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Note: This page contains sample records for the topic "dark energy camera" from the National Library of EnergyBeta (NLEBeta).
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1

New Camera Sheds Light on Dark Energy | Department of Energy  

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

New Camera Sheds Light on Dark Energy New Camera Sheds Light on Dark Energy New Camera Sheds Light on Dark Energy September 18, 2012 - 3:47pm Addthis Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. | Photo by Dark Energy Survey Collaboration. Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. | Photo by Dark Energy Survey Collaboration. Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science What does this project do? It is expected to discover and measure 4,000 supernovae, 100,000 galaxy clusters and 300 million galaxies. There's magic in the moment of opening one's eyes - especially for

2

New Camera Sheds Light on Dark Energy | Department of Energy  

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

Camera Sheds Light on Dark Energy Camera Sheds Light on Dark Energy New Camera Sheds Light on Dark Energy September 18, 2012 - 3:47pm Addthis Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. | Photo by Dark Energy Survey Collaboration. Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. | Photo by Dark Energy Survey Collaboration. Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science What does this project do? It is expected to discover and measure 4,000 supernovae, 100,000 galaxy clusters and 300 million galaxies. There's magic in the moment of opening one's eyes - especially for the first time: New sights, new possibilities, even new worlds spring into

3

Cooling the dark energy camera instrument  

Science Conference Proceedings (OSTI)

DECam, camera for the Dark Energy Survey (DES), is undergoing general design and component testing. For an overview see DePoy, et al in these proceedings. For a description of the imager, see Cease, et al in these proceedings. The CCD instrument will be mounted at the prime focus of the CTIO Blanco 4m telescope. The instrument temperature will be 173K with a heat load of 113W. In similar applications, cooling CCD instruments at the prime focus has been accomplished by three general methods. Liquid nitrogen reservoirs have been constructed to operate in any orientation, pulse tube cryocoolers have been used when tilt angles are limited and Joule-Thompson or Stirling cryocoolers have been used with smaller heat loads. Gifford-MacMahon cooling has been used at the Cassegrain but not at the prime focus. For DES, the combined requirements of high heat load, temperature stability, low vibration, operation in any orientation, liquid nitrogen cost and limited space available led to the design of a pumped, closed loop, circulating nitrogen system. At zenith the instrument will be twelve meters above the pump/cryocooler station. This cooling system expected to have a 10,000 hour maintenance interval. This paper will describe the engineering basis including the thermal model, unbalanced forces, cooldown time, the single and two-phase flow model.

Schmitt, R.L.; Cease, H.; /Fermilab; DePoy, D.; /Ohio State U.; Diehl, H.T.; Estrada, J.; Flaugher, B.; /Fermilab; Kuhlmann, S.; /Ohio State U.; Onal, Birce; Stefanik, A.; /Fermilab

2008-06-01T23:59:59.000Z

4

Dark energy camera to probe universe's biggest mysteries | Argonne...  

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

journey to Earth. On Sept. 12, that ancient starlight found its way to a mountaintop in Chile, where the newly-constructed Dark Energy Camera - the most powerful sky-mapping...

5

Status of the Dark Energy Survey Camera (DECam) Project  

SciTech Connect

The Dark Energy Survey Collaboration has completed construction of the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the remainder of the time, and after the survey, DECam will be available as a community instrument. All components of DECam have been shipped to Chile and post-shipping checkout finished in Jan. 2012. Installation is in progress. A summary of lessons learned and an update of the performance of DECam and the status of the DECam installation and commissioning will be presented.

Flaugher, Brenna L.; Abbott, Timothy M.C.; Angstadt, Robert; Annis, Jim; Antonik, Michelle, L.; Bailey, Jim; Ballester, Otger.; Bernstein, Joseph P.; Bernstein, Rebbeca; Bonati, Marco; Bremer, Gale; /Fermilab /Cerro-Tololo InterAmerican Obs. /ANL /Texas A-M /Michigan U. /Illinois U., Urbana /Ohio State U. /University Coll. London /LBNL /SLAC /IFAE

2012-06-29T23:59:59.000Z

6

The Dark Energy Spectrometer (DESpec): A Multi-Fiber Spectroscopic Upgrade of the Dark Energy Camera and Survey for the Blanco Telescope  

E-Print Network (OSTI)

We describe an initiative to build and use the Dark Energy Spectrometer (DESpec), a wide-field spectroscopic survey instrument for the Blanco 4 meter telescope at Cerro Tololo InterAmerican Observatory (CTIO) in Chile. A new system with about 4000 robotically positioned optical fibers will be interchangeable with the CCD imager of the existing Dark Energy Camera (DECam), accessing a field of view of 3.8 square degrees in a single exposure. The proposed instrument will be operated by CTIO and available for use by the astronomy community. Our collaboration proposes to use DESpec to conduct a wide, deep spectroscopic survey to study Dark Energy. In a survey of about 350 nights, the DESpec collaboration proposes to obtain spectroscopic redshifts for about 8 million galaxies over 5000 square degrees selected from the Dark Energy Survey (DES). This Dark Energy Spectroscopic Survey will advance our knowledge of cosmic expansion and structure growth significantly beyond that obtainable with imaging-only surveys. Sinc...

Abdalla, F; Bacon, D; Bridle, S; Castander, F; Colless, M; DePoy, D; Diehl, H T; Eriksen, M; Flaugher, B; Frieman, J; Gaztanaga, E; Hogan, C; Jouvel, S; Kent, S; Kirk, D; Kron, R; Kuhlmann, S; Lahav, O; Lawrence, J; Lin, H; Marriner, J; Marshall, J; Mohr, J; Nichol, R C; Sako, M; Saunders, W; Soares-Santos, M; Thomas, D; Wechsler, R; West, A; Wu, H

2012-01-01T23:59:59.000Z

7

Dark Energy  

E-Print Network (OSTI)

We review the problem of dark energy, including a survey of phenomenological models and some aspects of data fitting.

Li, Miao; Wang, Shuang; Wang, Yi

2011-01-01T23:59:59.000Z

8

dark matter dark energy inflation  

E-Print Network (OSTI)

theory dark matter dark energy inflation The National Science Foundation The Kavli Foundation NSF Site Review November 28-29, 2005 #12;dark matter dark energy inflation NSF Site Visit ­ November 28 Gravitation initial conditions beyond single-field slow roll #12;dark matter dark energy inflation NSF Site

Hu, Wayne

9

Dark Energy  

E-Print Network (OSTI)

After some remarks about the history and the mystery of the vacuum energy I shall review the current evidence for a cosmologically significant nearly homogeneous exotic energy density with negative pressure (`Dark Energy'). Special emphasis will be put on the recent polarization measurements by WMAP and their implications. I shall conclude by addressing the question: Do the current observations really imply the existence of a dominant dark energy component?

Norbert Straumann

2003-11-26T23:59:59.000Z

10

Dark Energy and Dark Matter  

E-Print Network (OSTI)

A brief overview of our current understanding of abundance and properties of dark energy and dark matter is presented. A more focused discussion of supersymmetric dark matter follows. Included is a frequentist approach to the supersymmetric parameter space and consequences for the direct detection of dark matter.

Keith A. Olive

2010-01-27T23:59:59.000Z

11

Dark energy without dark energy  

E-Print Network (OSTI)

It is proposed that the current acceleration of the universe is not originated by the existence of a mysterious dark energy fluid nor by the action of extra terms in the gravity Lagrangian, but just from the sub-quantum potential associated with the CMB particles. The resulting cosmic scenario corresponds to a benigner phantom model which is free from the main problems of the current phantom approaches.

Pedro F. Gonzalez-Diaz

2006-08-29T23:59:59.000Z

12

Photo Credit: Peter GinterSLAC National Accelerator Laboratory Dark Energy  

E-Print Network (OSTI)

Photo Credit: Peter GinterSLAC National Accelerator Laboratory #12;Dark Energy 70% Dark Matter 26 and Advanced Camera for Surveys #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70

Osheroff, Douglas D.

13

Pilgrim Dark Energy  

E-Print Network (OSTI)

In the present work, we reconsider the idea of holographic dark energy. One of its key points is the formation of black hole. And then, we propose the so-called "pilgrim dark energy" based on the speculation that the repulsive force contributed by the phantom-like dark energy ($wpilgrim dark energy by using the latest observational data. Of course, one can instead regard pilgrim dark energy as a purely phenomenological model without any physical motivation. We also briefly discuss this issue.

Wei, Hao

2012-01-01T23:59:59.000Z

14

Dark Energy and Dark Matter Models  

E-Print Network (OSTI)

We revisit the problems of dark energy and dark matter and several models designed to explain them, in the light of some latest findings.

Sidharth, Burra G

2013-01-01T23:59:59.000Z

15

Dark Energy and Dark Matter Models  

E-Print Network (OSTI)

We revisit the problems of dark energy and dark matter and several models designed to explain them, in the light of some latest findings.

