotational supernovae with resistivities  

Science Conference Proceedings (OSTI)

We numerically investigate the effects of electrical resistivity on the dynamics of core-collapse supernovae. Initially strong magnetic fields and rapid rotations are assumed together with high resistivities. We find that resistivity acts as a negative ... Keywords: core-collapse, electric resistivity, magnetohydrodynamics, supernovae

Hidetomo Sawai; Shoichi Yamada; Kei Kotake

2010-02-01T23:59:59.000Z

50

High Redshift Supernova Rates  

E-Print Network (OSTI)

We use a sample of 42 supernovae detected with the Advanced Camera for Surveys on-board the Hubble Space Telescope as part of the Great Observatories Origins Deep Survey to measure the rate of core collapse supernovae to z~0.7 and type Ia supernovae to z~1.6. This significantly increases the redshift range where supernova rates have been estimated from observations. The rate of core collapse supernovae can be used as an independent probe of the cosmic star formation rate. Based on the observations of 17 core collapse supernovae, we measure an increase in the core collapse supernova rate by a factor of 1.6 in the range 0.3rate. The increase in the rate in this redshift range in consistent with recent measurements of the star formation rate derived from UV-luminosity densities and IR datasets. Based on 25 type Ia supernovae, we find a SN Ia rate that is a factor 3-5 higher at z~1 compared to earlier estimates at lower redshifts (zrate traces a higher star formation rate at redshifts z>1 compared to low redshift. At higher redshift (z>1), we find a suggested decrease in the type Ia rate with redshift. This evolution of the Ia rate with redshift is consistent with a type Ia progenitor model where there is a substantial delay between the formation of the progenitor star and the explosion of the supernova. Assuming that the type Ia progenitor stars have initial main sequence masses 3-8 M_Sun, we find that 5-7% of the available progenitors explode as type Ia supernovae.

Tomas Dahlen; Louis-Gregory Strolger; Adam G. Riess; Bahram Mobasher; Ranga-Ram Chary; Christopher J. Conselice; Henry C. Ferguson; Andrew S. Fruchter; Mauro Giavalisco; Mario Livio; Piero Madau; Nino Panagia; John L. Tonry

2004-06-24T23:59:59.000Z

51

Cosmological and Environmental Influences on Hot Gas Observed in Elliptical Galaxies  

E-Print Network (OSTI)

The variation of temperature and density in the hot, X-ray emitting gas around massive, group dominant elliptical galaxies can be understood as a combination of gas ejected from evolving galactic stars and gas that accumulates in the outer halo by secondary cosmic infall. Beginning with an overdensity perturbation in a simple flat cosmology, we can duplicate observed properties of the hot gas. At some early time we form the stellar galaxy and release supernova energy, conserving dark and baryonic matter. Using a potential appropriate to the large elliptical NGC 4472, we follow the evolution of intergalactic and interstellar gas to the present time when the computed gas density and temperature agree with X-ray observations of NGC 4472. If the hot gas and dark matter halos are subject to differential tidal truncations or mass exchanges between group members, then the correlation between $L_x/L_B$ and the relative sizes of galactic X-ray images can be generated. The physical properties of hot interstellar gas observed in bright ellipticals today are sensitive to the cosmic baryon fraction, the time of maximum star formation and the amount of ``feedback'' energy delivered to the gas by Type II supernovae at the epoch of galaxy formation.

William G. Mathews; Fabrizio Brighenti

1998-06-26T23:59:59.000Z

52

Neutrino Nucleosynthesis in Supernovae  

Science Conference Proceedings (OSTI)

Neutrino nucleosynthesis is an important synthesis process for light elements in supernovae. One important physics input of neutrino nucleosynthesis is cross sections of neutrino-nucleus reactions. The cross sections of neutrino-{sup 12}C and {sup 4}He reactions are derived using new shell model Hamiltonians. With the new cross sections, light element synthesis of a supernova is investigated. The appropriate range of the neutrino temperature for supernovae is constrained to be between 4.3 MeV and 6.5 MeV from the {sup 11}B abundance in Galactic chemical evolution. Effects by neutrino oscillations are also discussed.

Yoshida, Takashi [Division of Theoretical Astronomy, National Astronomical Observatory of Japan (Japan); Suzuki, Toshio [Department of Physics, College of Humanities and Sciences, Nihon University (Japan); Chiba, Satoshi [Advanced Science Research Center, Japan Atomic Energy Agency (Japan); Kajino, Toshitaka [Division of Theoretical Astronomy, National Astronomical Observatory of Japan (Japan); Department of Astronomy, Graduate School of Science, University of Tokyo (Japan); Yokomakura, Hidekazu; Kimura, Keiichi [Department of Physics, Graduate School of Science, Nagoya University (Japan); Takamura, Akira [Department of Mathematics, Toyota National College of Technology (Japan); Hartmann, Dieter H. [Department of Physics and Astronomy, Clemson University (United States)

2009-05-04T23:59:59.000Z

53

The Fall 2004 SDSS Supernova Survey  

E-Print Network (OSTI)

In preparation for the Supernova Survey of the Sloan Digital Sky Survey (SDSS) II, a proposed 3-year extension to the SDSS, we have conducted an early engineering and science run during the fall of 2004, which consisted of approximately 20 scheduled nights of repeated imaging of half of the southern equatorial stripe. Transient supernova-like events were detected in near real-time and photometric measurements were made in the five SDSS filter bandpasses with a cadence of ~2 days. Candidate type Ia supernovae (SNe) were pre-selected based on their colors, light curve shape, and the properties of the host galaxy. Follow-up spectroscopic observations were performed with the Astrophysical Research Consortium 3.5m telescope and the 9.2m Hobby-Eberly Telescope to confirm their types and measure the redshifts. The 2004 campaign resulted in 22 spectroscopically confirmed SNe, which includes 16 type Ia, 5 type II, and 1 type Ib/c. These SN Ia will help fill in the sparsely sampled redshift interval of z = 0.05 - 0.35, the so-called 'redshift desert', in the Hubble diagram. Detailed investigation of the spectral properties of these moderate-redshift SNe Ia will also provide a bridge between local SNe and high-redshift objects, and will help us understand the systematics for future cosmological applications that require high photometric precision. Finally, the large survey volume also provides the opportunity to select unusual supernovae for spectroscopic study that are poorly sampled in other surveys. We report on some of the early results from this program and discuss potential future applications.

Masao Sako; Roger Romani; Josh Frieman; Jen Adelman-McCarthy; Andrew Becker; Fritz DeJongh; Ben Dilday; Juan Estrada; John Hendry; Jon Holtzman; Jared Kaplan; Rick Kessler; Hubert Lampeitl; John Marriner; Gajus Miknaitis; Adam Riess; Douglas Tucker; J. Barentine; R. Blandford; H. Brewington; J. Dembicky; M. Harvanek; S. Hawley; C. Hogan; D. Johnston; S. Kahn; B. Ketzeback; S. Kleinman; J. Krzesinski; D. Lamenti; D. Long; R. McMillan; P. Newman; A. Nitta; R. Nichol; R. Scranton; E. Sheldon; S. Snedden; C. Stoughton; D. York; the SDSS Collaboration

2005-04-20T23:59:59.000Z

54

Automated search for supernovae  

SciTech Connect

This thesis describes the design, development, and testing of a search system for supernovae, based on the use of current computer and detector technology. This search uses a computer-controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The system is now collecting test images of up to several hundred fields per night, with a sensitivity corresponding to a limiting magnitude (visual) of 17. At full speed and sensitivity, the search will examine some 6000 galaxies every three nights, with a limiting magnitude of 18 or fainter, yielding roughly two supernovae per week (assuming one supernova per galaxy per 50 years) at 5 to 50 percent of maximum light. An additional 500 nearby galaxies will be searched every night, to locate about 10 supernovae per year at one or two percent of maximum light, within hours of the initial explosion.

Kare, J.T.

1984-11-15T23:59:59.000Z

55

Berkeley automated supernova search  

SciTech Connect

The Berkeley automated supernova search employs a computer controlled 36-inch telescope and charge coupled device (CCD) detector to image 2500 galaxies per night. A dedicated minicomputer compares each galaxy image with stored reference data to identify supernovae in real time. The threshold for detection is m/sub v/ = 18.8. We plan to monitor roughly 500 galaxies in Virgo and closer every night, and an additional 6000 galaxies out to 70 Mpc on a three night cycle. This should yield very early detection of several supernovae per year for detailed study, and reliable premaximum detection of roughly 100 supernovae per year for statistical studies. The search should be operational in mid-1982.

Kare, J.T.; Pennypacker, C.R.; Muller, R.A.; Mast, T.S.; Crawford, F.S.; Burns, M.S.

1981-01-01T23:59:59.000Z

56

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

57

Cosmological Parameters and Quintessence From Radio Galaxies  

E-Print Network (OSTI)

FRIIb radio galaxies provide a tool to determine the coordinate distance to sources at redshifts from zero to two. The coordinate distance depends on the present values of global cosmological parameters, quintessence, and the equation of state of quintessence. The coordinate distance provides one of the cleanest determinations of global cosmological parameters because it does not depend on the clustering properties of any of the mass-energy components present in the universe. Two complementary methods that provide direct determinations of the coordinate distance to sources with redshifts out to one or two are the modified standard yardstick method utilizing FRIIb radio galaxies, and the modified standard candle method utilizing type Ia supernovae. These two methods are compared here, and are found to be complementary in many ways. The two methods do differ in some regards; perhaps the most significant difference is that the radio galaxy method is completely independent of the local distance scale and independent of the properties of local sources, while the supernovae method is very closely tied to the local distance scale and the properties of local sources. FRIIb radio galaxies provide one of the very few reliable probes of the coordinate distance to sources with redshifts out to two. This method indicates that the current value of the density parameter in non-relativistic matter, ?m, must be low, irrespective of whether the universe is spatially flat, and of whether a significant cosmological constant or quintessence pervades the universe at the present epoch. The effect of quintessence, with equation of state w, is considered. FRIIb radio galaxies indicate that the universe is currently accelerating in its expansion if the primary components of the universe at the present epoch are non-relativistic matter and quintessence, and the universe is spatially flat. 1.

A. Daly; Erick J. Guerra

2001-01-01T23:59:59.000Z

58

Entropy signature of the running cosmological constant  

E-Print Network (OSTI)

Renormalization group (RG) improved cosmologies based upon a RG trajectory of Quantum Einstein Gravity (QEG) with realistic parameter values are investigated using a system of cosmological evolution equations which allows for an unrestricted energy exchange between the vacuum and the matter sector. It is demonstrated that the scale dependence of the gravitational parameters, the cosmological constant in particular, leads to an entropy production in the matter system. The picture emerges that the Universe started out from a state of vanishing entropy, and that the radiation entropy observed today is essentially due to the coarse graining (RG flow) in the quantum gravity sector which is related to the expansion of the Universe. Furthermore, the RG improved field equations are shown to possess solutions with an epoch of power law inflation immediately after the initial singularity. The inflation is driven by the cosmological constant and ends automatically once the RG running has reduced the vacuum energy to the...

Bonanno, Alfio

2007-01-01T23:59:59.000Z

59

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

60

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 they probe the dependence of this dispersion on cosmological parameters and show that information about the amplitude of clustering, {sigma}{sub s}, is contained in the scatter. In principle, it will be possible to constrain {sigma}{sub s} to within 5% with observations of 2000 Type Ia Supernovae. They 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; /Fermilab /Chicago U., Astron. Astrophys. Ctr.; Vallinotto, Alberto; /Fermilab /Chicago U.

2005-11-01T23:59:59.000Z

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
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61

Dynamics and constraints of the unified dark matter flat cosmologies  

SciTech Connect

We study the dynamics of the scalar field Friedmann-Lemaitre-Robertson-Walker flat cosmological models within the framework of the unified dark matter (UDM) scenario. In this model we find that the main cosmological functions such as the scale factor of the Universe, the scalar field, the Hubble flow, and the equation of state parameter are defined in terms of hyperbolic functions. These analytical solutions can accommodate an accelerated expansion, equivalent to either the dark energy or the standard {lambda} models. Performing a joint likelihood analysis of the recent supernovae type Ia data and the baryonic acoustic oscillations traced by the Sloan Digital Sky Survey galaxies, we place tight constraints on the main cosmological parameters of the UDM cosmological scenario. Finally, we compare the UDM scenario with various dark energy models namely {lambda} cosmology, parametric dark energy model and variable Chaplygin gas. We find that the UDM scalar field model provides a large and small scale dynamics which are in fair agreement with the predictions by the above dark energy models although there are some differences especially at high redshifts.

Basilakos, Spyros [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, GR-11527, Athens (Greece); Lukes-Gerakopoulos, Georgios [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, GR-11527, Athens (Greece); University of Athens, Department of Physics, Section of Astrophysics, Astronomy and Mechanics (Greece)

2008-10-15T23:59:59.000Z

62

Supernova constraints on Multi-coupled Dark Energy  

E-Print Network (OSTI)

The persisting consistency of ever more accurate observational data with the predictions of the standard LCDM cosmological model puts severe constraints on possible alternative scenarios, but still does not shed any light on the fundamental nature of the cosmic dark sector.As large deviations from a LCDM cosmology are ruled out by data, the path to detect possible features of alternative models goes necessarily through the definition of cosmological scenarios that leave almost unaffected the background and -- to a lesser extent -- the linear perturbations evolution of the universe. In this context,the Multi-coupled DE (McDE) model was proposed by Baldi 2012 as a particular realization of an interacting Dark Energy field characterized by an effective screening mechanism capable of suppressing the effects of the coupling at the background and linear perturbation level. In the present paper, for the first time, we challenge the McDE scenario through a direct comparison with real data, in particular with the luminosity distance of Type Ia supernovae. By studying the existence and stability conditions of the critical points of the associated background dynamical system, we select only the cosmologically consistent solutions, and confront their background expansion history with data. Confirming previous qualitative results, the McDE scenario appears to be fully consistent with the adopted sample of Type Ia supernovae, even for coupling values corresponding to an associated scalar fifth-force about four orders of magnitude stronger than standard gravity. Our analysis demonstrates the effectiveness of the McDE background screening, and shows some new non-trivial asymptotic solutions for the future evolution of the universe. Our results show how the background expansion history might be highly insensitive to the fundamental nature and to the internal complexity of the dark sector. [Abridged

Arpine Piloyan; Valerio Marra; Marco Baldi; Luca Amendola

2013-05-14T23:59:59.000Z

63

Precision cosmology defeats void models for acceleration  

SciTech Connect

The suggestion that we occupy a privileged position near the center of a large, nonlinear, and nearly spherical void has recently attracted much attention as an alternative to dark energy. Putting aside the philosophical problems with this scenario, we perform the most complete and up-to-date comparison with cosmological data. We use supernovae and the full cosmic microwave background spectrum as the basis of our analysis. We also include constraints from radial baryonic acoustic oscillations, the local Hubble rate, age, big bang nucleosynthesis, the Compton y distortion, and for the first time include the local amplitude of matter fluctuations, {sigma}{sub 8}. These all paint a consistent picture in which voids are in severe tension with the data. In particular, void models predict a very low local Hubble rate, suffer from an ''old age problem,'' and predict much less local structure than is observed.

Moss, Adam; Zibin, James P.; Scott, Douglas [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

2011-05-15T23:59:59.000Z

64

Supernova Science Center  

Science Conference Proceedings (OSTI)

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

65

First-Year Spectroscopy for the SDSS-II Supernova Survey  

Science Conference Proceedings (OSTI)

This paper presents spectroscopy of supernovae discovered in the first season of the Sloan Digital Sky Survey-II Supernova Survey. This program searches for and measures multi-band light curves of supernovae in the redshift range z = 0.05-0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the supernova population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our supernova spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the supernova and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host galaxy contamination existing in the majority of our SN spectra.

Zheng, Chen; Romani, Roger W.; Sako, Masao; Marriner, John; Bassett, Bruce; Becker, Andrew; Choi, Changsu; Cinabro, David; DeJongh, Fritz; Depoy, Darren L.; Dilday, Ben; Doi, Mamoru; Frieman, Joshua A.; Garnavich, Peter M.; Hogan, Craig J.; Holtzman, Jon; Im, Myungshin; Jha, Saurabh; Kessler, Richard; Konishi, Kohki; Lampeitl, Hubert

2008-03-25T23:59:59.000Z

66

First-Year Spectroscopy for the SDSS-II Supernova Survey  

E-Print Network (OSTI)

This paper presents spectroscopy of supernovae discovered in the first season of the Sloan Digital Sky Survey-II Supernova Survey. This program searches for and measures multi-band light curves of supernovae in the redshift range z = 0.05 - 0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the supernova population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our supernova spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the supernova and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host galaxy contamination existing in the majority of our SN spectra.

Chen Zheng; Roger W. Romani; Masao Sako; John Marriner; Bruce Bassett; Andrew Becker; Changsu Choi; David Cinabro; Fritz DeJongh; Darren L. Depoy; Ben Dilday; Mamoru Doi; Joshua A. Frieman; Peter M. Garnavich; Craig J. Hogan; Jon Holtzman; Myungshin Im; Saurabh Jha; Richard Kessler; Kohki Konishi; Hubert Lampeitl; Jennifer L. Marshall; David McGinnis; Gajus Miknaitis; Robert C. Nichol; Jose Luis Prieto; Adam G. Riess; Michael W. Richmond; Donald P. Schneider; Mathew Smith; Naohiro Takanashi; Kouichi Tokita; Kurt van der Heyden; Naoki Yasuda; Roberto J. Assef; John Barentine; Ralf Bender; Roger D. Blandford; Malcolm Bremer; Howard Brewington; Chris A. Collins; Arlin Crotts; Jack Dembicky; Jason Eastman; Alastair Edge; Ed Elson; Michael E. Eyler; Alexei V. Filippenko; Ryan J. Foley; Stephan Frank; Ariel Goobar; Michael Harvanek; Ulrich Hopp; Yutaka Ihara; Steven Kahn; William Ketzeback; Scott J. Kleinman; Wolfram Kollatschny; Jurek Krzesi?ski; Giorgos Leloudas; Daniel C. Long; John Lucey; Elena Malanushenko; Viktor Malanushenko; Russet J. McMillan; Christopher W. Morgan; Tomoki Morokuma; Atsuko Nitta; Linda Ostman; Kaike Pan; A. Kathy Romer; Gabrelle Saurage; Katie Schlesinger; Stephanie A. Snedden; Jesper Sollerman; Maximilian Stritzinger; Linda C. Watson; Shannon Watters; J. Craig Wheeler; Donald York

2008-02-21T23:59:59.000Z

67

First-Year Spectroscopy for the SDSS-II Supernova Survey  

E-Print Network (OSTI)

This paper presents spectroscopy of supernovae discovered in the first season of the Sloan Digital Sky Survey-II Supernova Survey. This program searches for and measures multi-band light curves of supernovae in the redshift range z = 0.05 - 0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the supernova population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our supernova spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the supernova and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host galaxy contamination existi...

Zheng, Chen; Sako, Masao; Marriner, John; Bassett, Bruce; Becker, Andrew; Choi, Changsu; Cinabro, David; DeJongh, Fritz; Depoy, Darren L; Dilday, Ben; Doi, Mamoru; Frieman, Joshua A; Garnavich, Peter M; Hogan, Craig J; Holtzman, Jon; Im, Myungshin; Jha, Saurabh; Kessler, Richard; Konishi, Kohki; Lampeitl, Hubert; Marshall, Jennifer L; McGinnis, David; Miknaitis, Gajus; Nichol, Robert C; Prieto, Jose Luis; Riess, Adam G; Richmond, Michael W; Schneider, Donald P; Smith, Mathew; Takanashi, Naohiro; Tokita, Kouichi; van der Heyden, Kurt; Yasuda, Naoki; Assef, Roberto J; Barentine, John; Bender, Ralf; Blandford, Roger D; Bremer, Malcolm; Brewington, Howard; Collins, Chris A; Crotts, Arlin; Dembicky, Jack; Eastman, Jason; Edge, Alastair; Elson, Ed; Eyler, Michael E; Filippenko, Alexei V; Foley, Ryan J; Frank, Stephan; Goobar, Ariel; Harvanek, Michael; Hopp, Ulrich; Ihara, Yutaka; Kahn, Steven; Ketzeback, William; Kleinman, Scott J; Kollatschny, Wolfram; Krzesi?ski, Jurek; Leloudas, Giorgos; Long, Daniel C; Lucey, John; Malanushenko, Elena; Malanushenko, Viktor; McMillan, Russet J; Morgan, Christopher W; Morokuma, Tomoki; Nitta, Atsuko; Ostman, Linda; Pan, Kaike; Romer, A Kathy; Saurage, Gabrelle; Schlesinger, Katie; Snedden, Stephanie A; Sollerman, Jesper; Stritzinger, Maximilian; Watson, Linda C; Watters, Shannon; Wheeler, J Craig; York, Donald

2008-01-01T23:59:59.000Z

68

Supernova Discoveries from the Nearby Supernova Factory (SNfactory)  

DOE Data Explorer (OSTI)

The Nearby Supernova Factory is an experiment designed to collect data on more Type Ia supernovae than have ever been studied in a single project before, and in so doing, to answer some fundamental questions about the nature of the universe. Type Ia supernovae are extraordinarily bright, remarkably uniform objects which make excellent "standard candles" for measuring the expansion rate of the universe. However, such stellar explosions are very rare, occurring only a couple of times per millenium in a typical galaxy, and remaining bright enough to detect only for a few weeks. Previous studies of Type Ia supernovae led to the discovery of the mysterious "dark energy" that is causing the universe to expand at an accelerating rate. To reduce the statistical uncertainties in previous experimental data, extensive spectral and photometric monitoring of more Type Ia supernovae is required. The SNfactory collaboration has built an automated system consisting of specialized software and custom-built hardware that systematically searches the sky for new supernovae, screens potential candidates, then performs multiple spectral and photometric observations on each supernova. These observations are stored in a database to be made available to supernova researchers world-wide for further study and analysis [copied from http://snfactory.lbl.gov/snf/snf-about.html]. Users must register and agree to the open access honor system. Finding charts are in FITS format and may not be accessible through normal browser settings.

SNfactory International Collaboration,

69

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

2010-04-28T23:59:59.000Z

70

Dark gravity and cosmology  

E-Print Network (OSTI)

The previous version of this article was a first attempt to confront the Dark Gravity theory to cosmological data. However, more recent developments lead to the conclusion that the cosmological principle is probably not valid in Dark Gravity so that this kind of analysis is at best very premature. A more recent and living review of the Dark Gravity theory can be found in gr-qc/0610079

F. Henry-Couannier; A. Tilquin; C. Tao; A. Ealet

2005-09-05T23:59:59.000Z

71

Constraints on cosmological parameters from MAXIMA-1  

SciTech Connect

We set new constraints on a seven-dimensional space of cosmological parameters within the class of inflationary adiabatic models. We use the angular power spectrum of the cosmic microwave background measured over a wide range of l in the first flight of the MAXIMA balloon-borne experiment (MAXIMA-1) and the low-l results from the COBE Differential Microwave Radiometer experiment. We find constraints on the total energy density of the universe, Omega = 1.0(-0.30)(+0.15), the physical density of baryons, Omega (b)h(2) = 0.03 +/- 0.01, the physical density of cold dark matter, Omega (cdm)h(2) = 0.2(-0.1)(+0.2), and the spectral index of primordial scalar fluctuations, n(s) = 1.08 +/- 0.1,all at the 95 percent confidence level. By combining our results with measurements of high-redshift supernovae we constrain the value of the cosmological constant and the fractional amount of pressureless matter in the universe to 0.45<(Lambda)<0.75 and 0.25

Balbi, A.; Ade, P.; Bock, J.; Borrill, J.; Boscaleri, A.; DeBernardis, P.; Ferreira, P.G.; Hanany, S.; Hristov, V.; Jaffe, A.H.; Lee,A.T.; Oh, S.; Pascale; E.; Rabii, B.; Richards, R.L.; Smoot, G.F.; Stompor, R.; Winant, C.D.; Wu, J.H.P.

2006-05-08T23:59:59.000Z

72

Prospective Type Ia supernova surveys from Dome A  

E-Print Network (OSTI)

Prospective Type Ia Supernova Surveys From Dome A A. Kim a ,are conducive toward Type Ia supernova surveys forheterogeneities within the Type Ia supernova class, reducing

Kim, A.

2010-01-01T23:59:59.000Z

73

Nucleosynthesis in type Ia supernovae driven by asymmetric thermonuclear ignition  

Science Conference Proceedings (OSTI)

Type Ia Supernovae (SNe Ia) are believed to be thermonuclear explosions of a white dwarf. They can be used as mature cosmological standardized candles, leading to the discovery of the accelerating expansion of the Universe. However, the explosion mechanism has not yet been fully clarified. In this paper, we first present nucleosynthetic features of a leading explosion scenario, namely a delayed-detonation scenario. Based on this, we propose a new and strong observational constraint on the explosion mechanism through emission lines from neutron-rich Fe-peaks. Especially, we show that an asymmetry in the explosion is likely a generic feature. We further argue that the diversity arising from various viewing angles can be an origin of observational diversities of SNe Ia seen in their spectral features (suspected possible biases in cosmology) and colors (related to the extinction estimate in cosmology). Using these new insights could open up a possibility of using SNe Ia as more precise distance indicators than currently employed.

Maeda, Keiichi [Institute for the Physics and Mathematics of the Universe (IPMU), Todai Institutes for Advanced Study (TODIAS), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)

2012-11-12T23:59:59.000Z

74

The Lick Observatory Supernova Search  

Science Conference Proceedings (OSTI)

We report here the current status of the Lick Observatory Supernova Search (LOSS) with the Katzman Automatic Imaging Telescope (KAIT). The progress on both the hardware and the software of the system is described

W. D. Li; A. V. Filippenko; R. R. Treffers; A. Friedman; E. Halderson; R. A. Johnson; J. Y. King; M. Modjaz; M. Papenkova; Y. Sato; T. Shefler

2000-01-01T23:59:59.000Z

75

NERSC Played Key Role in Nobel Laureates Discovery  

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

left) with members of the Supernova Cosmology Project team. Nugent, now group lead for NERSC Analytics and head of the Computational Cosmology Center at Berkeley Lab, stands...

76

ON THE INTERPRETATION OF SUPERNOVA LIGHT ECHO PROFILES AND SPECTRA  

Science Conference Proceedings (OSTI)

The light echo (LE) systems of historical supernovae in the Milky Way and local group galaxies provide an unprecedented opportunity to reveal the effects of asymmetry on observables, particularly optical spectra. Scattering dust at different locations on the LE ellipsoid witnesses the supernova from different perspectives, and the light consequently scattered toward Earth preserves the shape of line profile variations introduced by asymmetries in the supernova photosphere. However, the interpretation of supernova LE spectra to date has not involved a detailed consideration of the effects of outburst duration and geometrical scattering modifications due to finite scattering dust filament dimension, inclination, and image point-spread function and spectrograph slit width. In this paper, we explore the implications of these factors and present a framework for future-resolved supernova LE spectra interpretation, and test it against Cas A and SN 1987A LE spectra. We conclude that the full modeling of the dimensions and orientation of the scattering dust using the observed LEs at two or more epochs is critical for the correct interpretation of LE spectra. Indeed, without doing so one might falsely conclude that differences exist when none are actually present.

Rest, A.; Narayan, G. [Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States); Sinnott, B.; Welch, D. L. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada); R. J. Foley; Mandel, K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Huber, M. E. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, 3400 North Charles Street, MD 21218 (United States); Blondin, S., E-mail: arest@stsci.edu [Centre de Physique des Particules de Marseille (CPPM), Aix-Marseille Universite, CNRS/IN2P3, 163 avenue de Luminy, 13288 Marseille Cedex 9 (France)

2011-05-01T23:59:59.000Z

77

Moving mesh cosmology: tracing cosmological gas accretion  

E-Print Network (OSTI)

We investigate the nature of gas accretion onto haloes and galaxies at z=2 using cosmological hydrodynamic simulations run with the moving mesh code AREPO. Implementing a Monte Carlo tracer particle scheme to determine the origin and thermodynamic history of accreting gas, we make quantitative comparisons to an otherwise identical simulation run with the smoothed particle hydrodynamics (SPH) code GADGET-3. Contrasting these two numerical approaches, we find significant physical differences in the thermodynamic history of accreted gas in haloes above 10^10.5 solar masses. In agreement with previous work, GADGET simulations show a cold fraction near unity for galaxies forming in massive haloes, implying that only a small percentage of accreted gas heats to an appreciable fraction of the virial temperature during accretion. The same galaxies in AREPO show a much lower cold fraction, gas accretion rate which, at this same halo mass, is an order o...

Nelson, Dylan; Genel, Shy; Sijacki, Debora; Keres, Dusan; Springel, Volker; Hernquist, Lars

2013-01-01T23:59:59.000Z

78

The tension of cosmological magnetic fields as a contribution to dark energy  

E-Print Network (OSTI)

We propose that cosmological magnetic fields generated in regions of finite spatial dimensions may manifest themselves in the global dynamics of the Universe as `dark energy'. We test our model in the context of spatially flat cosmological models by assuming that the Universe contains non-relativistic matter $\\rho_m\\propto \\alpha^{-3}$, dark energy $\\rho_{Q}\\propto \\alpha^{-3(1+w)}$, and an extra fluid with $\\rho_{B} \\propto \\alpha^{n-3}$ that corresponds to the magnetic field. We place constraints on the main cosmological parameters of our model by combining the recent supernovae type Ia data and the differential ages of passively evolving galaxies. In particular, we find that the model which best reproduces the observational data when $\\Omega_m=0.26$ is one with $\\Omega_{B}\\simeq 0.03$, $n\\simeq 7.68$, $\\Omega_{Q}\\simeq 0.71$ and $w\\simeq -0.8$.

Ioannis Contopoulos; Spyros Basilakos

2007-05-14T23:59:59.000Z

79

Unified phantom cosmologies  

E-Print Network (OSTI)

We present a general algorithm based on the concept of form-invariance which can be used for generating phantom cosmologies. It involves linear transformations between the kinetic energy and the potential of the scalar field, and transforms solutions of the Einstein-Klein-Gordon equations which preserve the weak energy condition into others which violate it, while keeping the energy density of the field positive. All known solutions representing phantom cosmologies are unified by this procedure. Using the general algorithm we obtain those solutions and show the relations between them. In addition, the scale factors of the product and seed solutions are related by a generalization of the well-known $a\\to a^{-1}$ duality.

Luis P. Chimento; Ruth Lazkoz

2004-05-26T23:59:59.000Z

80

Probing Dark Energy via Neutrino and Supernova Observatories  

SciTech Connect

A novel method for extracting cosmological evolution parameters is proposed, using a probe other than light: future observations of the diffuse anti-neutrino flux emitted from core-collapse supernovae (SNe), combined with the SN rate extracted from future SN surveys. The relic SN neutrino differential flux can be extracted by using future neutrino detectors such as Gadolinium-enriched, megaton, water detectors or 100-kiloton detectors of liquid Argon or liquid scintillator. The core-collapse SN rate can be reconstructed from direct observation of SN explosions using future precision observatories. Our method, by itself, cannot compete with the accuracy of the optical-based measurements but may serve as an important consistency check as well as a source of complementary information. The proposal does not require construction of a dedicated experiment, but rather relies on future experiments proposed for other purposes.

Hall, Lawrence; Hall, Lawrence J.; Murayama, Hitoshi; Papucci, Michele; Perez, Gilad

2006-07-10T23:59:59.000Z

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

Effects of Supernova Feedback on the Formation of Galaxies  

E-Print Network (OSTI)

We study the effects of Supernova (SN) feedback on the formation of galaxies using hydrodynamical simulations in a Lambda-CDM cosmology. We use an extended version of the code GADGET-2 which includes chemical enrichment and energy feedback by Type II and Type Ia SN, metal-dependent cooling and a multiphase model for the gas component. We focus on the effects of SN feedback on the star formation process, galaxy morphology, evolution of the specific angular momentum and chemical properties. We find that SN feedback plays a fundamental role in galaxy evolution, producing a self-regulated cycle for star formation, preventing the early consumption of gas and allowing disks to form at late times. The SN feedback model is able to reproduce the expected dependence on virial mass, with less massive systems being more strongly affected.

Cecilia Scannapieco; Patricia B. Tissera; Simon D. M. White; Volker Springel

2008-08-20T23:59:59.000Z

82

New Cosmological Model and Its Implications on Observational Data Interpretation  

E-Print Network (OSTI)

The paradigm of \\Lambda CDM cosmology works impressively well and with the concept of inflation it explains the universe after the time of decoupling. However there are still a few concerns; after much effort there is no detection of dark matter and there are significant problems in the theoretical description of dark energy. We will consider a variant of the cosmological spherical shell model, within FRW formalism and will compare it with the standard \\Lambda CDM model. We will show that our new topological model satisfies cosmological principles and is consistent with all observable data, but that it may require new interpretation for some data. Considered will be constraints imposed on the model, as for instance the range for the size and allowed thickness of the shell, by the supernovae luminosity distance and CMB data. In this model propagation of the light is confined along the shell, which has as a consequence that observed CMB originated from one point or a limited space region. It allows to interpret the uniformity of the CMB without inflation scenario. In addition this removes any constraints on the uniformity of the universe at the early stage and opens a possibility that the universe was not uniform and that creation of galaxies and large structures is due to the inhomogeneities that originated in the Big Bang.

B. Vlahovic

2013-03-03T23:59:59.000Z

83

Fluid Mechanics Explains Cosmology, Dark Matter, Dark Energy, and Life  

E-Print Network (OSTI)

Observations of the interstellar medium by the Herschel, Planck etc. infrared satellites throw doubt on standard {\\Lambda}CDMHC cosmological processes to form gravitational structures. According to the Hydro-Gravitational-Dynamics (HGD) cosmology of Gibson (1996), and the quasar microlensing observations of Schild (1996), the dark matter of galaxies consists of Proto-Globular-star-Cluster (PGC) clumps of Earth-mass primordial gas planets in metastable equilibrium since PGCs began star production at 0.3 Myr by planet mergers. Dark energy and the accelerating expansion of the universe inferred from SuperNovae Ia are systematic dimming errors produced as frozen gas dark matter planets evaporate to form stars. Collisionless cold dark matter that clumps and hierarchically clusters does not exist. Clumps of PGCs began diffusion from the Milky Way Proto-Galaxy upon freezing at 14 Myr to give the Magellanic Clouds and the faint dwarf galaxies of the 10^22 m diameter baryonic dark matter Galaxy halo. The first stars persist as old globular star clusters (OGCs). Water oceans and the biological big bang occurred at 2-8 Myr. Life inevitably formed and evolved in the cosmological primordial organic soup provided by 10^80 big bang planets and their hot oceans as they gently merged to form larger binary planets and small binary stars.

Carl H. Gibson

2012-11-02T23:59:59.000Z

84

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

85

Cosmological Consequences of String Axions  

E-Print Network (OSTI)

2005 Cosmological Consequences of String Axions ? Ben Kain for the model independent string axion we consider thefor two additional string axions. We do so independent of

Kain, Ben

2005-01-01T23:59:59.000Z

86

VELOCITY EVOLUTION AND THE INTRINSIC COLOR OF TYPE Ia SUPERNOVAE  

SciTech Connect

To understand how best to use observations of Type Ia supernovae (SNe Ia) to obtain precise and accurate distances, we investigate the relations between spectra of SNe Ia and their intrinsic colors. Using a sample of 1630 optical spectra of 255 SNe, based primarily on data from the CfA Supernova Program, we examine how the velocity evolution and line strengths of Si II {lambda}6355 and Ca II H and K are related to the B - V color at peak brightness. We find that the maximum-light velocity of Si II {lambda}6355 and Ca II H and K and the maximum-light pseudo-equivalent width of Si II {lambda}6355 are correlated with intrinsic color, with intrinsic color having a linear relation with the Si II {lambda}6355 measurements. Ca II H and K does not have a linear relation with intrinsic color, but lower-velocity SNe tend to be intrinsically bluer. Combining the spectroscopic measurements does not improve intrinsic color inference. The intrinsic color scatter is larger for higher-velocity SNe Ia-even after removing a linear trend with velocity-indicating that lower-velocity SNe Ia are more 'standard crayons'. Employing information derived from SN Ia spectra has the potential to improve the measurements of extragalactic distances and the cosmological properties inferred from them.

Foley, Ryan J.; Sanders, Nathan E.; Kirshner, Robert P., E-mail: rfoley@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-12-01T23:59:59.000Z

87

The Rate of Type Ia Supernovae at High Redshift  

E-Print Network (OSTI)

We derive the rates of Type Ia supernovae (SNIa) over a wide range of redshifts using a complete sample from the IfA Deep Survey. This sample of more than 100 SNIa is the largest set ever collected from a single survey, and therefore uniquely powerful for a detailed supernova rate (SNR) calculation. Measurements of the SNR as a function of cosmological time offer a glimpse into the relationship between the star formation rate (SFR) and Type Ia SNR, and may provide evidence for the progenitor pathway. We observe a progressively increasing Type Ia SNR between redshifts z~0.3-0.8. The Type Ia SNR measurements are consistent with a short time delay (t~1 Gyr) with respect to the SFR, indicating a fairly prompt evolution of SNIa progenitor systems. We derive a best-fit value of SFR/SNR 580 h_70^(-2) M_solar/SNIa for the conversion factor between star formation and SNIa rates, as determined for a delay time of t~1 Gyr between the SFR and the Type Ia SNR. More complete measurements of the Type Ia SNR at z>1 are necessary to conclusively determine the SFR--SNR relationship and constrain SNIa evolutionary pathways.

Brian J. Barris; John L. Tonry

2005-09-22T23:59:59.000Z

88

Determination of Primordial Metallicity and Mixing in the Type IIP Supernova 1993W  

DOE Green Energy (OSTI)

We present the results of a large grid of synthetic spectra and compare them to early spectroscopic observations of SN 1993W. This supernova was discovered close to its explosion date and at a recession velocity of 5400 km/s is located in the Hubble flow. We focus here on two early spectra that were obtained approximately 5 and 9 days after explosion. We parameterize the outer supernova envelope as a power-law density profile in homologous expansion. In order to extract information on the value of the parameters a large number of models was required. We show that very early spectra combined with detailed models can provide constraints on the value of the power law index, the ratio of hydrogen to helium in the surface of the progenitor, the progenitor metallicity and the amount of radioactive nickel mixed into the outer envelope of the supernova. The spectral fits reproduce the observed spectra exceedingly well. The spectral results combined with the early photometry predict that the explosion date was 4.7 {+-} 0.7 days before the first spectrum was obtained. The ability to obtain the metallicity from early spectra make SN IIP attractive probes of chemical evolution in the universe and by showing that we have the ability to pin down the parameters of the progenitor and mixing during the supernova explosion, it is likely to make SN IIP useful cosmological distance indicators which are at the same time complementary to SNe Ia.

Baron, E.; Nugent, Peter E.; Branch, David; Hauschildt, Peter H.; Turatto, M.; Cappellaro, E.

2002-12-11T23:59:59.000Z

89

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

90

Redshift-Independent Distances to Type Ia Supernovae  

E-Print Network (OSTI)

We describe a procedure for accurately determining luminosity distances to Type Ia supernovae (SNe Ia) without knowledge of redshift. This procedure, which may be used as an extension of any of the various distance determination methods currently in use, is based on marginalizing over redshift, removing the requirement of knowing $z$ a priori. We demonstrate that the Hubble diagram scatter of distances measured with this technique is approximately equal to that of distances derived from conventional redshift-specific methods for a set of 60 nearby SNe Ia. This indicates that accurate distances for cosmological SNe Ia may be determined without the requirement of spectroscopic redshifts, which are typically the limiting factor for the number of SNe that modern surveys can collect. Removing this limitation would greatly increase the number of SNe for which current and future SN surveys will be able to accurately measure distance. The method may also be able to be used for high-$z$ SNe Ia to determine cosmological density parameters without redshift information.

Brian J. Barris; John L. Tonry

2004-08-04T23:59:59.000Z

91

Chaplygin DGP cosmologies  

E-Print Network (OSTI)

A new class of braneworld models displaying late-time phantom acceleration without resorting to a phantom fluid is presented. In this scenario expansion is fuelled by dark matter together with some effective dark energy capable of crossing the phantom divide. Unlike a previous proposal of this nature, in these models the effective phantom behaviour remains valid at all redshifts for some choices of the free parameters of the models. The construction is based on the generalised Chaplygin gas, and the cosmological history interpolates between a standard CDM-like behaviour at early times and a de Sitter-like behaviour at late times, so no future singularity is reached.