Burra G. Sidharth

2013-03-14T23:59:59.000Z

16

Dark Energy and Dark Gravity  

E-Print Network (OSTI)

Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet. Explanations of cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are nearly all based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but all share one feature in common -- an inability to account for the gravitational properties of the vacuum energy. Speculative ideas from string theory may hold some promise, but it is fair to say that no convincing model has yet been proposed. An alternative to dark energy is that gravity itself may behave differently from general relativity on the largest scales, in such a way as to produce acceleration. The alternative approach of modified gravity (or dark gravity) provides a new angle on the problem, but also faces serious difficulties, including in all known cases severe fine-tuning and the problem of explaining why the vacuum energy does not gravitate. The lack of an adequate theoretical framework for the late-time acceleration of the universe represents a deep crisis for theory -- but also an exciting challenge for theorists. It seems likely that an entirely new paradigm is required to resolve this crisis.

Ruth Durrer; Roy Maartens

2007-11-01T23:59:59.000Z

17

The Dark Energy Paradigm  

E-Print Network (OSTI)

Though the concept of a dark energy driven accelerating universe was introduced by the author in 1997, to date dark energy itself, as described below has remained a paradigm. A model for the cosmological constant is suggested.

Burra G. Sidharth

2011-12-08T23:59:59.000Z

18

Matter Field, Dark Matter and Dark Energy  

E-Print Network (OSTI)

A model concerning particle theory and cosmology is proposed. Matter field, dark matter and dark energy are created by an energy flow from space to primordial matter fields at the phase transition in the early universe.

Masayasu Tsuge

2008-02-01T23:59:59.000Z

19

The Dark Energy Survey CCD imager design  

SciTech Connect

The Dark Energy Survey is planning to use a 3 sq. deg. camera that houses a {approx} 0.5m diameter focal plane of 62 2kx4k CCDs. The camera vessel including the optical window cell, focal plate, focal plate mounts, cooling system and thermal controls is described. As part of the development of the mechanical and cooling design, a full scale prototype camera vessel has been constructed and is now being used for multi-CCD readout tests. Results from this prototype camera are described.

Cease, H.; DePoy, D.; Diehl, H.T.; Estrada, J.; Flaugher, B.; Guarino, V.; Kuk, K.; Kuhlmann, S.; Schultz, K.; Schmitt, R.L.; Stefanik, A.; /Fermilab /Ohio State U. /Argonne

2008-06-01T23:59:59.000Z

20

Is dark energy evolving?  

E-Print Network (OSTI)

We look for evidence for the evolution in dark energy density by employing Principle Component Analysis (PCA). Distance redshift data from supernovae and baryon acoustic oscillations (BAO) and Observational Hubble data alongwith WMAP7 distance priors are used to put constraints on curvature parameter and dark energy parameters. The data sets are consistent with a flat Universe. The constraints on the dark energy evolution parameters obtained from supernovae and Hubble data (including CMB distance priors) are consistent with a flat Lambda-CDM Universe. On the other hand, the parameter estimates obtained from the addition of BAO data indicate a possible evolution in dark energy density. In this case the first two principle components, which characterize a non-constant contribution from dark energy, are non-zero at 1-sigma. This could be a systematic effect and future BAO data holds key to making more robust claims.

Nair, Remya

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Dark Energy in the Dark Ages  

E-Print Network (OSTI)

Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or ``reasonable'' canonical scalar fields. Such dark energy can be constrained tightly through investigation of the growth of structure, with limits of \\la2% of total energy density at z\\gg1 for many models. Intermediate dark energy can have effects distinct from its energy density; the dark ages acceleration can be constrained to last less than 5% of a Hubble e-fold time, exacerbating the coincidence problem. Both the total linear growth, or equivalently \\sigma_8, and the shape and evolution of the nonlinear mass power spectrum for zenergy behavior over the entire range z=0-1100.

Eric V. Linder

2006-03-21T23:59:59.000Z

22

Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe |  

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

Dark Energy Cam: Fermilab Expands Understanding of Expanding Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe March 12, 2012 - 12:06pm Addthis Researchers at Fermi National Lab team stand beside the 570-megapixels, five-ton Dark Energy camera, which will be capable of measuring the expansion of the universe - and developing better models about how dark energy works. | Photo by Reidar Hahn, Fermi National Lab Researchers at Fermi National Lab team stand beside the 570-megapixels, five-ton Dark Energy camera, which will be capable of measuring the expansion of the universe - and developing better models about how dark energy works. | Photo by Reidar Hahn, Fermi National Lab Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science

23

Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe |  

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

Dark Energy Cam: Fermilab Expands Understanding of Expanding Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe March 12, 2012 - 12:06pm Addthis Researchers at Fermi National Lab team stand beside the 570-megapixels, five-ton Dark Energy camera, which will be capable of measuring the expansion of the universe - and developing better models about how dark energy works. | Photo by Reidar Hahn, Fermi National Lab Researchers at Fermi National Lab team stand beside the 570-megapixels, five-ton Dark Energy camera, which will be capable of measuring the expansion of the universe - and developing better models about how dark energy works. | Photo by Reidar Hahn, Fermi National Lab Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science

24

Dark Matter and Dark Energy  

E-Print Network (OSTI)

This is a short review, aimed at a general audience, of several current subjects of research in cosmology. The topics discussed include the cosmic microwave background (CMB), with particular emphasis on its relevance for testing inflation; dark matter, with a brief review of astrophysical evidence and more emphasis on particle candidates; and cosmic acceleration and some of the ideas that have been put forward to explain it. A glossary of technical terms and acronyms is provided.

Marc Kamionkowski

2007-06-20T23:59:59.000Z

25

Dark Matter and Dark Energy  

E-Print Network (OSTI)

This is a short review, aimed at a general audience, of several current subjects of research in cosmology. The topics discussed include the cosmic microwave background (CMB), with particular emphasis on its relevance for testing inflation; dark matter, with a brief review of astrophysical evidence and more emphasis on particle candidates; and cosmic acceleration and some of the ideas that have been put forward to explain it. A glossary of technical terms and acronyms is provided.

Kamionkowski, Marc

2007-01-01T23:59:59.000Z

26

Unravelling the Dark Matter - Dark Energy Paradigm  

E-Print Network (OSTI)

The standard LambdaCDM model of cosmology is usually understood to arise from demanding that the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric satisfy the General Relativity dynamics for spacetime metrics. The FLRW data-based dominant parameter values, Omega_Lambda=0.73 and Omega_m=0.27 for the dark energy and dark matter+matter, respectively, are then determined by fitting the supernova red-shift data. However in the pressure-less flat-space case the LambdaCDM model is most easily derived from Newtonian gravity, and which was based on the special case of planetary motion in the solar system. Not surprisingly when extended to galactic rotations and cosmology Newtonian dynamics is found to be wanting, and the fix-up involves introducing dark matter and dark energy, as shown herein. However a different theory of gravity leads to a different account of galactic rotations and cosmology, and does not require dark matter nor dark energy to fit the supernova data. It is shown that fitting the LambdaCDM model to this new model, and so independently of the actual supernova data, requires the LambdaCDM model parameters to be those given above. Hence we conclude that dark energy and dark matter are no more than mathematical artifacts to fix-up limitations of Newtonian gravity. Various other data are also briefly reviewed to illustrate other successful tests of this new theory of gravity.

Reginald T Cahill

2009-01-26T23:59:59.000Z

27

Stable dark energy stars  

E-Print Network (OSTI)

The gravastar picture is an alternative model to the concept of a black hole, where there is an effective phase transition at or near where the event horizon is expected to form, and the interior is replaced by a de Sitter condensate. In this work, a generalization of the gravastar picture is explored, by considering a matching of an interior solution governed by the dark energy equation of state, $\\omega\\equiv p/ \\rhosolution at a junction interface. The motivation for implementing this generalization arises from the fact that recent observations have confirmed an accelerated cosmic expansion, for which dark energy is a possible candidate. Several relativistic dark energy stellar configurations are analyzed by imposing specific choices for the mass function. The first case considered is that of a constant energy density, and the second choice, that of a monotonic decreasing energy density in the star's interior. The dynamical stability of the transition layer of these dark energy stars to linearized spherically symmetric radial perturbations about static equilibrium solutions is also explored. It is found that large stability regions exist that are sufficiently close to where the event horizon is expected to form, so that it would be difficult to distinguish the exterior geometry of the dark energy stars, analyzed in this work, from an astrophysical black hole.

Francisco S. N. Lobo

2005-08-28T23:59:59.000Z

28

Dark energy and quantum entanglement  

E-Print Network (OSTI)

Entangled states in the universe may change interpretation of observations and even revise the concept of dark energy.

Mark Ya. Azbel'

2005-02-04T23:59:59.000Z

29

Unified Description of Dark Energy and Dark Matter  

E-Print Network (OSTI)

Dark energy in the universe is assumed to be vacuum energy. The energy-momentum of vacuum is described by a scale-dependent cosmological constant. The equations of motion imply for the density of matter (dust) the sum of the usual matter density (luminous matter) and an additional matter density (dark matter) similar to the dark energy. The scale-dependent cosmological constant is given up to an exponent which is approximated by the experimentally decided density parameters of dark matter and dark energy. This yields that dark matter is one third of dark energy for all times implying an explanation of the coincidence of dark matter and dark energy. In the final state, the universe becomes dark, consisting of dark matter and dark energy.

Walter Petry

2008-10-23T23:59:59.000Z

30

The Universe Adventure - Dark Energy  

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

Energy Energy Dark Energy An artist's conception of Dark Energy. Imagine you toss an apple straight up into the air. Due to gravity, one would expect the apple to come right back down to earth. But what if it doesn't? What if, due to some unseen force your apple continues going up, at an accelerated rate, no matter how much gravity pleads and begs for the apple to come back down. Could this really happen? Could there really be "anti-gravity?" On the scale of the Universe, there is; say "hello" to Dark Energy. In the most basic sense, Dark Energy is akin to negative gravity. Where gravity is attractive, Dark Energy is repulsive. Dark Energy causes the Universe to expand at an increasing rate. For example, to a viewer on earth, gravity would attract a distant galaxy towards Earth, but Dark

31

Dark Energy and CMB  

E-Print Network (OSTI)

The American Physical Society's Division of Particles and Fields initiated a long-term planning exercise over 2012-13, with the goal of developing the community's long term aspirations. The sub-group "Dark Energy and CMB" prepared a series of papers explaining and highlighting the physics that will be studied with large galaxy surveys and cosmic microwave background experiments. This paper summarizes the findings of the other papers, all of which have been submitted jointly to the arXiv.

Dodelson, S; Abazajian, K; Carlstrom, J; Huterer, D; Jain, B; Kim, A; Kirkby, D; Lee, A; Padmanabhan, N; Rhodes, J; Weinberg, D

2013-01-01T23:59:59.000Z

32

On the Nature of Dark Matter and Dark Energy  

E-Print Network (OSTI)

It is shown that some problems connected with dark matter and dark energy can be solved in the framework of the byuon theory

Yu. A. Baurov; I. F. Malov

2007-10-16T23:59:59.000Z

33

From Dark Energy and Dark Matter to Dark Metric  

E-Print Network (OSTI)

It is nowadays clear that General Relativity cannot be the definitive theory of Gravitation due to several shortcomings that come out both from theoretical and experimental viewpoints. At large scales (astrophysical and cosmological) the attempts to match it with the latest observational data lead to invoke Dark Energy and Dark Matter as the bulk components of the cosmic fluid. Since no final evidence, at fundamental level, exists for such ingredients, it is clear that General Relativity presents shortcomings at infrared scales. On the other hand, the attempts to formulate more general theories than Einstein's one give rise to mathematical difficulties that need workarounds that, in turn, generate problems from the interpretative viewpoint. We present here a completely new approach to the mathematical objects in terms of which a theory of Gravitation may be written in a first-order (a' la Palatini) formalism, and introduce the concept of Dark Metric which could completely bypass the introduction of disturbing concepts as Dark Energy and Dark Matter.

S. Capozziello; M. De Laurentis; M. Francaviglia; S. Mercadante

2008-05-23T23:59:59.000Z

34

The Dark Side: from Dark Energy & Dark Matter to Washington and Science Policy  

E-Print Network (OSTI)

The Dark Side: from Dark Energy & Dark Matter to Washington and Science Policy Presenter: Michael: The Map Room (www.maproom.com )1949 N. Hoyne #12;The Dark Side: from Dark Energy and Dark Matter to Washington and Science Policy Presenter: Michael S. Turner Time & Date: 7-9 PM Monday June 16, 2008 Location

Collar, Juan I.

35

Epoch Dependent Dark Energy  

E-Print Network (OSTI)

We present a model in which the equation of state parameter w approaches -1 near a particular value of z, and has significant negative values in a restricted range of z. For example, one can have w ~ -1 near z = 1, and w > -0.2 from z = 0 to z = 0.3, and for z > 9. The ingredients of the model are neutral fermions (which may be neutrinos, neutralinos, etc) which are very weakly coupled to a light scalar field. This model emphasises the importance of the proposed studies of the properties of dark energy into the region z > 1.

B. H. J. McKellar; T. Goldman; G. J. Stephenson, Jr.; P. M. Alsing

2009-08-06T23:59:59.000Z

36

Dark EnergyDark Energy from variation of thefrom variation of the  

E-Print Network (OSTI)

Dark EnergyDark Energy from variation of thefrom variation of the fundamental scalefundamental, soil ! #12;Dark EnergyDark Energy dominates the Universedominates the Universe EnergyEnergy -- density in the Universedensity in the Universe == Matter + Dark EnergyMatter + Dark Energy 25 % + 75 %25 % + 75 % #12;Abell 2255

Heermann, Dieter W.

37

Dark energy and particle mixing  

E-Print Network (OSTI)

We show that the vacuum condensate due to particle mixing is responsible of a dynamically evolving dark energy. In particular, we show that values of the adiabatic index close to -1 for vacuum condensates of neutrinos and quarks imply, at the present epoch, contributions to the vacuum energy compatible with the estimated upper bound on the dark energy.

A. Capolupo; S. Capozziello; G. Vitiello

2008-08-30T23:59:59.000Z

38

Light Thoughts on Dark Energy  

E-Print Network (OSTI)

The physical process leading to the acceleration of the expansion of the universe is unknown. It may involve new high energy physics or extensions to gravitation. Calling this generically dark energy, we examine the consistencies and relations between these two approaches, showing that an effective equation of state function w(z) is broadly useful in describing the properties of the dark energy. A variety of cosmological observations can provide important information on the dynamics of dark energy and the future looks bright for constraining dark energy, though both the measurements and the interpretation will be challenging. We also discuss a more direct relation between the spacetime geometry and acceleration, via “geometric dark energy ” from the Ricci scalar, and superacceleration or phantom energy where the fate of the universe may be more gentle than the Big Rip. 1

Eric V. Linder

2004-01-01T23:59:59.000Z

39

Light Thoughts on Dark Energy  

E-Print Network (OSTI)

The physical process leading to the acceleration of the expansion of the universe is unknown. It may involve new high energy physics or extensions to gravitation. Calling this generically dark energy, we examine the consistencies and relations between these two approaches, showing that an effective equation of state function w(z) is broadly useful in describing the properties of the dark energy. A variety of cosmological observations can provide important information on the dynamics of dark energy and the future looks bright for constraining dark energy, though both the measurements and the interpretation will be challenging. We also discuss a more direct relation between the spacetime geometry and acceleration, via ``geometric dark energy'' from the Ricci scalar, and superacceleration or phantom energy where the fate of the universe may be more gentle than the Big Rip.

Eric V. Linder

2004-04-01T23:59:59.000Z

40

Reconstructing and deconstructing dark energy  

SciTech Connect

The acceleration of the expansion of the universe, ascribed to a dark energy, is one of the most intriguing discoveries in science. In addition to precise, systematics controlled data, clear, robust interpretation of the observations is required to reveal the nature of dark energy. Even for the simplest question: is the data consistent with the cosmological constant? there are important subtleties in the reconstruction of the dark energy properties. We discuss the roles of analysis both in terms of the Hubble expansion rate or dark energy density {rho}DE(z) and in terms of the dark energy equation of state w(z), arguing that each has its carefully defined place. Fitting the density is best for learning about the density, but using it to probe the equation of state can lead to instability and bias.

Linder, Eric V.

2004-06-07T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Cosmological Evolution With Interaction Between Dark Energy And Dark Matter  

E-Print Network (OSTI)

In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).

Bolotin, Yu L; Lemets, O A; Yerokhin, D A

2013-01-01T23:59:59.000Z

42

Some Issues Concerning Holographic Dark Energy  

E-Print Network (OSTI)

We study perturbation of holographic dark energy, and find it be stable. We make a simple and phenomenological classification of the interacting holographic dark energy. We also discussed the cosmic coincidence problem in the context of holographic dark energy.

Li, Miao; Wang, Yi

2008-01-01T23:59:59.000Z

43

Evolving Dark Energy with w =/ -1  

E-Print Network (OSTI)

Why Now? ” problem is solved if theories for dark energy andand the “Dark Energy Why Now? ” problem. Why do we livethe usual “Dark Energy Why Now? ” problem, and we are led to

Hall, Lawrence J.

2009-01-01T23:59:59.000Z

44

Optimizing New Dark Energy Experiments  

SciTech Connect

Next generation “Stage IV” dark energy experiments under design during this grant, and now under construction, will enable the determination of the properties of dark energy and dark matter to unprecedented precision using multiple complementary probes. The most pressing challenge in these experiments is the characterization and understanding of the systematic errors present within any given experimental configuration and the resulting impact on the accuracy of our constraints on dark energy physics. The DETF and the P5 panel in their reports recommended “Expanded support for ancillary measurements required for the long-term program and for projects that will improve our understanding and reduction of the dominant systematic measurement errors.” Looking forward to the next generation Stage IV experiments we have developed a program to address the most important potential systematic errors within these experiments. Using data from current facilities it has been feasible and timely to undertake a detailed investigation of the systematic errors. In this DOE grant we studied of the source and impact of the dominant systematic effects in dark energy measurements, and developed new analysis tools and techniques to minimize their impact. Progress under this grant is briefly reviewed in this technical report. This work was a necessary precursor to the coming generations of wide-deep probes of the nature of dark energy and dark matter. The research has already had an impact on improving the efficiencies of all Stage III and IV dark energy experiments.

Tyson, J. Anthony [University of California, Davis

2013-08-26T23:59:59.000Z

45

Wormhole solutions supported by interacting dark matter and dark energy  

E-Print Network (OSTI)

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Folomeev, Vladimir

2013-01-01T23:59:59.000Z

46

Wormhole solutions supported by interacting dark matter and dark energy  

E-Print Network (OSTI)

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Vladimir Folomeev; Vladimir Dzhunushaliev

2013-08-13T23:59:59.000Z

47

DARK ENERGY AND NON–LINEAR PERTURBATIONS  

E-Print Network (OSTI)

Dark energy might have an influence on the formation of non–linear structures during the cosmic history. For example, in models in which dark energy couples to dark matter, it will be non–homogeneous and will influence on the collapse of a dark matter overdensity. We use the spherical collapse model to estimate how much influence dark energy might have. 1.