Mariam Bouhmadi-Lpez; Ruth Lazkoz

2007-06-26T23:59:59.000Z

92

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

93

Spinning fluid cosmology  

E-Print Network (OSTI)

The dynamics of a spinning fluid in a flat cosmological model is investigated. The space-time is itself generated by the spinning fluid which is characterized by an energy-momentum tensor consisting a sum of the usual perfect-fluid energy-momentum tensor and some Belinfante-Rosenfeld tensors. It is shown that the equations of motion admit a solution for which the fluid four-velocity and four-momentum are not co-linear in general. The momentum and spin densities of the fluid are expressed in terms of the scale factor.

Morteza Mohseni

2008-07-22T23:59:59.000Z

94

Spinning fluid cosmology  

E-Print Network (OSTI)

The dynamics of a spinning fluid in a flat cosmological model is investigated. The space-time is itself generated by the spinning fluid which is characterized by an energy-momentum tensor consisting a sum of the usual perfect-fluid energy-momentum tensor and some Belinfante-Rosenfeld tensors. It is shown that the equations of motion admit a solution for which the fluid four-velocity and four-momentum are not co-linear in general. The momentum and spin densities of the fluid are expressed in terms of the scale factor.

Mohseni, Morteza

2008-01-01T23:59:59.000Z

95

Cosmology: Recent and future developments  

Science Conference Proceedings (OSTI)

The precision with which the cosmological parameters have been determined has made dramatic progress in just the last two years. The author reviews this recent observational progress, highlights some of the key questions facing cosmology in the new millennium, and briefly discusses some of the projects now being mounted or contemplated to address them.

Joshua A. Frieman

2003-01-15T23:59:59.000Z

96

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

97

Bayesian analysis of Friedmannless cosmologies  

E-Print Network (OSTI)

Assuming only a homogeneous and isotropic universe and using both the 'Gold' Supernova Type Ia sample of Riess et al. and the results from the Supernova Legacy Survey, we calculate the Bayesian evidence of a range of different parameterizations of the deceleration parameter. We consider both spatially flat and curved models. Our results show that although there is strong evidence in the data for an accelerating universe, there is little evidence that the deceleration parameter varies with redshift.

Oystein Elgaroy; Tuomas Multamaki

2006-03-02T23:59:59.000Z

98

Visualizing Buoyant Burning Bubbles in Type Ia Supernovae at...  

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

Burning in Supernovae Buoyant Burning Bubbles in Type Ia Supernovae bubble-s.jpeg Flame ignition in type Ia supernovae leads to isolated bubbles of burning buoyant fluid. As a...

99

Comment on the preprint Neutrino Flavor Evolution Near a Supernova`s Core  

SciTech Connect

The revised version of the widely circulated preprint ``Neutrino Flavor Evolution Near A Supernova`s Core`` by J. Pantaleone (astro-ph 9405008 on the bulletin Board, Indiana University preprint IUHET-276) is wrong. It contains two errors which lead to incorrect conclusions regarding neutrino flavor transformation in the supernova environment. In this short note we discuss these errors.

Pantaleone, J.; Qian, Yong-Zhong; Fuller, G.M.

1994-08-01T23:59:59.000Z

100

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.'' T...

Habib, S; Habib, Salman; Kandrup, Henry E.

1992-01-01T23:59:59.000Z

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101

Turbulent Combustion in Type Ia Supernova Models  

E-Print Network (OSTI)

We review the astrophysical modeling of type Ia supernova explosions and describe numerical methods to implement numerical simulations of these events. Some results of such simulations are discussed.

F. K. Roepke; W. Hillebrandt

2006-09-15T23:59:59.000Z

102

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

2006-10-18T23:59:59.000Z

103

Inflationary cosmology and fundamental physics  

E-Print Network (OSTI)

This thesis is a collection of several papers at the interface between cosmology, particle physics, and field theory. In the first half, we examine topics that are directly related to inflation: axions, string theory, and ...

Hertzberg, Mark Peter

2010-01-01T23:59:59.000Z

104

Particle Production in Matrix Cosmology  

E-Print Network (OSTI)

We consider cosmological particle production in 1+1 dimensional string theory. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum fields in time-dependent backgrounds is resolved by the underlying matrix model. This leads to a finite energy density for the "in" state which cancels the effect of anomalous particle production.

Sumit R. Das; Joshua L. Davis; Finn Larsen; Partha Mukhopadhyay

2004-03-28T23:59:59.000Z

105

Cosmological milestones and energy conditions  

E-Print Network (OSTI)

Until recently, the physically relevant singularities occurring in FRW cosmologies had traditionally been thought to be limited to the "big bang", and possibly a "big crunch". However, over the last few years, the zoo of cosmological singularities considered in the literature has become considerably more extensive, with "big rips" and "sudden singularities" added to the mix, as well as renewed interest in non-singular cosmological events such as "bounces" and "turnarounds". In this talk, we present an extensive catalogue of such cosmological milestones, both at the kinematical and dynamical level. First, using generalized power series, purely kinematical definitions of these cosmological events are provided in terms of the behaviour of the scale factor a(t). The notion of a "scale-factor singularity" is defined, and its relation to curvature singularities (polynomial and differential) is explored. Second, dynamical information is extracted by using the Friedmann equations (without assuming even the existence of any equation of state) to place constraints on whether or not the classical energy conditions are satisfied at the cosmological milestones. Since the classification is extremely general, and modulo certain technical assumptions complete, the corresponding results are to a high degree model-independent.

Celine Cattoen; Matt Visser

2006-09-18T23:59:59.000Z

106

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

107

New ekpyrotic cosmology  

SciTech Connect

In this paper, we present a new scenario of the early universe that contains a pre-big bang ekpyrotic phase. By combining this with a ghost condensate, the theory explicitly violates the null energy condition without developing any ghostlike instabilities. Thus the contracting universe goes through a nonsingular bounce and evolves smoothly into the expanding post-big bang phase. The curvature perturbation acquires a scale-invariant spectrum well before the bounce in this scenario. It is sourced by the scale-invariant entropy perturbation engendered by two ekpyrotic scalar fields, a mechanism recently proposed by Lehners et al. Since the background geometry is nonsingular at all times, the curvature perturbation remains nearly constant on superhorizon scales. It emerges from the bounce unscathed and imprints a scale-invariant spectrum of density fluctuations in the matter-radiation fluid at the onset of the hot big bang phase. The ekpyrotic potential can be chosen so that the spectrum has a red tilt, in accordance with the recent data from WMAP. As in the original ekpyrotic scenario, the model predicts a negligible gravity wave signal on all observable scales. As such ''new ekpyrotic cosmology'' provides a consistent and distinguishable alternative to inflation to account for the origin of the seeds of large-scale structure.

Buchbinder, Evgeny I.; Khoury, Justin [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2L 2Y5 (Canada); Ovrut, Burt A. [Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6395 (United States)

2007-12-15T23:59:59.000Z

108

Carnegie Supernova Project: Observations of Type IIn Supernovae  

E-Print Network (OSTI)

The observational diversity displayed by various Type IIn supernovae (SNe IIn) is explored and quantified. In doing so a more coherent picture ascribing the variety of observed SNe IIn types to particular progenitor scenarios is sought. Carnegie Supernova Project (CSP) optical and near-infrared light curves and visual-wavelength spectroscopy of the Type IIn SNe 2005kj, 2006aa, 2006bo, 2006qq and 2008fq are presented. Combined with previously published observations of the Type IIn SNe 2005ip and 2006jd (Stritzinger et al. 2012), the full CSP sample is used to derive physical parameters which describe the nature of the interaction between the expanding SN ejecta and the circum-stellar material (CSM). For each SN of our sample we find counterparts, identifying objects similar to SNe 1994W (SN 2006bo), 1998S (SN 2008fq) and 1988Z (SN 2006qq). We present the unprecedented initial u-band plateau of SN 2006aa, and its peculiar late-time luminosity and temperature evolution. For each SN, assuming the CSM was formed b...

Taddia, F; Sollerman, J; Phillips, M M; Anderson, J P; Boldt, L; Campillay, A; Castelln, S; Contreras, C; Folatelli, G; Hamuy, M; Heinrich-Josties, E; Krzeminski, W; Morrell, N; Burns, C R; Freedman, W L; Madore, B F; Persson, S E; Suntzeff, N B

2013-01-01T23:59:59.000Z

109

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

110

Type 1a Supernovae Observations are Consistent with a Static Universe  

E-Print Network (OSTI)

The finding that the widths of type 1a supernovae light curves increase with redshift appears to provide strong evidence for an expanding universe. This paper argues that the observations are consistent with a static cosmology where redshift is produced by a tired-light mechanism. For type 1a supernovae there is a strong correlation between peak luminosity and the width of the light curve, the Phillips relation. In an expanding universe this relation is used to combine the absolute magnitude with the stretch factor to obtain a corrected apparent peak magnitude. In a model for a static universe where width rather than stretch factor is used there is different apparent peak magnitude. Since the analysis program explicitly uses the stretch factor rather than width in its use of the Phillips relation its application in a static universe produces a systematic bias in the peak magnitudes. In addition, the stretch selection that is valid for an expanding universe produces another small bias in the data that must be included in a static universe. The aim of this paper is to show that, using the Phillips relation, and allowing for these biases, the data are consistent with a static model. In a static model the density distribution of type 1a supernovae is independent of redshift. This prediction agrees with the observations.

David F. Crawford

2013-07-24T23:59:59.000Z

111

Timescape cosmology with radiation fluid  

E-Print Network (OSTI)

The timescape cosmology represents a potentially viable alternative to the standard homogeneous cosmology, without the need for dark energy. Although average cosmic evolution in the timescape scenario only differs substantially from that of Friedmann-Lemaitre model at relatively late epochs when the contribution from the energy density of radiation is negligible, a full solution of the Buchert equations to incorporate radiation is necessary to smoothly match parameters to the epoch of photon decoupling and to obtain constraints from cosmic microwave background data. Here we extend the matter-dominated solution found in earlier work to include radiation, providing series solutions at early times and an efficient numerical integration strategy for generating the complete solution. The numerical solution is used to directly calculate the scale of the sound horizon at decoupling, and at the baryon drag epoch. The constraints on these scales from the Planck satellite data yield bounds on the timescape cosmological...

Duley, James A G; Wiltshire, David L

2013-01-01T23:59:59.000Z

112

Theoretical cosmic Type Ia supernova rates  

E-Print Network (OSTI)

The aim of this work is the computation of the cosmic Type Ia supernova rates at very high redshifts (z>2). We adopt various progenitor models in order to predict the number of explosions in different scenarios for galaxy formation and to check whether it is possible to select the best delay time distribution model, on the basis of the available observations of Type Ia supernovae. We also computed the Type Ia supernova rate in typical elliptical galaxies of different initial luminous masses and the total amount of iron produced by Type Ia supernovae in each case. It emerges that: it is not easy to select the best delay time distribution scenario from the observational data and this is because the cosmic star formation rate dominates over the distribution function of the delay times; the monolithic collapse scenario predicts an increasing trend of the SN Ia rate at high redshifts whereas the predicted rate in the hierarchical scheme drops dramatically at high redshift; for the elliptical galaxies we note that the predicted maximum of the Type Ia supernova rate depends on the initial galactic mass. The maximum occurs earlier (at about 0.3 Gyr) in the most massive ellipticals, as a consequence of downsizing in star formation. We find that different delay time distributions predict different relations between the Type Ia supernova rate per unit mass at the present time and the color of the parent galaxies and that bluer ellipticals present higher supernova Type Ia rates at the present time.

R. Valiante; F. Matteucci; S. Recchi; F. Calura

2008-07-15T23:59:59.000Z

113

Stringy Model of Cosmological Dark Energy  

E-Print Network (OSTI)

A string field theory(SFT) nonlocal model of the cosmological dark energy providing w<-1 is briefly surveyed. We summarize recent developments and open problems, as well as point out some theoretical issues related with others applications of the SFT nonlocal models in cosmology, in particular, in inflation and cosmological singularity.

Irina Ya. Aref'eva

2007-10-16T23:59:59.000Z

114

Cosmological science enabled by Planck  

E-Print Network (OSTI)

Planck will be the first mission to map the entire cosmic microwave background (CMB) sky with mJy sensitivity and resolution better than 10'. The science enabled by such a mission spans many areas of astrophysics and cosmology. In particular it will lead to a revolution in our understanding of primary and secondary CMB anisotropies, the constraints on many key cosmological parameters will be improved by almost an order of magnitude (to sub-percent levels) and the shape and amplitude of the mass power spectrum at high redshift will be tightly constrained.

Martin White

2006-06-27T23:59:59.000Z

115

Supernova / Acceleration Probe: a Satellite Experiment to Study the Nature of the Dark Energy  

Science Conference Proceedings (OSTI)

The Supernova/Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universe's expansion by performing a series of complementary systematics-controlled astrophysical measurements. We here describe a self-consistent reference mission design that can accomplish this goal with the two leading measurement approaches being the Type Ia supernova Hubble diagram and a wide-area weak gravitational lensing survey. This design has been optimized to first order and is now under study for further modification and optimization. A 2-m three-mirror anastigmat wide-field telescope feeds a focal plane consisting of a 0.7 square-degree imager tiled with equal areas of optical CCDs and near infrared sensors, and a high-efficiency low-resolution integral field spectrograph. The instrumentation suite provides simultaneous discovery and light-curve measurements of supernovae and then can target individual objects for detailed spectral characterization. The SNAP mission will discover thousands of Type Ia supernovae out to z = 3 and will obtain high-signal-to-noise calibrated light-curves and spectra for a subset of > 2000 supernovae at redshifts between z = 0.1 and 1.7 in a northern field and in a southern field. A wide-field survey covering one thousand square degrees in both northern and southern fields resolves {approx} 100 galaxies per square arcminute, or a total of more than 300 million galaxies. With the PSF stability afforded by a space observatory, SNAP will provide precise and accurate measurements of gravitational lensing. The high-quality data available in space, combined with the large sample of supernovae, will enable stringent control of systematic uncertainties. The resulting data set will be used to determine the energy density of dark energy and parameters that describe its dynamical behavior. The data also provide a direct test of theoretical models for the dark energy, including discrimination of vacuum energy due to the cosmological constant and various classes of dynamical scalar fields. If we assume we live in a cosmological-constant-dominated Universe, the matter density, dark energy density, and flatness of space can all be measured with SNAP supernova and weak-lensing measurements to a systematics-limited accuracy of 1%. For a flat universe, the density-to-pressure ratio of dark energy or equation of state w(z) can be similarly measured to 5% for the present value w{sub 0} and {approx} 0.1 for the time variation w' {triple_bond} dw/d ln a|{sub z=1}. For a fiducial SUGRA-inspired universe, w{sub 0} and w' can be measured to an even tighter uncertainty of 0.03 and 0.06 respectively. Note that no external priors are needed. As more accurate theoretical predictions for the small-scale weak-lensing shear develop, the conservative estimates adopted here for space-based systematics should improve, allowing even tighter constraints. While the survey strategy is tailored for supernova and weak gravitational lensing observations, the large survey area, depth, spatial resolution, time-sampling, and nine-band optical to NIR photometry will support additional independent and/or complementary dark-energy measurement approaches as well as a broad range of auxiliary science programs.

Aldering, G.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstrom, L.; Bernstein, G.; Bester, M.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; Bower, C.; Brown, M.; Campbell, M.; Carithers, W.; Commins, E.; /LBL, Berkeley /SLAC /Stockholm U. /Fermilab /Paris U., VI-VII /Yale U. /Pennsylvania U. /UC, Berkeley /Michigan U. /Baltimore, Space Telescope Sci. /Marseille, CPPM /Indiana U. /American Astron. Society /Caltech /Case Western Reserve U. /Cambridge U. /Saclay /Lyon, IPN

2005-08-15T23:59:59.000Z

116

Supernova/Acceleration Probe: A Satellite Experiment to Study the Nature of the Dark Energy  

Science Conference Proceedings (OSTI)

The Supernova/Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universes expansion by performing a series of complementary systematics-controlled astrophysical measurements. We here describe a self-consistent reference mission design that can accomplish this goal with the two leading measurement approaches being the Type Ia supernova Hubble diagram and a wide-area weak gravitational lensing survey. This design has been optimized to first order and is now under study for further modification and optimization. A 2-m three-mirror anastigmat wide-field telescope feeds a focal plane consisting of a 0.7 square-degree imager tiled with equal areas of optical CCDs and near infrared sensors, and a high efficiency low-resolution integral field spectrograph. The instrumentation suite provides simultaneous discovery and light-curve measurements of supernovae and then can target individual objects for detailed spectral characterization. The SNAP mission will discover thousands of Type Ia supernovae out to z = 3 and will obtain high-signal-to-noise calibrated light-curves and spectra for a subset of > 2000 supernovae at redshifts between z = 0.1 and 1.7 in a northern field and in a southern field. A wide-field survey covering one thousand square degrees in both northern and southern fields resolves {approx} 100 galaxies per square arcminute, or a total of more than 300 million galaxies. With the PSF stability afforded by a space observatory, SNAP will provide precise and accurate measurements of gravitational lensing. The high-quality data available in space, combined with the large sample of supernovae, will enable stringent control of systematic uncertainties. The resulting data set will be used to determine the energy density of dark energy and parameters that describe its dynamical behavior. The data also provide a direct test of theoretical models for the dark energy, including discrimination of vacuum energy due to the cosmological constant and various classes of dynamical scalar fields. If we assume we live in a cosmological-constant-dominated Universe, the matter density, dark energy density, and flatness of space can all be measured with SNAP supernova and weak-lensing measurements to a systematics-limited accuracy of 1 percent. For a flat universe, the density-to-pressure ratio of dark energy or equation of state w(z) can be similarly measured to 5 percent for the present value w0 and {approx} 0.1 for the time variation w' is defined as dw/d ln a bar z = 1. For a fiducial SUGRA-inspired universe, w0 and w' can be measured to an even tighter uncertainty of 0.03 and 0.06 respectively. Note that no external priors are needed. As more accurate theoretical predictions for the small-scale weak-lensing shear develop, the conservative estimates adopted here for space-based systematics should improve, allowing even tighter constraints. While the survey strategy is tailored for supernova and weak gravitational lensing observations, the large survey area, depth, spatial resolution, time-sampling, and nine-band optical to NIR photometry will support additional independent and/or complementary dark-energy measurement approaches as well as a broad range of auxiliary science programs.

Aldering, G.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, E.; Bebek, C.; Bergstrom, L.; Bernstein, G.; Bester, M.; Bigelow, C.; Blandford, R.; Bohlin, R.; Bonissent, A.; Bower, C.; Brown, M.; Campbell, M.; Carithers, W.; Commins, E.; Craig, W.; Day, C.; DeJongh, F.; Deustua, S.; Diehl, T.; Dodelson, S.; Ealet, A.; Ellis, R.; Emmet, W.; Fouchez, D.; Frieman, J.; Fruchter, A.; Gerdes, D.; Gladney, L.; Goldhaber, G.; Goobar, A.; Groom, D.; Heetderks, H.; Hoff, M.; Holland, S.; Huffer, M.; Hui, L.; Huterer, D.; Jain, B.; Jelinsky, P.; Karcher, A.; Kent, S.; Kahn, S.; Kim, A.; Kolbe, W.; Krieger, B.; Kushner, G.; Kuznetsova, N.; Lafever, R.; Lamoureux, J.; Lampton, M.; Le Fevre, O.; Levi, M.; Limon, P.; Lin, H.; Linder, E.; Loken, S.; Lorenzon, W.; Malina, R.; Marriner, J.; Marshall, P.; Massey, R.; Mazure, A.; McKay, T.; McKee, S.; Miquel, R.; Morgan, N.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Peoples, J.; Perlmutter, S.; Prieto, E.; Rabinowitz, D.; Refregier, A.; Rhodes, J.; Roe, N.; Rusin, D.; Scarpine, V.; Schubnell, M.; Sholl, M.; Samdja, G.; Smith, R.M.; Smoot, G.; Snyder, J.; Spadafora, A.; Stebbine, A.; Stoughton, C.; Szymkowiak, A.; Tarle, G.; Taylor, K.; Tilquin, A.; Tomasch, A.; Tucker, D.; Vincent, D.; von der Lippe, H.; Walder, J-P.; Wang, G.; Wester, W.

2004-05-12T23:59:59.000Z

117

Fitting Type Ia supernovae with coupled dark energy  

E-Print Network (OSTI)

We discuss the possible consistency of the recently discovered Type Ia supernovae at z>1 with models in which dark energy is strongly coupled to a significant fraction of dark matter, and in which an (asymptotic) accelerated phase exists where dark matter and dark energy scale in the same way. Such a coupling has been suggested for a possible solution of the coincidence problem, and is also motivated by string cosmology models of "late time" dilaton interactions. Our analysis shows that, for coupled dark energy models, the recent data are still consistent with acceleration starting as early as at $z=3$ (to within 90% c.l.), although at the price of a large "non-universality" of the dark energy coupling to different matter fields. Also, as opposed to uncoupled models which seem to prefer a ``phantom'' dark energy, we find that a large amount of coupled dark matter is compatible with present data only if the dark energy field has a conventional equation of state w>-1.

Amendola, L; Piazza, F; Amendola, Luca; Gasperini, Maurizio; Piazza, Federico

2004-01-01T23:59:59.000Z

118

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

119

Conformal formulation of cosmological futures  

E-Print Network (OSTI)

We summarise the new conformal framework of an Anisotropic Future Endless Universe and an Anisotropic Future Singularity. Both new definitions are motivated by, but not restricted to quiescent cosmology and the Weyl curvature hypothesis, which previously only possessed a framework for a classical initial state of the universe, namely the Isotropic Singularity. Some of the features of the framework are briefly discussed.

Philipp A Hoehn; Susan M Scott

2010-01-22T23:59:59.000Z

120

Median statistics cosmological parameter values  

E-Print Network (OSTI)

We present median statistics central values and ranges for 12 cosmological parameters, using 582 measurements (published during 1990-2010) collected by Croft & Dailey (2011). On comparing to the recent Planck collaboration Ade et al. 2013 estimates of 11 of these parameters, we find good consistency in nine cases.

Crandall, Sara

2013-01-01T23:59:59.000Z

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.


121

Summary & Outlook: Particles and Cosmology  

E-Print Network (OSTI)

We review new results on strong and electroweak interactions, flavour physics, cosmic rays and cosmology, which were presented at this conference, focussing on physics beyond the Standard Models. Special emphasis is given to the Higgs sector of the Standard Model of Particle Physics and recent results on high-energy cosmic rays and their implications for dark matter.

Wilfried Buchmuller

2010-03-04T23:59:59.000Z

122

Inside the supernova a powerful convective engine  

E-Print Network (OSTI)

We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 Msun and 25 Msun) in two dimensions. Our calculations begin at the onset of core collapse and stop several 100 ms after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. (...) Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. (...) In essence, a Carnot cycle is established in which convection allows out-of-equilibrium heat transfer mediated by neutrinos to drive low entropy matter to higher entropy and therefore extracts mechanical energy from the heat generated by gravitational collapse. We argue that supernova explosions are ne...

Herant, M; Hix, W R; Fryer, C F; Colgate, S A; Marc Herant; Willy Benz; Chris F Fryer; Stirling Colgate

1994-01-01T23:59:59.000Z

123

A Massive Stellar Burst Before the Supernova  

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

a huge amount of mass only 40 days before the supernova was detected. They labeled the event, SN 2010mc. "After NERSC tools found SN 2010mc, we went back through the archives...

124

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

125

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

2006-04-03T23:59:59.000Z

126

Asymmetric Explosions of Thermonuclear Supernovae  

E-Print Network (OSTI)

A type Ia supernova explosion starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities (in particular, the Rayleigh-Taylor (R-T) instability) begin to act. In previous work (Ghezzi, de Gouveia Dal Pino, & Horvath 2001), we addressed the propagation of an initially laminar thermonuclear flame in presence of a magnetic field assumed to be dipolar. We were able to show that, within the framework of a fractal model for the flame velocity, the front is affected by the field through the quenching of the R-T instability growth in the direction perpendicular to the field lines. As a consequence, an asymmetry develops between the magnetic polar and the equatorial axis that gives a prolate shape to the burning front. We have here computed numerically the total integrated asymmetry as the flame front propagates outward through the expanding shells of decreasing density of the magnetized white dwarf progenitor, for several chemical compositions, and found that a total asymmetry of about 50 % is produced between the polar and equatorial directions for progenitors with a surface magnetic field B ~ 5 x 10^{7} G, and a composition C12 = 0.2 and O16 = 0.8 (in this case, the R-T instability saturates at scales \\~ 20 times the width of the flame front). This asymmetry is in good agreement with the inferred asymmetries from spectropolarimetric observations of very young supernova remnants, which have recently revealed intrinsic linear polarization interpreted as evidence of an asymmetric explosion in several objects,such as SN1999by, SN1996X, and SN1997dt. Larger magnetic field strengths will produce even larger asymmetries. We have also found that for lighter progenitors the total asymmetry is larger.

C. R. Ghezzi; E. M. de Gouveia Dal Pino; J. E. Horvath

2002-11-27T23:59:59.000Z

127

Nonstationary Rayleigh-Taylor instability in supernova ejecta  

SciTech Connect

This paper studies the effect of a nonstationary shell acceleration on the development of the Rayleigh-Taylor instability (RTI) in supernovae remnants (SNRs). Two groups of solutions describing acceleration and deceleration phase of the SNR shell are obtained. Using a special transformation (co-moving coordinate frame), an exact dispersion relation for nonstationary RTI is derived. It is shown that compressible and incompressible branches are separated for the spherically symmetric flow and only the former is unstable. The exact analytic solution is compared to a simpler WKB-like analysis and a good agreement is shown, which proves that this analysis can be useful and easily extended to further applications.

Ribeyre, X.; Hallo, L.; Tikhonchuk, V. T.; Bouquet, S.; Sanz, J. [Centre Lasers Intenses et Applications, Universite Bordeaux 1-CNRS-CEA, 33405 Talence Cedex (France); Commissariat a l'Energie Atomique, DIF/Departement de Physique Theorique et Appliquee, 91680, Bruyeres le Chatel (France); E.T.S.I., Aeronauticos, Universidad Politecnica de Madrid, Madrid 28040 (Spain)

2007-11-15T23:59:59.000Z

128

The Mechanism of Core-Collapse Supernova Explosions: A Status Report  

E-Print Network (OSTI)

We review the status of the current quest to understand the mechanism of core-collapse supernovae, if neutrino-driven. In the process, we discuss the spherical explosion paradigm and its problems, some results from our new suite of collapse calculations performed using a recently-developed 1D implicit, multi-group, Feautrier/tangent-ray, Boltzmann solver coupled to explicit predictor/corrector hydrodynamics, the basic energetics of supernova explosions, and the promise of multi-D radiation/hydro simulations to explain why the cores of massive stars explode.

Adam Burrows; Todd A. Thompson

2002-10-09T23:59:59.000Z

129

Cosmic ray physics in calculations of cosmological structure formation  

E-Print Network (OSTI)

Cosmic rays (CRs) play a decisive role within our own Galaxy. They provide partial pressure support against gravity, they trace past energetic events such as supernovae, and they reveal the underlying structure of the baryonic matter distribution through their interactions. To study the impact of CRs on galaxy and cosmic structure formation and evolution, we develop an approximative framework for treating dynamical and radiative effects of CRs in cosmological simulations. Our guiding principle is to try to find a balance between capturing as many physical properties of CR populations as possible while at the same time requiring as little extra computational resources as possible. We approximate the CR spectrum of each fluid element by a single power-law, with spatially and temporally varying normalisation, low-energy cut-off, and spectral index. Principles of conservation of particle number, energy, and pressure are then used to derive evolution equations for the basic variables describing the CR spectrum, both due to adiabatic and non-adiabatic processes. The processes considered include compression and rarefaction, CR injection via shocks in supernova remnants, injection in structure formation shock waves, in-situ re-acceleration of CRs, CR spatial diffusion, CR energy losses due to Coulomb interactions, ionisation losses, Bremsstrahlung losses, and, finally, hadronic interactions with the background gas, including the associated gamma-ray and radio emission due to subsequent pion decay. We show that the formalism reproduces CR energy densities, pressure, and cooling rates with an accuracy of ~10% in steady state conditions where CR injection balances cooling. Our framework is therefore well suited to be included into numerical simulation schemes of galaxy and structure formation. (abridged)

Torsten A. Ensslin; Christoph Pfrommer; Volker Springel; Martin Jubelgas

2006-03-17T23:59:59.000Z

130

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

131

Extending the redshift-distance relation in Cosmological General Relativity to higher redshifts  

E-Print Network (OSTI)

The redshift-distance modulus relation, the Hubble Diagram, derived from Cosmological General Relativity has been extended to arbitrarily large redshifts. Numerical methods were employed and a density function was found that results in a valid solution of the field equations at all redshifts. The extension has been compared to 302 type Ia supernova data as well as to 69 Gamma-ray burst data. The latter however do not not truly represent a `standard candle' as the derived distance modulii are not independent of the cosmology used. Nevertheless the analysis shows a good fit can be achieved without the need to assume the existence of dark matter. The Carmelian theory is also shown to describe a universe that is always spatially flat. This results from the underlying assumption of the energy density of a cosmological constant $\\Omega_{\\Lambda} = 1$, the result of vacuum energy. The curvature of the universe is described by a \\textit{spacevelocity} metric where the energy content of the curvature at any epoch is $\\Omega_K = \\Omega_{\\Lambda} - \\Omega = 1-\\Omega$, where $\\Omega$ is the matter density of the universe. Hence the total density is always $\\Omega_K + \\Omega = 1$

John G. Hartnett

2007-05-22T23:59:59.000Z

132

Quantum Weak Measurements and Cosmology  

E-Print Network (OSTI)

The indeterminism of quantum mechanics generally permits the independent specification of both an initial and a final condition on the state. Quantum pre-and-post-selection of states opens up a new, experimentally testable, sector of quantum mechanics, when combined with statistical averages of identical weak measurements. In this paper I apply the theory of weak quantum measurements combined with pre-and-post-selection to cosmology. Here, pre-selection means specifying the wave function of the universe or, in a popular semi-classical approximation, the initial quantum state of a subset of quantum fields propagating in a classical back-ground spacetime. The novel feature is post-selection: the additional specification of a condition on the quantum state in the far future. I discuss "natural" final conditions, and show how they may lead to potentially large and observable effects at the present cosmological epoch. I also discuss how pre-and-post-selected quantum contrast to the expectation value of the stress-energy-momentum tensor, resolving a vigorous debate from the 1970's. The paper thus provides a framework for computing large-scale cosmological effects arising from this new sector of quantum mechanics. A simple experimental test is proposed.

Paul Davies

2013-09-03T23:59:59.000Z

133

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

2007-12-14T23:59:59.000Z

134

A small but nonzero cosmological constant  

E-Print Network (OSTI)

Recent astrophysical observations seem to indicate that the cosmological constant is small but nonzero and positive. The old cosmological constant problem asks why it is so small; we must now ask, in addition, why it is nonzero, and why it is positive. In this essay, we try to kill these three metaphorical birds with one stone. That stone is the unimodular theory of gravity, which is the canonical theory of gravity, except for the way the cosmological constant arises in the theory.

Y. Jack Ng (a; H. Van Dam (b

1999-01-01T23:59:59.000Z

135

Fingerprints of a Local Supernova  

E-Print Network (OSTI)

The results of precise analysis of elements and isotopes in meteorites, comets, the Earth, the Moon, Mars, Jupiter, the solar wind, solar flares, and the solar photosphere since 1960 reveal fingerprints of a local supernova (SN), undiluted by interstellar material. Heterogeneous SN debris formed the planets. The Sun formed on the neutron (n) rich SN core. The ground-state masses of nuclei reveal repulsive n-n interactions that trigger n-emission and a series of nuclear reactions that generate solar luminosity, the solar wind, and the measured flux of solar neutrinos. The location of the Sun's high-density core shifts relative to the solar surface as gravitational forces exerted by the major planets cause the Sun to experience abrupt acceleration and deceleration, like a yoyo on a string, in its orbit about the ever-changing centre-of-mass of the solar system. Solar cycles (surface magnetic activity, solar eruptions, and sunspots) and major climate changes arise from changes in the depth of the energetic SN co...

Manuel, Oliver

2009-01-01T23:59:59.000Z

136

Fingerprints of a Local Supernova  

E-Print Network (OSTI)

The results of precise analysis of elements and isotopes in meteorites, comets, the Earth, the Moon, Mars, Jupiter, the solar wind, solar flares, and the solar photosphere since 1960 reveal fingerprints of a local supernova (SN), undiluted by interstellar material. Heterogeneous SN debris formed the planets. The Sun formed on the neutron (n) rich SN core. The ground-state masses of nuclei reveal repulsive n-n interactions that trigger n-emission and a series of nuclear reactions that generate solar luminosity, the solar wind, and the measured flux of solar neutrinos. The location of the Sun's high-density core shifts relative to the solar surface as gravitational forces exerted by the major planets cause the Sun to experience abrupt acceleration and deceleration, like a yoyo on a string, in its orbit about the ever-changing centre-of-mass of the solar system. Solar cycles (surface magnetic activity, solar eruptions, and sunspots) and major climate changes arise from changes in the depth of the energetic SN core remnant in the interior of the Sun.

Oliver Manuel; Hilton Ratcliffe

2009-05-05T23:59:59.000Z

137

Asymmetric Explosions of Thermonuclear Supernovae  

E-Print Network (OSTI)

A type Ia supernova explosion starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities (in particular, the Rayleigh-Taylor (R-T) instability) begin to act. In previous work (Ghezzi, de Gouveia Dal Pino, & Horvath 2001), we addressed the propagation of an initially laminar thermonuclear flame in presence of a magnetic field assumed to be dipolar. We were able to show that, within the framework of a fractal model for the flame velocity, the front is affected by the field through the quenching of the R-T instability growth in the direction perpendicular to the field lines. As a consequence, an asymmetry develops between the magnetic polar and the equatorial axis that gives a prolate shape to the burning front. We have here computed numerically the total integrated asymmetry as the flame front propagates outward through the expanding shells of decreasing density of the magnetized white dwarf progenitor, for several chemical compositions, and found...

Ghezzi, C R; Horvth, J E

2004-01-01T23:59:59.000Z

138

Asymmetric Explosions of Thermonuclear Supernovae  

E-Print Network (OSTI)

A type Ia supernova explosion starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities (in particular, the Rayleigh-Taylor (R-T) instability) begin to act. In previous work (Ghezzi, de Gouveia Dal Pino, & Horvath 2001), we addressed the propagation of an initially laminar thermonuclear flame in presence of a magnetic field assumed to be dipolar. We were able to show that, within the framework of a fractal model for the flame velocity, the front is affected by the field through the quenching of the R-T instability growth in the direction perpendicular to the field lines. As a consequence, an asymmetry develops between the magnetic polar and the equatorial axis that gives a prolate shape to the burning front. We have here computed numerically the total integrated asymmetry as the flame front propagates outward through the expanding shells of decreasing density of the magnetized white dwarf progenitor, for several chemical compositions, and found that a total asymmetry of about 50 % is produced between the polar and equatorial directions for progenitors with a surface magnetic field B ? 5 10 7 G, and

C. R. Ghezzi; J. E. Horvath; So Paulo

2003-01-01T23:59:59.000Z

139

Supernova rates and stellar populations  

E-Print Network (OSTI)

We discuss the results about the nature of type Ia Supernovae that can be derived by studying their rates in different stellar populations. While the evolution of SN photometry and spectra can constrain the explosion mechanism, the SN rate depends on the progenitor system. We review the current available data on rates as a function of parent galaxy color, morphology, star formation rate, radio luminosity and environment. By studying the variation of the rates with the color of the parent galaxy, a strong evidence was established that type Ia SNe come from both young and old stars. The dependence of the rates with the radio power of the parent galaxy is best reproduced by a bimodal distribution of delay time between the formation of the progenitor and its explosion as a SN. Cluster early-type galaxies show higher type Ia SN rate with respect to field galaxies, and this effect can be due either to traces of young stars or to differences in the delay time distribution.

F. Mannucci

2007-08-03T23:59:59.000Z

140

Imperfect fluids, Lorentz violations, and Finsler cosmology  

Science Conference Proceedings (OSTI)

We construct a cosmological toy model based on a Finslerian structure of space-time. In particular, we are interested in a specific Finslerian Lorentz violating theory based on a curved version of Cohen and Glashow's very special relativity. The osculation of a Finslerian manifold to a Riemannian manifold leads to the limit of relativistic cosmology, for a specified observer. A modified flat Friedmann-Robertson-Walker cosmology is produced. The analogue of a zero energy particle unfolds some special properties of the dynamics. The kinematical equations of motion are affected by local anisotropies. Seeds of Lorentz violations may trigger density inhomogeneities to the cosmological fluid.

Kouretsis, A. P.; Stathakopoulos, M.; Stavrinos, P. C. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); 1 Anastasiou Genadiou Street, 11474, Athens (Greece); Department of Mathematics, University of Athens, 15784 Greece (Greece)

2010-09-15T23:59:59.000Z

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.


141

Dynamical 3-Space: Supernovae and the Hubble Expansion - Older Universe and End of Dark Energy  

E-Print Network (OSTI)

We apply the new dynamics of 3-space to cosmology by deriving a Hubble expansion solution. This dynamics involves two constants; G and alpha - the fine structure constant. This solution gives an excellent parameter-free fit to the recent supernova and gamma-ray burst data without the need for `dark energy' or `dark matter'. The data and theory together imply an older age for the universe of some 14.7Gyrs. Various problems such as fine tuning, the event horizon problem etc are now resolved. A brief review discusses the origin of the 3-space dynamics and how that dynamics explained the bore hole anomaly, spiral galaxy flat rotation speeds, the masses of black holes in spherical galaxies, gravitational light bending and lensing, all without invoking `dark matter' or `dark energy'. These developments imply that a new understanding of the universe is now available.

Reginald T Cahill

2007-05-11T23:59:59.000Z

142

Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight  

E-Print Network (OSTI)

Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales - which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the...

Busti, V C; Clarkson, C

2013-01-01T23:59:59.000Z

143

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

E-Print Network (OSTI)

Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space

Meyers, Joshua Evan

2012-01-01T23:59:59.000Z

144

On the Brightness of Supernova Ia  

E-Print Network (OSTI)

Before 1998 the universe expansion was thought to be slowing down. After 1998 the universe expansion is thought to be accelerating up. The key evidence came from the observed brightness of high redshift supernovae Ia in 1998. Astronomers found that the observed brightness of high redshift supernovae Ia is fainter than expected. Astronomers believe this means that the universe expansion is accelerating up. In this paper it is argued that if the ionized gas in the universe space is taken into account, then the brightness of the high redshift supernova Ia should be fainter than expected. The universe expansion does not need to be accelerating up. The exotic form of energy (dark energy) does not need to be introduce

Yijia Zheng

2013-10-01T23:59:59.000Z

145

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,

146

Probing Exotic Physics With Supernova Neutrinos  

Science Conference Proceedings (OSTI)

Future galactic supernovae will provide an extremely long baseline for studying the properties and interactions of neutrinos. In this paper, we discuss the possibility of using such an event to constrain (or discover) the effects of exotic physics in scenarios that are not currently constrained and are not accessible with reactor or solar neutrino experiments. In particular, we focus on the cases of neutrino decay and quantum decoherence. We calculate the expected signal from a core-collapse supernova in both current and future water Cerenkov, scintillating, and liquid argon detectors, and find that such observations will be capable of distinguishing between many of these scenarios. Additionally, future detectors will be capable of making strong, model-independent conclusions by examining events associated with a galactic supernova's neutronization burst.

Kelso, Chris; Hooper, Dan

2010-09-01T23:59:59.000Z

147

A Measurement of the Rate of type-Ia Supernovae at Redshift $z\\approx$ 0.1 from the First Season of the SDSS-II Supernova Survey  

E-Print Network (OSTI)

We present a measurement of the rate of type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift $z\\le0.12$. Assuming a flat cosmology with $\\Omega_m = 0.3=1-\\Omega_\\Lambda$, we find a volumetric SN Ia rate of $[2.93^{+0.17}_{-0.04}({\\rm systematic})^{+0.90}_{-0.71}({\\rm statistical})] \\times 10^{-5} {\\rm SNe} {\\rm Mpc}^{-3} h_{70}^3 {\\rm year}^{-1}$, at a volume-weighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift-evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rat...