C. Van; De Bruck; D. F. Mota

2005-01-01T23:59:59.000Z

48

Dark Energy and Non-linear Perturbations  

E-Print Network (OSTI)

Dark energy might have an influence on the formation of non--linear structures during the cosmic history. For example, in models in which dark energy couples to dark matter, it will be non--homogeneous and will influence the collapse of a dark matter overdensity. We use the spherical collapse model to estimate how much influence dark energy might have.

C. van de Bruck; D. F. Mota

2005-01-14T23:59:59.000Z

49

Dark energy, dark matter and the Chaplygin gas  

E-Print Network (OSTI)

The possibility that the dark energy may be described by the Chaplygin gas is discussed. Some observational constraints are established. These observational constraints indicate that a unified model for dark energy and dark matter through the employement of the Chaplygin gas is favored.

R. Colistete Jr.; J. C. Fabris; S. V. B. Goncalves; P. E. de Souza

2002-10-23T23:59:59.000Z

50

Combinatorial Dark Energy  

E-Print Network (OSTI)

In this paper, we give a conceptual explanation of dark energy as a small negative residual scalar curvature present even in empty spacetime. This curvature ultimately results from postulating a discrete spacetime geometry, very closely related to that used in the dynamical triangulations approach to quantum gravity. In this model, there are no states which have total scalar curvature exactly zero. Moreover, numerical evidence in dimension three suggests that, at a fixed volume, the number of discrete-spacetime microstates strongly increases with decreasing curvature. Because of the resulting entropic force, any dynamics which push empty spacetime strongly toward zero scalar curvature would instead produce typically observed states with a small negative curvature. This provides a natural explanation for the empirically observed small positive value for the cosmological constant (Lambda is about 10^(-121) in Planck units.) In fact, we derive the very rough estimate Lambda=10^(-187) from a simple model containing only the two (highly-degenerate) quantum states with total scalar-curvature closest to zero.

Aaron Trout

2012-08-08T23:59:59.000Z

51

Cluster number counts dependence on dark energy inhomogeneities and coupling to dark matter  

E-Print Network (OSTI)

Cluster number counts can be used to test dark energy models. We investigate dark energy candidates which are coupled to dark matter. We analyze the cluster number counts dependence on the amount of dark matter coupled to dark energy. Further

M. Manera; D. F. Mota

2006-01-01T23:59:59.000Z

52

Dark Energy and Dark Matter as Inertial Effects  

E-Print Network (OSTI)

A globally rotating model of the universe is postulated. It is shown that dark energy and dark matter are cosmic inertial effects resulting from such a cosmic rotation, corresponding to centrifugal and a combination of centrifugal and the Coriolis forces, respectively. The physics and the cosmological and galactic parameters obtained from the model closely match those attributed to dark energy and dark matter in the standard {\\Lambda}-CDM model.

Serkan Zorba

2012-10-10T23:59:59.000Z

53

Dynamics of interacting dark energy  

E-Print Network (OSTI)

Dark energy and dark matter are only indirectly measured via their gravitational effects. It is possible that there is an exchange of energy within the dark sector, and this offers an interesting alternative approach to the coincidence problem. We consider two broad classes of interacting models where the energy exchange is a linear combination of the dark sector densities. The first class has been previously investigated, but we define new variables and find a new exact solution, which allows for a more direct, transparent and comprehensive analysis. The second class has not been investigated in general form before. We give general conditions on the parameters in both classes to avoid unphysical behavior (such as negative energy densities).

Caldera-Cabral, Gabriela; Urena-Lopez, L Arturo

2008-01-01T23:59:59.000Z

54

Dynamics of interacting dark energy  

E-Print Network (OSTI)

Dark energy and dark matter are only indirectly measured via their gravitational effects. It is possible that there is an exchange of energy within the dark sector, and this offers an interesting alternative approach to the coincidence problem. We consider two broad classes of interacting models where the energy exchange is a linear combination of the dark sector densities. The first class has been previously investigated, but we define new variables and find a new exact solution, which allows for a more direct, transparent and comprehensive analysis. The second class has not been investigated in general form before. We give general conditions on the parameters in both classes to avoid unphysical behavior (such as negative energy densities).

Gabriela Caldera-Cabral; Roy Maartens; L. Arturo Urena-Lopez

2008-12-10T23:59:59.000Z

55

Decoupling Dark Energy from Matter  

E-Print Network (OSTI)

We examine the embedding of dark energy in high energy models based upon supergravity and extend the usual phenomenological setting comprising an observable sector and a hidden supersymmetry breaking sector by including a third sector leading to the acceleration of the expansion of the universe. We find that gravitational constraints on the non-existence of a fifth force naturally imply that the dark energy sector must possess an approximate shift symmetry. When exact, the shift symmetry provides an example of a dark energy sector with a runaway potential and a nearly massless dark energy field whose coupling to matter is very weak, contrary to the usual lore that dark energy fields must couple strongly to matter and lead to gravitational inconsistencies. Moreover, the shape of the potential is stable under one-loop radiative corrections. When the shift symmetry is slightly broken by higher order terms in the Kähler potential, the coupling to matter remains small. However, the cosmological dynamics are largely affected by the shift symmetry breaking operators leading to the appearance of a minimum of the scalar potential such that dark energy behaves like an effective cosmological constant from very early on

Carsten Van De Bruck; Jérôme Martin; et al.

2009-01-01T23:59:59.000Z

56

Dark Energy From Fifth Dimension  

E-Print Network (OSTI)

Observational evidence for the existence of dark energy is strong. Here we suggest a model which is based on a modified gravitational theory in 5D and interpret the 5th dimension as a manifestation of dark energy in the 4D observable universe. We also obtain an equation of state parameter which varies with time. Finally, we match our model with observations by choosing the free parameters of the model.

H. Alavirad; N. Riazi

2008-01-21T23:59:59.000Z

57

The Dark Energy Survey instrument design  

SciTech Connect

We describe a new project, the Dark Energy Survey (DES), aimed at measuring the dark energy equation of state parameter, w, to a statistical precision of {approx}5%, with four complementary techniques. The survey will use a new 3 sq. deg. mosaic camera (DECam) mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo International Observatory (CTIO). DECam includes a large mosaic camera, a five element optical corrector, four filters (g,r,i,z), and the associated infrastructure for operation in the prime focus cage. The focal plane consists of 62 2K x 4K CCD modules (0.27''/pixel) arranged in a hexagon inscribed within the 2.2 deg. diameter field of view. We plan to use the 250 micron thick fully-depleted CCDs that have been developed at the Lawrence Berkeley National Laboratory (LBNL). At Fermilab, we will establish a packaging factory to produce four-side buttable modules for the LBNL devices, as well as to test and grade the CCDs. R&D is underway and delivery of DECam to CTIO is scheduled for 2009.

Flaugher, B.; /Fermilab

2006-05-01T23:59:59.000Z

58

Dark energy induced by neutrino mixing  

E-Print Network (OSTI)

The energy content of the vacuum condensate induced by the neutrino mixing is interpreted as dynamically evolving dark energy.

Antonio Capolupo; Salvatore Capozziello; Giuseppe Vitiello

2006-12-05T23:59:59.000Z

59

Gravitation and regular Universe without dark energy and dark matter  

E-Print Network (OSTI)

It is shown that isotropic cosmology in the Riemann-Cartan spacetime allows to solve the problem of cosmological singularity as well as the problems of invisible matter components - dark energy and dark matter. All cosmological models filled with usual gravitating matter satisfying energy dominance conditions are regular with respect to energy density, spacetime metrics and the Hubble parameter. At asymptotics cosmological solutions of spatially flat models describe accelerating Universe without dark energy and dark matter, and quantitatively their behaviour is identical to that of standard cosmological \\Lambda CDM-model.

A. V. Minkevich

2011-02-03T23:59:59.000Z

60

Unified Dark Energy-Dark Matter model with Inverse Quintessence  

E-Print Network (OSTI)

We consider a model where both dark energy and dark matter originate from the coupling of a scalar field with a non-conventional kinetic term to, both, a metric measure and a non-metric measure. An interacting dark energy/dark matter scenario can be obtained by introducing an additional scalar that can produce non constant vacuum energy and associated variations in dark matter. The phenomenology is most interesting when the kinetic term of the additional scalar field is ghost-type, since in this case the dark energy vanishes in the early universe and then grows with time. This constitutes an "inverse quintessence scenario", where the universe starts from a zero vacuum energy density state, instead of approaching it in the future.

Stefano Ansoldi; Eduardo I. Guendelman

2012-09-21T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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.