Dilday, Benjamin; Frieman, J A; Holtzman, J; Marriner, J; Miknaitis, G; Nichol, R C; Romani, R; Sako, M; Bassett, B; Becker, A; Cinabro, D; De Jongh, F; Depoy, D L; Doi, M; Garnavich, P M; Hogan, C J; Jha, S; Konishi, K; Lampeitl, H; Marshall, J L; McGinnis, D; Prieto, J L; Riess, A G; Richmond, M W; Schneider, D P; Smith, M; Takanashi, N; Tokita, K; van der Heyden, K; Zheng, N Yasuda C; Barentine, J; Brewington, H; Choi, C; Crotts, A; Dembicky, J; Harvanek, M; Im, M; Ketzeback, W; Kleinman, S J; Krzesi?ski, J; Long, D C; Malanushenko, E; Malanushenko, V; McMillan, R J; Nitta, A; Pan, K; Saurage, G; Snedden, S A; Watters, S; Wheeler, J C; York, D

2008-01-01T23:59:59.000Z

148

Nuclear Physics in Core-Collapse Supernovae  

SciTech Connect

Core-collapse and the launch of a supernova explosion form a very short episode of few seconds in the evolution of a massive star, during which an enormous gravitational energy of several times 1053 erg is transformed into observable neutrino-, kinetic-, and electromagnetic radiation energy. We emphasize the wide range of matter conditions that prevail in a supernova event and sort the conditions into distinct regimes in the density and entropy phase diagram to briefly discuss their different impact on the neutrino signal, gravitational wave emission, and ejecta.

Liebendoerfer, Matthias [Universitat Basel, Switzerland; Fischer, T. [University of Basel; Froelich, C. [University of Chicago; Hix, William Raphael [ORNL; Langanke, Karlheinz [Gesellschaft fur Schwerionenforschung (GSI), Germany; Martinez-Pinedo, Gabriel [Gesellschaft fur Schwerionenforschung (GSI), Germany; Mezzacappa, Anthony [ORNL; Scheidegger, Simon [Universitat Basel, Switzerland; Thielemann, Friedrich-Karl W. [Universitat Basel, Switzerland; Whitehouse, Stuart [Universitat Basel, Switzerland

2008-01-01T23:59:59.000Z

149

Nuclear Physics in Core-Collapse Supernovae  

SciTech Connect

Core collapse and the launch of a supernova explosion form a very short episode of a few seconds in the evolution of a massive star, during which an enormous gravitational energy of several times 10^{51} erg is transformed into observable neutrino, kinetic, and optical energy. We emphasize the wide range of matter conditions that prevail in a supernova event and sort the conditions into distinct regimes in the density and entropy phase diagram to briefly discuss their different impact on the neutrino signal, gravitational wave emission, and ejecta.

Liebendoerfer, M. [University of Basel; Fischer, T. [University of Basel; Froelich, C. [University of Chicago, Chicago, IL; Hix, William Raphael [ORNL; Langanke, Karlheinz [Gesellschaft f?r Schwerionenforschung (GSI), Germany; Mart?nez-Pinedo, Gabriel [Gesellschaft f?r Schwerionenforschung (GSI), Germany; Mezzacappa, Anthony [ORNL; Scheidegger, Simon [Universit?t Basel, Switzerland; Thielemann, F.-K. [University of Basel; Whitehouse, S. [University of Basel

2008-10-01T23:59:59.000Z

150

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

151

NERSC User Group 2013 Big Bang, Big Data, Big Iron Planck Satellite...  

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

User Group 2013 Big Bang, Big Data, Big Iron Planck Satellite Data Analysis At NERSC Julian Borrill Computational Cosmology Center, Berkeley Lab & Space Sciences Laboratory, UC...

152

Neutrinos in Cosmology and Astrophysics  

E-Print Network (OSTI)

We briefly review the recent developments in neutrino physics and astrophysics which have import for frontline research in nuclear physics. These developments, we argue, tie nuclear physics to exciting developments in observational cosmology and astrophysics in new ways. Moreover, the behavior of neutrinos in dense matter is itself a fundamental problem in many-body quantum mechanics, in some ways akin to well-known issues in nuclear matter and nuclei, and in some ways radically different, especially because of nonlinearity and quantum de-coherence. The self-interacting neutrino gas is the only many body system driven by the weak interactions.

A. B. Balantekin; G. M. Fuller

2013-03-15T23:59:59.000Z

153

A new perspective on early cosmology  

E-Print Network (OSTI)

We present a new perspective on early cosmology based on Loop Quantum Gravity. We use projected spinnetworks, coherent states and spinfoam techniques, to implement a quantum reduction of the full Kinematical Hilbert space of LQG, suitable to describe inhomogeneous cosmological models. Some preliminary results on the solutions of the Scalar constraint of the reduced theory are also presented.

Emanuele Alesci

2013-03-04T23:59:59.000Z

154

Supernova VLBI in the present and with the SKA  

E-Print Network (OSTI)

VLBI is the only technology that will allow sub-milliarcsecond resolution imaging in the near future. As such, it is the only way to image expanding supernovae in nearby galaxies. Such images potentially allow us to study the early evolution of neutron stars or black holes left behind by core-collapse supernovae, the circumstellar wind history of the supernova progenitor stars, the shock acceleration of cosmic-ray particles in supernovae as well as the evolutionary process by which supernova shells merge into, and enrich, the ISM. I will discuss the results of the on-going VLBI imaging campaigns on supernovae 1986J and 1993J. I will also discuss the impact on supernova VLBI of the proposed South-African Karoo Array Telescope and Australian ASKAP arrays, as well as the SKA itself, as these telescopes will greatly increase the sensitivity of the global VLBI network.

M. F. Bietenholz

2008-02-28T23:59:59.000Z

155

Supernova VLBI in the present and with the SKA  

E-Print Network (OSTI)

VLBI is the only technology that will allow sub-milliarcsecond resolution imaging in the near future. As such, it is the only way to image expanding supernovae in nearby galaxies. Such images potentially allow us to study the early evolution of neutron stars or black holes left behind by core-collapse supernovae, the circumstellar wind history of the supernova progenitor stars, the shock acceleration of cosmic-ray particles in supernovae as well as the evolutionary process by which supernova shells merge into, and enrich, the ISM. I will discuss the results of the ongoing VLBI imaging campaigns on supernova 1986J and 1993J. I will also discuss the impact on supernova VLBI of the proposed South-African Karoo Array Telescope and Australian ASKAP arrays, as well as the SKA itself, as these telescopes will greatly increase the sensitivity of the global VLBI network. From planets to dark energy: the modern radio universe

unknown authors

2007-01-01T23:59:59.000Z

156

Supernova VLBI in the present and with the SKA  

E-Print Network (OSTI)

VLBI is the only technology that will allow sub-milliarcsecond resolution imaging in the near future. As such, it is the only way to image expanding supernovae in nearby galaxies. Such images potentially allow us to study the early evolution of neutron stars or black holes left behind by core-collapse supernovae, the circumstellar wind history of the supernova progenitor stars, the shock acceleration of cosmic-ray particles in supernovae as well as the evolutionary process by which supernova shells merge into, and enrich, the ISM. I will discuss the results of the on-going VLBI imaging campaigns on supernovae 1986J and 1993J. I will also discuss the impact on supernova VLBI of the proposed South-African Karoo Array Telescope and Australian ASKAP arrays, as well as the SKA itself, as these telescopes will greatly increase the sensitivity of the global VLBI network.

Bietenholz, M F

2008-01-01T23:59:59.000Z

157

"Cosmologists have used these supernovae very pro-  

E-Print Network (OSTI)

bursts. For decades after their ini- tial discovery by military satel- lites in the 1960s, gamma-ray" bursts lasting more than two seconds) a gamma-ray burst accompanies the birth of a black hole from- ing new data on supernovae and gamma-ray bursts, and with computer scientists with expertise

Zhang, Yi

158

Symplectic method in quantum cosmology  

Science Conference Proceedings (OSTI)

In the present work, we study the quantum cosmology description of Friedmann-Robertson-Walker models in the presence of a generic perfect fluid and a cosmological constant, which may be positive or negative. We work in Schutz's variational formalism and the three-dimensional spatial sections may have positive, negative, or zero constant curvature. If one uses the scale factor and its canonically conjugated momentum as the phase space variables that describe the geometrical sector of these models, one obtains Wheeler-DeWitt equations with operator ordering ambiguities. In order to avoid those ambiguities and simplify the quantum treatment of the models, we follow references [Edesio M. Barbosa, Jr. and Nivaldo A. Lemos, Gen. Relativ. Gravit. 38, 1609 (2006).][Edesio M. Barbosa, Jr. and Nivaldo A. Lemos, Phys. Rev. D 78, 023504 (2008).] and introduce new phase space variables. We explicitly demonstrate, using the symplectic method, that the transformation leading from the old set of variables to the new one is canonical.

Silva, E. V. Correa; Monerat, G. A.; Oliveira-Neto, G.; Neves, C. [Departamento de Matematica e Computacao, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra, Km 298, Polo Industrial, CEP 27537-000, Resende-RJ (Brazil); Ferreira Filho, L. G. [Departamento de Mecanica e Energia, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra, Km 298, Polo Industrial, CEP 27537-000, Resende-RJ (Brazil)

2009-08-15T23:59:59.000Z

159

Inside the Supernova: A Powerful Convective Engine  

E-Print Network (OSTI)

Condensed Abstract: We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 Msun and 25 Msun) in two dimensions. Our calculations begin at the onset of core collapse and stop several 100 ms after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. (...) Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. (...) In essence, a Carnot cycle is established in which convection allows out-of-equilibrium heat transfer mediated by neutrinos to drive low entropy matter to higher entropy and therefore extracts mechanical energy from the heat generated by gravitational collapse. We argue that supernova explosions are nearly guaranteed and self-regulated by the high efficiency of the thermodynamic engine. (...) Convection continues to accumulate energy exterior to the neutron star until a successful explosion has occurred. At this time, the envelope is expelled and therefore uncoupled from the heat source (the neutron star) and the energy input ceases. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae which is effective under a wide range of physical parameters.

Marc Herant; Willy Benz; W. Raphael Hix; Chris F. Fryer; Stirling Colgate

1994-04-12T23:59:59.000Z

160

Radiation Dominated Universe for Jordan-Brans-Dicke Cosmology  

E-Print Network (OSTI)

Jordan-Brans-Dicke cosmology with a standard kinetic term for the scalar field and no mass term has the same radiation dominated solution as standard Einstein cosmology without the cosmological constant. Because of this, the primordial nucleosynthesis (Big - Bang nucleosynthesis) result obtained for standard cosmology remains the same for Jordan-Brans-Dicke cosmology. We show that Jordan-Brans-Dicke cosmology with a mass term for the scalar field as well as explaining dark energy for the present era, can also explain radiation dominated cosmology for the primordial nucleosynthesis era.

M. Arik; L. Amon Susam

2010-06-22T23:59:59.000Z

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.


161

Asymptotically safe gravity as a scalar-tensor theory and its cosmological implications  

E-Print Network (OSTI)

We study asymptotically safe gravity with Einstein-Hilbert truncation taking into account the renormalization group running of both gravitational and cosmological constants. We show the classical behavior of the theory is equivalent to a specific class of Jordan-Brans-Dicke theories with vanishing Brans-Dicke parameter, and potential determined by the renormalization group equation. The theory may be reformulated as an $f(R)$ theory. In the simplest cosmological scenario, we find large--field inflationary solutions near the Planck scale where the effective field theory description breaks down. Finally, we discuss the implications of a running gravitational constant to background dynamics via cosmological perturbation theory. We show that compatibility with General Relativity requires contributions from the running gravitational constant to the stress energy tensor to be taken into account in the perturbation analysis.

Yi-Fu Cai; Damien A. Easson

2011-07-28T23:59:59.000Z

162

Scalar perturbations in deflationary cosmological models  

E-Print Network (OSTI)

We consider scalar perturbations of energy--density for a class of cosmological models where an early phase of accelerated expansion evolves, without any fine--tuning for graceful exit, towards the standard Friedman eras of observed universe. The geometric procedure which generates such models agrees with results for string cosmology since it works if dynamics is dominated by a primordial fluid of extended massive objects. The main result is that characteristic scales of cosmological interest, connected with the extension of such early objects, are selected.}

S. Capozziello; G. Lambiase; G. Scarpetta

1998-06-09T23:59:59.000Z

163

From Microwave Anisotropies to Cosmology  

E-Print Network (OSTI)

Fluctuations in the temperature of the cosmic microwave background have now been detected over a wide range of angular scales, and a consistent picture seems to be emerging. This article describes some of the implications for cosmology. Analysis of all the published detections suggests the existence of a peak on degree scales of height 2.4 to 10 (90%CL) relative to the amplitude of the power spectrum at large angular scales. This result confirms an early prediction, implies that the universe did in fact recombine, and limits theories of structure formation. Illustrative examples are provided of how the comparison of microwave background and large-scale structure data will be a potentially powerful means of answering fundamental questions about the universe.

Douglas Scott; Joe Silk; Martin White

1995-05-04T23:59:59.000Z

164

Generating Cosmological Gaussian Random Fields  

E-Print Network (OSTI)

We present a generic algorithm for generating Gaussian random initial conditions for cosmological simulations on periodic rectangular lattices. We show that imposing periodic boundary conditions on the real-space correlator and choosing initial conditions by convolving a white noise random field results in a significantly smaller error than the traditional procedure of using the power spectrum. This convolution picture produces exact correlation functions out to separations of L/2, where L is the box size, which is the maximum theoretically allowed. This method also produces tophat sphere fluctuations which are exact at radii $ R \\le L/4 $. It is equivalent to windowing the power spectrum with the simulation volume before discretizing, thus bypassing sparse sampling problems. The mean density perturbation in the volume is no longer constrained to be zero, allowing one to assemble a large simulation using a series of smaller ones. This is especially important for simulations of Lyman-$\\alpha$ systems where sma...

Pen, U L

1997-01-01T23:59:59.000Z

165

Higgs Particle Mass in Cosmology  

E-Print Network (OSTI)

A version of the Standard Model is considered, where the electroweak symmetry breaking is provided by cosmological initial data given for the zeroth Fourier harmonic of the Higgs field $$. The initial data symmetry breaking mechanism removes the Higgs field contribution to the vacuum energy density, possible creation of monopoles, and tachion behavior at high energies, if one imposes an ``inertial'' condition on the Higgs potential $\\textsf{V}_{\\rm Higgs}()=0$. The requirement of zero radiative corrections to this {\\em inertial} condition coincides with the limiting point of the vacuum stability in the Standard Model. The latter together with the direct experimental limit gives the prediction for the mass of the Higgs boson to be in the range $114 < m_h \\lsim 134$ GeV.

A. B. Arbuzov; L. A. Glinka; V. N. Pervushin

2007-05-31T23:59:59.000Z

166

Are there cosmological evolution of Gamma-Ray Bursts?  

E-Print Network (OSTI)

The variability of gamma-ray burst (GRB) is thought to be correlated with its absolute peak luminosity, and this relation had been used to derive an estimate of the redshifts of GRBs. Recently Amati et al. present the results of spectral and energetic properties of several GRBs with know redshifts. Here we analyse the properties of two group GRBs, one group with known redshift from afterglow observation, and another group with redshift derived from the luminosity- variability relation. We study the redshift dependence of various GRBs features in their cosmological rest frames, including the burst duration, the isotropic luminosity and radiated energy, and the peak energy Ep of ?F? spectra. We find that the properties of these two group GRBs are very similar, which strongly implies that the redshift derived from the luminosity-variability relation may be reliable. If this is true, then we see that the burst properties, such as their intrinsic duration, luminosity, radiated energy and peak energy Ep, are all correlated with the redshift, which means that the GRBs features are redshift dependent, i.e. there are cosmological evolution of gamma-ray bursts, and this can provide an interesting clue to the nature of GRBs. Furthermore we find that the Ep- L relation strongly supports the idea that gamma-ray burst emission comes from the internal shock. Key words: gamma rays: bursts

D. M. Wei

2008-01-01T23:59:59.000Z

167

Dynamical System Analysis of Cosmologies with Running Cosmological Constant from Quantum Einstein Gravity  

E-Print Network (OSTI)

We discuss a mechanism that induces a time-dependent vacuum energy on cosmological scales. It is based on the instability induced renormalization triggered by the low energy quantum fluctuations in a Universe with a positive cosmological constant. We employ the dynamical systems approach to study the qualitative behavior of Friedmann-Robertson-Walker cosmologies where the cosmological constant is dynamically evolving according with this nonperturbative scaling at low energies. It will be shown that it is possible to realize a "two regimes" dark energy phases, where an unstable early phase of power-law evolution of the scale factor is followed by an accelerated expansion era at late times.

Bonanno, Alfio

2011-01-01T23:59:59.000Z

168

Constraining Palatini cosmological models using GRB data  

E-Print Network (OSTI)

New constraints on previously investigated Palatini cosmological models [arXiv:1109.3420] have been obtained by adding Gamma Ray Burst data [arXiv:1205.2954].

Michal Kamionka

2013-03-08T23:59:59.000Z

169

SLAC National Accelerator Laboratory - Astrophysics and Cosmology  

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

Astrophysics and Cosmology A night time aerial image of one of the labs at SLAC SLAC astrophysicists and cosmologists play leading roles in the study of the high-energy universe,...

170

A small but nonzero cosmological constant  

E-Print Network (OSTI)

Recent astrophysical observations seem to indicate that the cosmological constant is small but nonzero and positive. The old cosmological constant problem asks why it is so small; we must now ask, in addition, why it is nonzero (and is in the range found by recent observations), and why it is positive. In this essay, we try to kill these three metaphorical birds with one stone. That stone is the unimodular theory of gravity, which is the ordinary theory of gravity, except for the way the cosmological constant arises in the theory. We argue that the cosmological constant becomes dynamical, and eventually, in terms of the cosmic scale factor $R(t)$, it takes the form $\\Lambda(t) = \\Lambda(t_0)(R(t_0)/R(t))^2$, but not before the epoch corresponding to the redshift parameter $z \\sim 1$.

Y. Jack Ng; H. van Dam

1999-11-13T23:59:59.000Z

171

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

172

Saul Perlmutter, Distant Supernovae, Dark Energy, and the Accelerating...  

Office of Scientific and Technical Information (OSTI)

Saul Perlmutter, Distant Supernovae, Dark Energy, and the Accelerating Expansion of the Universe Resources with Additional Information Awards Saul Perlmutter Photo Courtesy of...

173

Turbulence-Flame Interactions in Type Ia Supernovae  

E-Print Network (OSTI)

Turbulence-Flame Interactions in Type Ia Supernovae A. J.Normalised time (e) Normalised flame speed Normalised time (length scale (cm) Laminar flame width Gibson scale Cell

Aspden, Andrew J; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2 & 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5)

2008-01-01T23:59:59.000Z

174

The Physics of Core-Collapse Supernovae  

E-Print Network (OSTI)

Supernovae are nature's grandest explosions and an astrophysical laboratory in which unique conditions exist that are not achievable on Earth. They are also the furnaces in which most of the elements heavier than carbon have been forged. Scientists have argued for decades about the physical mechanism responsible for these explosions. It is clear that the ultimate energy source is gravity, but the relative roles of neutrinos, fluid instabilities, rotation and magnetic fields continue to be debated.

S. Woosley; H. -T. Janka

2006-01-12T23:59:59.000Z

175

Quantum cosmology and late-time singularities  

E-Print Network (OSTI)

The development of dark energy models has stimulated interest to cosmological singularities, which differ from the traditional Big Bang and Big Crunch singularities. We review a broad class of phenomena connected with soft cosmological singularities in classical and quantum cosmology. We discuss the classification of singularities from the geometrical point of view and from the point of view of the behaviour of finite size objects, crossing such singularities. We discuss in some detail quantum and classical cosmology of models based on perfect fluids (anti-Chaplygin gas and anti-Chaplygin gas plus dust), of models based on the Born-Infeld-type fields and of the model of a scalar field with a potential inversely proportional to the field itself. We dwell also on the phenomenon of the phantom divide line crossing in the scalar field models with cusped potentials. Then we discuss the Friedmann equations modified by quantum corrections to the effective action of the models under considerations and the influence of such modification on the nature and the existence of soft singularities. We review also quantum cosmology of models, where the initial quantum state of the universe is presented by the density matrix (mixed state). Finally, we discuss the exotic singularities arising in the brane-world cosmological models.

A. Yu. Kamenshchik

2013-07-22T23:59:59.000Z

176

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

177

The Fall 2004 SDSS Supernova Survey  

E-Print Network (OSTI)

In preparation for the Supernova Survey of the Sloan Digital Sky Survey (SDSS) II, a proposed 3-year extension to the SDSS, we have conducted an early engineering and science run during the fall of 2004, which consisted of approximately 20 scheduled nights of repeated imaging of half of the southern equatorial stripe. Transient supernova-like events were detected in near real-time and photometric measurements were made in the five SDSS filter bandpasses with a cadence of ~2 days. Candidate type Ia supernovae (SNe) were pre-selected based on their colors, light curve shape, and the properties of the host galaxy. Follow-up spectroscopic observations were performed with the Astrophysical Research Consortium 3.5m telescope and the 9.2m Hobby-Eberly Telescope to confirm their types and measure the redshifts. The 2004 campaign resulted in 22 spectroscopically confirmed SNe, which includes 16 type Ia, 5 type II, and 1 type Ib/c. These SN Ia will help fill in the sparsely sampled redshift interval of z = 0.05 - 0.35,...

Sako, M; Frieman, J A; Adelman-McCarthy, J; Becker, A; De Jongh, F; Dilday, B; Estrada, J; Hendry, J; Holtzman, J; Kaplan, J; Kessler, R; Lampeitl, H; Marriner, J P; Miknaitis, G; Riess, A; Tucker, D; Barentine, J; Blandford, R D; Brewington, H; Dembicky, J; Harvanek, M; Hawley, S; Hogan, C; Johnston, D; Kahn, S; Ketzeback, B; Kleinman, S; Krzesnski, J; Lamenti, D; Long, D; McMillan, R; Newman, P; Nitta, A; Nichol, R; Scranton, R; Sheldon, E S; Snedden, S A; Stoughton, C; York, D; Sako, Masao; Romani, Roger; Frieman, Josh; Carthy, Jen Adelman-Mc; Becker, Andrew; Jongh, Fritz De; Dilday, Ben; Estrada, Juan; Hendry, John; Holtzman, Jon; Kaplan, Jared; Kessler, Rick; Lampeitl, Hubert; Marriner, John; Miknaitis, Gajus; Riess, Adam; Tucker, Douglas

2005-01-01T23:59:59.000Z

178

Distant Supernovae and the Accelerating Universe  

E-Print Network (OSTI)

The observation of SN 1997ff at redshift 1.7 has been claimed to refute alternative models such as grey dust or evolution for the faintness of distant supernovae, leaving only an accelerating Universe as a viable model. However, a very simple one parameter evolution model, with the peak luminosity varying as an exponential function of cosmic time, converts the flux vs. distance law of the critical density matter-dominated model into that of the concordance Omega_matter = 0.3 flat vacuum-dominated model with an error no larger than 0.03 mag over the range 0-2 in redshift. A grey dust model that matches this accuracy can easily be contrived but it still fails by overproducing the far-IR background or distorting the CMB. Models that involve oscillation between photons and axions could emulate an exponential function of cosmic time without violating these background constraints. Clearly a better and well-tested understanding of the Type Ia supernova explosion mechanism and the origin of the correlation between the decay rate and luminosity is needed before any effort to reduce statistical errors in the supernova Hubble diagram to very small levels.

E. L. Wright

2002-01-12T23:59:59.000Z

179

A Quantum Cosmology: No Dark Matter, Dark Energy nor Accelerating Universe  

E-Print Network (OSTI)

We show that modelling the universe as a pre-geometric system with emergent quantum modes, and then constructing the classical limit, we obtain a new account of space and gravity that goes beyond Newtonian gravity even in the non-relativistic limit. This account does not require dark matter to explain the spiral galaxy rotation curves, and explains as well the observed systematics of black hole masses in spherical star systems, the bore hole $g$ anomalies, gravitational lensing and so on. As well the dynamics has a Hubble expanding universe solution that gives an excellent parameter-free account of the supernovae and gamma-ray-burst red-shift data, without dark energy or dark matter. The Friedmann-Lema\\^{i}tre-Robertson-Walker (FLRW) metric is derived from this dynamics, but is shown not satisfy the General Relativity based Friedmann equations. It is noted that General Relativity dynamics only permits an expanding flat 3-space solution if the energy density in the pressure-less dust approximation is non-zero. As a consequence dark energy and dark matter are required in this cosmological model, and as well the prediction of a future exponential accelerating Hubble expansion. The FLRW $\\Lambda$CDM model data-based parameter values, $\\Omega_\\Lambda=0.73$, $\\Omega_{DM}=0.27$, are derived within the quantum cosmology model, but are shown to be merely artifacts of using the Friedmann equations in fitting the red-shift data.

Reginald T Cahill

2007-09-18T23:59:59.000Z

180

The diversity of Type Ia Supernovae: evidence for systematics?  

E-Print Network (OSTI)

The photometric and spectroscopic properties of 26 well observed Type Ia Supernovae (SNeIa) were analyzed with the aim to explore SNIa diversity. The sample includes (Branch-)normal SNe as well as extreme events like SNe 1991T and 1991bg, while the truly peculiar SNIa, SN2000cx and SN2002cx are not included in our sample . A statistical treatment reveals the existence of three different groups. The first group (FAINT) consists of faint SNeIa similar to SN1991bg, with low expansion velocities and rapid evolution of SiII velocity. A second group consists of ``normal'' SNeIa, also with high temporal velocity gradient (HVG), but with brighter mean absolute magnitude =-19.3 and higher expansion velocities than the FAINT SNe. The third group includes both ``normal'' and SN1991T-like SNeIa: these SNe populate a narrow strip in the SiII velocity evolution plot, with a small velocity gradient (SVG), but have absolute magnitudes similar to HVGs. While the FAINT and HVG SNeIa together seem to define a relation between RSi(II) and Dm15(B), the SVG ones either do not conform with that relation or define a new, looser one. The RSi(II) pre-maximum evolution of HVGs is strikingly different from that of SVGs. The impact of this evidence on the understanding of SNIa diversity, in terms of explosion mechanisms, degree of ejecta mixing, and ejecta-CSM interaction, is discussed.

S. Benetti; E. Cappellaro; P. A. Mazzali; M. Turatto; G. Altavilla; F. Bufano; N. Elias-Rosa; R. Kotak; G. Pignata; M. Salvo; V. Stanishev

2004-11-02T23:59:59.000Z

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.


181

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

182

Generating Cosmological Gaussian Random Fields  

E-Print Network (OSTI)

We present a generic algorithm for generating Gaussian random initial conditions for cosmological simulations on periodic rectangular lattices. We show that imposing periodic boundary conditions on the real-space correlator and choosing initial conditions by convolving a white noise random field results in a significantly smaller error than the traditional procedure of using the power spectrum. This convolution picture produces exact correlation functions out to separations of L/2, where L is the box size, which is the maximum theoretically allowed. This method also produces tophat sphere fluctuations which are exact at radii $ R \\le L/4 $. It is equivalent to windowing the power spectrum with the simulation volume before discretizing, thus bypassing sparse sampling problems. The mean density perturbation in the volume is no longer constrained to be zero, allowing one to assemble a large simulation using a series of smaller ones. This is especially important for simulations of Lyman-$\\alpha$ systems where small boxes with steep power spectra are routinely used. We also present an extension of this procedure which generates exact initial conditions for hierarchical grids at negligible cost.

Ue-Li Pen

1997-09-25T23:59:59.000Z

183

TERAPIXEL IMAGING OF COSMOLOGICAL SIMULATIONS  

SciTech Connect

The increasing size of cosmological simulations has led to the need for new visualization techniques. We focus on smoothed particle hydrodynamic (SPH) simulations run with the GADGET code and describe methods for visually accessing the entire simulation at full resolution. The simulation snapshots are rastered and processed on supercomputers into images that are ready to be accessed through a Web interface (GigaPan). This allows any scientist with a Web browser to interactively explore simulation data sets in both spatial and temporal dimensions and data sets which in their native format can be hundreds of terabytes in size or more. We present two examples, the first a static terapixel image of the MassiveBlack simulation, a P-GADGET SPH simulation with 65 billion particles, and the second an interactively zoomable animation of a different simulation with more than 1000 frames, each a gigapixel in size. Both are available for public access through the GigaPan Web interface. We also make our imaging software publicly available.

Feng Yu; Croft, Rupert A. C.; Di Matteo, Tiziana; Khandai, Nishikanta [Bruce and Astrid McWilliams Center for Cosmology, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Sargent, Randy; Nourbakhsh, Illah; Dille, Paul; Bartley, Chris [Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Springel, Volker [Heidelberger Institut fuer Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg (Germany); Jana, Anirban [Pittsburgh Supercomputing Center, Pittsburgh, PA 15213 (United States); Gardner, Jeffrey, E-mail: yfeng1@andrew.cmu.edu [Physics Department, University of Washington, Seattle, WA 98195 (United States)

2011-12-01T23:59:59.000Z

184

The Nuclear Physics of Solar and Supernova Neutrino Detection  

E-Print Network (OSTI)

This talk provides a basic introduction for students interested in the responses of detectors to solar, supernova, and other low-energy neutrino sources. Some of the nuclear physics is then applied in a discussion of nucleosynthesis within a Type II supernova, including the r-process and the neutrino process.

W. C. Haxton

1999-01-15T23:59:59.000Z

185

Burning Thermals in Type Ia Supernovae A. J. Aspden1  

E-Print Network (OSTI)

Burning Thermals in Type Ia Supernovae A. J. Aspden1 , J. B. Bell1 , S. Dong2 , and S. E. Woosley2 ABSTRACT We develop a one-dimensional theoretical model for thermals burning in Type Ia supernovae based for the burning and for the expansion of the thermal due to changes in the background stratification found

Bell, John B.

186

Infrared [Fe II] and Dust Emissions from Supernova Remnants  

E-Print Network (OSTI)

Supernova remnants (SNRs) are strong thermal emitters of infrared radiation. The most prominent lines in the near-infrared spectra of SNRs are [Fe II] lines. The [Fe II] lines are from shocked dense atomic gases, so they trace SNRs in dense environments. After briefly reviewing the physics of the [Fe II] emission in SNR shocks, I describe the observational results which show that there are two groups of SNRs bright in [Fe II] emission: middle-aged SNRs interacting with molecular clouds and young core-collapse SNRs in dense circumstellar medium. The SNRs belonging to the former group are also bright in near-infrared H$_2$ emission, indicating that both atomic and molecular shocks are pervasive in these SNRs. The SNRs belonging to the latter group have relatively small radii in general, implying that most of them are likely the remnants of SN IIL/b or SN IIn that had strong mass loss before the explosion. I also comment on the "[Fe II]-H$_2$ reversal" in SNRs and on using the [Fe II]-line luminosity as an indic...

Koo, Bon-Chul

2013-01-01T23:59:59.000Z

187

VHE Gamma-ray Supernova Remnants  

SciTech Connect

Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22T23:59:59.000Z

188

New approaches for modeling type Ia supernovae  

SciTech Connect

Type Ia supernovae (SNe Ia) are the largest thermonuclearexplosions in the Universe. Their light output can be seen across greatstances and has led to the discovery that the expansion rate of theUniverse is accelerating. Despite the significance of SNe Ia, there arestill a large number of uncertainties in current theoretical models.Computational modeling offers the promise to help answer the outstandingquestions. However, even with today's supercomputers, such calculationsare extremely challenging because of the wide range of length and timescales. In this paper, we discuss several new algorithms for simulationsof SNe Ia and demonstrate some of their successes.

Zingale, Michael; Almgren, Ann S.; Bell, John B.; Day, Marcus S.; Rendleman, Charles A.; Woosley, Stan

2007-06-25T23:59:59.000Z

189

Supernova shock revival by nuclear reactions  

Science Conference Proceedings (OSTI)

We performed hydrodynamic simulations of core collapse and bounce for a progenitor model with 15.0 solar mass, using ZEUS-MP code in axi-symmetric coordinate. Our numerical code is equipped with a nuclear reaction network including 13 alpha nuclei form {sup 4}He to {sup 56}Ni to investigate the potential role played by nuclear reactions in reviving a stalled shock wave at the central region of core-collapse supernovae. We found that the energy released by nuclear reactions is significantly helpful in accelerating shock waves and is able to produce energetic explosion even if inputted neutrino luminosity is low.

Nakamrua, Ko; Takiwaki, Tomoya; Kotake, Kei; Nishimura, Nobuya [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Department Physik, Universitaet Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)

2012-11-12T23:59:59.000Z

190

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

191

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

192

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

193

Matter Mixing in Axisymmetric Supernova Explosion  

E-Print Network (OSTI)

Growth of Rayleigh-Taylor (R-T) instabilities under the axisymmetric explosion are investigated by two-dimensional hydrodynamical calculations. The degree of the axisymmetric explosion and amplitude of the initial perturbation are varied parametrically to find the most favorable parameter for reproducing the observed line profile of heavy elements. It is found that spherical explosion can not produce $^{56}Ni$ travelling at high velocity ($\\sim 3000$km/sec), the presence of which is affirmed by the observation, even if the amplitude of initial perturbation is as large as 30%. On the other hand, strong axisymmetric explosion model produce high velocity $^{56}Ni$ too much. Weak axisymmetric explosion are favored for the reproduction of the observed line profile. We believe this result shows upper limit of the degree of the axisymmetric explosion. This fact will be important for the simulation of the collapse-driven supernova including rotation, magnetic field, and axisymmetric neutrino radiation, which have a possibility to cause axisymmetric supernova explosion. In addition, the origin of such a large perturbation does not seem to be the structure of the progenitor but the dynamics of the core collapse explosion itself since small perturbation can not produce the high velocity element even if the axisymmetric explosion models are adopted.

Shigehiro Nagataki; Tetsuya Shimizu; Katsuhiko Sato

1997-09-16T23:59:59.000Z

194

Supernovae as Nuclear and Particle Physics Laboratories  

Science Conference Proceedings (OSTI)

In the interior of supernovae, temperatures and densities exceed the range that is easily accessible by terrestrial experiments. With the improving sensitivities of neutrino and gravitational wave detectors, the chance of obtaining observations providing a deep view into the heart of a close-by supernova explosion is steadily increasing. Based on computational models, we investigate the imprint of the nuclear equation of state on the emission of neutrinos and gravitational waves. If a QCD phase transition to quark matter occurs during the immediate postbounce accretion phase, a strong second shock front is formed at a radius of order 10 km. Neutronized hadronic outer layers of the protoneutron star fall into it, are shock-heated, and lead to a rapid acceleration of the second shock wave. As soon as this shock reduces the electron degeneracy at the neutrinospheres, a sharp second neutrino burst is emitted, dominated by electron antineutrinos. Together with the abruptly increasing mean energies of {mu}- and {tau}-neutrinos, it may serve as a clear signature of the phase transition of the protoneutron star core to a more compact state.

Liebendoerfer, Matthias [Universitat Basel, Switzerland; Fischer, T. [University of Basel; Hempel, M. [Goethe University, Frankfurt, Germany; Mezzacappa, Anthony [ORNL; Pagliara, G. [Ruprecht-Karls-Universitaet, Heidelberg, Germany; Sagert, I. [Goethe University, Frankfurt, Germany; Schaffner-Bielich, J. [Ruprecht-Karls-Universitaet, Heidelberg, Germany; Scheidegger, Simon [Universitat Basel, Switzerland; Thielemann, Friedrich-Karl W. [Universitat Basel, Switzerland; Whitehouse, Stuart [Universitat Basel, Switzerland

2009-01-01T23:59:59.000Z

195

Could There Be A Hole In Type Ia Supernovae?  

E-Print Network (OSTI)

In the favored progenitor scenario, Type Ia supernovae arise from a white dwarf accreting material from a non-degenerate companion star. Soon after the white dwarf explodes, the ejected supernova material engulfs the companion star; two-dimensional hydrodynamical simulations by Marietta et. al. show that, in the interaction, the companion star carves out a conical hole of opening angle 30-40 degrees in the supernova ejecta. In this paper we use multi-dimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry. We calculate the variation of the spectrum, luminosity, and polarization with viewing angle for the aspherical supernova near maximum light. We find that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole. In the latter case, one sees into the deeper, hotter layers of ejecta. The supernova is relatively brighter and has a peculiar spectrum characterized by more highly ionized species, weaker absorption features, and lower absorption velocities. The spectrum viewed down the hole is comparable to the class of SN 1991T-like supernovae. We consider how the ejecta-hole asymmetry may explain the current spectropolarimetric observations of SNe Ia, and suggest a few observational signatures of the geometry. Finally, we discuss the variety currently seen in observed SNe Ia and how an ejecta-hole asymmetry may fit in as one of several possible sources of diversity.

Daniel Kasen; Peter Nugent; R. C. Thomas; Lifan Wang

2003-11-01T23:59:59.000Z

196

Cosmological singularities in Bakry-mery spacetimes  

E-Print Network (OSTI)

We consider spacetimes consisting of a manifold with Lorentzian metric and a weight function or scalar field. These spacetimes admit a Bakry-\\'Emery-Ricci tensor which is a natural generalization of the Ricci tensor. We impose an energy condition on the Bakry-\\'Emery-Ricci tensor and obtain singularity theorems of a cosmological type, both for zero and for positive cosmological constant. That is, we find conditions under which every timelike geodesic is incomplete. These conditions are given by "open" inequalities, so we examine the borderline (equality) cases and show that certain singularities are avoided in these cases only if the geometry is rigid; i.e., if it splits as a Lorentzian product or, for a positive cosmological constant, a warped product, and the weight function is constant along the time direction. Then the product case is future timelike geodesically complete while, in the warped product case, worldlines of conformally static observers are complete. Our results answer a question posed by J Case. We then apply our results to the cosmology of scalar-tensor gravitation theories. We focus on the Brans-Dicke family of theories in 4 spacetime dimensions, where we obtain "Jordan frame" singularity theorems for big bang singularities.

Gregory J Galloway; Eric Woolgar

2013-12-12T23:59:59.000Z

197

Primordial magnetic field limits from cosmological data  

SciTech Connect

We study limits on a primordial magnetic field arising from cosmological data, including that from big bang nucleosynthesis, cosmic microwave background polarization plane Faraday rotation limits, and large-scale structure formation. We show that the physically relevant quantity is the value of the effective magnetic field, and limits on it are independent of how the magnetic field was generated.

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, Ontario P3E 2C (Canada); Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Tevzadze, Alexander G. [Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Faculty of Exact and Natural Sciences, Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi, GE-0128 (Georgia); Sethi, Shiv K. [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Pandey, Kanhaiya [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2010-10-15T23:59:59.000Z

198

Encoding cosmological futures with conformal structures  

E-Print Network (OSTI)

Quiescent cosmology and the Weyl curvature hypothesis possess a mathematical framework, namely the definition of an Isotropic Singularity, but only for the initial state of the universe. A complementary framework is necessary to also encode appropriate cosmological futures. In order to devise a new framework we analyse the relation between regular conformal structures and (an)isotropy, the behaviour and role of a monotonic conformal factor which is a function of cosmic time, as well as four example cosmologies for further guidance. Finally, we present our new definitions of an Anisotropic Future Endless Universe and an Anisotropic Future Singularity which offer a promising realisation for the new framework. Their irregular, degenerate conformal structures differ significantly from those of the Isotropic Singularity. The combination of the three definitions together could then provide the first complete formalisation of the quiescent cosmology concept. For completeness we also present the new definitions of an Isotropic Future Singularity and a Future Isotropic Universe. The relation to other approaches, in particular to the somewhat dual dynamical systems approach, and other asymptotic scenarios is briefly discussed.

Philipp A Hoehn; Susan M Scott

2010-01-18T23:59:59.000Z

199

Cosmological parameter estimation from CMB experiments  

Science Conference Proceedings (OSTI)

I review the general aspects of cosmological parameter estimation from observations of the cosmic microwave background (CMB) temperature anisotropies in the framework of inflationary adiabatic models. The most recent CMB datasets are starting to give good constraints on the relevant parameters of inflationary adiabatic models. They point toward a model consistent with the basic predictions of inflation: a nearly flat universe

Amedeo Balbi

2001-01-01T23:59:59.000Z

200

LHC/ILC/cosmology interplay  

Science Conference Proceedings (OSTI)

[15] LEP Working Group on Higgs Boson Searches: R Barate et al, Phys. Lett. B565, 61. (2003), hep-ex/0306033. [16] A Pilaftsis, Phys. Lett. B435, 88 (1998)...

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

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

202

Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight  

E-Print Network (OSTI)

Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales - which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the inferred density parameters, but also introduces a bias in the posterior value.

V. C. Busti; R. F. L. Holanda; C. Clarkson

2013-09-25T23:59:59.000Z

203

Progenitors of type Ia supernovae in elliptical galaxies  

Science Conference Proceedings (OSTI)

Although there is a nearly universal agreement that type Ia supernovae are associated with the thermonuclear disruption of a CO white dwarf, the exact nature of their progenitors is still unknown. The single degenerate scenario envisages a white dwarf accreting matter from a non-degenerate companion in a binary system. Nuclear energy of the accreted matter is released in the form of electromagnetic radiation or gives rise to numerous classical nova explosions prior to the supernova event. We show that combined X-ray output of supernova progenitors and statistics of classical novae predicted in the single degenerate scenario are inconsistent with X-ray and optical observations of nearby early type galaxies and galaxy bulges. White dwarfs accreting from a donor star in a binary system and detonating at the Chandrasekhar mass limit can account for no more than {approx}5% of type Ia supernovae observed in old stellar populations.

Gilfanov, M.; Bogdan, A.

2011-09-21T23:59:59.000Z

204

The GALEX View of Supernova Hosts  

E-Print Network (OSTI)

We exploit the accumulating, high-quality, multi-wavelength imaging data of nearby supernova (SN) hosts to explore the relationship between SN production and host galaxy evolution. The Galaxy Evolution Explorer (GALEX, Martin et al., 2005) provides ultraviolet (UV) imaging in two bands, complementing data in the optical and infra-red (IR). We compare host properties, derived from spectral energy distribution (SED) fitting, with nearby, well-observed SN Ia light curve properties. We also explore where the hosts of different types of SNe fall relative to the red and blue sequences on the galaxy UV-optical color-magnitude diagram (CMD, Wyder et al., 2007). We conclude that further exploration and larger samples will provide useful results for constraining the progenitors of SNe.

Neill, James D; Seibert, Mark

2008-01-01T23:59:59.000Z

205

The GALEX View of Supernova Hosts  

E-Print Network (OSTI)

We exploit the accumulating, high-quality, multi-wavelength imaging data of nearby supernova (SN) hosts to explore the relationship between SN production and host galaxy evolution. The Galaxy Evolution Explorer (GALEX, Martin et al., 2005) provides ultraviolet (UV) imaging in two bands, complementing data in the optical and infra-red (IR). We compare host properties, derived from spectral energy distribution (SED) fitting, with nearby, well-observed SN Ia light curve properties. We also explore where the hosts of different types of SNe fall relative to the red and blue sequences on the galaxy UV-optical color-magnitude diagram (CMD, Wyder et al., 2007). We conclude that further exploration and larger samples will provide useful results for constraining the progenitors of SNe.

James D. Neill; Mark Sullivan; Mark Seibert

2008-12-22T23:59:59.000Z

206

Carbon Monoxide in type II supernovae  

E-Print Network (OSTI)

Infrared spectra of two type II supernovae 6 months after explosion are presented. The spectra exhibit a strong similarity to the observations of SN 1987A and other type II SNe at comparable epochs. The continuum can be fitted with a cool black body and the hydrogen lines have emissivities that are approximately those of a Case B recombination spectrum. The data extend far enough into the thermal region to detect emission by the first overtone of carbon monoxide. The molecular emission is modeled and compared with that in the spectra of SN 1987A. It is found that the flux in the CO first overtone is comparable to that found in SN 1987A. We argue that Carbon Monoxide forms in the ejecta of all type II SNe during the first year after explosion.

J. Spyromilio; B. Leibundgut; R. Gilmozzi

2001-07-16T23:59:59.000Z

207

Spectral diversity of Type Ia Supernovae  

E-Print Network (OSTI)

We use published spectroscopic and photometric data for 8 Type Ia supernovae to construct a dispersion spectrum for this class of object, showing their diversity over the wavelength range 3700A to 7100A. We find that the B and V bands are the spectral regions with the least dispersion, while the U band below 4100A is more diverse. Some spectral features such as the Si line at 6150A are also highly diverse. We then construct two objective measures of 'peculiarity' by (i) using the deviation of individual objects from the average SN Ia spectrum compared to the typical dispersion and (ii) applying principle component analysis. We demonstrate these methods on several SNe Ia that have previously been classified as peculiar.

J. Berian James; Tamara M. Davis; Brian P. Schmidt; Alex G. Kim

2006-05-05T23:59:59.000Z

208

Halo expansion in cosmological hydro simulations: towards a baryonic solution of the cusp/core problem in massive spirals  

E-Print Network (OSTI)

A clear prediction of the Cold Dark Matter model is the existence of cuspy dark matter halo density profiles on all mass scales. This is not in agreement with the observed rotation curves of spiral galaxies, challenging on small scales the otherwise successful CDM paradigm. In this work we employ high resolution cosmological hydro-dynamical simulations to study the effects of dissipative processes on the inner distribution of dark matter in Milky-Way like objects (M~1e12 Msun). Our simulations include supernova feedback, and the effects of the radiation pressure of massive stars before they explode as supernovae. The increased stellar feedback results in the expansion of the dark matter halo instead of contraction with respect to N-body simulations. Baryons are able to erase the dark matter cuspy distribution creating a flat, cored, dark matter density profile in the central several kpc of a massive Milky-Way like halo. The profile is well fit by a Burkert profile, with fitting parameters consistent with the ...

Maccio', Andrea V; Brook, Chris B; Wadsley, James; Couchman, H M P; Shen, Sijing; Gibson, Brad K; Quinn, Tom

2011-01-01T23:59:59.000Z

209

HALO EXPANSION IN COSMOLOGICAL HYDRO SIMULATIONS: TOWARD A BARYONIC SOLUTION OF THE CUSP/CORE PROBLEM IN MASSIVE SPIRALS  

Science Conference Proceedings (OSTI)

A clear prediction of the cold dark matter (CDM) model is the existence of cuspy dark matter halo density profiles on all mass scales. This is not in agreement with the observed rotation curves of spiral galaxies, challenging on small scales the otherwise successful CDM paradigm. In this work we employ high-resolution cosmological hydrodynamical simulations to study the effects of dissipative processes on the inner distribution of dark matter in Milky Way like objects (M Almost-Equal-To 10{sup 12} M{sub Sun }). Our simulations include supernova feedback, and the effects of the radiation pressure of massive stars before they explode as supernovae. The increased stellar feedback results in the expansion of the dark matter halo instead of contraction with respect to N-body simulations. Baryons are able to erase the dark matter cuspy distribution, creating a flat, cored, dark matter density profile in the central several kiloparsecs of a massive Milky-Way-like halo. The profile is well fit by a Burkert profile, with fitting parameters consistent with the observations. In addition, we obtain flat rotation curves as well as extended, exponential stellar disk profiles. While the stellar disk we obtain is still partially too thick to resemble the Milky Way thin disk, this pilot study shows that there is enough energy available in the baryonic component to alter the dark matter distribution even in massive disk galaxies, providing a possible solution to the long-standing problem of cusps versus cores.

Maccio, A. V.; Stinson, G. [Max-Planck-Institut fuer Astronomie, 69117 Heidelberg (Germany); Brook, C. B.; Gibson, B. K. [University of Central Lancashire, Jeremiah Horrocks Institute for Astrophysics and Supercomputing, Preston PR1 2HE (United Kingdom); Wadsley, J.; Couchman, H. M. P. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada); Shen, S. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Quinn, T., E-mail: maccio@mpia.de, E-mail: stinson@mpia.de [Astronomy Department, University of Washington, Seattle, WA 98195-1580 (United States)

2012-01-15T23:59:59.000Z

210

Analytical Models for the Energetics of Cosmic Accretion Shocks, their Cosmological Evolution, and the Effect of Environment  

E-Print Network (OSTI)

We present an analytical description of the energetics of the population of cosmic accretion shocks, for a concordance cosmology. We calculate how the shock-processed accretion power and mass current are distributed among different shock Mach numbers, and how they evolve with cosmic time. We calculate the cumulative energy input of cosmic accretion shocks of any Mach number to the intergalactic medium as a function of redshift, and we compare it with the energy output of supernova explosions as well as with the energy input required to reionize the universe. In addition, we investigate and quantify the effect of environmental factors, such as local clustering properties and filament preheating on the statistical properties of these shocks. We find that the energy processed by accretion shocks is higher than the supernova energy output for z<3 and that it becomes more than an order of magnitude higher in the local universe. The energy processed by accretion shocks alone becomes comparable to the energy required to reionize the universe by z~3.5. Finally, we establish both qualitative and quantitatively that both local clustering as well as filament compression and preheating are important factors in determining the statistical properties of the cosmic accretion shock population.

Vasiliki Pavlidou; Brian D. Fields

2006-11-29T23:59:59.000Z

211

Toward Radiation-Magnetohydrodynamic Simulations in Core-Collapse Supernovae  

E-Print Network (OSTI)

We report a current status of our radiation-magnetohydrodynamic code for the study of core-collapse supernovae. In this contribution, we discuss the accuracy of our newly developed numerical code by presenting the test problem in a static background model. We also present the application to the spherically symmetric core-collapse simulations. Since close comparison with the previously published models is made, we are now applying it for the study of magnetorotational core-collapse supernovae.

Kotake, K; Yamada, S; Sato, K; Kotake, Kei; Ohnishi, Naofumi; Yamada, Shoichi; Sato, Katsuhiko

2006-01-01T23:59:59.000Z

212

Toward Radiation-Magnetohydrodynamic Simulations in Core-Collapse Supernovae  

E-Print Network (OSTI)

We report a current status of our radiation-magnetohydrodynamic code for the study of core-collapse supernovae. In this contribution, we discuss the accuracy of our newly developed numerical code by presenting the test problem in a static background model. We also present the application to the spherically symmetric core-collapse simulations. Since close comparison with the previously published models is made, we are now applying it for the study of magnetorotational core-collapse supernovae.

Kei Kotake; Naofumi Ohnishi; Shoichi Yamada; Katsuhiko Sato

2005-11-30T23:59:59.000Z

213

Nucleosynthesis and Clump Formation in a Core Collapse Supernova  

E-Print Network (OSTI)

High-resolution two-dimensional simulations were performed for the first five minutes of the evolution of a core collapse supernova explosion in a 15 solar mass blue supergiant progenitor. The computations start shortly after bounce and include neutrino-matter interactions by using a light-bulb approximation for the neutrinos, and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout the inner half of the helium core by Rayleigh-Taylor instabilities at the Ni+Si/O and C+O/He interfaces, seeded by convective overturn during the early stages of the explosion. Fast moving nickel mushrooms with velocities up to about 4000 km/s are observed. This offers a natural explanation for the mixing required in light curve and spectral synthesis studies of Type Ib explosions. A continuation of the calculations to later times, however, indicates that the iron velocities observed in SN 1987 A cannot be reproduced because of a strong deceleration of the clumps in the dense shell left behind by the shock at the He/H interface.

K. Kifonidis; T. Plewa; H. -Th. Janka; E. Mueller

1999-11-10T23:59:59.000Z

214

Conformal Structures Admitted by a Class of FRW Cosmologies  

E-Print Network (OSTI)

In this paper we demonstrate that there are large classes of Friedmann-Robertson-Walker (FRW) cosmologies that admit isotropic conformal structures of Quiescent Cosmology. FRW models have long been known to admit singularities such as Big Bangs and Big Crunches [1, 2] but recently it has been shown that there are other cosmological structures that these solutions contain. These structures are Big Rips, Sudden Singularities and Extremality Events [1, 2]. Within the Quiescent Cosmology framework [3] there also exist structures consistent with a cosmological singularity known as the Isotropic Past Singularity (IPS) [4, 5]. There also exists a cosmological final state known as a Future Isotropic Universe (FIU) [4], which strictly speaking, doesn't fit with the fundamental ideals of Quiescent Cosmology. In this paper, we compare the cosmological events of a large class of FRW solutions to the conformal structures of Quiescent Cosmology [4]. In the first section of this paper we present the relevant background information and our motivation. In the second section of this paper we construct conformal relationships for relevant FRW models. The third section contains a thorough discussion of a class of FRW solutions that cannot represent any of the previously constructed isotropic conformal structures from Quiescent Cosmology. The final section contains our remarks and future outlook for further study of this field.

Philip Threlfall; Susan M. Scott

2012-11-26T23:59:59.000Z

215

THE SDSS-II SUPERNOVA SURVEY: PARAMETERIZING THE TYPE Ia SUPERNOVA RATE AS A FUNCTION OF HOST GALAXY PROPERTIES  

Science Conference Proceedings (OSTI)

Using data from the Sloan Digital Sky Supernova Survey-II (SDSS-II SN Survey), we measure the rate of Type Ia supernovae (SNe Ia) as a function of galaxy properties at intermediate redshift. A sample of 342 SNe Ia with 0.05 0.15) SNe Ia in highly star-forming galaxies. We consider that the high levels of dust in these systems may be obscuring the reddest and faintest SNe Ia.

Smith, Mathew [Department of Physics, University of Western Cape, Bellville 7530, Cape Town (South Africa); Nichol, Robert C. [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom); Dilday, Benjamin [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117 (United States); Marriner, John; Frieman, Joshua [Center for Particle Astrophysics, Fermilab, P.O. Box 500, Batavia, IL 60510 (United States); Kessler, Richard [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave, Chicago, IL 60637 (United States); Bassett, Bruce [African Institute for Mathematical Sciences, 6-8 Melrose Road, Muizenberg 7945 (South Africa); Cinabro, David [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States); Garnavich, Peter [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Jha, Saurabh W. [Department of Physics and Astronomy, Rutgers, State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Lampeitl, Hubert [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa); Sako, Masao [Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Sollerman, Jesper, E-mail: matsmith2@gmail.com [Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University, SE-106 91 Stockholm (Sweden)

2012-08-10T23:59:59.000Z

216

A Cosmology Forecast Toolkit -- CosmoLib  

E-Print Network (OSTI)

The package CosmoLib is a combination of a cosmological Boltzmann code and a simulation toolkit to forecast the constraints on cosmological parameters from future observations. In this paper we describe the released linear-order part of the package. We discuss the stability and performance of the Boltzmann code. This is written in Newtonian gauge and including dark energy perturbations. In CosmoLib the integrator that computes the CMB angular power spectrum is optimized for a $\\ell$-by-$\\ell$ brute-force integration, which is useful for studying inflationary models predicting sharp features in the primordial power spectrum of metric fluctuations. The numerical code and its documentation are available at http://www.cita.utoronto.ca/~zqhuang/CosmoLib.

Zhiqi Huang

2012-01-28T23:59:59.000Z

217

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

2004-12-11T23:59:59.000Z

218

Shock Waves and Cosmological Matrix Models  

E-Print Network (OSTI)

We find the shock wave solutions in a class of cosmological backgrounds with a null singularity, each of these backgrounds admits a matrix description. A shock wave solution breaks all supersymmetry meanwhile indicates that the interaction between two static D0-branes cancel, thus provides basic evidence for the matrix description. The probe action of a D0-brane in the background of another suggests that the usual perturbative expansion of matrix model breaks down.

Miao Li; Wei Song

2005-07-19T23:59:59.000Z

219

Forecasting Cosmological Constraints from Redshift Surveys  

E-Print Network (OSTI)

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up of cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity. In this paper we present a formalism for forecasting the constraints on the growth of structure which would arise in an idealized survey. This Fisher matrix based formalism can be used to study the power and aid in the design of future surveys.

Martin White; Yong-Seon Song; Will J. Percival

2008-10-08T23:59:59.000Z

220

Consistent probabilities in loop quantum cosmology  

E-Print Network (OSTI)

A fundamental issue for any quantum cosmological theory is to specify how probabilities can be assigned to various quantum events or sequences of events such as the occurrence of singularities or bounces. In previous work, we have demonstrated how this issue can be successfully addressed within the consistent histories approach to quantum theory for Wheeler-DeWitt-quantized cosmological models. In this work, we generalize that analysis to the exactly solvable loop quantization of a spatially flat, homogeneous and isotropic cosmology sourced with a massless, minimally coupled scalar field known as sLQC. We provide an explicit, rigorous and complete decoherent histories formulation for this model and compute the probabilities for the occurrence of a quantum bounce vs. a singularity. Using the scalar field as an emergent internal time, we show for generic states that the probability for a singularity to occur in this model is zero, and that of a bounce is unity, complementing earlier studies of the expectation values of the volume and matter density in this theory. We also show from the consistent histories point of view that all states in this model, whether quantum or classical, achieve arbitrarily large volume in the limit of infinite `past' or `future' scalar `time', in the sense that the wave function evaluated at any arbitrary fixed value of the volume vanishes in that limit. Finally, we briefly discuss certain misconceptions concerning the utility of the consistent histories approach in these models.

David A. Craig; Parampreet Singh

2013-06-26T23:59:59.000Z

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221

Planck 2013 results. XVI. Cosmological parameters  

E-Print Network (OSTI)

We present the first results based on Planck measurements of the CMB temperature and lensing-potential power spectra. The Planck spectra at high multipoles are extremely well described by the standard spatially-flat six-parameter LCDM cosmology. In this model Planck data determine the cosmological parameters to high precision. We find a low value of the Hubble constant, H0=67.3+/-1.2 km/s/Mpc and a high value of the matter density parameter, Omega_m=0.315+/-0.017 (+/-1 sigma errors) in excellent agreement with constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent-level precision using Planck CMB data alone. We present results from an analysis of extensions to the standard cosmology, using astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured significantly over standard LCDM. The deviation of the scalar spectral index from unity is insensitive to the additi...

Ade, P A R; Armitage-Caplan, C; Arnaud, M; Ashdown, M; Atrio-Barandela, F; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Battaner, E; Benabed, K; Benot, A; Benoit-Lvy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bobin, J; Bock, J J; Bonaldi, A; Bond, J R; Borrill, J; Bouchet, F R; Bridges, M; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cappellini, B; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chary, R -R; Chen, X; Chiang, L -Y; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Delouis, J -M; Dsert, F -X; Dickinson, C; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Dor, O; Douspis, M; Dunkley, J; Dupac, X; Efstathiou, G; Elsner, F; Enlin, T A; Eriksen, H K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Gaier, T C; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giardino, G; Giraud-Hraud, Y; Gjerlw, E; Gonzlez-Nuevo, J; Grski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Haissinski, J; Hamann, J; Hansen, F K; Hanson, D; Harrison, D; Henrot-Versill, S; Hernndez-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hou, Z; Hovest, W; Huffenberger, K M; Jaffe, T R; Jaffe, A H; Jewell, J; Jones, W C; Juvela, M; Keihnen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Knox, L; Kunz, M; Kurki-Suonio, H; Lagache, G; Lhteenmki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Laureijs, R J; Lawrence, C R; Leach, S; Leahy, J P; Leonardi, R; Len-Tavares, J; Lesgourgues, J; Lewis, A; Liguori, M; Lilje, P B; Linden-Vrnle, M; Lpez-Caniego, M; Lubin, P M; Macas-Prez, J F; Maffei, B; Maino, D; Mandolesi, N; Maris, M; Marshall, D J; Martin, P G; Martnez-Gonzlez, E; Masi, S; Matarrese, S; Matthai, F; Mazzotta, P; Meinhold, P R; Melchiorri, A; Melin, J -B; Mendes, L; Menegoni, E; Mennella, A; Migliaccio, M; Millea, M; Mitra, S; Miville-Deschnes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nrgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; O'Dwyer, I J; Osborne, S; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Partridge, B; Pasian, F; Patanchon, G; Pearson, D; Pearson, T J; Peiris, H V; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Platania, P; Pointecouteau, E; Polenta, G; Ponthieu, N; Popa, L; Poutanen, T; Pratt, G W; Przeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Ricciardi, S; Riller, T; Ristorcelli, I; Rocha, G; Rosset, C; Roudier, G; Rowan-Robinson, M; Rubio-Martn, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Starck, J -L; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sureau, F; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Tavagnacco, D; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Trler, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Vittorio, N; Wade, L A; Wandelt, B D; Wehus, I K; White, M; White, S D M; Wilkinson, A; Yvon, D; Zacchei, A; Zonca, A

2013-01-01T23:59:59.000Z

222

Decaying Higgs Fields and Cosmological Dark Energy  

E-Print Network (OSTI)

The observed dark energy in the universe might give particles inertial mass. We investigate one realization of this idea, that the dark energy field might be a decayed scalar component of a supermultiplet field in the early universe that creates inertial mass through spontaneous symmetry breaking, e.g. a Higgs field. To investigate this possibility, the cosmological Friedmann equation of energy balance is augmented in a standard way to incorporate a minimally coupled cosmological Higgs. For epochs where the expansion of the universe is driven by matter and radiation and not the scalar field, the observed hidden nature of the Higgs field can be codified into a single differential equation that we call the "hidden higgs" condition. The resulting differential equation is solved for the time dependant scalar field and a simple and interesting solution is found analytically. Such a Higgs field decays from Planck scale energies rapidly and approximately exponentially from onset, leaving only the initially negligible constant term of the potential as a final cosmological constant. Such evolution replaces the hierarchy problem with the problem of explaining why such evolution is physically justified.

Robert J. Nemiroff; Bijunath Patla

2004-09-27T23:59:59.000Z

223

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

224

A Cosmology Calculator for the World Wide Web  

E-Print Network (OSTI)

A cosmology calculator that computes times and distances as a function of redshift for user-defined cosmological parameters is available on the World Wide Web. This note gives the formulae used by the cosmology calculator and discusses some of its implementation. A version of the calculator that allows one to specify the equation of state parameter w and w' and neutrino masses, and a version for converting the light travel times usually given in the popular press into redshifts are also available.

Edward L. Wright

2006-09-20T23:59:59.000Z

225

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

226

A new multidimensional AMR Hydro+Gravity Cosmological code  

E-Print Network (OSTI)

A new cosmological multidimensional hydrodynamic and N-body code based on an Adaptive Mesh Refinement scheme is described and tested. The hydro part is based on modern high-resolution shock-capturing techniques, whereas N-body approach is based on the Particle Mesh method. The code has been specifically designed for cosmological applications. Tests including shocks, strong gradients, and gravity have been considered. A cosmological test based on Santa Barbara cluster is also presented. The usefulness of the code is discussed. In particular, this powerful tool is expected to be appropriate to describe the evolution of the hot gas component located inside asymmetric cosmological structures.

Vicent Quilis

2004-05-20T23:59:59.000Z

227

Birth of the Universe, Direct Numerical Simulations of Cosmological...  

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

Simulations of Cosmological Reionization November 30, 2011 Tweet EmailPrint In this video from SC11, Michael Norman (SDSC), Joseph Insley (MCS), and Rick Wagner (SDSC) describe...

228

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

229

THE EXTENDED HUBBLE SPACE TELESCOPE SUPERNOVA SURVEY: THE RATE OF CORE COLLAPSE SUPERNOVAE TO z {approx} 1  

SciTech Connect

We use a sample of 45 core collapse supernovae detected with the Advanced Camera for Surveys on board the Hubble Space Telescope to derive the core collapse supernova rate in the redshift range 0.1 < z < 1.3. In redshift bins centered on (z) = 0.39, (z) = 0.73, and (z) = 1.11, we find rates of 3.00{sup +1.28}{sub -0.94} {sup +1.04}{sub -0.57}, 7.39{sup +1.86}{sub -1.52} {sup +3.20}{sub -1.60}, and 9.57{sup +3.76}{sub -2.80} {sup +4.96}{sub -2.80}, respectively, given in units of yr{sup -1} Mpc{sup -3} 10{sup -4} h {sup 3}{sub 70}. The rates have been corrected for host galaxy extinction, including supernovae missed in highly dust-enshrouded environments in infrared bright galaxies. The first errors are statistical while the second ones are the estimated systematic errors. We perform a detailed discussion of possible sources of systematic errors and note that these start to dominate over statistical errors at z > 0.5, emphasizing the need to better control the systematic effects. For example, a better understanding of the amount of dust extinction in the host galaxies and knowledge of the supernova luminosity function, in particular the fraction of faint M {approx}> -15 supernovae, is needed to better constrain the rates. When comparing our results with the core collapse supernova rate based on the star formation rate, we find a good agreement, consistent with the supernova rate following the star formation rate, as expected.

Dahlen, Tomas; Riess, Adam G. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Strolger, Louis-Gregory [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States); Mattila, Seppo; Kankare, Erkki [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Vaeisaelaentie 20, FI-21500 Piikkioe (Finland); Mobasher, Bahram, E-mail: dahlen@stsci.edu [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)

2012-09-20T23:59:59.000Z

230

Aspects of Neutrino Production in Supernovae  

E-Print Network (OSTI)

I discuss neutrino production in supernovae (SNe) and the detection of both Galactic core collapse events and the diffuse extra-galactic MeV neutrino background expected from the integrated history of star formation. In particular, I consider what processes might affect our expectations for both. I focus on ``rapid'' rotation, defined as leading to millisecond initial neutron star spin periods. Rotation affects the neutrino luminosity, the average neutrino energy, the duration of the Kelvin-Helmholtz cooling epoch, and the ratios of luminosities and average energies between neutrino species; it can strongly suppresses the anti-electron as well as mu, anti-mu, tau, and anti-tau neutrino fluxes relative to those for the electron neutrinos. As a result, depending on the prevalence of rapid rotation in SN progenitors through cosmic time, this may affect predictions for the MeV neutrino background and the history of nucleosynthetic enrichment. I emphasize connections between the MeV neutrino background and tracers of the star formation rate density at high redshift in other neutrino and photon wavebands.

Todd A. Thompson

2006-08-10T23:59:59.000Z

231

Cosmic Ray Spectrum in Supernova Remnant Shocks  

E-Print Network (OSTI)

We perform kinetic simulations of diffusive shock acceleration (DSA) in Type Ia supernova remnants (SNRs) expanding into a uniform interstellar medium (ISM). Bohm-like diffusion assumed, and simple models for Alfvenic drift and dissipation are adopted. Phenomenological models for thermal leakage injection are considered as well. We find that the preshock gas temperature is the primary parameter that governs the cosmic ray (CR) acceleration efficiency and energy spectrum, while the CR injection rate is a secondary parameter. For SNRs in the warm ISM, if the injection fraction is larger than 10^{-4}, the DSA is efficient enough to convert more than 20 % of the SN explosion energy into CRs and the accelerated CR spectrum exhibits a concave curvature flattening to E^{-1.6}. Such a flat source spectrum near the knee energy, however, may not be reconciled with the CR spectrum observed at Earth. On the other hand, SNRs in the hot ISM, with an injection fraction smaller than 10^{-4}, are inefficient accelerators with...

Kang, Hyesung

2010-01-01T23:59:59.000Z

232

Cosmic Rays and the Monogem Supernova Remnant  

E-Print Network (OSTI)

Recent findings indicate that the Monogem Ring supernova remnant (SNR) and the associated pulsar B0656+14 may be the 'Single Source' responsible for the knee in the cosmic ray (CR) energy spectrum at ~3 PeV. We estimate the contribution of this pulsar to CR in the PeV region. We conclude that although the pulsar can contribute to the formation of the knee, it cannot be the domimant source and a SNR is still needed. We also examine the possibility of the pulsar giving the peak of the extensive air shower (EAS) intensity observed from the region inside the Monogem Ring. If the experimental EAS results concerning a narrow source are confirmed, they can be important, since they give evidence: (i) for the acceleration of protons and heavier nuclei by the pulsar; (ii) for the existence of the confinement mechanism in SNR; (iii) that CR produced by the Monogem Ring SNR and associated pulsar B0656+14 were released recently giving rise to the formation of the knee and the observed narrow peak in the EAS intensity; (iv) for the Monogem Ring and the associated pulsar B0656+14 being identified as the Single Source proposed in our Single Source Model of the knee. A number of predictions of the examined scenario are made.

A. D. Erlykin; A. W. Wolfendale

2004-04-27T23:59:59.000Z

233

Distributed Flames in Type Ia Supernovae  

E-Print Network (OSTI)

In the distributed burning regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning depends on the turbulent Damkohler number (Da), which steadily declines from much greater than one to less that one as the density decreases to a few 10^6 g/cc. Scaling arguments predict that the turbulent flame speed s, normalized by the turbulent intensity u, follows s/u=Da^1/2 for Da1, and that localized excursions to as much as five times u can occur. The lambda-flame speed and width can be predicted based on the turbulence in the star and the turbulent nuclear burning time scale of the fuel. We propose a practical method for measuring these based on the scaling relations and small-scale computationally-inexpensive simulations. This suggests that a simple turbulent flame model can be easily constructed suitable for large-scale distributed supernovae flames.

Aspden, A J; Woosley, S E; 10.1088/0004-637X/710/2/1654

2011-01-01T23:59:59.000Z

234

Gauss-Bonnet Quintessence: Background Evolution, Large Scale Structure and Cosmological Constraints  

E-Print Network (OSTI)

We investigate a string-inspired dark energy scenario featuring a scalar field with a coupling to the Gauss-Bonnet invariant. Such coupling can trigger the onset of late dark energy domination after a scaling matter era. The universe may then cross the phantom divide and perhaps also exit from the acceleration. We discuss extensively the cosmological and astrophysical implications of the coupled scalar field. Data from the Solar system, supernovae Ia, cosmic microwave background radiation, large scale structure and big bang nucleosynthesis is used to constrain the parameters of the model. A good Newtonian limit may require to fix the coupling. With all the data combined, there appears to be some tension with the nucleosynthesis bound, and the baryon oscillation scale seems to strongly disfavor the model. These possible problems might be overcome in more elaborate models. In addition, the validity of these constraints in the present context is not strictly established. Evolution of fluctuations in the scalar field and their impact to clustering of matter is studied in detail and more model-independently. Small scale limit is derived for the perturbations and their stability is addressed. A divergence is found and discussed. The general equations for scalar perturbations are also presented and solved numerically, confirming that the Gauss-Bonnet coupling can be compatible with the observed spectrum of cosmic microwave background radiation as well as the matter power spectrum inferred from large scale surveys.

Tomi Koivisto; David F. Mota

2006-09-22T23:59:59.000Z

235

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

236

Geological isotope anomalies as signatures of nearby supernovae  

E-Print Network (OSTI)

Nearby supernova explosions may cause geological isotope anomalies via the direct deposition of debris or by cosmic-ray spallation in the earth's atmosphere. We estimate the mass of material deposited terrestrially by these two mechanisms, showing the dependence on the supernova distance. A number of radioactive isotopes are identified as possible diagnostic tools, such as Be-10, Al-26, Cl-36, Mn-53, Fe-60, and Ni-59, as well as the longer-lived I-129, Sm-146, and Pu-244. We discuss whether the 35 and 60 kyr-old Be-10 anomalies observed in the Vostok antarctic ice cores could be due to supernova explosions. Combining our estimates for matter deposition with results of recent nucleosynthesis yields, we calculate the expected signal from nearby supernovae using ice cores back to \\sim 300 kyr ago, and we discuss using deep ocean sediments back to several hundred Myr. In particular, we examine the prospects for identifying isotope anomalies due to the Geminga supernova explosion, and signatures of the possibility...

Ellis, Jonathan Richard; Schramm, David N; Ellis, John; Fields, Brian D; Schramm, David N

1996-01-01T23:59:59.000Z

237

FIRST LABORATORY OBSERVATION OF SILICA GRAINS FROM CORE COLLAPSE SUPERNOVAE  

SciTech Connect

We report the discovery of two supernova silica (SiO{sub 2}) grains in the primitive carbonaceous chondrites LaPaZ 031117 and Grove Mountains 021710. Only five presolar silica grains have been previously reported from laboratory measurements but they all exhibit enrichments in {sup 17}O relative to solar, indicating origins in the envelopes of asymptotic giant branch stars. The two SiO{sub 2} grains identified in this study are characterized by moderate enrichments in {sup 18}O relative to solar, indicating that they originated in Type II supernova ejecta. If compared to theoretical models, the oxygen isotopic compositions of these grains can be reproduced by mixing of different supernova zones. While both theoretical models of grain condensation and recent NASA Spitzer Space Telescope observations have suggested the presence of silica in supernova ejecta, no such grains had been identified, until now, in meteorites. The discovery of these two silica grains provides definitive evidence of the condensation of silica dust in supernova ejecta.

Haenecour, Pierre; Floss, Christine; Zinner, Ernst [Laboratory for Space Sciences, McDonnell Center for the Space Sciences and Physics Department, Washington University, One Brookings Drive, St. Louis, MO 63130-4899 (United States); Zhao Xuchao; Lin Yangting, E-mail: haenecour@wustl.edu [Key Laboratory of the Earth's Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China)

2013-05-01T23:59:59.000Z

238

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

239

The farthest known supernova: Support for an accelerating universeand a glimpse of the epoch of deceleration  

Science Conference Proceedings (OSTI)

We present photometric observations of an apparent Type Iasupernova (SN Ia) at a redshift of approximately 1.7, the farthest SNobserved to date. The supernova, SN 1997, was discovered in a repeatobservation by the Hubble Space Telescope (HST) of the Hubble DeepField{North (HDF-N), and serendipitously monitored with NICMOS on HSTthroughout the Thompson et al. GTO campaign. The SN type can bedetermined from the host galaxy type: an evolved, red elliptical lackingenough recent star formation to provide a significant population ofcore-collapse supernovae. The classification is further supported bydiagnostics available from the observed colors and temporal behavior ofthe SN, both of which match a typical SN Ia. The photometric record ofthe SN includes a dozen flux measurements in the I, J, and H bandsspanning 35 days in the observed frame. The redshift derived from the SNphotometry, z = 1:7 plus or minus 0:1, is in excellent agreement with theredshift estimate of z = 1:65 plus or minus 0:15 derived from the U_300B_450 V_-606 I_814 J_110 J_125 H_160 H_165 K_s photometry of the galaxy.Optical and near-infrared spectra of the host provide a very tentativespectroscopic redshift of 1.755. Fits to observations of the SN provideconstraints for the redshift-distance relation of SNe Ia and a powerfultest of the current accelerating Universe hypothesis. The apparent SNbrightness is consistent with that expected in the decelerating phase ofthe preferred cosmological model, Omega_M approximately equal to 1/3;Omega_Lambda approximately equal to 2/3. It is inconsistent with greydust or simple luminosity evolution, candidate astrophysical effectswhich could mimic previous evidence for an accelerating Universe from SNeIa at z approximately equal to 0:5. We consider several sources ofpotential systematic error including gravitational lensing, supernovamisclassification, sample selection bias, and luminosity calibrationerrors. Currently, none of these effects alone appears likely tochallenge our conclusions. Additional SNe Ia at z>1 will be requiredto test more exotic alternatives to the accelerating Universe hypothesisand to probe the nature of dark energy.

Riess, Adam G.; Nugent, Peter E.; Schmidt, Brian P.; Tonry, John; Dickinson, Mark; Gilliland, Ronald L.; Thompson, Rodger I.; Budavari,Tamas; Casertano, Stefano; Evans, Aaron S.; Filippenko, Alexei V.; Livio,Mario; Sanders, David B.; Shapley, Alice E.; Spinrad, Hyron; Steidel,Charles C.; Stern, Daniel; Surace, Jason; Veilleux, Sylvain

2001-04-01T23:59:59.000Z

240

Controls Group  

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

Status and Schedule Safety and Training Divisions APS Engineering Support Division AES Groups Accelerator Systems Division ASD Groups X-ray Science Division XSD Groups...

Note: This page contains sample records for the topic "group supernova cosmology" from the National Library of EnergyBeta (NLEBeta).
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241

Boiling of nuclear liquid in core-collapse supernova explosions  

E-Print Network (OSTI)

We investigate the possibility of boiling instability of nuclear liquid in the inner core of the proto-neutron star formed in the core collapse of a type II supernova. We derive a simple criterion for boiling to occur. Using this criterion for one of best described equations of state of supernova matter, we find that boiling is quite possible under the conditions realized inside the proto-neutron star. We discuss consequences of this process such as the increase of heat transfer rate and pressure in the boiling region. We expect that taking this effect into account in the conventional neutrino-driven delayed-shock mechanism of type II supernova explosions can increase the explosion energy and reduce the mass of the neutron-star remnant.

Peter Fomin; Dmytro Iakubovskyi; Yuri Shtanov

2007-08-31T23:59:59.000Z

242

Boiling of nuclear liquid in core-collapse supernova explosions  

E-Print Network (OSTI)

We investigate the possibility of boiling instability of nuclear liquid in the inner core of the proto-neutron star formed in the core collapse of a type II supernova. We derive a simple criterion for boiling to occur. Using this criterion for one of best described equations of state of supernova matter, we find that boiling is quite possible under the conditions realized inside the proto-neutron star. We discuss consequences of this process such as the increase of heat transfer rate and pressure in the boiling region. We expect that taking this effect into account in the conventional neutrino-driven delayed-shock mechanism of type II supernova explosions can increase the explosion energy and reduce the mass of the neutron-star remnant.

Fomin, Peter; Shtanov, Yuri

2007-01-01T23:59:59.000Z

243

The cosmological simulation code GADGET-2  

E-Print Network (OSTI)

We discuss the cosmological simulation code GADGET-2, a new massively parallel TreeSPH code, capable of following a collisionless fluid with the N-body method, and an ideal gas by means of smoothed particle hydrodynamics (SPH). Our implementation of SPH manifestly conserves energy and entropy in regions free of dissipation, while allowing for fully adaptive smoothing lengths. Gravitational forces are computed with a hierarchical multipole expansion, which can optionally be applied in the form of a TreePM algorithm, where only short-range forces are computed with the `tree'-method while long-range forces are determined with Fourier techniques. Time integration is based on a quasi-symplectic scheme where long-range and short-range forces can be integrated with different timesteps. Individual and adaptive short-range timesteps may also be employed. The domain decomposition used in the parallelisation algorithm is based on a space-filling curve, resulting in high flexibility and tree force errors that do not depend on the way the domains are cut. The code is efficient in terms of memory consumption and required communication bandwidth. It has been used to compute the first cosmological N-body simulation with more than 10^10 dark matter particles, reaching a homogeneous spatial dynamic range of 10^5 per dimension in a 3D box. It has also been used to carry out very large cosmological SPH simulations that account for radiative cooling and star formation, reaching total particle numbers of more than 250 million. We present the algorithms used by the code and discuss their accuracy and performance using a number of test problems. GADGET-2 is publicly released to the research community.

Volker Springel

2005-05-02T23:59:59.000Z

244

Energy Conservation in Flat FRW Cosmology  

E-Print Network (OSTI)

The consequence of energy conservation in the flat Friedmannn-Robertson-Walker (FRW) cosmology is a strictly positive accelerating expansion. A mechanism is proposed for this expansion due to the effect of the attractive (negative) gravitational potential of matter as it is being included within the expanding horizon, and the offsetting work of metric expansion, which takes place at sub-luminal speed. In our semi-classical treatment, we deal with a quintic as the equation for the scale parameter. Implications for modeling the earliest parts of the primordial expansion are discussed.

Steven Maxson

2009-01-07T23:59:59.000Z

245

About non standard Lagrangians in cosmology  

Science Conference Proceedings (OSTI)

A review of non standard Lagrangians present in modern cosmological models will be considered. Well known example of non standard Lagrangian is Dirac-Born-Infeld (DBI) type Lagrangian for tachyon field. Another type of non standard Lagrangian under consideration contains scalar field which describes open p-adic string tachyon and is called p-adic string theory Lagrangian. We will investigate homogenous cases of both DBI and p-adic fields and obtain Lagrangians of the standard type which have the same equations of motions as aforementioned non standard one.