61

Dark matter, dark energy and gravitational proprieties of antimatter  

E-Print Network (OSTI)

We suggest that the eventual gravitational repulsion between matter and antimatter may be a key for understanding of the nature of dark matter and dark energy. If there is gravitational repulsion, virtual particle-antiparticle pairs in the vacuum, may be considered as gravitational dipoles. We use a simple toy model to reveal a first indication that the gravitational polarization of such a vacuum, caused by baryonic matter in a Galaxy, may produce the same effect as supposed existence of dark matter. In addition, we argue that cancellation of gravitational charges in virtual particle-antiparticle pairs, may be a basis for a solution of the cosmological constant problem and identification of dark energy with vacuum energy. Hence, it may be that dark matter and dark energy are not new, unknown forms of matter-energy but an effect of complex interaction between quantum vacuum and known baryonic matter.

Dragan Slavkov Hajdukovic

2008-10-19T23:59:59.000Z

62

DARK ENERGY- A PEDAGOGIC REVIEW  

E-Print Network (OSTI)

In an introductory manner, the nature of dark energy is addressed, how it is observed and what further tests are needed to reconstruct its properties. Several theoretical approaches to dark energy will be discussed. 1 Plan of the Talk • What observations and theoretical assumptions underly dark energy (DE)? • If general relativity (GR) holds at all length scales, the most conservative assumption, then DE follows from the supernovae Type 1A (SNe1A) or, independently, from the Cosmic Microwave Background (CMB) combined with Large Scale Structure (LSS). • Should we seriously query GR at large distance scales? 2 Einstein-Friedmann Equation The Einstein equations relate geometry on the Left-Hand-Side (LHS) to the distribution of mass-energy on the Right-Hand-Side (RHS) Gµ? = ?8?GTµ? (1) We hesitate to change the LHS but it is really checked with precision only at Solar System (SS) scales. At cosmological length scales, we may consider using a modification such as higherdimensional

Paul H. Frampton

2004-01-01T23:59:59.000Z

63

Correspondence between Ricci and other dark energies  

E-Print Network (OSTI)

Purpose of the present paper is to view the correspondence between Ricci and other dark energies. We have considered the Ricci dark energy in presence of dark matter in non-interacting situation. Subsequently, we have derived the pressure and energy density for Ricci dark energy. The equation of state parameter has been generated from these pressure and energy density. Next, we have considered the correspondence between Ricci and other dark energy models, namely tachyonic field, DBI-essence and new agegraphic dark energy without any interaction and investigated possible cosmological consequences.

Surajit Chattopadhyay; Ujjal Debnath

2010-09-26T23:59:59.000Z

64

Dark energy and possible alternatives  

E-Print Network (OSTI)

We present a brief review of various approaches to late time acceleration of universe. The cosmological relevance of scaling solutions is emphasized in case of scalar field models of dark energy. The underlying features of a variety of scalar field models is highlighted. Various alternatives to dark energy are discussed including the string curvature corrections to Einstein-Hilbert action, higher dimensional effects, non-locally corrected gravity and $f(R)$ theories of gravity. The recent developments related to $f(R)$ models with disappearing cosmological constant are reviewed.

Sami, M

2009-01-01T23:59:59.000Z

65

Freezing Out Early Dark Energy  

E-Print Network (OSTI)

A phenomenological model of dark energy that tracks the baryonic and cold dark matter at early times but resembles a cosmological constant at late times is explored. In the transition between these two regimes, the dark energy density drops rapidly as if it were a relic species that freezes out, during which time the equation of state peaks at +1. Such an adjustment in the dark energy density, as it shifts from scaling to potential-domination, could be the signature of a trigger mechanism that helps explain the late-time cosmic acceleration. We show that the non-negligible dark energy density at early times, and the subsequent peak in the equation of state at the transition, leave an imprint on the cosmic microwave background anisotropy pattern and the rate of growth of large scale structure. The model introduces two new parameters, consisting of the present-day equation of state and the redshift of the freeze-out transition. A Monte Carlo Markov Chain analysis of a ten-dimensional parameter space is performed to compare the model with pre-Planck cosmic microwave background, large scale structure and supernova data and measurements of the Hubble constant. We find that the transition described by this model could have taken place as late as a redshift z~400. We explore the capability of future cosmic microwave background and weak lensing experiments to put tighter constraints on this model. The viability of this model may suggest new directions in dark-energy model building that address the coincidence problem.

Jannis Bielefeld; W. L. Kimmy Wu; Robert R. Caldwell; Olivier Dore

2013-05-09T23:59:59.000Z

66

From Inflation to Dark Energy  

E-Print Network (OSTI)

It is proposed that after the macroscopic fluctuation of energy density that is responsible for inflation dies away, a class of microscopic fluctuations, always present, survives to give the present day dark energy. This latter is simply a reinterpretation of the causet mechanism of Ahmed, Dodelson, Green and Sorkin, wherein the emergence of space is dropped but only energy considerations are maintained. At postinflation times, energy is exchanged between the "cisplanckian" cosmos and an unknown foam-like transplanckian reservoir. Whereas during inflation, the energy flows only from the latter to the former after inflation it fluctuates in sign thereby accounting for the tiny effective cosmological constant that seems to account for dark energy.

Robert Brout

2005-08-04T23:59:59.000Z

67

Agegraphic Chaplygin gas model of dark energy  

E-Print Network (OSTI)

We establish a connection between the agegraphic models of dark energy and Chaplygin gas energy density in non-flat universe. We reconstruct the potential of the agegraphic scalar field as well as the dynamics of the scalar field according to the evolution of the agegraphic dark energy. We also extend our study to the interacting agegraphic generalized Chaplygin gas dark energy model.

Ahmad Sheykhi

2010-02-07T23:59:59.000Z

68

Dark energy and 3-manifold topology  

E-Print Network (OSTI)

We show that the differential-geometric description of matter by differential structures of spacetime leads to a unifying model of the three types of energy in the cosmos: matter, dark matter and dark energy. Using this model we are able to calculate the ratio of dark energy to the total energy of the cosmos.

Torsten Asselmeyer-Maluga; Helge Rose

2007-10-08T23:59:59.000Z

69

Astrophysikalisches Institut Potsdam Probes of Dark Energy  

E-Print Network (OSTI)

Astrophysikalisches Institut Potsdam Probes of Dark Energy using Cosmological Simulations Nonlinear component, called dark energy. This unknown energy causes the expansion of the universe to accelerate theoretical model of dark energy has been developed. Instead a number of models have been proposed that range

70

Dark Energy: Is It of Torsion Origin?  

E-Print Network (OSTI)

{\\it "Dark Energy"} is a term recently used to interpret supernovae type Ia observation. In the present work we give two arguments on a possible relation between dark energy and torsion of space-time.

M. I. Wanas

2010-06-10T23:59:59.000Z

71

Instability of agegraphic dark energy models  

E-Print Network (OSTI)

We investigate the agegraphic dark energy models which were recently proposed to explain the dark energy-dominated universe. For this purpose, we calculate their equation of states and squared speeds of sound. We find that the squared speed for agegraphic dark energy is always negative. This means that the perfect fluid for agegraphic dark energy is classically unstable. Furthermore, it is shown that the new agegraphic dark energy model could describe the matter (radiation)-dominated universe in the far past only when the parameter $n$ is chosen to be $n>n_c$, where the critical values are determined to be $n_c=2.6878(2.5137752)$ numerically. It seems that the new agegraphic dark energy model is no better than the holographic dark energy model for the description of the dark energy-dominated universe, even though it resolves the causality problem.

Kyoung Yee Kim; Hyung Won Lee; Yun Soo Myung

2007-09-18T23:59:59.000Z

72

Interacting agegraphic tachyon model of dark energy  

E-Print Network (OSTI)

Scalar-field dark energy models like tachyon are often regarded as an effective description of an underlying theory of dark energy. In this Letter, we implement the interacting agegraphic dark energy models with tachyon field. We demonstrate that the interacting agegraphic evolution of the universe can be described completely by a single tachyon scalar field. We thus reconstruct the potential as well as the dynamics of the tachyon field according to the evolutionary behavior of interacting agegraphic dark energy.

A. Sheykhi

2009-07-15T23:59:59.000Z

73

UNIFYING DARK ENERGY AND DARK MATTER WITH A SCALAR FIELD  

E-Print Network (OSTI)

Abstract. The standard model of cosmology considers the existence of two components of unknown nature, “dark matter ” and “dark energy”, which determine the cosmological evolution. Their nature remains unknown, and other models can also be considered. In particular, it may be possible to reinterpret the recent cosmological observations so that the Universe does not contain two fluids of unknown natures, but only one fluid with particular properties. After a brief review of constraints on this unifying “dark fluid”, we will discuss a specific model of dark fluid based on a complex scalar fluid. 1

G. Mamon; F. Combes; C. Deffayet; B. Fort (eds; Arbey A

2005-01-01T23:59:59.000Z

74

On the Ricci dark energy model  

E-Print Network (OSTI)

We study the Ricci dark energy model (RDE) which was introduced as an alternative to the holographic dark energy model. We point out that an accelerating phase of the RDE is that of a constant dark energy model. This implies that the RDE may not be a new model of explaining the present accelerating universe.

Kim, Kyoung Yee; Myung, Yun Soo

2008-01-01T23:59:59.000Z

75

REPORT OF THE DARK ENERGY TASK FORCE  

E-Print Network (OSTI)

REPORT OF THE DARK ENERGY TASK FORCE Andreas Albrecht, University of California, Davis Gary. Suntzeff, Texas A&M University Dark energy appears to be the dominant component of the physical Universe a full understanding of the cosmic acceleration. For these reasons, the nature of dark energy ranks among

Hu, Wayne

76

On the Ricci dark energy model  

E-Print Network (OSTI)

We study the Ricci dark energy model (RDE) which was introduced as an alternative to the holographic dark energy model. We point out that an accelerating phase of the RDE is that of a constant dark energy model. This implies that the RDE may not be a new model of explaining the present accelerating universe.

Kyoung Yee Kim; Hyung Won Lee; Yun Soo Myung

2008-12-22T23:59:59.000Z

77

Dark radiation as a signature of dark energy  

E-Print Network (OSTI)

We propose a simple dark energy model with the following properties: the model predicts a late-time dark radiation component that is not ruled out by current observational data, but which produces a distinctive time-dependent equation of state w(z) for z volts.

Sourish Dutta; Stephen D. H. Hsu; David Reeb; Robert J. Scherrer

2009-02-26T23:59:59.000Z

78

From confinement to dark energy  

E-Print Network (OSTI)

The infrared divergence of the self-energy of a color charge is due to an enhancement of the long wavelength modes of the color Coulomb potential field. There are also long wavelength contributions to the QCD vacuum energy that are similarly enhanced. Vacuum modes of Hubble scale wavelengths may be affected in a cosmological setting and this can lead to a residual positive energy density of the form $H^d\\Lambda_{\\rm QCD}^{4-d}$. Lattice studies constrain $d$. If the dark energy takes this form then the universe is driven towards de Sitter expansion, and we briefly study this cosmology when $d$ is just slightly above unity.

B. Holdom

2010-12-02T23:59:59.000Z

79

Origin of holographic dark energy models  

E-Print Network (OSTI)

We investigate the origin of holographic dark energy models which were recently proposed to explain the dark energy-dominated universe. For this purpose, we introduce the spacetime foam uncertainty of $\\delta l \\ge l_{\\rm p}^{\\alpha}l^{\\alpha-1}$. It was argued that the case of $\\alpha=2/3$ could describe the dark energy with infinite statistics, while the case of $\\alpha=1/2$ can describe the ordinary matter with Bose-Fermi statistics. However, two cases may lead to the holographic energy density if the latter recovers from the geometric mean of UV and IR scales. Hence the dark energy with infinite statistics based on the entropy bound is not an ingredient for deriving the holographic dark energy model. Furthermore, it is shown that the agegraphic dark energy models are the holographic dark energy model with different IR length scales.

Yun Soo Myung; Min-Gyun Seo

2008-03-20T23:59:59.000Z

80

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

Note: This page contains sample records for the topic "dark energy camera" 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

Reconstructing Quintom from Ricci Dark Energy  

E-Print Network (OSTI)

The holographic dark energy with Ricci scalar as IR cutoff called Ricci dark energy(RDE) probes the nature of dark energy with respect to the holographic principle of quantum gravity theory. The scalar field dark energy models like quintom are often viewed as effective description of the underlying field theory of dark energy. In this letter, we assume RDE model as the underlying field theory to find how the generalized ghost condensate model(GGC) that can easily realize quintom behavior can be used to effectively describe it and reconstruct the function $h(\\phi)$ of the generalized ghost condensate model.

Chao-Jun Feng

2008-10-15T23:59:59.000Z

82

RESULTS FROM THE CHANDRA MULTIVERSE. III. THE PHYSICAL NATURE OF DARK MATTER AND DARK ENERGY  

E-Print Network (OSTI)

RESULTS FROM THE CHANDRA MULTIVERSE. III. THE PHYSICAL NATURE OF DARK MATTER AND DARK ENERGY TOM ABSTRACT This paper solves the dark-matter and dark-energy problem by taking into account that our universe because there already are theoretical studies of them as dark matter. Dark energy has been used

Gehrels, Tom

83

Dark Matter and Dark Energy: A Physicist's Perspective  

E-Print Network (OSTI)

For physicists, recent developments in astrophysics and cosmology present exciting challenges. We are conducting "experiments" in energy regimes some of which will be probed by accelerators in the near future, and others which are inevitably the subject of more speculative theoretical investigations. Dark matter is an area where we have hope of making discoveries both with accelerator experiments and dedicated searches. Inflation and dark energy lie in regimes where presently our only hope for a fundamental understanding lies in string theory.

Michael Dine

2001-07-30T23:59:59.000Z

84

Clustering Properties of Dynamical Dark Energy Models  

E-Print Network (OSTI)

We provide a generic but physically clear discussion of the clustering properties of dark energy models. We explicitly show that in quintessence-type models the dark energy fluctuations, on scales smaller than the Hubble radius, are of the order of the perturbations to the Newtonian gravitational potential, hence necessarily small on cosmological scales. Moreover, comparable fluctuations are associated with different gauge choices. We also demonstrate that the often used homogeneous approximation is unrealistic, and that the so-called dark energy mutation is a trivial artifact of an effective, single fluid description. Finally, we discuss the particular case where the dark energy fluid is coupled to dark matter.

P. P. Avelino; L. M. G. Beca; C. J. A. P. Martins

2008-02-01T23:59:59.000Z

85

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

86

Dark energy from bulk matter  

SciTech Connect

We consider the possibility of getting accelerated expansion and w=-1 crossing in the context of a braneworld cosmological setup, endowed with a bulk energy-momentum tensor. For a given ansatz of the bulk content, we demonstrate that the bulk pressures dominate the dynamics at late times and can lead to accelerated expansion. We also analyze the constraints under which we can get a realistic profile for the effective equation of state and conclude that matter in the bulk has the effect of dark energy on the brane. Furthermore, we show that it is possible to simulate the behavior to a Chaplygin gas using nonexotic bulk matter.

Bogdanos, C.; Dimitriadis, A.; Tamvakis, K. [Physics Department, University of Ioannina, Ioannina GR451 10 (Greece)

2007-04-15T23:59:59.000Z

87

astro-ph/0212275 Dark Group: Dark Energy and Dark Matter  

E-Print Network (OSTI)

We study the possibility that a dark group, a gauge group with particles interacting with the standard model particles only via gravity, is responsible for containing the dark energy and dark matter required by present day observations. We show that it is indeed possible and we determine the constrains for the dark group. The non-perturbative effects generated by a strong gauge coupling constant can de determined and a scalar potential for the dark meson fields is generated parameterizing the dark energy. On the other hand it is the massive particles, e.g. dark baryons, of the dark gauge group that give the corresponding dark matter. The mass of the dark particles is of the order of the condensation scale ?c and the temperature is 4-5 times smaller then the photon’s temperature. The dark matter is of the warm matter type and it gives good fit to structure formation. The only parameters of the model are the number of particles of the dark group. The conditions to not introduce any fine tuning of the energy density at the condensation scale plus the CMB spectrum constrains the condensation scale to 0.2 eV dark matter with mass m = 42eV, a temperature TDM = T?/4.85 and a free streaming scale ?fs = 1.6Mpc with a contain mass M = 4 × 10 11 M ? (M ? is the solar mass). The dark energy has an equation of state parameter today wo = ?0.9 and the model agrees well with the CMB data. The cosmological observations are pushing the condensation scale to an epoch close to radiation and matter equality and this late time phase transition is the reason why the universe is accelerating at present time. 1

A. De La Macorra

2002-01-01T23:59:59.000Z

88

Testing generic predictions of dark energy  

E-Print Network (OSTI)

Constraints on the expansion history of the universe from measurements of cosmological distances make predictions for large-scale structure growth. Since these predictions depend on assumptions about dark energy evolution and spatial curvature, they can be used to test general classes of dark energy models by comparing predictions for those models with direct measurements of the growth history. I present predictions from current distance measurements for the growth history of dark energy models including a cosmological constant and quintessence. Although a time-dependent dark energy equation of state significantly weakens predictions for growth from measured distances, for quintessence there is a generic limit on the growth evolution that could be used to falsify the whole class of quintessence models. Understanding the allowed range of growth for dark energy models in the context of general relativity is a crucial step for efforts to distinguish dark energy from modified gravity.

Mortonson, Michael J

2010-01-01T23:59:59.000Z

89

On the Chemical Potential of Dark Energy  

E-Print Network (OSTI)

It is widely assumed that the observed universe is accelerating due to the existence of a new fluid component called dark energy. In this article, the thermodynamics consequences of a nonzero chemical potential on the dark energy component is discussed with special emphasis to the phantom fluid case. It is found that if the dark energy fluid is endowed with a negative chemical potential, the phantom field hypothesis becomes thermodynamically consistent with no need of negative temperatures as recently assumed in the literature.

S. H. Pereira

2008-06-23T23:59:59.000Z

90

The possible nature of dark energy and dark matter Nathalie Olivi-Tran1,2  

E-Print Network (OSTI)

The possible nature of dark energy and dark matter Nathalie Olivi-Tran1,2 1 Laboratoire Charles of curvature have gravitational effects and deviate radiations. While we question dark energy, as another the nature of time. Keywords: dark matter; dark energy; nature of time 1 hal-00719998,version1-23Jul2012

Paris-Sud XI, Université de

91

A Field Theory Model for Dark Matter and Dark Energy in Interaction  

E-Print Network (OSTI)

We propose a field theory model for dark energy and dark matter in interaction. Comparing the classical solutions of the field equations with the observations of the CMB shift parameter, BAO, lookback time and Gold supernovae sample, we observe a possible interaction between dark sectors with energy decay from dark energy into dark matter. The observed interaction provides an alleviation to the coincidence problem.