Dimitrijevic, Dragoljub D.; Milosevic, Milan [Department of Physics, Faculty of Science and Mathematics, University of Nis, Visegradska 33, P.O. Box 224, 18000 Nis (Serbia)

2012-08-17T23:59:59.000Z

246

Cosmological implications of light element abundances: Theory  

DOE Green Energy (OSTI)

Primordial nucleosynthesis provides (with the microwave background radiation) one of the two quantitative experimental tests of the hot Big Bang cosmological model (versus alternative explanations for the observed Hubble expansion). The standard homogeneous-isotopic calculation fits the light element abundances ranging from [sup 1]H at 76% and [sup 4]He at 24% by mass through [sup 2]H and [sup 3]He at parts in 10[sup 5] down to [sup 7]Li at parts in 10[sup 10]. It is also noted how the recent Large Electron Positron Collider (and Stanford Linear Collider) results on the number of neutrinos (N[sub [nu

Schramm, D.N. (Univ. of Chicago, IL (United States) Fermi National Accelerator Lab., Batavia, IL (United States))

1993-06-01T23:59:59.000Z

247

Dependent component analysis for cosmology: a case study  

Science Conference Proceedings (OSTI)

In this paper, we discuss various dependent component analysis approaches available in the literature and study their performances on the problem of separation of dependent cosmological sources from multichannel microwave radiation maps of the sky. Realisticaly ... Keywords: cosmic microwave background radiation, cosmological source separation, dependent component analysis

Ercan E. Kuruoglu

2010-09-01T23:59:59.000Z

248

Exact cosmological solutions of models with an interacting dark sector  

E-Print Network (OSTI)

We extend the First Order Formalism for cosmological models, developed including an interaction between a fermionic and a scalar field. Cosmological exact solutions, describing universes filled with interacting dark energy and dark matter, have been obtained. We suggest some alternative couplings that yield solutions for the scalar field that could model the present expansion of our universe.

Pavan, A B; Micheletti, S; Ferreira, E G M; de Souza, J C C

2011-01-01T23:59:59.000Z

249

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

250

Stability and Evolution of Supernova Fallback Disks  

E-Print Network (OSTI)

We show that thin accretion disks made of Carbon or Oxygen are subject to the same thermal ionization instability as Hydrogen and Helium disks. We argue that the instability applies to disks of any metal content. The relevance of the instability to supernova fallback disks probably means that their power-law evolution breaks down when they first become neutral. We construct simple analytical models for the viscous evolution of fallback disks to show that it is possible for these disks to become neutral when they are still young (ages of a few 10^3 to 10^4 years), compact in size (a few 10^9 cm to 10^11 cm) and generally accreting at sub-Eddington rates (Mdot ~ a few 10^14 - 10^18 g/s). Based on recent results on the nature of viscosity in the disks of close binaries, we argue that this time may also correspond to the end of the disk activity period. Indeed, in the absence of a significant source of viscosity in the neutral phase, the entire disk will likely turn to dust and become passive. We discuss various applications of the evolutionary model, including anomalous X-ray pulsars and young radio pulsars. Our analysis indicates that metal-rich fallback disks around newly-born neutron stars and black holes become neutral generally inside the tidal truncation radius (Roche limit) for planets, at \\~10^11 cm. Consequently, the efficiency of the planetary formation process in this context will mostly depend on the ability of the resulting disk of rocks to spread via collisions beyond the Roche limit. It appears easier for the merger product of a doubly degenerate binary, whether it is a massive white dwarf or a neutron star, to harbor planets because it can spread beyond the Roche limit before becoming neutral.[Abridged

Kristen Menou; Rosalba Perna; Lars Hernquist

2001-02-27T23:59:59.000Z

251

A Measurement of the Rate of type-Ia Supernovae at Redshift $z\\approx$ 0.1 from the First Season of the SDSS-II Supernova Survey  

E-Print Network (OSTI)

We present a measurement of the rate of type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift $z\\le0.12$. Assuming a flat cosmology with $\\Omega_m = 0.3=1-\\Omega_\\Lambda$, we find a volumetric SN Ia rate of $[2.93^{+0.17}_{-0.04}({\\rm systematic})^{+0.90}_{-0.71}({\\rm statistical})] \\times 10^{-5} {\\rm SNe} {\\rm Mpc}^{-3} h_{70}^3 {\\rm year}^{-1}$, at a volume-weighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift-evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rate, $r_V \\propto (1+z)^{\\beta}$, we obtain a value of $\\beta = 1.5 \\pm 0.6$, i.e. the SN Ia rate is determined to be an increasing function of redshift at the $\\sim 2.5 \\sigma$ level. Fitting the results to a model in which the volumetric SN rate, $r_V=A\\rho(t)+B\\dot \\rho(t)$, where $\\rho(t)$ is the stellar mass density and $\\dot \\rho(t)$ is the star formation rate, we find $A = (2.8 \\pm 1.2) \\times 10^{-14} \\mathrm{SNe} \\mathrm{M}_{\\sun}^{-1} \\mathrm{year}^{-1}$, $B = (9.3^{+3.4}_{-3.1})\\times 10^{-4} \\mathrm{SNe} \\mathrm{M}_{\\sun}^{-1}$.

Benjamin Dilday; R. Kessler; J. A. Frieman; J. Holtzman; J. Marriner; G. Miknaitis; R. C. Nichol; R. Romani; M. Sako; B. Bassett; A. Becker; D. Cinabro; F. DeJongh; D. L. Depoy; M. Doi; P. M. Garnavich; C. J. Hogan; S. Jha; K. Konishi; H. Lampeitl; J. L. Marshall; D. McGinnis; J. L. Prieto; A. G. Riess; M. W. Richmond; D. P. Schneider; M. Smith; N. Takanashi; K. Tokita; K. van der Heyden; N. Yasuda; C. Zheng; J. Barentine; H. Brewington; C. Choi; A. Crotts; J. Dembicky; M. Harvanek; M. Im; W. Ketzeback; S. J. Kleinman; J. Krzesi?ski; D. C. Long; E. Malanushenko; V. Malanushenko; R. J. McMillan; A. Nitta; K. Pan; G. Saurage; S. A. Snedden; S. Watters; J. C. Wheeler; D. York

2008-01-22T23:59:59.000Z

252

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

253

Diversity of supernovae Ia determined using equivalent widths of Si II 4000  

E-Print Network (OSTI)

Spectroscopic and photometric properties of low and high-z supernovae Ia (SNe Ia) have been analyzed in order to achieve a better understanding of their diversity and to identify possible SN Ia sub-types. We use wavelet transformed spectra in which one can easily measure spectral features. We investigate the \\ion{Si}{II} 4000 equivalent width ($EW_w\\lbrace\\ion{Si}{II}\\rbrace$). The ability and, especially, the ease in extending the method to SNe at high-$z$ is demonstrated. We applied the method to 110 SNe Ia and found correlations between $EW_w\\lbrace\\ion{Si}{II}\\rbrace$ and parameters related to the light-curve shape for 88 supernovae with available photometry. No evidence for evolution of $EW_w\\lbrace\\ion{Si}{II}\\rbrace$ with redshift is seen. Three sub-classes of SNe Ia were confirmed using an independent cluster analysis with only light-curve shape, colour, and $EW_w\\lbrace\\ion{Si}{II}\\rbrace$. SNe from high-$z$ samples seem to follow a similar grouping to nearby objects. The $EW_w\\lbrace\\ion{Si}{II}\\rbrace$ value measured on a single spectrum may point towards SN Ia sub-classification, avoiding the need for expansion velocity gradient calculations.

V. Arsenijevic; S. Fabbro; A. M. Mourao; A. J. Rica da Silva

2008-09-18T23:59:59.000Z

254

Revealing Type Ia supernova physics with cosmic rates and nuclear gamma rays  

E-Print Network (OSTI)

Type Ia supernovae (SNIa) remain mysterious despite their central importance in cosmology and their rapidly increasing discovery rate. The progenitors of SNIa can be probed by the delay time between progenitor birth and explosion as SNIa. The explosions and progenitors of SNIa can be probed by MeV nuclear gamma rays emitted in the decays of radioactive nickel and cobalt into iron. We compare the cosmic star formation and SNIa rates, finding that their different redshift evolution requires a large fraction of SNIa to have large delay times. A delay time distribution of the form t^{-1.0 +/- 0.3} provides a good fit, implying 50% of SNIa explode more than ~ 1 Gyr after progenitor birth. The extrapolation of the cosmic SNIa rate to z = 0 agrees with the rate we deduce from catalogs of local SNIa. We investigate prospects for gamma-ray telescopes to exploit the facts that escaping gamma rays directly reveal the power source of SNIa and uniquely provide tomography of the expanding ejecta. We find large improvements relative to earlier studies by Gehrels et al. in 1987 and Timmes & Woosley in 1997 due to larger and more certain SNIa rates and advances in gamma-ray detectors. The proposed Advanced Compton Telescope, with a narrow-line sensitivity ~ 60 times better than that of current satellites, would, on an annual basis, detect up to ~ 100 SNIa (3 sigma) and provide revolutionary model discrimination for SNIa within 20 Mpc, with gamma-ray light curves measured with ~ 10 sigma significance daily for ~ 100 days. Even more modest improvements in detector sensitivity would open a new and invaluable astronomy with frequent SNIa gamma-ray detections.

Shunsaku Horiuchi; John F. Beacom

2010-06-30T23:59:59.000Z

255

Supernova Reverse Shocks and SiC Growth  

E-Print Network (OSTI)

We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t = 10 6 s; reverse shock from the presupernova wind near 10 8-10 9 s; reverse shock from the ISM near 10 10 s. Using 1-D hydrodynamics we show that the first creates a dense shell of Si and C atoms near 10 6 s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated gas of different isotopic composition, during which implantation, sputtering and further condensation occur simultaneously. The third reverse shock causes only further ion implantation and sputtering, which may affect trace element isotopic compositions. Using a 25M ? supernova model we propose solutions to the following unsolved questions: where does SiC condense?; why does SiC condense in preference to graphite?; why is condensed SiC 28 Si-rich?; why is O richness no obstacle to SiC condensation?; how many atoms of each isotope are impacted by a grain that condenses at time t0 at radial coordinate r0? These many considerations are put forward as a road map for interpreting SiC X grains found in meteorites and their meaning for supernova physics. Subject headings: supernova remnants dust extinction infrared:stars astrochemistry 1.

Ethan A. -n. Deneault; Donald D. Clayton

2003-01-01T23:59:59.000Z

256

Could a nearby supernova explosion have caused a mass extinction?  

E-Print Network (OSTI)

We examine the possibility that a nearby supernova explosion could have caused one or more of the mass extinctions identified by palaeontologists. We discuss the likely rate of such events in the light of the recent identification of Geminga as a supernova remnant less than 100 pc away and the discovery of a millisecond pulsar about 150 pc away, and observations of SN 1987A. The fluxes of $\\gamma$ radiation and charged cosmic rays on the Earth are estimated, and their effects on the Earth's ozone layer discussed. A supernova explosion of the order of 10 pc away could be expected every few hundred million years, and could destroy the ozone layer for hundreds of years, letting in potentially lethal solar ultraviolet radiation. In addition to effects on land ecology, this could entail mass destruction of plankton and reef communities, with disastrous consequences for marine life as well. A supernova extinction should be distinguishable from a meteorite impact such as the one that presumably killed the dinosaurs.

John Ellis; David N. Schramm

1993-03-02T23:59:59.000Z

257

The Number of Supernovae From Primordial Stars in the Universe  

DOE Green Energy (OSTI)

Recent simulations of the formation of the first luminous objects in the universe predict isolated very massive stars to form in dark matter halos with virial temperatures large enough to allow significant amounts of molecular hydrogen to form. We construct a semi-analytic model based on the Press-Schechter formalism and calibrate the minimum halos mass that may form a primordial star with the results from extensive adaptive mesh refinement simulations. The model also includes star formation in objects with virial temperatures in excess of ten thousand Kelvin. The free parameters are tuned to match the optical depth measurements by the WMAP satellite. The models explicitly includes the negative feedback of the destruction of molecular hydrogen by a soft UV background which is computed self-consistently. We predict high redshift supernova rates as one of the most promising tools to test the current scenario of primordial star formation. The supernova rate from primordial stars peaks at redshifts {approx}20. Using an analytic model for the luminosities of pair-instability supernovae we predict observable magnitudes and discuss possible observational strategies. Such supernovae would release enough metals corresponding to a uniform enrichment to a few hundred thousands of solar metalicity. If some of these stars produce gamma ray bursts our rates will be directly applicable to understanding the anticipated results from the SWIFT satellite. This study highlights the great potential for the James Webb space telescope in probing cosmic structure at redshifts greater than 20.

Wise, J

2004-12-15T23:59:59.000Z

258

DISTRIBUTED FLAMES IN TYPE Ia SUPERNOVAE  

Science Conference Proceedings (OSTI)

At a density near a few x10{sup 7} g cm{sup -3}, the subsonic burning in a Type Ia supernova (SN) enters the distributed regime (high Karlovitz number). In this regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning in this distributed regime depends on the turbulent Damkoehler number (Da{sub T}), which steadily declines from much greater than one to less than one as the density decreases to a few x10{sup 6} g cm{sup -3}. Classical scaling arguments predict that the turbulent flame speed s{sub T} , normalized by the turbulent intensity u-check, follows s{sub T}/u-check = Da{sub T}{sup 1/2} for Da{sub T} {approx}burns as a turbulently broadened effective unity Lewis number flame. This flame burns locally with speed s{sub l}ambda and width l{sub l}ambda, and we refer to this kind of flame as a lambda-flame. The burning becomes a collection of lambda-flames spread over a region approximately the size of the {integral} scale. While the total burning rate continues to have a well-defined average, s{sub T}{approx}u-check, the burning is unsteady. We present a theoretical framework, supported by both one-dimensional and three-dimensional numerical simulations, for the burning in these two regimes. Our results indicate that the average value of s{sub T} can actually be roughly twice u-check for Da{sub T} {approx}> 1, and that localized excursions to as much as 5 times u-check can occur. We also explore the properties of the individual flames, which could be sites for a transition to detonation when Da{sub T} {approx} 1. The lambda-flame speed and width can be predicted based on the turbulence in the star (specifically the energy dissipation rate epsilon*) and the turbulent nuclear burning timescale of the fuel tau {sup T}{sub nuc}. We propose a practical method for measuring s{sub l}ambda and l{sub l}ambda based on the scaling relations and small-scale computationally inexpensive simulations. This suggests that a simple turbulent flame model can be easily constructed suitable for large-scale distributed SNe flames. These results will be useful both for characterizing the deflagration speed in larger full-star simulations, where the flame cannot be resolved, and for predicting when detonation occurs.

Aspden, A. J.; Bell, J. B. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (United States); Woosley, S. E. [Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

2010-02-20T23:59:59.000Z

259

Asymptotic analysis of perturbed dust cosmologies to second order  

E-Print Network (OSTI)

Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a positive cosmological constant have recently attracted considerable attention. In this paper our first goal is to compare the evolution of the first and second order perturbations by determining their asymptotic behaviour at late times in ever-expanding models. We show that in the presence of spatial curvature K or a positive cosmological constant, the density perturbation approaches a finite limit both to first and second order, but the rate of approach depends on the model, being power law in the scale factor if the cosmological constant is positive but logarithmic if it is zero and and Kdoes not die away, i.e. it contributes on an equal footing as the growing mode to the asymptotic expression for the density perturbation. On the other hand, the future asymptotic regime of the Einstein-de Sitter universe (for which the cosmological constant and the spatial curvature are both zero) is completely different, as exemplified by the density perturbation which diverges; moreover, the second order perturbation diverges faster than the first order perturbation, which suggests that the Einstein-de Sitter universe is unstable to perturbations, and that the perturbation series do not converge towards the future. We conclude that the presence of spatial curvature or a cosmological constant stabilizes the perturbations. Our second goal is to derive an explicit expression for the second order density perturbation that can be used to study the effects of including a cosmological constant and spatial curvature.

Claes Uggla; John Wainwright

2013-03-19T23:59:59.000Z

260

Cosmological evolution of the cosmological plasma with interpartial scalar interaction. II. Formulation of mathematical model  

E-Print Network (OSTI)

On the basis of the relativistic kinetic theory the relativistic statistical systems with scalar interaction particles are investigated. The self-consistent system of the equations describing self-gravitating plasma with interpartial scalar interaction is formulated, macroscopical laws of preservation are received. The closed system of the equations describing cosmological models to which the matter is presented by plasma with interpartial scalar interaction is received.

Yu. G. Ignat'ev

2013-07-09T23:59:59.000Z

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

Quantum groups  

Science Conference Proceedings (OSTI)

The theory of Quantum groups, although rather young, since the expression Quantum ... introduction of a suitable form of the quantum group, the algebra A...

262

Physics and Cosmology : the Milli-Electron-Volt Scale  

E-Print Network (OSTI)

A short review about vacuum energy and the cosmological constant is presented. The observed acceleration of the universe introduces a new meV energy scale. The problem is that, theoretically, the predicted vacuum energy is many orders of magnitude larger than $10^{-3}$ eV. The problem is a link between two Standard Models, namely the Standard Model of Particles and their Interactions (where the vacuum energy appears) and the Standard Cosmological Model (where a cosmological constant is a good fit to data), and perhaps it is a clue in our search for new physics.

Eduard Masso

2009-02-27T23:59:59.000Z

263

Cosmological perturbations in singularity-free, deflationary models  

E-Print Network (OSTI)

We consider scalar perturbations of energy-density for a class of cosmological models where an early phase of accelerated expansion evolves, without any fine-tuning for graceful exit, towards the standard Friedman eras of observed universe. The quantum geometric procedure which generates such models agrees with results for string cosmology since it works if dynamics is dominated by a primordial fluid of extended massive objects. The main result is that characteristic scales of cosmological interest, connected with the extension of such early objects, are selected.

S. Capozziello; G. Lambiase; G. Scarpetta

1998-05-13T23:59:59.000Z

264

Environment-induced superselection in cosmology  

SciTech Connect

Interaction between a quantum system and its environment can be often regarded as a measurement, in the course of which one of the system observables influences the evolution of the external degrees of freedom and is thus monitored'' by the environment. This causes the system to decohere.'' Loss of quantum coherence erases part of the density matrix responsible for the correlations between the eigenstates of the monitored observables. This mechanism is very efficient even in the limit of weak coupling to the environment. The classical limit of quantum theory -- that is, both classical irreversible equations of motion and classical states (trajectories in phase space rather than their superpositions) obtains in the limit in which the coupling strength and the Planck constant simultaneously tend to zero. Transition from quantum to classical in the inflationary cosmological model can be justified in the framework of environment induced susperselection. 24 refs., 2 figs.

Zurek, W.H.

1990-01-01T23:59:59.000Z

265

Green's function of the cosmological thermalization problem  

E-Print Network (OSTI)

Energy release in the early Universe leads to spectral distortions of the cosmic microwave background (CMB) which in the future might allow probing different physical processes in the pre-recombination (z>~10^3) epoch. Depending on the energy injection history, the associated distortion partially thermalizes due to the combined action of Compton scattering, double Compton scattering and Bremsstrahlung emission, a problem that in general is hard to solve. Various analytic approximations describing the resulting distortion exist, however, for small distortions and fixed background cosmology the Green's function of the problem can be computed numerically. Here we show that this approach gives very accurate results for general thermal histories, allowing fast and quasi-exact computation of the spectral distortion given the energy release rate. Our method can thus be used to forecast possible constraints on early-universe physics obtained from future measurements of the CMB spectrum.

Chluba, Jens

2013-01-01T23:59:59.000Z

266

Scaling cosmological solutions with Horndeski Lagrangian  

E-Print Network (OSTI)

We find the most general coupled scalar field Lagrangian linear in $\\Box\\phi$ and with a general kinetic term that contains cosmological scaling solutions, i.e. solutions on which the ratio of matter to field density and the equation of state remains constant. Scaling solutions of this kind may help solving the coincidence problem since in this case the presently observed ratio of matter to dark energy does not depend on initial conditions but rather on the theoretical parameters. Extending previous results we find that it is impossible to join in a single solution a matter era and the scaling attractor. This is an additional step towards finding the most general scaling Lagrangian within the Horndeski class, i.e. general scalar-tensor models with second order equations of motion.

Gomes, A R

2013-01-01T23:59:59.000Z

267

String spectra near some null cosmological singularities  

Science Conference Proceedings (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 analyze 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 wave functions. We find that for low-lying string modes (finite oscillation number), the classical near-singularity string mode functions are nondivergent for various families of singularities. Furthermore, for any infinitesimal regularization of the vicinity of the singularity, we find a tower of string modes of ultrahigh oscillation number which propagate essentially freely in the background. The resulting picture suggests that string interactions are non-negligible near the singularity.

Madhu, Kallingalthodi [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India); Narayan, K. [Chennai Mathematical Institute, SIPCOT IT Park, Padur PO, Siruseri 603103 (India)

2009-06-15T23:59:59.000Z

268

Radion Physics, Stability and Cosmological issues  

Science Conference Proceedings (OSTI)

Moduli fields are a known ingredient of models that involve extra compact dimensions, as the Kaluza-Klein theories, String theory, and models with compact extra dimensions. They are scalar fields that emerge when the configuration of the compact space is perturbed. The radion is a particular example of this type of fields, which is associated to the variations of the total volume of compact space. Radions usually couple to all other fields, affecting the definition of coupling constants and gravity strength. They also modify gravitational potentials in a way that may be tested in table top experiments. Usually, these fields are run away modes which manifest the difficulties to stabilize the shape of the compact manifold of extra space. This is feature that can be a threat for cosmology on the early Universe. Here we provide a brief discussion of these general aspects of the radion physics.

Perez-Lorenzana, Abdel [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del I.P.N. Apdo. Post. 14-740, 07000, Mexico, D.F. (Mexico); Santos, Eli [Centro de Estudios en Fisica y Matematicas Basicas y Aplicadas, UNACH, 4a Oriente Norte 1428, C.P. 29000 Tuxtla Gutierrez, Chiapas (Mexico); Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo Edificio C-3, Ciudad Universitaria, CP. 58040 Morelia, Michoacan (Mexico)

2010-07-12T23:59:59.000Z

269

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

270

Projective Structures in Loop Quantum Cosmology  

E-Print Network (OSTI)

Projective structures have successfully been used for the construction of measures in the framework of loop quantum gravity. In the present paper we establish such a structure for the space $R \\sqcup R_Bohr$ recently constructed in the context of homogeneous isotropic loop quantum cosmology. This space has the advantage to be canonically embedded into the quantum configuration space of the full theory, but, in contrast to the traditional space $R_Bohr$, there exists no Haar measure on $R \\sqcup R_Bohr$. The introduced projective structure, however, allows to construct a family of canonical measures on $R \\sqcup R_Bohr$ whose corresponding Hilbert spaces of square integrable functions we finally investigate.

Maximilian Hanusch

2013-09-03T23:59:59.000Z

271

BRST technique for the cosmological density matrix  

E-Print Network (OSTI)

The microcanonical density matrix in closed cosmology has a natural definition as a projector on the space of solutions of Wheeler-DeWitt equations, which is motivated by the absence of global non-vanishing charges and energy in spatially closed gravitational systems. Using the BRST/BFV formalism in relativistic phase space of gauge and ghost variables we derive the path integral representation for this projector and the relevant statistical sum. This derivation circumvents the difficulties associated with the open algebra of noncommutative quantum Dirac constraints and the construction/regularization of the physical inner product in the subspace of BRS singlets. This inner product is achieved via the Batalin-Marnelius gauge fixing in the space of BRS-invariant states, which in its turn is shown to be a result of truncation of the BRST/BFV formalism to the "matter" sector of relativistic phase space.

Andrei O. Barvinsky

2013-08-14T23:59:59.000Z

272

Emergent universe in spatially flat cosmological model  

E-Print Network (OSTI)

The scenario of an emergent universe provides a promising resolution to the big bang singularity in universes with positive or negative spatial curvature. It however remains unclear whether the scenario can be successfully implemented in a spatially flat universe which seems to be favored by present cosmological observations. In this paper, we study the stability of Einstein static state solutions in a spatially flat Shtanov-Sahni braneworld scenario. With a negative dark radiation term included and assuming a scalar field as the only matter energy component, we find that the universe can stay at an Einstein static state past eternally and then evolve to an inflation phase naturally as the scalar field climbs up its potential slowly. In addition, we also propose a concrete potential of the scalar field that realizes this scenario.

Kaituo Zhang; Puxun Wu; Hongwei Yu

2013-11-16T23:59:59.000Z

273

LATE-TIME LIGHT CURVES OF TYPE II SUPERNOVAE: PHYSICAL PROPERTIES OF SUPERNOVAE AND THEIR ENVIRONMENT  

Science Conference Proceedings (OSTI)

We present BVRIJHK-band photometry of six core-collapse supernovae, SNe 1999bw, 2002hh, 2003gd, 2004et, 2005cs, and 2006bc, measured at late epochs (>2 yr) based on the Hubble Space Telescope (HST), and the Gemini North, and WIYN telescopes. We also show the JHK light curves of supernova impostor SN 2008S up to day 575 because it was serendipitously in our SN 2002hh field of view. Of our 43 HST observations in total, 36 observations are successful in detecting the light from the SNe alone and measuring magnitudes of all the targets. HST observations show a resolved scattered light echo around SN 2003gd at day 1520 and around SN 2002hh at day 1717. Our Gemini and WIYN observations detected SNe 2002hh and 2004et as well. Combining our data with previously published data, we show VRIJHK-band light curves and estimate decline magnitude rates at each band in four different phases. Our prior work on these light curves and other data indicate that dust is forming in our targets from days {approx}300 to 400, supporting SN dust formation theory. In this paper we focus on other physical properties derived from late-time light curves. We estimate {sup 56}Ni masses for our targets (0.5-14 Multiplication-Sign 10{sup -2} M{sub Sun }) from the bolometric light curve of each of days {approx}150-300 using SN 1987A as a standard (7.5 Multiplication-Sign 10{sup -2} M{sub Sun }). The flattening or sometimes increasing fluxes in the late-time light curves of SNe 2002hh, 2003gd, 2004et, and 2006bc indicate the presence of light echoes. We estimate the circumstellar hydrogen density of the material causing the light echo and find that SN 2002hh is surrounded by relatively dense materials (n(H) >400 cm{sup -3}) and SNe 2003gd and 2004et have densities more typical of the interstellar medium ({approx}1 cm{sup -3}). We analyze the sample as a whole in the context of physical properties derived in prior work. The {sup 56}Ni mass appears well correlated with progenitor mass with a slope of 0.31 Multiplication-Sign 10{sup -2}, supporting the previous work by Maeda et al., who focus on more massive Type II SNe. The dust mass does not appear to be correlated with progenitor mass.

Otsuka, Masaaki; Meixner, Margaret; Panagia, Nino [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Fabbri, Joanna; Barlow, Michael J.; Wesson, Roger [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Clayton, Geoffrey C.; Andrews, Jennifer E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Gallagher, Joseph S. [Department of Mathematics, Physics, and Computer Science, Raymond Walters College, 9555 Plain field Rd., Blue Ash, OH 45236 (United States); Sugerman, Ben E. K. [Department of Physics and Astronomy, Goucher College, 1021 Dulaney Valley Road, Baltimore, MD 21204 (United States); Ercolano, Barbara [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, 81679 Muenchen (Germany); Welch, Douglas, E-mail: otsuka@stsci.edu, E-mail: otsuka@asiaa.sinica.edu.tw [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

2012-01-01T23:59:59.000Z

274

Supernova rates from the Southern inTermediate Redshift ESO Supernova Search (STRESS)  

E-Print Network (OSTI)

To measure the supernova (SN) rates at intermediate redshift we performed the Southern inTermediate Redshift ESO Supernova Search (STRESS). Unlike most of the current high redshift SN searches, this survey was specifically designed to estimate the rate for both type Ia and core collapse (CC) SNe. We counted the SNe discovered in a selected galaxy sample measuring SN rate per unit blue band luminosity. Our analysis is based on a sample of ~43000 galaxies and on 25 spectroscopically confirmed SNe plus 64 selected SN candidates. Our approach is aimed at obtaining a direct comparison of the high redshift and local rates and at investigating the dependence of the rates on specific galaxy properties, most notably their colour. The type Ia SN rate, at mean redshift z=0.3, amounts to 0.22^{+0.10+0.16}_{-0.08 -0.14} h_{70}^2 SNu, while the CC SN rate, at z=0.21, is 0.82^{+0.31 +0.30}_{-0.24 -0.26} h_{70}^2 SNu. The quoted errors are the statistical and systematic uncertainties. With respect to local value, the CC SN rate at z=0.2 is higher by a factor of ~2 already at redshift, whereas the type Ia SN rate remains almost constant. This implies that a significant fraction of SN Ia progenitors has a lifetime longer than 2-3 Gyr. We also measured the SN rates in the red and blue galaxies and found that the SN Ia rate seems to be constant in galaxies of different colour, whereas the CC SN rate seems to peak in blue galaxies, as in the local Universe. SN rates per unit volume were found to be consistent with other measurements showing a steeper evolution with redshift for CC SNe with respect to SNe Ia. Finally we have exploited the link between star formation (SF) and SN rates to predict the evolutionary behaviour of the SN rates and compare it with the path indicated by observations.

M. T. Botticella; M. Riello; E. Cappellaro; S. Benetti; G. Altavilla; A. Pastorello; M. Turatto; L. Greggio; F. Patat; S. Valenti; L. Zampieri; A. Harutyunyan; G. Pignata; S. Taubenberger

2007-10-19T23:59:59.000Z

275

A new type of second order cosmological lagrangians  

E-Print Network (OSTI)

We investigate a possible connection between Galileon gravity and teleparallel gravity. We also propose a new type of second order cosmological lagrangian and study a some of its properties.

P. Tretyakov

2013-02-26T23:59:59.000Z

276

Dynamical eigenfunctions and critical density in loop quantum cosmology  

E-Print Network (OSTI)

We offer a new, physically transparent argument for the existence of the critical, universal maximum matter density in loop quantum cosmology for the case of a flat Friedmann-Lemaitre-Robertson-Walker cosmology with scalar matter. The argument is based on the existence of a sharp exponential ultraviolet cutoff in momentum space on the eigenfunctions of the quantum cosmological dynamical evolution operator (the gravitational part of the Hamiltonian constraint), attributable to the fundamental discreteness of spatial volume in loop quantum cosmology. The existence of the cutoff is proved directly from recently found exact solutions for the eigenfunctions for this model. As a consequence, the operators corresponding to the momentum of the scalar field and the spatial volume approximately commute. The ultraviolet cutoff then implies that the scalar momentum, though not a bounded operator, is in effect bounded on subspaces of constant volume, leading to the upper bound on the expectation value of the matter densit...

Craig, David A

2012-01-01T23:59:59.000Z

277

The Darboux Transformation and Exactly Solvable Cosmological Models  

E-Print Network (OSTI)

We present a simple and effective method for constructing exactly solvable cosmological models containing inflation with exit. This method does not involve any parameter fitting. We discuss the problems arising with solutions that violate the weak energy condition.

A. V. Yurov; S. D. Vereshchagin

2005-02-10T23:59:59.000Z

278

Applicability of the linearly perturbed FRW metric and Newtonian cosmology  

E-Print Network (OSTI)

It has been argued that the effect of cosmological structure formation on the average expansion rate is negligible, because the linear approximation to the metric remains applicable in the regime of non-linear density perturbations. We discuss why the arguments based on the linear theory are not valid. We emphasise the difference between Newtonian gravity and the weak field, small velocity limit of general relativity in the cosmological setting.

Syksy Rasanen

2010-02-25T23:59:59.000Z

279

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

2009-03-21T23:59:59.000Z

280

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

Science Conference Proceedings (OSTI)

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

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.


281

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

282

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

283

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

284

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

285

Type Ia Supernovae Rates and Galaxy Clustering from the CFHT Supernova Legacy Survey  

E-Print Network (OSTI)

The Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS) has created a large homogeneous database of intermediate redshift (0.2 rates, properties, and host galaxy star formation rates. The SNLS SN Ia database has now been combined with a photometric redshift galaxy catalog and an optical galaxy cluster catalog to investigate the possible influence of galaxy clustering on the SN Ia rate, over and above the expected effect due to the dependence of SFR on clustering through the morphology-density relation. We identify three cluster SNe Ia, plus three additional possible cluster SNe Ia, and find the SN Ia rate per unit mass in clusters at intermediate redshifts is consistent with the rate per unit mass in field early-type galaxies and the SN Ia cluster rate from low redshift cluster targeted surveys. We also find the number of SNe Ia in cluster environments to be within a factor of two of expectations from the two component SNIa rate model.

M. L. Graham; C. J. Pritchet; M. Sullivan; S. D. J. Gwyn; J. D. Neill; E. Y. Hsiao; P. Astier; D. Balam; C. Balland; S. Basa; R. G. Carlberg; A. Conley; D. Fouchez; J. Guy; D. Hardin; I. M. Hook; D. A. Howell; R. Pain; K. Perrett; N. Regnault; S. Baumont; J. Le Du; C. Lidman; S. Perlmutter; P. Ripoche; N. Suzuki; E. S. Walker; T. Zhang

2008-01-31T23:59:59.000Z

286

Dark Energy Constraints from the Cosmic Age and Supernova  

E-Print Network (OSTI)

Using the low limit of cosmic ages from globular cluster and the white dwarfs: $t_0 > 12$Gyr, together with recent new high redshift supernova observations from the HST/GOODS program and previous supernova data, we give a considerable estimation of the equation of state for dark energy, with uniform priors as weak as $0.2paper a new scenario of dark energy dubbed Quintom, which gives rise to the equation of state larger than -1 in the past and less than -1 today, satisfying current observations. In addition we've also considered the implications of recent X-ray gas mass fraction data on dark energy, which favors a negative running of the equation of state.

Bo Feng; Xiulian Wang; Xinmin Zhang

2004-04-11T23:59:59.000Z

287

Gamma-ray Emission from Crushed Clouds in Supernova Remnants  

E-Print Network (OSTI)

It is shown that the radio and gamma-ray emission observed from newly-found "GeV-bright" supernova remnants (SNRs) can be explained by a model, in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed by the supernova blastwave as a result of formation of a radiative cloud shock. Simple reacceleration of pre-existing CRs is generally sufficient to power the observed gamma-ray emission through the decays of neutral pions produced in hadronic interactions between high-energy protons (nuclei) and gas in the compressed-cloud layer. This model provides a natural account of the observed synchrotron radiation in SNRs W51C, W44 and IC 443 with flat radio spectral index, which can be ascribed to a combination of secondary and reaccelerated electrons and positrons.

Uchiyama, Yasunobu; Funk, Stefan; Tajima, Hiroyasu; Tanaka, Takaaki

2010-01-01T23:59:59.000Z

288

Role of dense matter in collective supernova neutrino transformations  

E-Print Network (OSTI)

For neutrinos streaming from a supernova (SN) core, dense matter suppresses self-induced flavor transformations if the electron density n_e significantly exceeds the neutrino density n_nu in the conversion region. If n_e is comparable to n_nu one finds multi-angle decoherence, whereas the standard self-induced transformation behavior requires that in the transformation region n_nu is safely above n_e. This condition need not be satisfied in the early phase after supernova core bounce. Our new multi-angle effect is a subtle consequence of neutrinos traveling on different trajectories when streaming from a source that is not point-like.

A. Esteban-Pretel; A. Mirizzi; S. Pastor; R. Tomas; G. G. Raffelt; P. D. Serpico; G. Sigl

2008-07-07T23:59:59.000Z

289

Neutrino Processes in Supernovae and the Physics of Protoneutron Star Winds  

E-Print Network (OSTI)

In preparation for a set of hydrodynamical simulations of core-collapse supernovae and protoneutron star winds, we investigate the rates of production and thermalization of $\

Todd A. Thompson; Adam Burrows

2000-09-28T23:59:59.000Z

290

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

291

On the hydrogen emission from the type Ia supernova 2002ic  

DOE Green Energy (OSTI)

The discovery of SN 2002ic by the Supernova Factory and the subsequent spectroscopic studies have led to the surprising finding that SN 2002ic is a type Ia supernova with strong ejecta-circumstellar interaction. Here we show that nearly 1 year after the explosion the supernova has become fainter overall, but the H-alpha emission has brightened and broadened dramatically compared to earlier observations. We have obtained spectropolarimetry data which show that the hydrogen-rich matter is highly aspherically distributed. These observations suggest that the supernova exploded inside a dense, clumpy, disk-like circumstellar environment.

Wang, Lifan; Baade, Dietrich; Hoflich, Peter; Wheeler, J. Craig; Kawabata, Koji; Nomoto, Ken'ichi

2003-12-10T23:59:59.000Z

292

Viscosity and Rotation in Core-Collapse Supernovae  

E-Print Network (OSTI)

We construct models of core-collapse supernovae in one spatial dimension, including rotation, angular momentum transport, and viscous dissipation employing an alpha-prescription. We compare the evolution of a fiducial 11 M_sun non-rotating progenitor with its evolution including a wide range of imposed initial rotation profiles (1.25supernova shock. This effect yields qualitatively new dynamics in models of supernovae. We explore several potential mechanisms for viscosity in the core-collapse environment: neutrino viscosity, turbulent viscosity caused by the magnetorotational instability (MRI), and turbulent viscosity by entropy- and composition-gradient-driven convection. We argue that the MRI is the most effective. We find that for rotation periods in the range P_0<~5 s, and a range of viscous stresses, that the post-bounce dynamics is significantly effected by the inclusion of this extra energy deposition mechanism; in several cases we obtain strong supernova explosions.

Todd A. Thompson; Eliot Quataert; Adam Burrows

2004-03-09T23:59:59.000Z

293

Core-Collapse Supernovae Induced by Anisotropic Neutrino Radiation  

E-Print Network (OSTI)

We demonstrate the important role of anisotropic neutrino radiation on the mechanism of core-collapse supernova explosions. Through a new parameter study with a fixed radiation field of neutrinos, we show that prolate explosions caused by globally anisotropic neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This is suggestive of the fact that the expanding materials of SN 1987A has a prolate geometry.

Yuko Motizuki; Hideki Madokoro; Tetsuya Shimizu

2004-06-11T23:59:59.000Z

294

Core collapse supernovae in the QCD phase diagram  

SciTech Connect

We compare two classes of hybrid equations of state with a hadron-to-quark matter phase transition in their application to core collapse supernova simulations. The first one uses the quark bag model and describes the transition to three-flavor quark matter at low critical densities. The second one employs a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with parameters describing a phase transition to two-flavor quark matter at higher critical densities. These models possess a distinctly different temperature dependence of their transition densities which turns out to be crucial for the possible appearance of quark matter in supernova cores. During the early post-bounce accretion phase quark matter is found only if the phase transition takes place at sufficiently low densities as in the study based on the bag model. The increase critical density with increasing temperature, as obtained for our PNJL parametrization, prevents the formation of quark matter. The further evolution of the core collapse supernova as obtained applying the quark bag model leads to a structural reconfiguration of the central protoneutron star where, in addition to a massive pure quark matter core, a strong hydrodynamic shock wave forms and a second neutrino burst is released during the shock propagation across the neutrinospheres. We discuss the severe constraints in the freedom of choice of quark matter models and their parametrization due to the recently observed 2M{sub Circled-Dot-Operator} pulsar and their implications for further studies of core collapse supernovae in the QCD phase diagram.

Fischer, T., E-mail: t.fischer@gsi.de [Helmholtzzentrum fuer Schwerionenforschung GmbH, GSI (Germany); Blaschke, D. [University of Wroclaw, Institute for Theoretical Physics (Poland); Hempel, M. [University of Basel, Department of Physics (Switzerland); Klaehn, T.; Lastowiecki, R. [University of Wroclaw, Institute for Theoretical Physics (Poland); Liebendoerfer, M. [University of Basel, Department of Physics (Switzerland); Martinez-Pinedo, G. [Helmholtzzentrum fuer Schwerionenforschung GmbH, GSI (Germany); Pagliara, G.; Sagert, I. [Ruprecht-Karls-Universitaet, Institut fuer Theoretische Physik (Germany); Sandin, F. [Lulea Tekniska Universitet, Department of Computer Science and Electrical Engineering, EISLAB (Sweden); Schaffner-Bielich, J. [Ruprecht-Karls-Universitaet, Institut fuer Theoretische Physik (Germany); Typel, S. [Helmholtzzentrum fuer Schwerionenforschung GmbH, GSI (Germany)

2012-05-15T23:59:59.000Z

295

Supernovae constraints on dark energy and modified gravity models  

E-Print Network (OSTI)

We use the Type Ia Supernova gold sample to constrain the parameters of dark energy models namely the Cardassian, Dvali-Turner (DT) and generalized Chaplygin gas (GCG) models. In our best fit analysis for these dark energy proposals we consider flat and the non-flat priors. For all models, we find that relaxing the flatness condition implies that data favors a positive curvature; moreover, the GCG model is nearly flat, as required by Cosmic Microwave Background (CMB) observations.