Sandro Micheletti; Elcio Abdalla; Bin Wang

2009-02-02T23:59:59.000Z

92

Interacting holographic dark energy with logarithmic correction  

E-Print Network (OSTI)

The holographic dark energy (HDE) is considered to be the most promising candidate of dark energy. Its definition is originally motivated from the entropy-area relation which depends on the theory of gravity under consideration. Recently a new definition of HDE is proposed with the help of quantum corrections to the entropy-area relation in the setup of loop quantum cosmology. Using this new definition, we investigate the model of interacting dark energy and derive its effective equation of state. Finally we establish a correspondence between generalized Chaplygin gas and entropy-corrected holographic dark energy.

Mubasher Jamil; M. Umar Farooq

2010-02-07T23:59:59.000Z

93

Statefinder Diagnostic for Dilaton Dark Energy  

E-Print Network (OSTI)

Statefinder diagnostic is a useful method which can differ one dark energy model from the others. The Statefinder pair $\\{r, s\\}$ is algebraically related to the equation of state of dark energy and its first time derivative. We apply in this paper this method to the dilaton dark energy model based on Weyl-Scaled induced gravitational theory. We investigate the effect of the coupling between matter and dilaton when the potential of dilaton field is taken as the Mexican hat form. We find that the evolving trajectory of our model in the $r-s$ diagram is quite different from those of other dark energy models.

Z. G. Huang; X. M. Song; H. Q. Lu; W. Fang

2008-02-16T23:59:59.000Z

94

The Fully Quantized Axion and Dark Energy  

E-Print Network (OSTI)

This letter reviews the exact evolution equation for the axion effective potential with the axion scale factor f and phenomenological consequences of the flat effective potential solution are discussed. It is shown that the corresponding vacuum energy can be consistent with Dark Energy, and we compare this result to other studies relating the axion and Dark Energy.

Dylan Tanner

2012-12-17T23:59:59.000Z

95

Dark Energy with w>-4/3  

E-Print Network (OSTI)

Acceleration of the universe might be driven by a continuous elastic medium -- elastic dark energy (Bucher and Spergel 1999). Elastic dark energy can stably support equations of state with pressure to energy ratio w > -4/3. Stable expansion with wenergy'' leads to exotic possibilities such as Expanding Cyclic Universe -- an ever-expanding universe with periodically repeating inflationary epochs.

Andrei Gruzinov

2004-05-05T23:59:59.000Z

96

Dark Energy and Modified Gravity  

E-Print Network (OSTI)

Explanations of the late-time cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are mostly based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but all share one feature in common -- an inability to account for the gravitational properties of the vacuum energy, and a failure to solve the so-called coincidence problem. Two broad alternatives to dark energy have emerged as candidate models: these typically address only the coincidence problem and not the vacuum energy problem. The first is based on general relativity and attempts to describe the acceleration as an effect of inhomogeneity in the universe. If this alternative could be shown to work, then it would provide a dramatic resolution of the coincidence problem; however, a convincing demonstration of viability has not yet emerged. The second alternative is based on infra-red modifications to general relativity, leading to a weakening of gravity on the largest scales and thus to acceleration. Most examples investigated so far are scalar-tensor or brane-world models, and we focus on the simplest candidates of each type: $f(R)$ models and DGP models respectively. Both of these provide a new angle on the problem, but they also face serious difficulties. However, investigation of these models does lead to valuable insights into the properties of gravity and structure formation, and it also leads to new strategies for testing the validity of General Relativity itself on cosmological scales.

Ruth Durrer; Roy Maartens

2008-11-25T23:59:59.000Z

97

#LabChat: What is Dark Energy? Oct 25 at 2pm ET | Department of Energy  

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

What is Dark Energy? Oct 25 at 2pm ET What is Dark Energy? Oct 25 at 2pm ET #LabChat: What is Dark Energy? Oct 25 at 2pm ET October 23, 2012 - 3:03pm Q&A #LabChat Oct 25, 2 pm ET | These physicists are using advanced telescopes and cameras to look for proof of dark energy. Ask them your questions. Ask Us Addthis What is dark energy? Learn about the force we think accounts for three-quarters of the mass and energy in the known universe. What is dark energy? Learn about the force we think accounts for three-quarters of the mass and energy in the known universe. Michael Hess Michael Hess Former Digital Communications Specialist, Office of Public Affairs How can I participate? Send us your questions via Twitter (@ENERGY) using #labchat. Email us your questions at newmedia@hq.doe.gov. This Thursday, October 25, at 2 p.m. EDT, three physicists studying dark

98

Investigating Dark Energy with Black Hole Binaries  

E-Print Network (OSTI)

The accelerated expansion of the universe is ascribed to the existence of dark energy. Black holes accretion of dark energy induces a mass change proportional to the energy density and pressure of the background dark energy fluid. The time scale during which the mass of black holes changes considerably is too long relative to the age of the universe, thus beyond detection possibilities. We propose to take advantage of the modified black hole masses for exploring the equation of state $w[z]$ of dark energy, by investigating the evolution of supermassive black hole binaries on a dark energy background. Deriving the signatures of dark energy accretion on the evolution of binaries, we find that dark energy imprints on the emitted gravitational radiation and on the changes in the orbital radius of the binary can be within detection limits for certain supermassive black hole binaries. In this talk I describe how binaries can provide a useful tool in obtaining complementary information on the nature of dark energy, based on the work done with A.Kelleher.

Laura Mersini-Houghton; Adam Kelleher

2009-06-08T23:59:59.000Z

99

Singularity-free dark energy star  

E-Print Network (OSTI)

We propose a model for an anisotropic dark energy star where we assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density. We discuss various physical features of our model and show that the model satisfies all the regularity conditions and stable as well as singularity-free.

Farook Rahaman; Anil Kumar Yadav; Saibal Ray; Raju Maulick; Ranjan Sharma

2011-02-07T23:59:59.000Z

100

1 The Quintom Model of Dark Energy  

E-Print Network (OSTI)

In this paper I give a brief review on the recently proposed new scenario of dark energy model dubbed Quintom. Quintom describes the dynamical dark energy models where the equation of state getting across the cosmological constant boundary during evolutions. I discuss some aspects on the quintom model buildings and the observational consequences. 1

Bo Feng A B

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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.


101

Stability Issues for w Dark Energy  

E-Print Network (OSTI)

Precision cosmological data hint that a dark energy with equation of state $w = P/\\rho 0$ to $\\Lambda = 0$ in a first-order phase transition. The critical radius is argued to be at least of galactic size and the corresponding nucleation rate is glacial, thus underwriting the dark energy's stability and rendering remote any microscopic effect.

Paul H. Frampton

2003-02-01T23:59:59.000Z

102

Gamma-Ray Bursts and Dark Energy - Dark Matter interaction  

E-Print Network (OSTI)

In this work Gamma Ray Burst (GRB) data is used to place constraints on a putative coupling between dark energy and dark matter. Type Ia supernovae (SNe Ia) constraints from the Sloan Digital Sky Survey II (SDSS-II) first-year results, the cosmic microwave background radiation (CMBR) shift parameter from WMAP seven year results and the baryon acoustic oscillation (BAO) peak from the Sloan Digital Sky Survey (SDSS) are also discussed. The prospects for the field are assessed, as more GRB events become available.

T. Barreiro; O. Bertolami; P. Torres

2010-04-26T23:59:59.000Z

103

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

104

Holographic tachyon model of dark energy  

E-Print Network (OSTI)

In this paper we consider a correspondence between the holographic dark energy density and tachyon energy density in FRW universe. Then we reconstruct the potential and the dynamics of the tachyon field which describe tachyon cosmology.

M R Setare

2007-05-24T23:59:59.000Z

105

Understanding the Fundamental Properties of Dark Matter and Dark Energy in Structure Formation and Cosmology  

Science Conference Proceedings (OSTI)

The program was concerned with developing and verifying the validity of observational methods for constraining the properties of dark matter and dark energy in the Universe.

Ellis, Richard S.

2012-09-30T23:59:59.000Z

106

Inconsistences in Interacting Agegraphic Dark Energy Models  

E-Print Network (OSTI)

It is found that the origin agegraphic dark energy tracks the matter in the matter-dominated epoch and then the subsequent dark-energy-dominated epoch becomes impossible. It is argued that the difficulty can be removed when the interaction between the agegraphic dark energy and dark matter is considered. In the note, by discussing three different interacting models, we find that the difficulty still stands even in the interacting models. Furthermore, we find that in the interacting models, there exists the other serious inconsistence that the existence of the radiation/matter-dominated epoch contradicts the ability of agegraphic dark energy in driving the accelerated expansion. The contradiction can be avoided in one of the three models if some constraints on the parameters hold.