M. C. Bento; O. Bertolami; N. M. C. Santos; A. A. Sen

2005-12-03T23:59:59.000Z

296

Investigating the Flame Microstructure in Type Ia Supernovae  

E-Print Network (OSTI)

We present a numerical model to study the behavior of thermonuclear flames in the discontinuity approximation. This model is applied to investigate the Landau-Darrieus instability under conditions found in Type Ia supernova explosions of Chandrasekhar mass white dwarfs. This is a first step to explore the flame microstructure in these events. The model reproduces Landau's linearized stability analysis in early stages of the flame evolution and the stabilization in a cellular flame structure in the nonlinear stage.

F. K. Roepke; W. Hillebrandt; J. C. Niemeyer

2002-04-02T23:59:59.000Z

297

An Estimate of Lambda in Resummed Quantum Gravity in the Context of Asymptotic Safety and Planck Scale Cosmology: Constraints on SUSY GUTS  

E-Print Network (OSTI)

We use the amplitude-based resummation of Feynman`s formulation of Einstein`s theory to arrive at a UV finite approach to quantum gravity. We show that we recover the UV fixed point recently claimed by the exact field-space renormalization group approach. We use our approach in the context of the attendant Planck scale cosmology formulation of Bonanno and Reuter to estimate the value of the cosmological constant as \\rho_\\Lambda=(0.0024 eV)^4. We show that the closeness of this estimate to experiment constrains susy GUT models.

B. F. L. Ward

2013-02-04T23:59:59.000Z

298

Diffuse supernova neutrino background is detectable in Super-Kamiokande  

Science Conference Proceedings (OSTI)

The diffuse supernova neutrino background (DSNB) provides an immediate opportunity to study the emission of MeV thermal neutrinos from core-collapse supernovae. The DSNB is a powerful probe of stellar and neutrino physics, provided that the core-collapse rate is large enough and that its uncertainty is small enough. To assess the important physics enabled by the DSNB, we start with the cosmic star formation history of Hopkins and Beacom (2006) and confirm its normalization and evolution by cross-checks with the supernova rate, extragalactic background light, and stellar mass density. We find a sufficient core-collapse rate with small uncertainties that translate into a variation of {+-}40% in the DSNB event spectrum. Considering thermal neutrino spectra with effective temperatures between 4-6 MeV, the predicted DSNB is within a factor 4-2 below the upper limit obtained by Super-Kamiokande in 2003. Furthermore, detection prospects would be dramatically improved with a gadolinium-enhanced Super-Kamiokande: the backgrounds would be significantly reduced, the fluxes and uncertainties converge at the lower threshold energy, and the predicted event rate is 1.2-5.6 events yr{sup -1} in the energy range 10-26 MeV. These results demonstrate the imminent detection of the DSNB by Super-Kamiokande and its exciting prospects for studying stellar and neutrino physics.

Horiuchi, Shunsaku [Department of Physics, School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Beacom, John F. [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Astronomy, Ohio State University, Columbus, Ohio 43210 (United States); Dwek, Eli [Observational Cosmology Lab, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2009-04-15T23:59:59.000Z

299

Supernova Reverse Shocks and SiC Growth  

E-Print Network (OSTI)

We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t = 10$^6$s; reverse shock from the presupernova wind near 10$^8-10^9$s; reverse shock from the ISM near 10$^{10}$s. Using 1-D hydrodynamics we show that the first creates a dense shell of Si and C atoms near 10$^6$s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated gas of different isotopic composition, during which implantation, sputtering and further condensation occur simultaneously. The third reverse shock causes only further ion implantation and sputtering, which may affect trace element isotopic compositions. Using a 25M$_{\\odot}$ supernova model we propose solutions to the following unsolved questions: where does SiC condense?; why does SiC condense in preference to graphite?; why is condensed SiC $^{28}$Si-rich?; why is O richness no obstacle to SiC condensation?; how many atoms of each isotope are impacted by a grain that condenses at time t$_0$ at radial coordinate r$_0$? These many considerations are put forward as a road map for interpreting SiC X grains found in meteorites and their meaning for supernova physics.

E. A. -N. Deneault; D. D. Clayton; A. Heger

2003-02-06T23:59:59.000Z

300

Neutron star/supernova remnant associations: the view from Tbilisi  

E-Print Network (OSTI)

We propose a new approach for studying the neutron star/supernova remnant associations, based on the idea that the supernova remnants (SNRs) can be products of an off-centered supernova (SN) explosion in a preexisting bubble created by the wind of a moving massive star. A cavity SN explosion of a moving star results in a considerable offset of the neutron star (NS) birth-place from the geometrical center of the SNR. Therefore: a) the high transverse velocities inferred for a number of NSs through their association with SNRs can be reduced; b) the proper motion vector of a NS should not necessarily point away from the geometrical center of the associated SNR. Taking into account these two facts allow us to enlarge the circle of possible NS/SNR associations, and could significantly affect the results of previous studies of associations. The possibilities of our approach are illustrated with some examples. We also show that the concept of an off-centered cavity SN explosion could be used to explain the peculiar structures of a number of SNRs and for searches for stellar remnants possibly associated with them.

V. V. Gvaramadze

2002-08-01T23:59:59.000Z

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301

Neutron Stars and the Cosmological Constant Problem  

E-Print Network (OSTI)

The gravitational aether theory is a modification of general relativity that decouples vacuum energy from gravity, and thus can potentially address the cosmological constant problem. The classical theory is distinguishable from general relativity only in the presence of relativistic pressure (or vorticity). Since the interior of neutron stars has high pressure and as their mass and radius can be measured observationally, they are the perfect laboratory for testing the validity of the aether theory. In this paper, we solve the equations of stellar structure for the gravitational aether theory and find the predicted mass-radius relation of non-rotating neutron stars using two different realistic proposals for the equation of state of nuclear matter. We find that the maximum neutron star mass predicted by the aether theory is 12% - 16% less than the maximum mass predicted by general relativity assuming these two equations of state. We also show that the effect of aether is similar to modifying the equation of state in general relativity. The effective pressure of the neutron star given by the aether theory at a fiducial density differs from the values given by the two nuclear equations of state to an extent that can be constrained using future gravitational wave observations of neutron stars in compact systems. This is a promising way to test the aether theory if further progress is made in constraining the equation of state of nuclear matter in densities above the nuclear saturation density.

Farbod Kamiab; Niayesh Afshordi

2011-04-29T23:59:59.000Z

302

Cosmological properties of a gauged axion  

SciTech Connect

We analyze the most salient cosmological features of axions in extensions of the standard model with a gauged anomalous extra U(1) symmetry. The model is built by imposing the constraint of gauge invariance in the anomalous effective action, which is extended with Wess-Zumino counterterms. These generate axionlike interactions of the axions to the gauge fields and a gauged shift symmetry. The scalar sector is assumed to acquire a nonperturbative potential after inflation, at the electroweak phase transition, which induces a mixing of the Stueckelberg field of the model with the scalars of the electroweak sector, and at the QCD phase transition. We discuss the possible mechanisms of sequential misalignments which could affect the axions of these models, and generated, in this case, at both transitions. We compute the contribution of these particles to dark matter, quantifying their relic densities as a function of the Stueckelberg mass. We also show that models with a single anomalous U(1) in general do not account for the dark energy, due to the presence of mixed U(1)-SU(3) anomalies.

Coriano, Claudio; Mariano, Antonio [Dipartimento di Fisica, Universita del Salento, Via Arnesano 73100 Lecce (Italy) and INFN Sezione di Lecce, Via Arnesano 73100 Lecce (Italy); Guzzi, Marco [Department of Physics, Southern Methodist University, Dallas Texas 75275 (United States); Lazarides, George [Physics Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

2010-09-15T23:59:59.000Z

303

ASPHERICAL SUPERNOVA SHOCK BREAKOUT AND THE OBSERVATIONS OF SUPERNOVA 2008D  

Science Conference Proceedings (OSTI)

Shock breakout is the earliest, readily observable emission from a core-collapse supernova (SN) explosion. Observing SN shock breakout may yield information about the nature of the SN shock prior to exiting the progenitor and, in turn, about the core-collapse SN mechanism itself. X-ray outburst 080109, later associated with SN 2008D, is a very well-observed example of shock breakout from a core-collapse SN. Despite excellent observational coverage and detailed modeling, fundamental information about the shock breakout, such as the radius of breakout and driver of the light curve timescale, is still uncertain. The models constructed for explaining the shock breakout emission from SN 2008D all assume spherical symmetry. We present a study of the observational characteristics of aspherical shock breakout from stripped-envelope core-collapse SNe surrounded by a wind. We conduct two-dimensional, jet-driven SN simulations from stripped-envelope progenitors and calculate the resulting shock breakout X-ray spectra and light curves. The X-ray spectra evolve significantly in time as the shocks expand outward and are not fit well by single-temperature and radius blackbodies. The timescale of the X-ray burst light curve of the shock breakout is related to the shock crossing time of the progenitor, and not to the much shorter light crossing time that sets the light curve timescale in spherical breakouts. This could explain the long shock breakout light curve timescale observed for XRO 080109/SN 2008D. We also comment on the distribution of intermediate-mass elements in asymmetric explosions.

Couch, Sean M.; Wheeler, J. Craig; Milosavljevic, Milos [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Pooley, David [Eureka Scientific, Inc., Austin, TX 78756 (United States)

2011-02-01T23:59:59.000Z

304

The type Ia supernova SNLS-03D3bb from a super-Chandrasekhar-mass white dwarf star  

E-Print Network (OSTI)

The absolute magnitudes of Type IA supernovae. Astrophys. J.in a Sublu- o minous Type Ia Supernova: SpectropolarimetryL. Could There Be a Hole in Type Ia Super- novae? Astrophys.

2008-01-01T23:59:59.000Z

305

VLT observations of the Central Compact Object in the Vela Jr. supernova remnant  

E-Print Network (OSTI)

X-ray observations have unveiled the existence of enigmatic point-like sources at the center of young (a few kyrs) supernova remnants. These sources, known as Central Compact Objects (CCOs), are thought to be neutron stars produced by the supernova explosion, although their X-ray phenomenology makes them markedly different from all the other young neutron stars discovered so far.The aim of this work is to search for the optical/IR counterpart of the Vela Junior CCO and to understand the nature of the associated Halpha nebula discovered by Pellizzoni et al. (2002).}{We have used deep optical (R band) and IR (J,H,Ks bands) observations recently performed by our group with the ESO VLT to obtain the first deep, high resolution images of the field with the goal of resolving the nebula structure and pinpointing a point-like source possibly associated with the neutron star.Our R-band image shows that both the nebula's flux and its structure are very similar to the Halpha ones, suggesting that the nebula spectrum is dominated by pure Halpha line emission. However, the nebula is not detected in our IR observations, whick makes it impossible to to constrain its spectrum. A faint point-like object (J>22.6, H~21.6, Ks ~ 21.4) compatible with the neutron star's Chandra X-ray position is detected in our IR images (H and Ks) but not in the optical one (R > 25.6), where it is buried by the nebula background. The nebula is most likely a bow-shock produced by the neutron star motion through the ISM or, alternatively, a photo-ionization nebula powered by UV radiation from a hot neutron star.

R. P. Mignani; A. De Luca; S. Zaggia; D. Sester; A. Pellizzoni; S. Mereghetti; P. A. Caraveo

2007-07-06T23:59:59.000Z

306

Direct measurement of the $^{44}$Ti($\\alpha$,p) reaction of importance to supernovae, using reclaimed $^{44}$Ti  

E-Print Network (OSTI)

Direct measurement of the $^{44}$Ti($\\alpha$,p) reaction of importance to supernovae, using reclaimed $^{44}$Ti

CERN. Geneva; Lindroos, Mats; CERN. Geneva. ISOLDE and Neutron Time-of-Flight Experiments Committee; INTC

2007-01-01T23:59:59.000Z

307

Integration of D-dimensional 2-factor spaces cosmological models by reducing to the generalized Emden-Fowler equation  

E-Print Network (OSTI)

The D-dimensional cosmological model on the manifold $M = R \\times M_{1} \\times M_{2}$ describing the evolution of 2 Einsteinian factor spaces, $M_1$ and $M_2$, in the presence of multicomponent perfect fluid source is considered. The barotropic equation of state for mass-energy densities and the pressures of the components is assumed in each space. When the number of the non Ricci-flat factor spaces and the number of the perfect fluid components are both equal to 2, the Einstein equations for the model are reduced to the generalized Emden-Fowler (second-order ordinary differential) equation, which has been recently investigated by Zaitsev and Polyanin within discrete-group analysis. Using the integrable classes of this equation one generates the integrable cosmological models. The corresponding metrics are presented. The method is demonstrated for the special model with Ricci-flat spaces $M_1,M_2$ and the 2-component perfect fluid source.

V. R. Gavrilov; V. N. Melnikov

1998-01-13T23:59:59.000Z

308

Deep-Ocean Crusts as Telescopes: Using Live Radioisotopes to Probe Supernova Nucleosynthesis  

E-Print Network (OSTI)

Live 60Fe has recently been detected in a deep-ocean ferromanganese crust, isolated in layers dating from about 3 Myr ago. Since 60Fe has a mean life of 2.2 Myr, a near-Earth supernova is the only likely source for such a signal, and we explore here the consequences of a supernova origin. We combine the 60Fe data with several supernova nucleosynthesis models to calculate the supernova distance as a function of progenitor mass, finding an allowed range of 15-120 pc. We also predict the signals expected for several other radioisotopes, which are independent of the supernova distance. Species likely to be present near or above background levels are 10Be, 26Al, 53Mn, 182Hf and 244Pu. Of these, 182Hf and 244Pu are nearly background-free, presenting the best opportunities to provide strong confirmation of the supernova origin of the 60Fe signal, and to demonstrate that at least some supernovae are the source for the r-process. The accuracies of our predictions are hampered by large uncertainties in the predicted 60Fe yields for supernovae of different masses, so the new crust data motivate a redoubled theoretical attack on this problem.

Brian D. Fields; Kathrin A. Hochmuth; John Ellis

2004-10-22T23:59:59.000Z

309

What does cosmology tell us about particle physics beyond the Standard Model?  

Science Conference Proceedings (OSTI)

Cosmology demands particle physics beyond the Standard Model: we need to explain the nature of dark matter and dark energy

Eiichiro Komatsu

2012-01-01T23:59:59.000Z

310

On some physical aspects of isotropic cosmology in Riemann-Cartan spacetime  

E-Print Network (OSTI)

Isotropic cosmology built in the framework of the Poincar\\'e gauge theory of gravity based on sufficiently general expression of gravitational Lagrangian is considered. The derivation of cosmological equations and equations for torsion functions in the case of the most general homogeneous isotropic models is given. Physical aspects of isotropic cosmology connected with possible solution of dark energy problem and problem of cosmological singularity are discussed.

A. V. Minkevich; A. S. Garkun; V. I. Kudin

2013-02-11T23:59:59.000Z

311

Theoretical Research in Cosmology, High-Energy Physics and String Theory  

Science Conference Proceedings (OSTI)

The research was in the area of Theoretical Physics: Cosmology, High-Energy Physics and String Theory

Ng, Y Jack; Dolan, Louise; Mersini-Houghton, Laura; Frampton, Paul

2013-07-29T23:59:59.000Z

312

Thermalization of Starlight in the Steady-State Cosmology  

E-Print Network (OSTI)

We investigate the fate of starlight in the Steady-State Cosmology. We discover that it is largely unaffected by the presence of ions in intergalactic space as it gets progressively red-shifted from the visible all the way down to the plasma frequency of the intergalactic matter. At that point, after about 450 Gyr - and contrary to previously published claims - the radiation will be thermalized. Under the assumptions adopted by Gold, Bondi, Hoyle, Narlikar, Burbidge and others concerning the creation of matter in the Steady-State Cosmology, and using reasonable estimates for the baryonic mass-density and mass-fraction of 4He, the analysis predicts a universal radiation field matching the CMB, i.e. having a black-body spectrum and temperature of about 2.7 K. The Steady-state Cosmology predicts that this radiation field will appear to originate from the intergalactic plasma.

M. Ibison

2009-10-15T23:59:59.000Z

313

Cosmological toolkit project featured on DOE energy website | Argonne  

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

Cosmological toolkit project featured on DOE energy website Cosmological toolkit project featured on DOE energy website October 2, 2013 Tweet EmailPrint Researchers from Argonne National Laboratory, in partnership with Fermilab and Lawrence Berkeley National Laboratory, are developing a state-of-the-art toolkit for analyzing cosmological simulation data. The work was recently featured on the DOE website Energy.gov. Leading the Argonne team are Salman Habib, senior physicist and computational scientist in Argonne's High Energy Physics and Mathematics and Computer Science Divisions, and Ravi Madduri, project manager in the MCS Division. The multilaboratory team seeks to create an open platform with a web-based front end that will allow scientists to transfer, search, and analyze the complex data being generated by galaxy-formation simulations. Key to this

314

Quiescent cosmology and the final state of the universe  

E-Print Network (OSTI)

It has long been a primary objective of cosmology to understand the apparent isotropy in our universe and to provide a mathematical formulation for its evolution. A school of thought for its explanation is quiescent cosmology, which already possesses a mathematical framework, namely the definition of an Isotropic Singularity, but only for the initial state of the universe. A complementary framework is necessary in order to also describe possible final states of the universe. Our new definitions of an Anisotropic Future Endless Universe and an Anisotropic Future Singularity, whose structure and properties differ significantly from those of the Isotropic Singularity, offer a promising realisation for this framework. The combination of the three definitions together may then provide the first complete formalisation of the quiescent cosmology concept.

Philipp A Hoehn; Susan M Scott

2010-01-18T23:59:59.000Z

315

Thermodynamics of de Sitter Black Holes: Thermal Cosmological Constant  

E-Print Network (OSTI)

We study the thermodynamic properties associated with the black hole event horizon and the cosmological horizon for black hole solutions in asymptotically de Sitter spacetimes. We examine thermodynamics of these horizons on the basis of the conserved charges according to Teitelboim's method. In particular, we have succeeded in deriving the generalized Smarr formula among thermodynamical quantities in a simple and natural way. We then show that cosmological constant must decrease when one takes into account the quantum effect. These observations have been obtained if and only if cosmological constant plays the role of a thermodynamical state variable. We also touch upon the relation between inflation of our universe and a phase transition of black holes.

Yuichi Sekiwa

2006-02-25T23:59:59.000Z

316

Crisis in Cosmology : Observational Constraints on Omega and H_0  

E-Print Network (OSTI)

Thanks to new technology of observations and fresh inputs from particle physics, cosmology has advanced on both observational and theoretical fronts. It is therefore opportune that we take stock of the cosmological situation today and examine the observational and theoretical constraints as they are now. The bottom line in this review is that despite the availability of the cosmological constant as an extra parameter for flat Friedmann models, the allowed parameter space for such models is very small. The observations that we consider here include the ages of globular clusters, measurement of Hubble's constant, abundance of rich clusters of galaxies, fraction of mass contributed by baryons in rich clusters and abundance of high redshift objects.

J. S. Bagla; T. Padmanabhan; J. V. Narlikar

1995-11-22T23:59:59.000Z

317

COSMOLOGICAL POST-NEWTONIAN APPROXIMATION COMPARED WITH PERTURBATION THEORY  

Science Conference Proceedings (OSTI)

We compare the cosmological first-order post-Newtonian (1PN) approximation with the relativistic cosmological linear perturbation theory in a zero-pressure medium with the cosmological constant. We compare equations and solutions in several different gauge conditions available in both methods. In the PN method we have perturbation equations for density, velocity, and gravitational potential independently of the gauge condition to 1PN order. However, correspondences with these 1PN equations are available only in certain gauge conditions in the perturbation theory. Equations of perturbed velocity and the perturbed gravitational potential in the zero-shear gauge exactly coincide with the Newtonian equations, which remain valid even to 1PN order (the same is true for perturbed velocity identified in the comoving gauge), and equations of perturbed density in the zero-shear gauge and the uniform-expansion gauge coincide to 1PN order. We identify other correspondences available in different gauge conditions of the perturbation theory.

Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejon 305-348 (Korea, Republic of); Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701 (Korea, Republic of)

2012-10-01T23:59:59.000Z

318

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

319

Cosmological mass limits on neutrinos, axions, and other light particles  

E-Print Network (OSTI)

The small-scale power spectrum of the cosmological matter distribution together with other cosmological data provides a sensitive measure of the hot dark matter fraction, leading to restrictive neutrino mass limits. We extend this argument to generic cases of low-mass thermal relics. We vary the cosmic epoch of thermal decoupling, the radiation content of the universe, and the new particle's spin degrees of freedom. Our treatment covers various scenarios of active plus sterile neutrinos or axion-like particles. For three degenerate massive neutrinos, we reproduce the well-known limit of m_nu solar eV-mass axions to be discovered by the CAST experiment.

Steen Hannestad; Georg Raffelt

2003-12-11T23:59:59.000Z

320

Cosmological Solutions in Biconnection and Bimetric Gravity Theories  

E-Print Network (OSTI)

We show how generic off--diagonal cosmological solutions depending, in general, on all spacetime coordinates can be constructed in massive gravity using the anholonomic frame deformation method. Such metrics describe the late time acceleration due to effective cosmological terms induced by nonlinear off--diagonal interactions and graviton mass and include matter, graviton mass and other effective sources modelling nonlinear gravitational and matter fields interactions with polarization of physical constants and deformations of metrics, which may explain certain dark energy and dark matter effects.

Sergiu I. Vacaru

2013-04-02T23:59:59.000Z

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321

General properties of cosmological models with an Isotropic Singularity  

E-Print Network (OSTI)

Much of the published work regarding the Isotropic Singularity is performed under the assumption that the matter source for the cosmological model is a barotropic perfect fluid, or even a perfect fluid with a $\\gamma$-law equation of state. There are, however, some general properties of cosmological models which admit an Isotropic Singularity, irrespective of the matter source. In particular, we show that the Isotropic Singularity is a point-like singularity and that vacuum space-times cannot admit an Isotropic Singularity. The relationships between the Isotropic Singularity, and the energy conditions, and the Hubble parameter is explored. A review of work by the authors, regarding the Isotropic Singularity, is presented.

Geoffery Ericksson; Susan M. Scott

2003-02-25T23:59:59.000Z

322

Towards a holographic theory of cosmology -- threads in a tapestry  

E-Print Network (OSTI)

In this Essay we address several fundamental issues in cosmology: What is the nature of dark energy and dark matter? Why is the dark sector so different from ordinary matter? Why is the effective cosmological constant non-zero but so incredibly small? What is the reason behind the emergence of a critical acceleration parameter of magnitude $10^{-8} cm/sec^2$ in galactic dynamics? We suggest that the holographic principle is the linchpin in a unified scheme to understand these various issues.

Y. Jack Ng

2013-05-16T23:59:59.000Z

323

Interplanetary Measures Can Not Bound the Cosmological Constant  

E-Print Network (OSTI)

The effect of a cosmological constant on the precession of the line of apsides is O(\\Lambda c^2 r^3/GM) which is 3(H_\\circ P)^2/8\\pi^2 \\approx 10^{-23} for a vacuum-dominated Universe with Hubble constant H_\\circ = 65 km/sec/Mpc and for the orbital period P = 88 days of Mercury. This is unmeasurably small, so planetary perturbations cannot be used to limit the cosmological constant, contrary to the suggestion by Cardona & Tejeiro (1998).

Edward L. Wright

1998-05-21T23:59:59.000Z

324

Turbulence-Flame Interactions in Type Ia Supernovae  

SciTech Connect

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 x 107 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 x 107 g cm-3 where the nature of the burning changes ualitatively. By 1 x 107 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.

Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2& 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5); Aspden, Andrew J; Aspden, Andrew J.; Bell, John B.; Day, Marc S.; Woosley, Stan E.; Zingale, Mike

2008-05-27T23:59:59.000Z

325

OPTICAL SIGNATURES OF CIRCUMSTELLAR INTERACTION IN TYPE IIP SUPERNOVAE  

E-Print Network (OSTI)

We propose new diagnostics for circumstellar interaction in Type IIP supernovae (SNe IIP) by the detection of high velocity (HV) absorption features in H? and HeI 10830 ?A lines during the photospheric stage. To demonstrate the method, we compute the ionization and excitation of H and He in supernova ejecta taking into account time-dependent effects and X-ray irradiation. We find that the interaction with a typical red supergiant wind should result in the enhanced excitation of the outer layers of unshocked ejecta and the emergence of corresponding HV absorption, i.e. a depression in the blue absorption wing of H? and a pronounced absorption of HeI 10830 ?A at a radial velocity of about ?10 4 km s ?1. We identify HV absorption in H? and HeI 10830 ?A lines of SN 1999em and in H? of SN 2004dj as being due to this effect. The derived mass loss rate is close to 10 ?6 M ? yr ?1 for both supernovae, assuming a wind velocity 10 km s ?1. We argue that, in addition to the HV absorption formed in the unshocked ejecta, spectra of SN 2004dj and SN 1999em show a HV notch feature that is formed in the cool dense shell (CDS) modified by the Rayleigh-Taylor instability. The CDS results from both shock breakout and radiative cooling of gas that has passed through the reverse shock wave. The notch becomes dominant in the HV absorption during the late photospheric phase, ? 60 d. The wind density deduced from the velocity of the CDS is consistent with the wind density found from the HV absorption produced by unshocked ejecta.

Nikolai N. Chugai; Roger A. Chevalier; Victor P. Utrobin

2007-01-01T23:59:59.000Z

326

Optical Signatures of Circumstellar Interaction in Type IIP Supernovae  

E-Print Network (OSTI)

We propose new diagnostics for circumstellar interaction in Type IIP supernovae by the detection of high velocity (HV) absorption features in Halpha and He I 10830 A lines during the photospheric stage. To demonstrate the method, we compute the ionization and excitation of H and He in supernova ejecta taking into account time-dependent effects and X-ray irradiation. We find that the interaction with a typical red supergiant wind should result in the enhanced excitation of the outer layers of unshocked ejecta and the emergence of corresponding HV absorption, i.e. a depression in the blue absorption wing of Halpha and a pronounced absorption of He I 10830 A at a radial velocity of about -10,000 km/s. We identify HV absorption in Halpha and He I 10830 A lines of SN 1999em and in Halpha of SN 2004dj as being due to this effect. The derived mass loss rate is close to 10^{-6} Msun/yr for both supernovae, assuming a wind velocity 10 km/s. We argue that, in addition to the HV absorption formed in the unshocked ejecta, spectra of SN 2004dj and SN 1999em show a HV notch feature that is formed in the cool dense shell (CDS) modified by the Rayleigh-Taylor instability. The CDS results from both shock breakout and radiative cooling of gas that has passed through the reverse shock wave. The notch becomes dominant in the HV absorption during the late photospheric phase, ~60 d. The wind density deduced from the velocity of the CDS is consistent with the wind density found from the HV absorption produced by unshocked ejecta.

Nikolai N. Chugai; Roger A. Chevalier; Victor P. Utrobin

2007-03-17T23:59:59.000Z

327

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

328

Cerenkov radiation by neutrinos in a supernova core  

E-Print Network (OSTI)

Neutrinos with a magnetic dipole moment propagating in a medium with a velocity larger than the phase velocity of light emit photons by the Cerenkov process. The Cerenkov radiation is a helicity flip process via which a left-handed neutrino in a supernova core may change into a sterile right-handed one and free-stream out of the core. Assuming that the luminosity of such sterile right-handed neutrinos is less than $10^{53}$ ergs/sec gives an upper bound on the neutrino magnetic dipole moment $\\mu_\

Subhendra Mohanty; Manoj K. Samal

1995-06-21T23:59:59.000Z

329

Supernova Relic Neutrino Search at Super-Kamiokande  

E-Print Network (OSTI)

A new Super-Kamiokande (SK) search for Supernova Relic Neutrinos (SRNs) was conducted using 2853 live days of data. Sensitivity is now greatly improved compared to the 2003 SK result, which placed a flux limit near many theoretical predictions. This more detailed analysis includes a variety of improvements such as increased efficiency, a lower energy threshold, and an expanded data set. New combined upper limits on SRN flux are between 2.8 and 3.0 nu_e cm^-2 s^-1 > 16 MeV total positron energy (17.3 MeV E_nu).

The Super-Kamiokande Collaboration; :; K. Bays; T. Iida; K. Abe; Y. Hayato; K. Iyogi; J. Kameda; Y. Koshio; L. Marti; M. Miura; S. Moriyama; M. Nakahata; S. Nakayama; Y. Obayashi; H. Sekiya; M. Shiozawa; Y. Suzuki; A. Takeda; Y. Takenaga; K. Ueno; K. Ueshima S. Yamada T. Yokozawa H. Kaji T. Kajita; K. Kaneyuki; T. McLachlan; K. Okumura; L. K. Pik; K. Martens; M. Vagins; L. Labarga; E. Kearns; M. Litos; J. L. Raaf; J. L. Stone; L. R. Sulak; W. R. Kropp; S. Mine; C. Regis; A. Renshaw; M. B. Smy; H. W. Sobel; K. S. Ganezer; J. Hill; W. E. Keig; S. Cho; J. S. Jang; J. Y. Kim; I. T. Lim; J. Albert; K. Scholberg; C. W. Walter; R. Wendell; T. Wongjirad; T. Ishizuka; S. Tasaka; J. G. Learned; S. Matsuno; S. Smith; T. Hasegawa; T. Ishida; T. Ishii; T. Kobayashi; T. Nakadaira; K. Nakamura; K. Nishikawa; Y. Oyama; K. Sakashita; T. Sekiguchi; T. Tsukamoto; A. T. Suzuki; Y. Takeuchi; M. Ikeda; K. Matsuoka; A. Minamino; A. Murakami; T. Nakaya; Y. Fukuda; Y. Itow; G. Mitsuka; M. Miyake; T. Tanaka; J. Hignight; J. Imber; C. K. Jung; I. Taylor; C. Yanagisawa; A. Kibayashi; H. Ishino; S. Mino; M. Sakuda; T. Mori; H. Toyota; Y. Kuno; S. B. Kim; B. S. Yang; H. Okazawa; Y. Choi; K. Nishijima; M. Koshiba; Y. Totsuka; M. Yokoyama; Y. Heng; S. Chen; H. Zhang; Z. Yang; P. Mijakowski; K. Connolly; M. Dziomba; R. J. Wilkes

2011-11-21T23:59:59.000Z

330

EVALUATING SYSTEMATIC DEPENDENCIES OF TYPE Ia SUPERNOVAE: THE INFLUENCE OF CENTRAL DENSITY  

SciTech Connect

We present a study exploring a systematic effect on the brightness of Type Ia supernovae using numerical models that assume the single-degenerate paradigm. Our investigation varied the central density of the progenitor white dwarf at flame ignition, and considered its impact on the explosion yield, particularly the production and distribution of radioactive {sup 56}Ni, which powers the light curve. We performed a suite of two-dimensional simulations with randomized initial conditions, allowing us to characterize the statistical trends that we present. The simulations indicate that the production of Fe-group material is statistically independent of progenitor central density, but the mass of stable Fe-group isotopes is tightly correlated with central density, with a decrease in the production of {sup 56}Ni at higher central densities. These results imply that progenitors with higher central densities produce dimmer events. We provide details of the post-explosion distribution of {sup 56}Ni in the models, including the lack of a consistent centrally located deficit of {sup 56}Ni, which may be compared to observed remnants. By performing a self-consistent extrapolation of our model yields and considering the main-sequence lifetime of the progenitor star and the elapsed time between the formation of the white dwarf and the onset of accretion, we develop a brightness-age relation that improves our prediction of the expected trend for single degenerates and we compare this relation with observations.

Krueger, Brendan K.; Jackson, Aaron P.; Calder, Alan C. [Department of Physics and Astronomy, State University of New York-Stony Brook, Stony Brook, NY (United States); Townsley, Dean M. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL (United States); Brown, Edward F. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI (United States); Timmes, Francis X., E-mail: brendan.krueger@stonybrook.edu [Joint Institute for Nuclear Astrophysics, Notre Dame, IN (United States)

2012-10-01T23:59:59.000Z

331

Exploring the Outer Solar System with the ESSENCE Supernova Survey  

Science Conference Proceedings (OSTI)

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

332

Role of isospin physics in supernova matter and neutron stars  

E-Print Network (OSTI)

We investigate the liquid-gas phase transition of hot protoneutron stars shortly after their birth following supernova explosion and the composition and structure of hyperon-rich (proto)neutron stars within a relativistic mean-field model where the nuclear symmetry energy has been constrained from the measured neutron skin thickness of finite nuclei. Light clusters are abundantly formed with increasing temperature well inside the neutrino-sphere for an uniform supernova matter. Liquid-gas phase transition is found to suppress the cluster yield within the coexistence phase as well as decrease considerably the neutron-proton asymmetry over a wide density range. We find symmetry energy has a modest effect on the boundaries and the critical temperature for the liquid-gas phase transition, and the composition depends more sensitively on the number of trapped neutrinos and temperature of the protoneutron star. The influence of hyperons in the dense interior of stars makes the overall equation of state soft. However, neutrino trapping distinctly delays the appearance of hyperons due to abundance of electrons. We also find that a softer symmetry energy further makes the onset of hyperon less favorable. The resulting structures of the (proto)neutron stars with hyperons and with liquid-gas phase transition are discussed.

Bharat K. Sharma; Subrata Pal

2010-10-28T23:59:59.000Z

333

Troubles with quantum anisotropic cosmological models: loss of unitarity  

E-Print Network (OSTI)

The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. It is shown that the resulting model is non-unitary. This breaks the equivalence between the many-worlds and dBB interpretations of quantum mechanics.

F. G. Alvarenga; A. B. Batista; J. C. Fabris; S. V. B. Goncalves

2004-02-25T23:59:59.000Z

334

Problems of Cosmological Variability of Fundamental Physical Constants  

E-Print Network (OSTI)

of the fundamental constants which govern most of the common phenomena and are usually given in the handbooks. NoteProblems of Cosmological Variability of Fundamental Physical Constants #3; D. A. Varshalovich, A. Y and astronomical observations aimed at testing the possible space-time variability of fundamental physical

335

FRW quantum cosmology with a generalized Chaplygin gas  

SciTech Connect

Cosmologies with a Chaplygin gas have recently been explored with the objective of explaining the transition from a dust dominated epoch towards an accelerating expansion stage. In this context, we consider the hypothesis that this transition involves a quantum mechanical process. Our analysis is entirely analytical, with the objective of finding explicit mathematical expressions for the different quantum mechanical states and their cosmological implications. We employ a Friedmann-Robertson-Walker (FRW) minisuperspace model, characterized by two Lorentzian sectors, separated by a classically forbidden region. This is the configuration associated with the evolution of a generalized Chaplygin gas in a FRW universe. The Hartle-Hawking and Vilenkin wave functions are then computed, together with the transition amplitudes towards the accelerating epoch. Furthermore, for specific initial conditions we found that the generalized Chaplygin gas parameters become related through an expression involving an integer n. We also introduce a phenomenological association between some brane-world scenarios and a FRW minisuperspace cosmology with a generalized Chaplygin gas. The aim is to promote a discussion and subsequent research on the quantum creation of brane cosmologies from such a perspective. Additional results in this paper suggest that the brane tension would become related with the generalized Chaplygin gas parameters through another expression involving an integer.

Bouhmadi-Lopez, Mariam; Moniz, Paulo Vargas [Institute of Cosmology and Gravitation, University of Portsmouth, Mercantile House, Hampshire Terrace, Portsmouth PO1 2EG (United Kingdom); Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)

2005-03-15T23:59:59.000Z

336

An Alternative Solution to the Cosmological Constant Problem  

E-Print Network (OSTI)

In this paper it is analyzed the consecuences of a (1,1) dimensional space time at Planck scales. With this hypothesis is proposed an alternative solution to the density energy and the coincidence problem of the cosmological constant. Similarly it is predicted that the density of the dark energy is 4/9 of the critical density in the Universe.

Angel, Garcia Aspeitia Miguel

2010-01-01T23:59:59.000Z

337

Dark Energy: The Cosmological Challenge of the T. Padmanabhan  

E-Print Network (OSTI)

Dark Energy: The Cosmological Challenge of the Millennium T. Padmanabhan IUCAA, Pune Observational. It is made of a very exotic species called dark energy which exerts negative pressure. This is more esoteric per cent dark 1 #12;energy. The key direct evidence, however, came in late ninetees from the analysis

Udgaonkar, Jayant B.

338

Kaluza-Klein Cosmology With Modified Holographic Dark Energy  

E-Print Network (OSTI)

We investigate the compact Kaluza-Klein cosmology in which modified holographic dark energy is interacting with dark matter. Using this scenario, we evaluate equation of state parameter as well as equation of evolution of the modified holographic dark energy. Further, it is shown that the generalized second law of thermodynamics holds without any constraint.

M. Sharif; Farida Khanum

2011-06-13T23:59:59.000Z

339

Three fluid cosmological model using Lie and Noether symmetries  

E-Print Network (OSTI)

We employ a three fluid model in order to construct a cosmological model in the Friedmann Robertson Walker flat spacetime, which contains three types of matter dark energy, dark matter and a perfect fluid with a linear equation of state. Dark matter is described by dust and dark energy with a scalar field with potential V({\\phi}). In order to fix the scalar field potential we demand Lie symmetry invariance of the field equations, which is a model-independent assumption. The requirement of an extra Lie symmetry selects the exponential scalar field potential. The further requirement that the analytic solution is invariant under the point transformation generated by the Lie symmetry eliminates dark matter and leads to a quintessence and a phantom cosmological model containing a perfect fluid and a scalar field. Next we assume that the Lagrangian of the system admits an extra Noether symmetry. This new assumption selects the scalar field potential to be exponential and forces the perfect fluid to be stiff. Furthermore the existence of the Noether integral allows for the integration of the dynamical equations. We find new analytic solutions to quintessence and phantom cosmologies which contain all three fluids. Using these solutions one is able to compute analytically all main cosmological functions, such as the scale factor, the scalar field, the Hubble expansion rate, the deceleration parameter etc.

Michael Tsamparlis; Andronikos Paliathanasis

2011-11-23T23:59:59.000Z

340

Cosmological Constraints from the SDSS maxBCG Cluster Catalog  

Science Conference Proceedings (OSTI)

We use the abundance and weak lensing mass measurements of the SDSS maxBCG cluster catalog to simultaneously constrain cosmology and the richness-mass relation of the clusters. Assuming a flat {Lambda}CDM cosmology, we find {sigma}{sub 8}({Omega}{sub m}/0.25){sup 0.41} = 0.832 {+-} 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, the primary two being the absolute mass scale of the weak lensing masses of the maxBCG clusters, and uncertainty in the scatter of the richness-mass relation. Our constraints are fully consistent with the WMAP five-year data, and in a joint analysis we find {sigma}{sub 8} = 0.807 {+-} 0.020 and {Omega}{sub m} = 0.265 {+-} 0.016, an improvement of nearly a factor of two relative to WMAP5 alone. Our results are also in excellent agreement with and comparable in precision to the latest cosmological constraints from X-ray cluster abundances. The remarkable consistency among these results demonstrates that cluster abundance constraints are not only tight but also robust, and highlight the power of optically-selected cluster samples to produce precision constraints on cosmological parameters.

Rozo, Eduardo; /CCAPP; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Rykoff, Eli S.; /UC, Santa Barbara; Annis, James T.; /Fermilab; Becker, Matthew R.; /Chicago U. /KICP, Chicago; Evrard, August E.; /Michigan U. /Michigan U., MCTP; Frieman, Joshua A.; /Fermilab /KICP, Chicago /Chicago U.; Hansen, Sarah M.; /UC, Santa Cruz; Hao, Jia; /Michigan U.; Johnston, David E.; /Northwestern U.; Koester, Benjamin P.; /KICP, Chicago /Chicago U.; McKay, Timothy A.; /Michigan U. /Michigan U., MCTP; Sheldon, Erin S.; /Brookhaven; Weinberg, David H.; /CCAPP /Ohio State U.

2009-08-03T23:59:59.000Z

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.


341

The quantization of unimodular gravity and the cosmological constant problem  

E-Print Network (OSTI)

A quantization of unimodular gravity is described, which results in a quantum effective action which is also unimodular, ie a function of a metric with fixed determinant. A consequence is that contributions to the energy momentum tensor of the form of the metric times a spacetime constant, whether classical or quantum, are not sources of curvature in the equations of motion derived from the quantum effective action. This solves the first cosmological constant problem, which is suppressing the enormous contributions to the cosmological constant coming from quantum corrections. We discuss several forms of uniodular gravity and put two of them, including one proposed by Henneaux and Teitelboim, in constrained Hamiltonian form. The path integral is constructed from the latter. Furthermore, the second cosmological constant problem, which is why the measured value is so small, is also addressed by this theory. We argue that a mechanism first proposed by Ng and van Dam for suppressing the cosmological constant by quantum effects obtains at the semiclassical level.

Lee Smolin

2009-04-30T23:59:59.000Z

342

Comments on the Quasi-Steady-State Cosmology  

E-Print Network (OSTI)

The Quasi-Steady-State Cosmology as proposed by Hoyle, Burbidge and Narlikar does not fit the observed facts of the Universe. In particular, it predicts that 75-90\\% of the radio sources in the brightest sample that shows steeper than Euclidean source counts should be blueshifted.

Edward L. Wright

1994-10-20T23:59:59.000Z

343

Pre-Big Bang, vacuum and noncyclic cosmologies  

E-Print Network (OSTI)

WMAP and Planck open the way to unprecedented Big Bang phenomenology, potentially allowing to test the standard Big Bang model as well as less conventional approaches including noncyclic pre-Big Bang cosmologies that would incorporate a new fundamental scale beyond the Planck scale and, possibly, new ultimate constituents of matter. Alternatives to standard physics can be considered from a cosmological point of view concerning vacuum structure, the nature of space-time, the origin and evolution of our Universe, the validity of quantum field theory and conventional symmetries, solutions to the cosmological constant problem, inflationary scenarios, dark matter and dark energy, the interpretation of string-like theories... Lorentz-like symmetries for the properties of matter (standard or superbradyonic) can then be naturally stable space-time configurations resulting from general cosmological scenarios that incorporate physics beyond the Planck scale and describe the formation and evolution of the present vacuum. But an even more primordial question seems to be that of the origin of half-integer spins, that cannot be generated through orbital angular momentum in the usual real space-time. It turns out that the use of a spinorial space-time with two complex coordinates instead of the conventional four real ones presents several attractive features. Taking the cosmic time to be the modulus of a SU(2) spinor leads by purely geometric means to a naturally expanding universe, with a ratio between cosmic relative velocities and distances equal to the inverse of the age of the Universe. No reference to standard matter, hidden fields, gravitation or relativity is required to get such a result that looks quite reasonable from an observational point of view. We discuss basic ideas and phenomenological issues for noncyclic pre-Big Bang cosmologies in the present context.

Luis Gonzalez-Mestres

2012-12-12T23:59:59.000Z

344

Neutrino-Matter Interaction Rates in Supernovae: The Essential Microphysics of Core Collapse  

E-Print Network (OSTI)

Neutrino-matter interaction rates are central to the core collapse phenomenon and, perhaps, to the viability of the mechanism of core-collapse supernova explosions. In this paper we catalog and discuss the major neutrino scattering, absorption, and production processes that together influence the outcome of core collapse and the cooling of protoneutron stars. These are the essential inputs into the codes used to simulate the supernova phenomenon and an understanding of these processes is a prerequisite to continuing progress in supernova theory.

Adam Burrows; Todd A. Thompson

2002-11-18T23:59:59.000Z

345

Dedicated Supernova Detection by a Network of Neutral Current Spherical TPC's  

E-Print Network (OSTI)

Supernova neutrinos can easily be detected by a spherical gaseous TPC detector measuring very low energy nuclear recoils. The expected rates are quite large for a neutron rich target since the neutrino nucleus neutral current interaction yields a coherent contribution of all neutrons. As a matter of fact for a typical supernova at 10 kpc, about 1000 events are expected using a spherical detector of radius 4 m with Xe gas at a pressure of 10 Atm. A world wide network of several such simple, stable and low cost supernova detectors with a running time of a few centuries is quite feasible.

J. D. Vergados; Y. Giomataris

2005-11-16T23:59:59.000Z

346

Dedicated Supernova Detection by a Network of Neutral Current Spherical TPC's  

E-Print Network (OSTI)

Supernova neutrinos can easily be detected by a spherical gaseous TPC detector measuring very low energy nuclear recoils. The expected rates are quite large for a neutron rich target since the neutrino nucleus neutral current interaction yields a coherent contribution of all neutrons. As a matter of fact for a typical supernova at 10 kpc, about 1000 events are expected using a spherical detector of radius 4 m with Xe gas at a pressure of 10 Atm. A world wide network of several such simple, stable and low cost supernova detectors with a running time of a few centuries is quite feasible.

Vergados, J D

2005-01-01T23:59:59.000Z

347

A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey  

E-Print Network (OSTI)

ABRIDGED We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <0.17 and 27 SN events in 492 maxBCG clusters at 0.1 < z < 0.3$. We find values for the cluster SN Ia rate of $({0.37}^{+0.17+0.01}_{-0.12-0.01}) \\mathrm{SNu}r h^{2}$ and $({0.55}^{+0.13+0.02}_{-0.11-0.01}) \\mathrm{SNu}r h^{2}$ ($\\mathrm{SNu}x = 10^{-12} L_{x\\sun}^{-1} \\mathrm{yr}^{-1}$) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be $({0.31}^{+0.18+0.01}_{-0.12-0.01}) \\mathrm{SNu}r h^{2}$ and $({0.49}^{+0.15+0.02}_{-0.11-0.01})$ $\\mathrm{SNu}r h^{2}$ in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be $({2.04}^{+1.99+0.07}_{-1.11-0.04}) \\mathrm{SNu}r h^{2}$ and $({0.36}^{+0.84+0.01}_...

Dilday, Benjamin; Becker, Andrew; Bender, Ralf; Castander, Francisco; Cinabro, David; Frieman, Joshua A; Galbany, Llus; Garnavich, Peter; Goobar, Ariel; Hopp, Ulrich; Ihara, Yutaka; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Moll, Mercedes; Nichol, Robert C; Nordin, Jakob; Riess, Adam G; Sako, Masao; Schneider, Donald P; Smith, Mathew; Sollerman, Jesper; Wheeler, J Craig; stman, Linda; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie

2010-01-01T23:59:59.000Z

348

Spectroscopic confirmation of a redshift 1.55 supernova host galaxy from the Subaru Deep Field Supernova Survey  

E-Print Network (OSTI)

The Subaru Deep Field (SDF) Supernova Survey discovered 10 Type Ia supernovae (SNe Ia) in the redshift range $1.5

Frederiksen, Teddy F; Hjorth, Jens; Maoz, Dan; Poznanski, Dovi

2012-01-01T23:59:59.000Z

349

f(R) Gravity from the renormalisation group  

E-Print Network (OSTI)

We explore the cosmological dynamics of an effective f(R) model constructed from a renormalisation group (RG) improvement of the Einstein--Hilbert action, using the non-perturbative beta functions of the exact renormalisation group equation. The resulting f(R) model has some remarkable properties. It naturally exhibits an unstable de Sitter era in the ultraviolet (UV), dynamically connected to a stable de Sitter era in the IR, via a period of radiation and matter domination, thereby describing a non-singular universe. We find that the UV de Sitter point is one of an infinite set, which make the UV RG fixed point inaccessible to classical cosmological evolution. In the vicinity of the fixed point, the model behaves as R^2 gravity, while it correctly recovers General Relativity at solar system scales. In this simplified model, the fluctuations are too large to be the observed ones, and more ingredients in the action are needed.

Mark Hindmarsh; Ippocratis D. Saltas

2012-03-18T23:59:59.000Z

350

NUMERICAL STUDY OF THE VISHNIAC INSTABILITY IN SUPERNOVA REMNANTS  

Science Conference Proceedings (OSTI)

The Vishniac instability is thought to explain the complex structure of radiative supernova remnants in their Pressure-Driven Thin Shell (PDTS) phase after a blast wave (BW) has propagated from a central explosion. In this paper, the propagation of the BW and the evolution of the PDTS stage are studied numerically with the two-dimensional (2D) code HYDRO-MUSCL for a finite-thickness shell expanding in the interstellar medium (ISM). Special attention is paid to the adiabatic index, {gamma}, and three distinct values are taken for the cavity ({gamma}{sub 1}), the shell ({gamma}{sub 2}), and the ISM ({gamma}{sub 3}) with the condition {gamma}{sub 2} < {gamma}{sub 1}, {gamma}{sub 3}. This low value of {gamma}{sub 2} accounts for the high density in the shell achieved by a strong radiative cooling. Once the spherical background flow is obtained, the evolution of a 2D-axisymmetric perturbation is computed from the linear to the nonlinear regime. The overstable mechanism, previously demonstrated theoretically by E. T. Vishniac in 1983, is recovered numerically in the linear stage and is expected to produce and enhance anisotropies and clumps on the shock front, leading to the disruption of the shell in the nonlinear phase. The period of the increasing oscillations and the growth rate of the instability are derived from several points of view (the position of the perturbed shock front, mass fluxes along the shell, and density maps), and the most unstable mode differing from the value given by Vishniac is computed. In addition, the influence of several parameters (the Mach number, amplitude and wavelength of the perturbation, and adiabatic index) is examined and for wavelengths that are large enough compared to the shell thickness, the same conclusion arises: in the late stage of the evolution of the radiative supernova remnant, the instability is dampened and the angular initial deformation of the shock front is smoothed while the mass density becomes uniform with the angle. As a result, our model shows that the supernova remnant returns to a stable evolution and the Vishniac instability does not lead to the fragmentation of the shock as predicted by the theory.

Michaut, C.; Cavet, C.; Bouquet, S. E.; Roy, F.; Nguyen, H. C., E-mail: claire.michaut@obspm.fr [LUTH, Observatoire de Paris, CNRS, Universite Paris-Diderot, F-92190 Meudon (France)

2012-11-10T23:59:59.000Z

351

The WiggleZ Dark Energy Survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant supernovae  

E-Print Network (OSTI)

Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable consequences in many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has proven very difficult to measure directly. We present a new determination of the cosmic expansion history by combining distant supernovae observations with a geometrical analysis of large-scale galaxy clustering within the WiggleZ Dark Energy Survey, using the Alcock-Paczynski test to measure the distortion of standard spheres. Our result constitutes a robust and non-parametric measurement of the Hubble expansion rate as a function of time, which we measure with 10-15% precision in four bins within the redshift range 0.1 < z < 0.9. We demonstrate that the cosmic expansion is accelerating, in a manner independent of the parameterization of the cosmological model (although assuming cosmic homogeneity in our data analy...

Blake, Chris; Davis, Tamara; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Drinkwater, Michael J; Forster, Karl; Gilbank, David; Gladders, Mike; Jelliffe, Ben; Jurek, Russell J; Li, I-hui; Madore, Barry; Martin, Chris; Pimbblet, Kevin; Poole, Gregory; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted; Yee, Howard

2011-01-01T23:59:59.000Z

352

nu-Process Nucleosynthesis in Population III Core-Collapse Supernovae  

E-Print Network (OSTI)

We investigate the effects of neutrino-nucleus interactions (the nu-process) on the production of iron-peak elements in Population III core-collapse supernovae. The nu-process and the following proton and neutron capture reactions produce odd-Z iron-peak elements in complete and incomplete Si burning region. This reaction sequence enhances the abundances of Sc, Mn, and Co in the supernova ejecta. The supernova explosion models of 15 M_sol and 25 M_sol stars with the nu-process well reproduce the averaged Mn/Fe ratio observed in extremely metal-poor halo stars. In order to reproduce the observed Mn/Fe ratio, the total neutrino energy in the supernovae should be 3 - 9 x 10^{53} ergs. Stronger neutrino irradiation and other production sites are necessary to reproduce the observed Sc/Fe and Co/Fe ratios, although these ratios increase by the nu-process.

Takashi Yoshida; Hideyuki Umeda; Ken'ichi Nomoto

2007-10-01T23:59:59.000Z

353

GRB 020410: A Gamma-ray burst afterglow discovered by its supernova light  

E-Print Network (OSTI)

Training Network Gamma-Ray Bursts: An Enigma and a Tool,Journal GRB 020410: A Gamma-Ray Burst Afterglow DiscoveredSubject headings: gamma rays: bursts supernova: general

2004-01-01T23:59:59.000Z

354

Mtrologie des supernovae de type Ia pour la cosmologie : instrumentation et analyse calorimtrique.  

E-Print Network (OSTI)

??L'utilisation des supernovae de type Ia comme indicateurs de distance est un pilier du modle de concordance actuel en cosmologie. Le travail d'instrumentation prsent dans (more)

Juramy, Claire

2006-01-01T23:59:59.000Z

355

Toward Exascale Computing of Type Ia and Ib,c Supernovae: V&V...  

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

Toward Exascale Computing of Type Ia and Ib,c Supernovae: V&V of Current Models PI Name: Don Lamb PI Email: lamb@oddjob.uchicago.edu Institution: University Of Chicago Allocation...

356

Cosmological evolution of the cosmological plasma with interpartial scalar interaction. III. Model with the attraction of the like scalar charged particles  

E-Print Network (OSTI)

On the basis of the relativistic kinetic theory the mathematical model of cosmological plasmas with an attraction of the like charged scalar particles is formulated. It is shown, that cosmological the model, based on a classical scalar field with an attraction, is unsatisfactory, that leads to necessity of attraction of phantom models of a scalar field for systems with an attraction.

Yu. G. Ignat'ev

2013-07-09T23:59:59.000Z

357

Nuclear liquid-gas phase transition and supernovae evolution  

E-Print Network (OSTI)

It is shown that the large density fluctuations appearing at the onset of the first order nuclear liquid-gas phase transition can play an important role in the supernovae evolution. Due to these fluctuations, the neutrino gas may be trapped inside a thin layer of matter near the proto-neutron star surface. The resulting increase of pressure may induce strong particle ejection a few hundred milliseconds after the bounce of the collapse, contributing to the revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range nucleon-nucleon effective interaction, is employed to estimate the effects of the neutrino trapping due to the strong density fluctuations, and to discuss qualitatively the consequences of the suggested new scenario.

Jerome Margueron; Jesus Navarro; Patrick Blottiau

2004-01-26T23:59:59.000Z

358

Stardust, Supernovae and the Chirality of the Amino Acids  

SciTech Connect

A mechanism for creating enantiomerism in the amino acids, the building blocks of the proteins, that involves global selection of one chirality by interactions between the amino acids and neutrinos from core-collapse supernovae is described. The selection involves the dependence of the interaction cross sections on the orientations of the spins of the neutrinos and the 14N nuclei in the amino acids, or in precursor molecules, which in turn couple to the molecular chirality. The subsequent chemical evolution and galactic mixing would ultimately populate the Galaxy with the selected species. The resulting amino acids could either be the source thereof on Earth, or could have triggered the chirality that was ultimately achieved for Earth's amino acids.

Boyd, R N; Kajino, T; Onaka, T

2011-03-09T23:59:59.000Z

359

Fission Cycling in Supernova Nucleosynthesis: Active-Sterile Neutrino Oscillations  

E-Print Network (OSTI)

We investigate nucleosynthesis in the supernovae post-core bounce neutrino-driven wind environment in the presence of active-sterile neutrino transformation. We consider active-sterile neutrino oscillations for a range of mixing parameters: vacuum mass-squared differences of 0.1 eV^2 10^-4. We find a consistent r-process pattern for a large range of mixing parameters that is in rough agreement with the halo star CS 22892-052 abundances and the pattern shape is determined by fission cycling. We find that the allowed region for the formation of the r-process peaks overlaps the LSND and NSBL (3+1) allowed region.

J. Beun; G. C. McLaughlin; R. Surman; W. R. Hix

2006-02-01T23:59:59.000Z

360

Neutrino signature of supernova hydrodynamical instabilities in three dimensions  

E-Print Network (OSTI)

The first full-scale three-dimensional (3D) core-collapse supernova (SN) simulations with sophisticated neutrino transport show pronounced effects of the standing accretion shock instability (SASI) for two high-mass progenitors (20 and 27 M_sun). In a low-mass progenitor (11.2 M_sun), large-scale convection is the dominant nonradial hydrodynamic instability in the postshock accretion layer. The SASI-associated modulation of the neutrino signal (80 Hz in our two examples) will be clearly detectable in IceCube or the future Hyper-Kamiokande detector, depending on progenitor properties, distance, and observer location relative to the main SASI sloshing direction. The neutrino signal from the next galactic SN can therefore diagnose the nature of the hydrodynamic instability.

Irene Tamborra; Florian Hanke; Bernhard Mueller; Hans-Thomas Janka; Georg Raffelt

2013-07-30T23:59:59.000Z

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

Comment on Cerenkov radiation by neutrinos in a supernova core  

E-Print Network (OSTI)

It had been pointed out by Mohanty and Samal[1] that the helicity flipping Cerenkov process ?L ? ?R +? or ? +?L ? ?R could be an important cooling mechanism for the supernova core. Comparing the neutrino emissivity by the Cerenkov process with observations of SN1987A, a restrictive bound on the neutrino magnetic moment was established. Subsequently it was pointed out by Raffelt[2] that, this result was based on a numerical error in the calculation of the refractive index of the SN core and using the correct numbers it was shown that the photons in a SN core do not have a space-like dispersion relation, so the Cerenkov helicity flip process would not occur. Here we show that the earlier estimate of refractive index was based on the thermodynamic formula for susceptibility which turns out to be invalid for real photons or plasmons even in the static limit. However an analysis of the dispersion relations of plasmons in an

Subhendra Mohanty; Sarira Sahu

1997-01-01T23:59:59.000Z

362

Comment on ''Cerenkov radiation by neutrinos in a supernova core"  

E-Print Network (OSTI)

The helicity changing Cerenkov radiation in a supernova core was used earlier to put a restrictive bound on the neutrino magnetic moment. Subsequently it was pointed out, that this result was based on a numerical error in the calculationn of the refractive index of the SN core and using the correct numbers it was shown that the photons in a SN core do not have a space-like dispersion relation, so the Cerenkov process would not occur. Here we show that the earlier estimate of refractive index was based on the thermodynamic formula for susceptibility which is inapplicable for real photons or plasmons. However in an ultrarelativistic plasma the plasmon has a space-like branch in the dispersion relation hence the Cerenkov radiation of a plasmon is kinematically allowed. We show that the observations of neutrino flux from SN1987A put a constraint on the neutrino magnetic moment $\\mu_{\

Subhendra Mohanty; Sarira Sahu

1997-10-07T23:59:59.000Z

363

Type Ia Supernova Spectral Line Ratios as LuminosityIndicators  

SciTech Connect

Type Ia supernovae have played a crucial role in thediscovery of the dark energy, via the measurement of their light curvesand the determination of the peak brightness via fitting templates to theobserved lightcurve shape. Two spectroscopic indicators are also known tobe well correlated with peak luminosity. Since the spectroscopicluminosity indicators are obtained directly from observed spectra, theywill have different systematic errors than do measurements usingphotometry. Additionally, these spectroscopic indicators may be usefulfor studies of effects of evolution or age of the SNe~;Ia progenitorpopulation. We present several new variants of such spectroscopicindicators which are easy to automate and which minimize the effects ofnoise. We show that these spectroscopic indicators can be measured byproposed JDEM missions such as snap and JEDI.

Bongard, Sebastien; Baron, E.; Smadja, G.; Branch, David; Hauschildt, Peter H.

2005-12-07T23:59:59.000Z

364

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

365

Properties of heavy and superheavy nuclei in supernova environments  

SciTech Connect

The properties of nuclei embedded in an electron gas are studied within the relativistic mean-field approach. These studies are relevant for nuclear properties in astrophysical environments such as neutron-star crusts and supernova explosions. The electron gas is treated as a constant background in the Wigner-Seitz cell approximation. We investigate the stability of nuclei with respect to {alpha} and {beta} decay. We find that the presence of the electrons leads to stabilizing effects for {alpha} decay at high electron densities. Furthermore, the screening effect shifts the proton dripline to more proton-rich nuclei, and the stability line with respect to {beta}-decay is shifted to more neutron-rich nuclei. Implications for the creation and survival of very heavy nuclear systems are discussed.

Buervenich, T. J.; Mishustin, I. N.; Greiner, W. [Frankfurt Institute for Advanced Studies Johann Wolfgang Goethe University, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany)

2008-05-12T23:59:59.000Z

366

Reduced Beta Decay Rates of Iron Isotopes for Supernova Physics  

SciTech Connect

During the late phases of stellar evolution beta decay on iron isotopes, in the core of massive stars, plays a crucial role in the dynamics of core-collapse. The beta decay contributes in maintaining a 'respectable' lepton-to-baryon ratio (PSI{sub e}) of the core prior to collapse which results in a larger shock energy to power the explosion. It is indeed a fine tuning of the parameter PSI{sub e} at various stages of supernova physics which can lead to a successful transformation of the collapse into an explosion. The calculations presented here might help in fine-tuning of PSI{sub e} for the collapse simulators of massive stars.

Nabi, Jameel-Un [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23460, N.W.F.P. (Pakistan)

2009-07-07T23:59:59.000Z

367

ANALYTIC APPROXIMATION OF CARBON CONDENSATION ISSUES IN TYPE II SUPERNOVAE  

SciTech Connect

I present analytic approximations for some issues related to condensation of graphite, TiC, and silicon carbide in oxygen-rich cores of supernovae of Type II. Increased understanding, which mathematical analysis can support, renders researchers more receptive to condensation in O-rich supernova gases. Taking SN 1987A as typical, my first analysis shows why the abundance of CO molecules reaches an early maximum in which free carbon remains more abundant than CO. This analysis clarifies why O-rich gas cannot oxidize C if {sup 56}Co radioactivity is as strong as in SN 1987A. My next analysis shows that the CO abundance could be regarded as being in chemical equilibrium if the CO molecule is given an effective binding energy rather than its laboratory dissociation energy. The effective binding energy makes the thermal dissociation rate of CO equal to its radioactive dissociation rate. This preserves possible relevance for the concept of chemical equilibrium. My next analysis shows that the observed abundances of CO and SiO molecules in SN 1987A rule out frequent suggestions that equilibrium condensation of SUNOCONs has occurred following atomic mixing of the He-burning shell with more central zones in such a way as to reproduce roughly the observed spectrum of isotopes in SUNOCONs while preserving C/O > 1. He atoms admixed along with the excess carbon would destroy CO and SiO molecules, leaving their observed abundances unexplained. The final analysis argues that a chemical quasiequilibrium among grains (but not gas) may exist approximately during condensation, so that its computational use is partially justified as a guide to which mineral phases would be stable against reactions with gas. I illustrate this point with quasiequilibrium calculations by Ebel and Grossman that have shown that graphite is stable even when O/C >1 if prominent molecules are justifiably excluded from the calculation of chemical equilibrium.

Clayton, Donald D., E-mail: claydonald@gmail.com [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States)

2013-01-01T23:59:59.000Z

368

The Rise and Fall of Type Ia Supernova Light Curves in the SDSS-II Supernova Survey  

Science Conference Proceedings (OSTI)

We analyze the rise and fall times of Type Ia supernova (SN Ia) light curves discovered by the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. From a set of 391 light curves k-corrected to the rest-frame B and V bands, we find a smaller dispersion in the rising portion of the light curve compared to the decline. This is in qualitative agreement with computer models which predict that variations in radioactive nickel yield have less impact on the rise than on the spread of the decline rates. The differences we find in the rise and fall properties suggest that a single 'stretch' correction to the light curve phase does not properly model the range of SN Ia light curve shapes. We select a subset of 105 light curves well observed in both rise and fall portions of the light curves and develop a '2-stretch' fit algorithm which estimates the rise and fall times independently. We find the average time from explosion to B-band peak brightness is 17.38 {+-} 0.17 days, but with a spread of rise times which range from 13 days to 23 days. Our average rise time is shorter than the 19.5 days found in previous studies; this reflects both the different light curve template used and the application of the 2-stretch algorithm. The SDSS-II supernova set and the local SNe Ia with well-observed early light curves show no significant differences in their average rise-time properties. We find that slow-declining events tend to have fast rise times, but that the distribution of rise minus fall time is broad and single peaked. This distribution is in contrast to the bimodality in this parameter that was first suggested by Strovink (2007) from an analysis of a small set of local SNe Ia. We divide the SDSS-II sample in half based on the rise minus fall value, t{sub r} - t{sub f} {approx} 2 days, to search for differences in their host galaxy properties and Hubble residuals; we find no difference in host galaxy properties or Hubble residuals in our sample.

Hayden, Brian T.; /Notre Dame U.; Garnavich, Peter M.; /Notre Dame U.; Kessler, Richard; /KICP, Chicago /Chicago U., EFI; Frieman, Joshua A.; /KICP, Chicago /Chicago U. /Fermilab; Jha, Saurabh W.; /Stanford U., Phys. Dept. /Rutgers U., Piscataway; Bassett, Bruce; /Cape Town U., Dept. Math. /South African Astron. Observ.; Cinabro, David; /Wayne State U.; Dilday, Benjamin; /Rutgers U., Piscataway; Kasen, Daniel; /UC, Santa Cruz; Marriner, John; /Fermilab; Nichol, Robert C.; /Portsmouth U., ICG /Baltimore, Space Telescope Sci. /Johns Hopkins U.

2010-01-01T23:59:59.000Z

369

Presentation of the Second Big Challenge Symposium - The Big Challenge of Cosmological Understanding: Gravitation, Dark Matter and Dark Energy. Towards New Scenarios  

E-Print Network (OSTI)

This Symposium is devoted to the Memory of Lev Kofman, June-17-1957-November-12-2009. The accelerated expansion of the Universe, which is today observed, shows that cosmological dynamics is dominated by the so-called Dark Energy field which provides a large negative pressure. This is the standard picture, in which such new ingredient is considered as a source of the right hand side of the field equations. It should be some form of non-clustered non-zero vacuum energy which, together with the clustered Dark Matter, drives the global dynamics. This is the so-called "concordance model" (ACDM) which gives, in agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to understand the today observed Universe. However, it presents several shortcomings as the well known "coincidence" and "cosmological constant" problems . An alternative approach is to have a better understanding of the energy concept in General Relativity and also to change the left hand side of the field equations, and check if observed cosmic dynamics can be achieved by extending general relativity. In this different context, it is not required to search candidates for Dark Energy and Dark Matter, which till now have not been found. Rather, one can only stand on the "observed" ingredients: curvature and baryon matter, to account for the observations. Considering this point of view, one can think of that gravity is not scale-invariant. The goal of this Symposium is to obtain a tapestry of the present status of theory and observations concerning Gravitation and Dark Universe.

Christian Corda

2010-07-23T23:59:59.000Z

370

The First Five Minutes of a Core Collapse Supernova: Multidimensional Hydrodynamic Models  

E-Print Network (OSTI)

We present results of high-resolution two-dimensional simulations which follow the first five minutes of a core collapse supernova explosion in a 15 solar mass blue supergiant progenitor. The computations start shortly after core bounce and include neutrino-matter interactions by using a light-bulb approximation for the neutrinos, and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout a significant fraction of the stellar helium core by the concerted action of convective and Rayleigh-Taylor instabilities. Fast moving nickel mushrooms with velocities up to 4000 km/s are observed. A continuation of the calculations to later times, however, indicates, that the iron velocities observed in SN 1987 A cannot be reproduced due to a strong deceleration of the clumps during their interaction with the dense shell left behind by the shock at the He/H interface. Therefore, we cannot confirm the claim that convective "premixing" of the nickel in the early phases of the explosion solves the problem of the high iron velocities.

K. Kifonidis; T. Plewa; H. -Th. Janka; E. Mueller

1999-11-22T23:59:59.000Z

371

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

372

Non-Abelian Einstein-Born-Infeld-Dilaton Cosmology  

E-Print Network (OSTI)

The non-abelian Einstein-Born-Infeld-Dilaton theory, which rules the dynamics of tensor-scalar gravitation coupled to a $su(2)$-valued gauge field ruled by Born-Infeld lagrangian, is studied in a cosmological framework. The microscopic energy exchange between the gauge field and the dilaton which results from a non-universality of the coupling to gravity modifies the usual behaviour of tensor-scalar theories coupled to matter fluids. General cosmological evolutions are derived for different couplings to gravitation and a comparison to universal coupling is highlighted. Evidences of cosmic acceleration are presented when the evolution is interpreted in the Jordan physical frame of a matter respecting the weak equivalence principle. The importance for the mechanism of cosmic acceleration of the dynamics of the Born-Infeld gauge field, the attraction role of the matter fluid and the non-universality of the gravitational couplings is briefly outlined.

A. Fuzfa; J. -M. Alimi

2005-11-16T23:59:59.000Z

373

Cosmological and astrophysical constraints on superconducting cosmic strings  

E-Print Network (OSTI)

We investigate the cosmological and astrophysical constraints on superconducting cosmic strings (SCSs). SCS loops emit strong bursts of electromagnetic waves, which might affect various cosmological and astrophysical observations. We take into account the effect on the CMB anisotropy, CMB blackbody spectrum, BBN, observational implications on radio wave burst and X-ray or gamma-ray events, and stochastic gravitational wave background measured by pulsar timing experiments. We then derive constraints on the parameters of SCS from current observations and estimate prospects for detecting SCS signatures in on-going observations. As a result, we find that these constraints exclude broad parameter regions, and also that on-going radio wave observations can probe large parameter space.

Koichi Miyamoto; Kazunori Nakayama

2012-12-30T23:59:59.000Z

374

Photon-Axion-Like Particle Coupling Constant and Cosmological Observations  

E-Print Network (OSTI)

We estimated the photon-pseudoscalar particle mixing constant from the effect of cosmological alignment and cosmological rotation of polarization plane of distant QSOs. This effect is explained in terms of birefringent phenomenon due to photon-pseudoscalar (axion-like) particle mixing in a cosmic magnetic field. On the contrary, one can estimate the strength of the cosmic magnetic field using the constraints on the photon-axion-like particle coupling constant from the CAST experiment and from SNe Ia dimming effect. In a result, the lower limit on the intergalactic ($z\\approx 1\\div 2$) magnetic field appears at the level of about $4\\times 10^{-10}\\div 10^{-11}$ G.

M. Yu. Piotrovich; Yu. N. Gnedin; T. M. Natsvlishvili

2008-05-23T23:59:59.000Z

375

Nuclear and particle physics, astrophysics and cosmology (NPAC) capability review  

Science Conference Proceedings (OSTI)

The present document represents a summary self-assessment of the status of the Nuclear and Particle Physics, Astrophysics and Cosmology (NPAC) capability across Los Alamos National Laboratory (LANL). For the purpose of this review, we have divided the capability into four theme areas: Nuclear Physics, Particle Physics, Astrophysics and Cosmology, and Applied Physics. For each theme area we have given a general but brief description of the activities under the area, a list of the Laboratory divisions involved in the work, connections to the goals and mission of the Laboratory, a brief description of progress over the last three years, our opinion of the overall status of the theme area, and challenges and issues.

Redondo, Antonio [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

376

Interacting Dark Energy in Ho?ava-Lifshitz Cosmology  

E-Print Network (OSTI)

In the usual Ho\\v{r}ava-Lifshitz cosmological models, the scalar field is responsible for dark matter. Using an additional scalar field, Saridakis \\cite{sari} has formulated Ho\\v{r}ava-Lifshitz cosmology with an effective dark energy sector. In the paper \\cite{sari} the scalar fields do not interact with each other, here we extend this work to the interacting case, where matter scalar field $\\phi$ interact with dark energy scalar field $\\sigma$. We will show that in contrast with \\cite{sari}, where $\\sigma$-filed is absent, we can obtain $w_d ^{\\rm eff}dark energy presenting phantom behaviour. This behaviour is pure effect of the interaction.

M R Setare

2009-09-02T23:59:59.000Z

377

Spin flip of neutrinos with magnetic moment in core-collapse supernova  

Science Conference Proceedings (OSTI)

Neutrinos with magnetic moment experience chirality flips while scattering off charged particles. It is known that if neutrino is a Dirac fermion, then such chirality flips lead to the production of sterile right-handed neutrinos inside the core of a star during the stellar collapse, which may facilitate the supernova explosion and modify the supernova neutrino signal. In the present paper we reexamine the production of right-handed neutrinos during the collapse using a dynamical model of the collapse. We refine the estimates of the values of the Dirac magnetic moment which are necessary to substantially alter the supernova dynamics and neutrno signal. It is argued in particular that Super-Kamiokande will be sensitive at least to {mu}{sub {nu}Dirac} = 10{sup -13{mu}}{sub B} in case of a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed out that in the inner supernova core spin flips may quickly equilibrate electron neutrinos with nonelectron antineutrinos if {mu}{sub {nu}Majorana} {>=} 10{sup -12{mu}}{sub B}. This may lead to various consequences for supernova physics.

Lychkovskiy, O. V., E-mail: lychkovskiy@itep.ru; Blinnikov, S. I. [Institute for Theoretical and Experimental Physics (Russian Federation)

2010-04-15T23:59:59.000Z

378

Properties of Intra-group Stars and Galaxies in Galaxy Groups: "Normal" versus "Fossil" Groups  

E-Print Network (OSTI)

Cosmological LCDM simulations of 12 M_vir~10^14 Msun galaxy groups have been performed, invoking star formation, chemical evolution with non-instantaneous recycling, metallicity dependent radiative cooling, strong star-burst driven galactic super-winds and effects of a meta-galactic UV field. At z=0, intra-group light (IGL) fractions are found to be 12-45%. Low values refer to groups with only a small difference between the R-band magnitudes of the first and second ranked group galaxy, large are typical of "fossil" groups (FGs). The IG stars in the 4 FGs are 0.3-0.5 Gyr older than in the 8 nonFGs. For the IGL, B-R=~1.4, in good agreement with observations. For FGs/nonFGs the iron abundance of the IG stars is slightly sub-solar in the central parts (r~100 kpc) decreasing to about 40% solar at about 0.5 r_vir The IG stars are alpha-element enhanced with [O/Fe] increasing with r, and an overall [O/Fe]~0.45, indicating predominant SNII enrichment. The velocity distributions of the IG stars and group galaxies are, at r>~30 kpc, significantly more radially anisotropic for FGs than for nonFGs. So a characteristic of FG formation, apart from formation time (D'Onghia et al.), may be the "initial" velocity distribution of the group galaxies. For FGs one can dynamically infer the (dark matter dominated) mass distribution of the groups all the way to r_vir, from the kinematics of the IG stars or group galaxies. For the nonFGs this method overestimates the group mass at r>~200 kpc, by up to a factor of two at r_vir. This is interpreted as FGs being, in general, more relaxed than nonFGs. Finally, FGs of the above M_vir should host ~500 planetary nebulae at projected distances between 100 and 1000 kpc from the first ranked galaxy. All results appear consistent with the FG formation scenario of D'Onghia et al.

Jesper Sommer-Larsen

2005-09-28T23:59:59.000Z

379

Equation of state and singularities in FLRW cosmological models  

E-Print Network (OSTI)

We consider FLRW cosmological models with standard Friedmann equations, but leaving free the equation of state. We assume that the dark energy content of the universe is encoded in an equation of state $p=f(\\rho)$, which is expressed with most generality in the form of a power expansion. The inclusion of this expansion in Friedmann equations allows us to construct a perturbative solution and to relate the coefficients of the equation of state with the formation of singularities of different types.

L. Fernandez-Jambrina; R. Lazkoz

2010-01-18T23:59:59.000Z

380

Nonexpanding impulsive gravitational waves with an arbitrary cosmological constant  

E-Print Network (OSTI)

Exact solutions for nonexpanding impulsive waves in a background with nonzero cosmological constant are constructed using a `cut and paste' method. These solutions are presented using a unified approach which covers the cases of de Sitter, anti-de Sitter and Minkowski backgrounds. The metrics are presented in continuous and distributional forms, both of which are conformal to the corresponding metrics for impulsive pp-waves, and for which the limit as $\\Lambda\\to 0$ can be made explicitly.

J. Podolsky; J. B. Griffiths

1999-08-02T23:59:59.000Z

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381

Brane World Cosmology In Jordan-Brans-Dicke Theory  

E-Print Network (OSTI)

We consider the embedding of 3+1 dimensional cosmology in 4+1 dimensional Jordan-Brans-Dicke theory. We show that exponentially growing and power law scale factors are implied. Whereas the 4+1 dimensional scalar field is approximately constant for each, the effective 3+1 dimensional scalar field is constant for exponentially growing scale factor and time dependent for power law scale factor.

M. Arik; D. Ciftci

2005-06-17T23:59:59.000Z

382

Self-Consistent Cosmological Simulations of DGP Braneworld Gravity  

Science Conference Proceedings (OSTI)

We perform cosmological N-body simulations of the Dvali-Gabadadze-Porrati braneworld model, by solving the full non-linear equations of motion for the scalar degree of freedom in this model, the brane bending mode. While coupling universally to matter, the brane-bending mode has self-interactions that become important as soon as the density field becomes non-linear. These self-interactions lead to a suppression of the field in high-density environments, and restore gravity to General Relativity. The code uses a multi-grid relaxation scheme to solve the non-linear field equation in the quasi-static approximation. We perform simulations of a flat self-accelerating DGP model without cosmological constant. However, the type of non-linear interactions of the brane-bending mode, which are the focus of this study, are generic to a wide class of braneworld cosmologies. The results of the DGP simulations are compared with standard gravity simulations assuming the same expansion history, and with DGP simulations using the linearized equation for the brane bending mode. This allows us to isolate the effects of the non-linear self-couplings of the field which are noticeable already on quasi-linear scales. We present results on the matter power spectrum and the halo mass function, and discuss the behavior of the brane bending mode within cosmological structure formation. We find that, independently of CMB constraints, the self-accelerating DGP model is strongly constrained by current weak lensing and cluster abundance measurements.

Schmidt, Fabian; /Chicago U., Astron. Astrophys. Ctr. /KICP, Chicago

2009-09-01T23:59:59.000Z

383

Thermodynamics of the apparent horizon in massive cosmology  

E-Print Network (OSTI)

Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive cosmological model proposed lately, the corrected entropic formula of the apparent horizon is obtained with the help of the modified Friedmann equations. This entropy-area relation, together with the identified internal energy, verifies the first law of thermodynamics for the apparent horizon with a volume change term for consistency. On the other hand, by means of the corrected entropy-area formula and the Clausius relation $\\delta Q=T dS$, the modified Friedmann equations governing the dynamical evolution of the universe are reproduced with the known energy density and pressure of massive graviton. The integration constant is found to correspond to a cosmological term which could be absorbed into the energy density of matter. Having established the correspondence of massive cosmology with the unified first law of thermodynamics on the apparent horizon, the validity of the generalized second law of thermodynamics is also discussed by assuming the thermal equilibrium between the apparent horizon and the matter field bounded by the apparent horizon. It is found that, in the limit $H_c\\rightarrow 0$ which recovers the Minkowski reference metric solution in the flat case, the generalized second law of thermodynamics holds if $\\alpha_3+4\\alpha_4<0$. Apart from that, even for the simplest model of dRGT massive cosmology with $\\alpha_3=\\alpha_4=0$, the generalized second law of thermodynamics could be violated.

Hui Li; Yi Zhang

2013-04-17T23:59:59.000Z

384

Specially Coupled Dark Energy in the Oscillating FRW Cosmology  

E-Print Network (OSTI)

We consider a four-dimensional flat-space Friedman universe, which is filled with two interacting ideal fluids (the coupling of dark energy with dark matter of special form). The gravitational equations of motion are solved. It is shown that in some cases there appears a periodic universe with finite-time cosmological singularities and also the universe becomes static in the remote future.

A. V. Timoshkin

2009-05-18T23:59:59.000Z

385

Post-Newtonian Celestial Dynamics in Cosmology: Field Equations  

E-Print Network (OSTI)

The present paper outlines theoretical principles of the post-Newtonian mechanics in the expanding universe. It is based upon the gauge-invariant theory of the Lagrangian perturbations of cosmological manifold caused by an isolated astronomical N-body system. We postulate that the background manifold is described by Friedman-Lemaitre-Robertson-Walker (FLRW) metric governed by two primary components - the dark matter and the dark energy. The dark matter is treated as an ideal fluid. The dark energy is described by a single scalar field with a potential which is hold unspecified as long as the theory permits. The Lagrangian of the dark matter and that of the scalar field are formulated in terms of the field variables. We use variational calculus to derive the gauge-invariant field equations of the post-Newtonian celestial mechanics of an isolated astronomical system in an expanding universe. These equations generalize the field equations of the post-Newtonian theory in asymptotically-flat spacetime by taking into account the cosmological effects explicitly. We introduce a new cosmological gauge which generalizes the harmonic gauge of the post-Newtonian theory in asymptotically-flat spacetime. This gauge significantly simplifies the gravitational field equations and allows finding out the approximations where the field equations can be fully decoupled and solved analytically. The residual gauge freedom is explored. The results of the present paper can be useful in the solar system for calculating more precise ephemerides of the solar system bodies on extremely long time intervals, in galactic astronomy to study the dynamics of clusters of galaxies, and in gravitational wave astronomy for discussing the impact of cosmology on generation and propagation of gravitational waves emitted by coalescing binaries and/or merging galactic nuclei.

Sergei Kopeikin; Alexander Petrov

2013-01-24T23:59:59.000Z

386

The Quantum Configuration Space of Loop Quantum Cosmology  

E-Print Network (OSTI)

The article gives an account of several aspects of the space known as the Bohr compactification of the line, featuring as the quantum configuration space in loop quantum cosmology, as well as of the corresponding configuration space realization of the so-called polymer representation. Analogies with loop quantum gravity are explored, providing an introduction to (part of) the mathematical structure of loop quantum gravity, in a technically simpler context.

J. M. Velhinho

2007-04-18T23:59:59.000Z

387

Neutron beta-decay, Standard Model and cosmology  

E-Print Network (OSTI)

The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. The neutron lifetime recently obtained, 878.5 +/- 0.7stat +/- 0.3sys s, is the most accurate one to date. The new result for the neutron lifetime differs from the world average value by 6.5 standard deviations. The impact of the new result on testing of Standard Model and on data analysis for the primordial nucleosynthesis model is scrutinized.

A. P. Serebrov

2006-11-22T23:59:59.000Z

388

Red Galaxies from Hot Halos in Cosmological Hydro Simulations  

E-Print Network (OSTI)

I highlight three results from cosmological hydrodynamic simulations that yield a realistic red sequence of galaxies: 1) Major galaxy mergers are not responsible for shutting off star-formation and forming the red sequence. Starvation in hot halos is. 2) Massive galaxies grow substantially (about a factor of 2 in mass) after being quenched, primarily via minor (1:5) mergers. 3) Hot halo quenching naturally explains why galaxies are red when they either (a) are massive or (b) live in dense environments.

Gabor, Jared

2012-01-01T23:59:59.000Z

389

The metamorphosis of Supernova SN2008D/XRF080109: a link between Supernovae and GRBs/Hypernovae  

E-Print Network (OSTI)

The only supernovae (SNe) to have shown early gamma-ray or X-ray emission thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe). Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SNIc HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN 2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We derive that SN 2008D was originally a ~30Msun star. When it collapsed a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

Paolo A. Mazzali; Stefano Valenti; Massimo Della Valle; Guido Chincarini; Daniel N. Sauer; Stefano Benetti; Elena Pian; Tsvi Piran; Valerio D'Elia; Nancy Elias-Rosa; Raffaella Margutti; Francesco Pasotti; L. Angelo Antonelli; Filomena Bufano; Sergio Campana; Enrico Cappellaro; Stefano Covino; Paolo D'Avanzo; Fabrizio Fiore; Dino Fugazza; Roberto Gilmozzi; Deborah Hunter; Kate Maguire; Elisabetta Maiorano; Paola Marziani; Nicola Masetti; Felix Mirabel; Hripsime Navasardyan; Ken'ichi Nomoto; Eliana Palazzi; Andrea Pastorello; Nino Panagia; Leonardo J. Pellizza; Re'em Sari; Stephen Smartt; Gianpiero Tagliaferri; Masaomi Tanaka; Stefan Taubenberger; Nozomu Tominaga; Carrie Trundle; Massimo Turatto

2008-07-10T23:59:59.000Z

390

FRW Quantum Cosmology with a Generalized Chaplygin Gas  

E-Print Network (OSTI)

Cosmologies with a Chaplygin gas have recently been explored with the objective of explaining the transition from a dust dominated epoch towards an accelerating expansion stage. We consider the hypothesis that the transition to the accelerated period involves a quantum mechanical process. Three physically admissible cases are possible. In particular, we identify a minisuperspace configuration with two Lorentzian sectors, separated by a classically forbidden region. The Hartle-Hawking and Vilenkin wave functions are computed, together with the transition amplitudes towards the accelerating epoch. Furthermore, it is found that for specific initial conditions, the parameters characterizing the generalized Chaplygin gas become related through an expression involving an integer $n$. We also introduce a phenomenological association between some brane-world scenarios and a FRW minisuperspace cosmology with a generalized Chaplygin gas. The aim is to promote a discussion and subsequent research on the quantum creation of brane cosmologies from such a perspective. Results suggest that the brane tension would become related with generalized Chaplygin gas parameters through another expression involving an integer.

Mariam Bouhmadi-Lopez; Paulo Vargas Moniz

2004-04-27T23:59:59.000Z

391

Conformal symmetry of gravity and the cosmological constant problem  

E-Print Network (OSTI)

In absence of matter Einstein gravity with a cosmological constant $\\La$ can be formulated as a scale-free theory depending only on the dimensionless coupling constant G \\Lambda where G is Newton constant. We derive the conformal field theory (CFT) and its improved stress-energy tensor that describe the dynamics of conformally flat perturbations of the metric. The CFT has the form of a constrained \\lambda \\phi^{4} field theory. In the cosmological framework the model describes the usual Friedmann-Robertson-Walker flat universe. The conformal symmetry of the gravity sector is broken by coupling with matter. The dimensional coupling constants G and \\Lambda are introduced by different terms in this coupling. If the vacuum of quantum matter fields respects the symmetry of the gravity sector, the vacuum energy has to be zero and the ``physical'' cosmological constant is generated by the coupling of gravity with matter. This could explain the tiny value of the observed energy density driving the accelerating expansion of the universe.

Mariano Cadoni

2006-06-29T23:59:59.000Z

392

Non-minimal Higgs inflation and frame dependence in cosmology  

Science Conference Proceedings (OSTI)

We investigate a very general class of cosmological models with scalar fields non-minimally coupled to gravity. A particular representative in this class is given by the non-minimal Higgs inflation model in which the Standard Model Higgs boson and the inflaton are described by one and the same scalar particle. While the predictions of the non-minimal Higgs inflation scenario come numerically remarkably close to the recently discovered mass of the Higgs boson, there remains a conceptual problem in this model that is associated with the choice of the cosmological frame. While the classical theory is independent of this choice, we find by an explicit calculation that already the first quantum corrections induce a frame dependence. We give a geometrical explanation of this frame dependence by embedding it into a more general field theoretical context. From this analysis, some conceptional points in the long lasting cosmological debate: 'Jordan frame vs. Einstein frame' become more transparent and in principle can be resolved in a natural way.

Steinwachs, Christian F. [School of Mathematical Sciences, University of Nottingham University Park, Nottingham, NG7 2RD (United Kingdom); Kamenshchik, Alexander Yu. [Dipartimento di Fisica e Astronomia and INFN, Via Irnerio 46, 40126 Bologna, Italy and L.D. Landau Institute for Theoretical Physics of the Russian Academy of Sciences, Kosygin str. 2, 119334 Moscow (Russian Federation)

2013-02-21T23:59:59.000Z

393

The trace anomaly and dynamical vacuum energy in cosmology  

Science Conference Proceedings (OSTI)

The trace anomaly of conformal matter implies the existence of massless scalar poles in physical amplitudes involving the stress-energy tensor. These poles may be described by a local effective action with massless scalar fields, which couple to classical sources, contribute to gravitational scattering processes, and can have long range gravitational effects at macroscopic scales. In an effective field theory approach, the effective action of the anomaly is an infrared relevant term that should be added to the Einstein-Hilbert action of classical General Relativity to take account of macroscopic quantum effects. The additional scalar degrees of freedom contained in this effective action may be understood as responsible for both the Casimir effect in flat spacetime and large quantum backreaction effects at the horizon scale of cosmological spacetimes. These effects of the trace anomaly imply that the cosmological vacuum energy is dynamical, and its value depends on macroscopic boundary conditions at the cosmological horizon scale, rather than sensitivity to the extreme ultraviolet Planck scale.

Mottola, Emil [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

394

Cosmological lepton asymmetry with a nonzero mixing angle $\\theta_{13}$  

E-Print Network (OSTI)

While the baryon asymmetry of the Universe is nowadays well measured by cosmological observations, the bounds on the lepton asymmetry in the form of neutrinos are still significantly weaker. We place limits on the relic neutrino asymmetries using some of the latest cosmological data, taking into account the effect of flavor oscillations. We present our results for two different values of the neutrino mixing angle \\theta_{13}, and show that for large \\theta_{13} the limits on the total neutrino asymmetry become more stringent, diluting even large initial flavor asymmetries. In particular, we find that the present bounds are still dominated by the limits coming from Big Bang Nucleosynthesis, while the limits on the total neutrino mass from cosmological data are essentially independent of \\theta_{13}. Finally, we perform a forecast for COrE, taken as an example of a future CMB experiment, and find that it could improve the limits on the total lepton asymmetry approximately by up to a factor 5.

Castorina, Emanuele; Lattanzi, Massimiliano; Lesgourgues, Julien; Mangano, Gianpiero; Melchiorri, Alessandro; Pastor, Sergio

2012-01-01T23:59:59.000Z

395

Information content in the halo-model dark-matter power spectrum II: Multiple cosmological parameters  

E-Print Network (OSTI)

We investigate the cosmological Fisher information in the non-linear dark-matter power spectrum in the context of the halo model. We find that there is a plateau in information content on translinear scales which is generic to all cosmological parameters we tried. There is a rise in information on smaller scales, but we find that it is quite degenerate among different cosmological parameters (except, perhaps, the tilt). This suggests that it could be difficult to constrain cosmological parameters using the non-linear regime of the dark-matter power spectrum. We suggest ways to get around this problem, such as removing the largest haloes from consideration in survey analysis.

Mark C. Neyrinck; Istvn Szapudi

2006-10-06T23:59:59.000Z

396

LUMINOSITY DISTRIBUTION OF GAMMA-RAY BURST HOST GALAXIES AT REDSHIFT z = 1 IN COSMOLOGICAL SMOOTHED PARTICLE HYDRODYNAMIC SIMULATIONS: IMPLICATIONS FOR THE METALLICITY DEPENDENCE OF GRBs  

SciTech Connect

We study the relationship between the metallicity of gamma-ray burst (GRB) progenitors and the probability distribution function (PDF) of GRB host galaxies as a function of luminosity using cosmological hydrodynamic simulations of galaxy formation. We impose a maximum limit to the gas metallicity in which GRBs can occur and examine how the predicted luminosity PDF of GRB host galaxies changes in the simulation. We perform the Kolmogorov-Smirnov test and show that the result from our simulation agrees with the observed luminosity PDF of core-collapse supernovae (SNe) host galaxies when we assume that the core-collapse SNe trace star formation. When we assume that GRBs occur only in a low-metallicity environment with Z {approx}< 0.1 Z{sub sun}, GRBs occur in lower luminosity galaxies, and the simulated luminosity PDF becomes quantitatively consistent with the observed one. The observational bias against the host galaxies of optically dark GRBs owing to dust extinction may be another reason for the lower luminosities of GRB host galaxies, but the observed luminosity PDF of GRB host galaxies cannot be reproduced solely by the dust bias in our simulation.

Niino, Yuu; Totani, Tomonori [Department of Astronomy, School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Choi, Jun-Hwan; Nagamine, Kentaro; Zhang Bing [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154-4002 (United States); Kobayashi, Masakazu A. R., E-mail: niinou@kusastro.kyoto-u.ac.jp [Optical and Infrared Astronomy Division, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

2011-01-10T23:59:59.000Z

397

Measurements of the Rate of Type Ia Supernovae at Redshift z < ~0.3 from the SDSS-II Supernova Survey  

E-Print Network (OSTI)

We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z \\lesssim 0.3, of which 270 (52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04+1.61-0.95 % of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume a SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used t...

Dilday, Benjamin; Bassett, Bruce; Becker, Andrew; Bender, Ralf; Castander, Francisco; Cinabro, David; Filippenko, Alexei V; Frieman, Joshua A; Galbany, Lluis; Garnavich, Peter M; Goobar, Ariel; Hopp, Ulrich; Ihara, Yutaka; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Molla, Mercedes; Nichol, Robert C; Nordin, Jakob; Riess, Adam G; Sako, Masao; Schneider, Donald P; Sollerman, Jesper; Wheeler, J Craig; Ostman, Linda; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie

2010-01-01T23:59:59.000Z

398

FERMI LARGE AREA TELESCOPE OBSERVATION OF SUPERNOVA REMNANT S147  

Science Conference Proceedings (OSTI)

We present an analysis of gamma-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope in the region around supernova remnant (SNR) S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5{sigma} confidence level. The gamma-ray flux is (3.8 {+-} 0.6) Multiplication-Sign 10{sup -8} photons cm{sup -2} s{sup -1}, corresponding to a luminosity of 1.3 Multiplication-Sign 10{sup 34} (d/1.3 kpc){sup 2} erg s{sup -1} in this energy range. The gamma-ray emission exhibits a possible spatial correlation with the prominent H{alpha} filaments of SNR S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral {pi} mesons produced through the proton-proton collisions in the filaments. The reacceleration of the pre-existing cosmic rays and subsequent adiabatic compression in the filaments is sufficient to provide the energy density required of high-energy protons.

Katsuta, J.; Uchiyama, Y.; Tanaka, T.; Tajima, H.; Bechtol, K.; Funk, S.; Lande, J. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Hanabata, Y. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Lemoine-Goumard, M. [Universite Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, 33175 Gradignan (France); Takahashi, T., E-mail: katsuta@slac.stanford.edu, E-mail: uchiyama@slac.stanford.edu [Institute of Space and Astronautical Science, Japanese Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2012-06-20T23:59:59.000Z

399

Type Iax Supernovae: A New Class of Stellar Explosion  

E-Print Network (OSTI)

We describe observed properties of the Type Iax class of supernovae (SNe Iax), consisting of SNe observationally similar to its prototypical member, SN 2002cx. The class currently has 25 members, and we present optical photometry and/or optical spectroscopy for most of them. SNe Iax are spectroscopically similar to SNe Ia, but have lower maximum-light velocities (2000 M_V,peak > -18.9 mag), and most have hot photospheres. Relative to SNe Ia, SNe Iax have low luminosities for their light-curve shape. There is a correlation between luminosity and light-curve shape, similar to that of SNe Ia, but offset from that of SNe Ia and with larger scatter. Despite a host-galaxy morphology distribution that is highly skewed to late-type galaxies without any SNe Iax discovered in elliptical galaxies, there are several indications that the progenitor stars are white dwarfs (WDs): evidence of C/O burning in their maximum-light spectra, low ejecta masses, strong Fe lines in their late-time spectra, a lack of X-ray detections...

Foley, Ryan J; Chornock, R; Ganeshalingam, M; Li, W; Marion, G H; Morrell, N I; Pignata, G; Stritzinger, M D; Silverman, J M; Wang, X; Anderson, J P; Filippenko, A V; Freedman, W L; Hamuy, M; Jha, S W; Kirshner, R P; McCully, C; Persson, S E; Phillips, M M; Reichart, D E; Soderberg, A M

2012-01-01T23:59:59.000Z

400

Reflections on Reflexions: I. Light Echoes in Type Ia Supernovae  

E-Print Network (OSTI)

In the last ten years, observational evidences about a possible connection between Type Ia Supernovae (SNe) properties and the environment where they explode have been steadily growing. In this paper I discuss, from a theoretical point of view but with an observer's perspective, the usage of light echoes (LEs) to probe the CSM around SNe of Type Ia since, in principle, they give us a unique opportunity of getting a three-dimensional description of the SN environment. In turn, this can be used to check the often suggested association of some Ia's with dusty/star forming regions, which would point to a young population for the progenitors. After giving a brief introduction to the LE phenomenon in single scattering approximation, I derive analytical and numerical solutions for the optical light and colour curves for a few simple dust geometries. A fully 3D multiple scattering treatment has also been implemented in a Monte Carlo code, which I have used to investigate the effects of multiple scattering. In particu...

Patat, F

2004-01-01T23:59:59.000Z

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401

Fission Cycling in a Supernova r-process  

E-Print Network (OSTI)

Recent halo star abundance observations exhibit an important feature of consequence to the r-process: the presence of a main r-process between the second and third peaks which is consistent among halo stars. We explore fission cycling and steady-beta flow as the driving mechanisms behind this feature. The presence of fission cycling during the r-process can account for nucleosynthesis yields between the second and third peaks, whereas the presence of steady-beta flow can account for consistent r-process patterns, robust under small variations in astrophysical conditions. We employ the neutrino-driven wind of the core-collapse supernova to examine fission cycling and steady-beta flow in the r-process. As the traditional neutrino-driven wind model does not produce the required very neutron-rich conditions for these mechanisms, we examine changes to the neutrino physics necessary for fission cycling to occur in the neutrino-driven wind environment, and we explore under what conditions steady-beta flow is obtained.

J. Beun; G. C. McLaughlin; R. Surman; W. R. Hix

2007-07-30T23:59:59.000Z

402

Detecting extra-galactic supernova neutrinos in the Antarctic ice  

E-Print Network (OSTI)

Building on the technological success of the IceCube neutrino telescope, we outline a prospective low-energy extension that utilizes the clear ice of the South Pole. Aiming at a 10 Mton effective volume and a 10 MeV threshold, the detector would provide sufficient sensitivity to detect neutrino bursts from core-collapse supernovae (SNe) in nearby galaxies. The detector geometry and required density of instrumentation are discussed along with the requirements to control the various sources of background. We find that the resulting detector will be able to detect SNe from beyond 10 Mpc, delivering between 11 and 46 regular core-collapse SN detections per decade. It would further allow to study more speculative phenomena, such as optically dark (failed) SNe, where the collapse proceeds directly to a black hole, at a detection rate similar to the regular SNe. We find that the biggest technological challenge lies in the required large number of large area photo-sensors, with simultaneous strict limits on the allowed noise rates. If both can be realized, the detector concept we present will reach the required sensitivity in a cost effective manner and hence offers a route to future routine observations of SNe with neutrinos.

Sebastian Bser; Marek Kowalski; Lukas Schulte; Nora Linn Strotjohann; Markus Voge

2013-04-09T23:59:59.000Z

403

Observational Evidence from Supernovae for a Contracting Universe  

E-Print Network (OSTI)

New precision in measuring extragalactic distances using supernovae has confirmed with high probability an accelerating increase in redshift with distance. This has been interpreted as implying the existence of dark energy in an expanding and accelerating, flat universe. A more logical explanation of these observations follows directly from an observation made by Erwin Schrodinger in 1939 that in a closed Friedmann universe every quantum wave function changes with spacetime geometry. Double the size of the universe and both the wavelengths of photons and the sizes of atoms double. When the evolution of atoms and photons are combined, the meaning of Hubble redshift is reversed. Redshift is characteristic of contracting universes. The magnitude-redshift curve for a contracting universe has exactly the accelerating form recently observed and is in excellent quantitative agreement with the data of Riess et al. 1998, Knop et al. 2003, and others. An observed maximum redshift of 1.3 gives a minimum age estimate for the universe of 114 billion years. The time until collapse is estimated to be 15 billion years or less.

William Q. Sumner

2004-02-28T23:59:59.000Z

404

Diversity of the Supernova - Gamma-Ray Burst Connection  

E-Print Network (OSTI)

The connection between the long Gamma Ray Bursts (GRBs) and Type Ic Supernovae (SNe) has revealed interesting diversity. We review the following types of the GRB-SN connection. (1) GRB-SNe: The three SNe all explode with energies much larger than those of typical SNe, thus being called Hypernovae (HNe). They are massive enough for forming black holes. (2) Non-GRB HNe/SNe: Some HNe are not associated with GRBs. (3) XRF-SN: SN 2006aj associated with X-Ray Flash 060218 is dimmer than GRB-SNe and has very weak oxygen lines. Its progenitor mass is estimated to be small enough to form a neutron star rather than a black hole. (4) Non-SN GRB: Two nearby long GRBs were not associated SNe. Such ``dark HNe'' have been predicted in this talk (i.e., just before the discoveries) in order to explain the origin of C-rich (hyper) metal-poor stars. This would be an important confirmation of the Hypernova-First Star connection. We will show our attempt to explain the diversity in a unified manner with the jet-induced explosion model.

K. Nomoto; N. Tominaga; M. Tanaka; K. Maeda; T. Suzuki; J. S. Deng; P. A. Mazzali

2007-02-19T23:59:59.000Z

405

LINKING TYPE Ia SUPERNOVA PROGENITORS AND THEIR RESULTING EXPLOSIONS  

Science Conference Proceedings (OSTI)

Comparing the ejecta velocities at maximum brightness and narrow circumstellar/interstellar Na D absorption line profiles of a sample of 23 Type Ia supernovae (SNe Ia), we determine that the properties of SN Ia progenitor systems and explosions are intimately connected. As demonstrated by Sternberg et al., half of all SNe Ia with detectable Na D absorption at the host-galaxy redshift in high-resolution spectroscopy have Na D line profiles with significant blueshifted absorption relative to the strongest absorption component, which indicates that a large fraction of SN Ia progenitor systems have strong outflows. In this study, we find that SNe Ia with blueshifted circumstellar/interstellar absorption systematically have higher ejecta velocities and redder colors at maximum brightness relative to the rest of the SN Ia population. This result is robust at a 98.9%-99.8% confidence level, providing the first link between the progenitor systems and properties of the explosion. This finding is further evidence that the outflow scenario is the correct interpretation of the blueshifted Na D absorption, adding additional confirmation that some SNe Ia are produced from a single-degenerate progenitor channel. An additional implication is that either SN Ia progenitor systems have highly asymmetric outflows that are also aligned with the SN explosion or SNe Ia come from a variety of progenitor systems where SNe Ia from systems with strong outflows tend to have more kinetic energy per unit mass than those from systems with weak or no outflows.

Foley, Ryan J.; Kirshner, Robert P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Simon, Joshua D.; Burns, Christopher R. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Gal-Yam, Avishay [Benoziyo Center for Astrophysics, Faculty of Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Hamuy, Mario [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Morrell, Nidia I.; Phillips, Mark M. [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile); Shields, Gregory A. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Sternberg, Assaf, E-mail: rfoley@cfa.harvard.edu [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching (Germany)

2012-06-20T23:59:59.000Z

406

THE TYPE IIb SUPERNOVA 2011dh FROM A SUPERGIANT PROGENITOR  

Science Conference Proceedings (OSTI)

A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star-with R {approx} 200 R{sub Sun }-is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the supernova (SN) in deep pre-explosion images is the progenitor star. From the main peak of the bolometric LC and expansion velocities, we constrain the mass of the ejecta to be Almost-Equal-To 2 M{sub Sun }, the explosion energy to be E = (6-10) Multiplication-Sign 10{sup 50} erg, and the {sup 56}Ni mass to be approximately 0.06 M{sub Sun }. The progenitor star was composed of a helium core of 3-4 M{sub Sun} and a thin hydrogen-rich envelope of Almost-Equal-To 0.1M{sub Sun} with a main-sequence mass estimated to be in the range of 12-15 M{sub Sun }. Our models rule out progenitors with helium-core masses larger than 8 M{sub Sun }, which correspond to M{sub ZAMS} {approx}> 25M{sub Sun }. This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.

Bersten, Melina C.; Nomoto, Ken'ichi; Folatelli, Gaston; Maeda, Keiichi [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Benvenuto, Omar G. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA La Plata (Argentina); Ergon, Mattias; Sollerman, Jesper [The Oskar Klein Centre, Department of Astronomy, AlbaNova, SE-106 91 Stockholm (Sweden); Benetti, Stefano; Ochner, Paolo; Tomasella, Lina [INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy); Botticella, Maria Teresa [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Fraser, Morgan; Kotak, Rubina, E-mail: melina.bersten@ipmu.jp [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom)

2012-09-20T23:59:59.000Z

407

Slowly fading super-luminous supernovae that are not pair-instability explosions  

E-Print Network (OSTI)

Super-luminous supernovae that radiate more than 10^44 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-30 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of 56Ni are synthesized; this isotope decays to 56Fe via 56Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae...

Nicholl, M; Jerkstrand, A; Inserra, C; McCrum, M; Kotak, R; Fraser, M; Wright, D; Chen, T -W; Smith, K; Young, D R; Sim, S A; Valenti, S; Howell, D A; Bresolin, F; Kudritzki, R P; Tonry, J L; Huber, M E; Rest, A; Pastorello, A; Tomasella, L; Cappellaro, E; Benetti, S; Mattila, S; Kankare, E; Kangas, T; Leloudas, G; Sollerman, J; Taddia, F; Berger, E; Chornock, R; Narayan, G; Stubbs, C W; Foley, R J; Lunnan, R; Soderberg, A; Sanders, N; Milisavljevic, D; Margutti, R; Kirshner, R P; Elias-Rosa, N; Morales-Garoffolo, A; Taubenberger, S; Botticella, M T; Gezari, S; Urata, Y; Rodney, S; Riess, A G; Scolnic, D; Wood-Vasey, W M; Burgett, W S; Chambers, K; Flewelling, H A; Magnier, E A; Kaiser, N; Metcalfe, N; Morgan, J; Price, P A; Sweeney, W; Waters, C

2013-01-01T23:59:59.000Z

408

The First Generation of Stars in Lambda-CDM Cosmology  

DOE Green Energy (OSTI)

We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics (SPH) to study the formation of the first luminous objects in the {Lambda}CDM cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from z {approx} 10 to z {approx} 50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass, or assembly history of the host halo. The collapse of proto-stellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical timescales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disk-like structures which are nearly rotational supported; others form flattened spheroids; still others form bars. All of them develop a single protostellar ''seed'' which does not fragment into multiple objects up to the moment that the central gas becomes optically thick to H{sub 2} cooling lines. At this time, the instantaneous mass accretion rate onto the centre varies significantly from object to object, with disk-like structures having the smallest mass accretion rates. The formation epoch and properties of the star-forming clouds are sensitive to the values of cosmological parameters.

Gao, Liang; /Durham U. /Garching, Max Planck Inst.; Abel, T.; /KIPAC, Menlo Park; Frenk, C.S.; Jenkins, A.; /Durham U.; Springel, V.; /Garching, Max Planck Inst.; Yoshida,; /Nagoya U.

2006-10-10T23:59:59.000Z

409

Equations of State in the Brans-Dicke cosmology  

E-Print Network (OSTI)

We investigate the Brans-Dicke (BD) theory with the potential as cosmological model to explain the present accelerating universe. In this work, we consider the BD field as a perfect fluid with the energy density and pressure in the Jordan frame. Introducing the power-law potential and the interaction with the cold dark matter, we obtain the phantom divide which is confirmed by the native and effective equation of state. Also we can describe the metric $f(R)$ gravity with an appropriate potential, which shows a future crossing of phantom divide in viable $f(R)$ gravity models when employing the native and effective equations of state.

Hyung Won Lee; Kyoung Yee Kim; Yun Soo Myung

2010-10-27T23:59:59.000Z

410

Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant  

E-Print Network (OSTI)

Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its General Relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation -> dark matter -> dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the General Relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favorably examined.

Aharon Davidson

2004-09-15T23:59:59.000Z

411

Comment on the Appropriate Null Hypothesis for Cosmological Birefringence  

E-Print Network (OSTI)

A recent paper (Nodland and Ralston, PRL 78, 3043, astro-ph/9704196) claims to have detected evidence for birefringence in the propagation of radio waves across cosmological distances. In order to assess the statistical significance of their results, the authors analyze simulated data sets, finding a stronger correlation in the real data than in the simulations. Unfortunately, the procedure used for generating the simulated data sets is based on an incorrect null hypothesis. Furthermore, the correct null hypothesis would lead to a stronger correlation in the simulated data sets, weakening the case for birefringence. We conclude that the paper's analysis does not provide statistically significant evidence of birefringence.

Daniel J. Eisenstein; Emory F. Bunn

1997-04-24T23:59:59.000Z

412

Statefinder hierarchy of bimetric and galileon models for concordance cosmology  

E-Print Network (OSTI)

In this paper, we use Statefinder hierarchy method to distinguish between bimetric theory of massive gravity, galileon modified gravity and DGP models applied to late time expansion of the universe. We also carry out comparison between bimetric and DGP models using Statefinder pairs {r, s} and {r, q}. We show that statefinder diagnostic can differentiate between {\\Lambda}CDM and above mentioned cosmological models of dark energy, and finally show that Statefinder S2 is an excellent discriminant of {\\Lambda}CDM and modified gravity models.

R. Myrzakulov; M. Shahalam

2013-02-28T23:59:59.000Z

413

Gamma ray burst distances and the timescape cosmology  

E-Print Network (OSTI)

Gamma ray bursts can potentially be used as distance indicators, providing the possibility of extending the Hubble diagram to redshifts ~7. Here we follow the analysis of Schaefer (2007), with the aim of distinguishing the timescape cosmological model from the \\LambdaCDM model by means of the additional leverage provided by GRBs in the range 2 < z < 7. We find that the timescape model fits the GRB sample slightly better than the \\LambdaCDM model, but that the systematic uncertainties are still too little understood to distinguish the models.

Peter R. Smale

2011-07-27T23:59:59.000Z

414

Bianchi type-II cosmological model: some remarks  

E-Print Network (OSTI)

Within the framework of Bianchi type-II (BII) cosmological model the behavior of matter distribution has been considered. It is shown that the non-zero off-diagonal component of Einstein tensor implies some severe restriction on the choice of matter distribution. In particular for a locally rotationally symmetric Bianchi type-II (LRS BII) space-time it is proved that the matter distribution should be strictly isotropic if the corresponding matter field possesses only non-zero diagonal components of the energy-momentum tensor.

Bijan Saha

2010-10-09T23:59:59.000Z

415

2HOT: an improved parallel hashed oct-tree n-body algorithm for cosmological simulation  

Science Conference Proceedings (OSTI)

We report on improvements made over the past two decades to our adaptive treecode N-body method (HOT). A mathematical and computational approach to the cosmological N-body problem is described, with performance and scalability measured up to 256k (218) ... Keywords: N-body, computational cosmology, fast multipole method

Michael S. Warren

2013-11-01T23:59:59.000Z

416

Cosmological non-Gaussian signature detection: comparing performance of different statistical tests  

Science Conference Proceedings (OSTI)

Currently, it appears that the best method for non-Gaussianity detection in the cosmic microwave background (CMB) consists in calculating the kurtosis of the wavelet coefficients. We know that wavelet-kurtosis outperforms other methods such as the bispectrum, ... Keywords: cosmological microwave background, cosmology, curvelet, multiscale method, non-Gaussianity detection, wavelet

J. Jin; J.-L. Starck; D. L. Donoho; N. Aghanim; O. Forni

2005-01-01T23:59:59.000Z

417

Solutions to Cosmological Problems with Energy Conservation and Varying c, G and Lambda  

E-Print Network (OSTI)

The flatness and cosmological constant problems are solved with varying speed of light c, gravitational coupling strength G and cosmological parameter Lambda, by explicitly assuming energy conservation of observed matter. The present solution to the flatness problem is the same as the previous solution in which energy conservation was absent.

P. Gopakumar; G. V. Vijayagovindan

2000-03-26T23:59:59.000Z

418

NEW TWO-DIMENSIONAL MODELS OF SUPERNOVA EXPLOSIONS BY THE NEUTRINO-HEATING MECHANISM: EVIDENCE FOR DIFFERENT INSTABILITY REGIMES IN COLLAPSING STELLAR CORES  

Science Conference Proceedings (OSTI)

The neutrino-driven explosion mechanism for core-collapse supernovae in its modern flavor relies on the additional support of hydrodynamical instabilities in achieving shock revival. Two possible candidates, convection and the so-called standing accretion shock instability (SASI), have been proposed for this role. In this paper, we discuss new successful simulations of supernova explosions that shed light on the relative importance of these two instabilities. While convection has so far been observed to grow first in self-consistent hydrodynamical models with multi-group neutrino transport, we here present the first such simulation in which the SASI grows faster while the development of convection is initially inhibited. We illustrate the features of this SASI-dominated regime using an explosion model of a 27 M{sub Sun} progenitor, which is contrasted with a convectively dominated model of an 8.1 M{sub Sun} progenitor with subsolar metallicity, whose early post-bounce behavior is more in line with previous 11.2 M{sub Sun} and 15 M{sub Sun} explosion models. We analyze the conditions discriminating between the two different regimes, showing that a high mass-accretion rate and a short advection timescale are conducive for strong SASI activity. We also briefly discuss some important factors for capturing the SASI-driven regime, such as general relativity, the progenitor structure, a nuclear equation of state leading to a compact proto-neutron star, and the neutrino treatment. Finally, we evaluate possible implications of our findings for two-dimensional and three-dimensional supernova simulations.

Mueller, Bernhard; Janka, Hans-Thomas [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Heger, Alexander, E-mail: bjmuellr@mpa-garching.mpg.de, E-mail: thj@mpa-garching.mpg.de, E-mail: alexander.heger@monash.edu [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

2012-12-10T23:59:59.000Z

419

The observed neutron star mass distribution as a probe of the supernova explosion mechanism  

E-Print Network (OSTI)

The observed distribution of neutron star (NS) masses reflects the physics of core-collapse supernova explosions and the structure of the massive stars that produce them at the end of their evolution. We present a Bayesian analysis that directly compares the NS mass distribution observed in double NS systems to theoretical models of NS formation. We find that models with standard binary mass ratio distributions are strongly preferred over independently picking the masses from the initial mass function, although the strength of the inference depends on whether current assumptions for identifying the remnants of the primary and secondary stars are correct. Second, NS formation models with no mass fallback are favored because they reduce the dispersion in NS masses. The double NS system masses thus directly point to the mass coordinate where the supernova explosion was initiated, making them an excellent probe of the supernova explosion mechanism. If we assume no fallback and simply vary the mass coordinate sepa...

Pejcha, Ondrej; Kochanek, Christopher S

2012-01-01T23:59:59.000Z

420

An optical and near infrared search for a pulsar in Supernova 1987A  

SciTech Connect

We describe a search for an optical pulsar in the remnant of Supernova 1987A. We have performed over one hundred separate observations of the supernova, covering wavelengths from 3500 angstroms to 1.8 microns, with sensitivity to pulsations as faint as magnitude 22.7. As of September 26, 1990, we have not seen evidence for pulsations due to a pulsar in the supernova. We discuss the implications of this result on predictions of pulsar optical luminosity. We have constructed for the search two photodiode detectors and a data system. We describe their design, calibration and performance. These detectors have allowed us to increase our sensitivity as much as a factor of 5 over standard photomultiplier tubes, and extend this search to near infrared wavelengths. 59 refs., 10 figs., 1 tab.

Sasseen, T.P.

1990-12-01T23:59:59.000Z

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421

Signals of the QCD Phase Transition in Core-Collapse Supernovae  

Science Conference Proceedings (OSTI)

We explore the implications of the QCD phase transition during the postbounce evolution of core-collapse supernovae. Using the MIT bag model for the description of quark matter and assuming small bag constants, we find that the phase transition occurs during the early postbounce accretion phase. This stage of the evolution can be simulated with general relativistic three-flavor Boltzmann neutrino transport. The phase transition produces a second shock wave that triggers a delayed supernova explosion. If such a phase transition happens in a future galactic supernova, its existence and properties should become observable as a second peak in the neutrino signal that is accompanied by significant changes in the energy of the emitted neutrinos.

Sagert, I. [Goethe University, Frankfurt, Germany; Hempel, M. [Goethe University, Frankfurt, Germany; Pagliara, G. [Goethe University, Frankfurt, Germany; Schaffner-Bielich, J. [Goethe University, Frankfurt, Germany; Fischer, T. [University of Basel; Mezzacappa, Anthony [ORNL; Thielemann, F.-K. [University of Basel; Liebendoerfer, M. [University of Basel

2009-01-01T23:59:59.000Z

422

Detecting the QCD phase transition in the next Galactic supernova neutrino burst  

SciTech Connect

Predictions of the thermodynamic conditions for phase transitions at high baryon densities and large chemical potentials are currently uncertain and largely phenomenological. Neutrino observations of core-collapse supernovae can be used to constrain the situation. Recent simulations of stellar core collapse that include a description of quark matter predict a sharp burst of {nu}{sub e} several hundred milliseconds after the prompt {nu}{sub e} neutronization burst. We study the observational signatures of that {nu}{sub e} burst at current neutrino detectors--IceCube and Super-Kamiokande. For a Galactic core-collapse supernova, we find that signatures of the QCD phase transition can be detected, regardless of the neutrino oscillation scenario. The detection would constitute strong evidence of a phase transition in the stellar core, with implications for the equation of state at high matter density and the supernova explosion mechanism.

Dasgupta, Basudeb [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Fischer, Tobias; Liebendoerfer, Matthias [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Horiuchi, Shunsaku [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Mirizzi, Alessandro [II Institut fuer Theoretische Physik, Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Sagert, Irina [Institut fuer Theoretische Physik, Goethe Universitaet, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); Institut fuer Theoretische Physik, Ruprecht-Karls-Universitaet, Philosophenweg 16, 69120 Heidelberg (Germany); Schaffner-Bielich, Juergen [Institut fuer Theoretische Physik, Ruprecht-Karls-Universitaet, Philosophenweg 16, 69120 Heidelberg (Germany)

2010-05-15T23:59:59.000Z

423

Search for supernova {sup 60}Fe in the Earth's microfossil record  

Science Conference Proceedings (OSTI)

Approximately 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of {sup 60}Fe in a deep-sea ferromanganese crust. The signature for this supernova event should also reside in magnetite (Fe{sub 3}O{sub 4}) microfossils produced by magnetotactic bacteria extant at the time of the Earth-supernova interaction, provided the bacteria preferentially uptake iron from fine-grained iron oxides and ferric hydroxides. Using empirically derived microfossil concentrations in a deep-sea drill core, we deduce a conservative estimate of the {sup 60}Fe fraction as {sup 60}Fe/Fe Almost-Equal-To 3.6 Multiplication-Sign 10{sup -15}. This value sits comfortably within the sensitivity limit of present accelerator mass spectrometry capabilities.

Bishop, S.; Ludwig, P.; Egli, R.; Faestermann, T.; Korschinek, G.; Rugel, G. [Technische Universitaet Muenchen, James Franck Str. 1, D-85748 Garching (Germany); Department of Earth and Environmental Sciences, Ludwig-Maximilians University, Theresienstrasse 41 80333 Munich (Germany); Technische Universitaet Muenchen, James Franck Str. 1, D-85748 Garching (Germany); Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstra. 400, D-01328 Dresden (Germany)

2012-11-12T23:59:59.000Z

424

The Reduction of the Electron Abundance during the Pre-explosion Simmering in White Dwarf Supernovae  

E-Print Network (OSTI)

Prior to the explosion of a carbon-oxygen white dwarf in a Type Ia supernova there is a long "simmering," during which the 12C + 12C reaction gradually heats the white dwarf on a long (~ 1000 yr) timescale. Piro & Bildsten showed that weak reactions during this simmering set a maximum electron abundance Ye at the time of the explosion. We investigate the nuclear reactions during this simmering with a series of self-heating, at constant pressure, reaction network calculations. Unlike in AGB stars, proton captures onto 22Ne and heavier trace nuclei do not play a significant role. The 12C abundance is sufficiently high that the neutrons preferentially capture onto 12C, rather than iron group nuclei. As an aid to hydrodynamical simulations of the simmering phase, we present fits to the rates of heating, electron capture, change in mean atomic mass, and consumption of 12C in terms of the screened thermally averaged cross section for 12C + 12C. Our evaluation of the net heating rate includes contributions from electron captures into the 3.68 MeV excited state of 13C. This results in a slightly larger energy release, per 12C consumed, than that found by Piro & Bildsten, but less than that released for