C. Y. Sun; Yu Song

2010-08-04T23:59:59.000Z

107

The Dark Energy Survey Data Management System  

SciTech Connect

The Dark Energy Survey (DES) is a project with the goal of building, installing and exploiting a new 74 CCD-camera at the Blanco telescope, in order to study the nature of cosmic acceleration. It will cover 5000 square degrees of the southern hemisphere sky and will record the positions and shapes of 300 million galaxies up to redshift 1.4. The survey will be completed using 525 nights during a 5-year period starting in 2012. About O(1 TB) of raw data will be produced every night, including science and calibration images. The DES data management system has been designed for the processing, calibration and archiving of these data. It is being developed by collaborating DES institutions, led by NCSA. In this contribution, we describe the basic functions of the system, what kind of scientific codes are involved and how the Data Challenge process works, to improve simultaneously the Data Management system algorithms and the Science Working Group analysis codes.

Sevilla, I.; /Madrid, CIEMAT; Armstrong, R.; Jarvis, M.; /Pennsylvania U.; Bertin, E.; /Paris, Inst. Astrophys.; Carlson, A.; Desai, S.; Mohr, J.; /Munich U.; Daues, G.; Gower, M.; Gruendl, R.; Petravick, D.; /Illinois U., Urbana /Illinois U., Urbana /Chicago U. /Fermilab /Brookhaven /Harvard-Smithsonian Ctr. Astrophys.

2011-09-01T23:59:59.000Z

108

#LabChat Recap: What is Dark Energy  

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

The Dark Energy #LabChat on Oct. 25 yielded a lively discussion with three physicists about inflation, super symmetry, black holes and, of course, dark energy.

109

DOE Science Showcase - Dark Matter and Dark Energy | OSTI, US Dept of  

Office of Scientific and Technical Information (OSTI)

Dark Matter and Dark Energy Dark Matter and Dark Energy The nature of dark energy or invisible energy is one of the universe's most compelling mysteries and its resolution is likely to completely change our understanding of matter, space, and time. For more information, see In the OSTI Collections: Dark Matter and Dark Energy, by Dr. William Watson, Physicist, OSTI staff. Gravitational lensing, or the warping of light around massive objects is one sign of dark energy Image Credit: NASA/Andy Fruchter/ERO team Dark energy research information: Temperature and Density Conditions for Nucleogenesis by Fusion Processes in Stars, William Fowler, DOE R&D Accomplishments Saul Perlmutter, Distant Supernovae, Dark Energy, and the Accelerating Expansion of the Universe, DOE R&D Accomplishments

110

Dark Energy, Inflation and Extra Dimensions  

E-Print Network (OSTI)

We consider how accelerated expansion, whether due to inflation or dark energy, imposes strong constraints on fundamental theories obtained by compactification from higher dimensions. For theories that obey the null energy condition (NEC), we find that inflationary cosmology is impossible for a wide range of compactifications; and a dark energy phase consistent with observations is only possible if both Newton's gravitational constant and the dark energy equation-of-state vary with time. If the theory violates the NEC, inflation and dark energy are only possible if the NEC-violating elements are inhomogeneously distributed in thecompact dimensions and vary with time in precise synchrony with the matter and energy density in the non-compact dimensions. Although our proofs are derived assuming general relativity applies in both four and higher dimensions and certain forms of metrics, we argue that similar constraints must apply for more general compactifications.

Paul J. Steinhardt; Daniel Wesley

2008-11-11T23:59:59.000Z

111

Neutron Scatter Camera for Radiaton Detection - Energy ...  

Patent 7,741,613: Neutron scatter camera An instrument that will directly image the fast fission neutrons from a special nuclear material source has ...

112

Is Hubble's Expansion due to Dark Energy  

E-Print Network (OSTI)

{\\it The universe is expanding} is known (through Galaxy observations) since 1929 through Hubble's discovery ($V = H D$). Recently in 1999, it is found (through Supernovae observations) that the universe is not simply expanding but is accelerating too. We, however, hardly know only $4\\%$ of the universe. The Wilkinson Microwave Anisotropy Probe (WMAP) satellite observational data suggest $73\\%$ content of the universe in the form of dark-energy, $23\\%$ in the form of non-baryonic dark-matter and the rest $4\\%$ in the form of the usual baryonic matter. The acceleration of the universe is ascribed to this dark-energy with bizarre properties (repulsive-gravity). The question is that whether Hubble's expansion is just due to the shock of big-bang & inflation or it is due to the repulsive-gravity of dark-energy? Now, it is believed to be due to dark-energy, say, by re-introducing the once-discarded cosmological-constant $\\Lambda$. In the present paper, it is shown that `the formula for acceleration due to dark-energy' is (almost) exactly of same-form as `the acceleration formula from the Hubble's law'. Hence, it is concluded that: yes, `indeed it is the dark-energy responsible for the Hubble's expansion too, in-addition to the current on-going acceleration of the universe'.

R. C. Gupta; Anirudh Pradhan

2010-10-19T23:59:59.000Z

113

Holographic dark matter and dark energy with second order invariants  

E-Print Network (OSTI)

One of the main goals of modern cosmology remains to summon up a self consistent policy, able to explain, in the framework of the Einstein's theory, the cosmic speed up and the presence of Dark Matter in the Universe. Accordingly to the Holographic principle, which postulates the existence of a minimal size of a physical region, we argue, in this paper, that if this size exists for the Universe and it is accrued from the independent geometrical second order invariants, it would be possible to ensure a surprising source for Dark Matter and a viable candidate for explaining the late acceleration of the Universe. Along the work, we develop low redshift tests, such as Supernovae Ia and kinematical analysis complied by the use of Cosmography and we compare the outcomes with higher redshift tests, such as CMB peak and anisotropy of the cosmic power spectrum. All the results indicate that the models presented here can be interpreted as unified models that are capable to describe both the dark matter and the dark energy.

Alejandro Aviles; Luca Bonanno; Orlando Luongo; Hernando Quevedo

2011-09-14T23:59:59.000Z

114

G-corrected holographic dark energy model  

E-Print Network (OSTI)

Here we investigate the holographic dark energy model in the framework of FRW cosmology where the Newtonian gravitational constant,$G$, is varying with cosmic time. Using the complementary astronomical data which support the time dependency of $G$, the evolutionary treatment of EoS parameter and energy density of dark energy model are calculated in the presence of time variation of $G$. It has been shown that in this case, the phantom regime can be achieved at the present time. We also calculate the evolution of $G$- corrected deceleration parameter for holographic dark energy model and show that the dependency of $G$ on the comic time can influence on the transition epoch from decelerated expansion to the accelerated phase. Finally we perform the statefinder analysis for $G$- corrected holographic model and show that this model has a shorter distance from the observational point in $s-r$ plane compare with original holographic dark energy model.

Malekjani, M

2013-01-01T23:59:59.000Z

115

Dark Energy May Probe String Theory  

E-Print Network (OSTI)

The problem of dark energy arises due to its self-gravitating properties. Therefore explaining vacuum energy may become a question for the realm of quantum gravity, that can be addressed within string theory context. In this talk I concentrate on a recent, string-inspired model, that relies on nonlinear physics of short-distance perturbation modes, for explaining dark energy without any fine-tuning. Dark energy can be observationally probed by its equation of state, w. Different models predict different types of equations of state and string-inspired ones have a time dependent w(z) as their unique signature. Exploring the link between dark energy and string theory may provide indirect evidence for the latter, by means of precision cosmology data.

L. Mersini; M. Bastero-Gil

2002-12-13T23:59:59.000Z

116

Tommaso Treu, UC Santa Barbara What is the nature of dark energy and dark matter?  

E-Print Network (OSTI)

Tommaso Treu, UC Santa Barbara What is the nature of dark energy and dark matter? I will describe on the equation of state of dark energy and flatness comparable to those obtained with the best probes. The second the presence of dark subhalos independent of their stellar content. This tests a fundamental prediction

Glashausser, Charles

117

Solution to the Dark Energy Problem  

E-Print Network (OSTI)

I present a simple, and hopefully convincing, discussion of a solution to the dark energy problem, which arises because the visible universe is well approximated by a black hole.

Frampton, Paul Howard

2010-01-01T23:59:59.000Z

118

Particle mixing, flavor condensate and dark energy  

E-Print Network (OSTI)

The mixing of neutrinos and quarks generate a vacuum condensate that, at the present epoch, behaves as a cosmological constant. The value of the dark energy is constrained today by the very small breaking of the Lorentz invariance.

Massimo Blasone; Antonio Capolupo; Giuseppe Vitiello

2009-12-08T23:59:59.000Z

119

Entropic dark energy and sourced Friedmann equations  

E-Print Network (OSTI)

In this paper we show that a recent attempt to derive dark energy as an entropic force suffers from the same problems as earlier attempts motivated by holography. The possible remedy is again the introduction of source terms.

Ulf H. Danielsson

2010-03-03T23:59:59.000Z

120

Neutrino mixing, flavor states and dark energy  

E-Print Network (OSTI)

We shortly summarize the quantum field theory formalism for the neutrino mixing and report on recent results showing that the vacuum condensate induced by neutrino mixing can be interpreted as a dark energy component of the Universe.

M. Blasone; A. Capolupo; S. Capozziello; G. Vitiello

2007-11-06T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Probing Dark Energy through Scale Dependence  

E-Print Network (OSTI)

We consider the consequences of having no prior knowledge of the true dark energy model for the interpretation of cosmological observations. The magnitude of redshift-space distortions and weak-lensing shear is determined by the metric on the geodesics of which galaxies and light propagate. We show that, given precise enough observations, we can use these data to completely reconstruct the metric on our past lightcone and therefore to measure the scale- and time-dependence of the anisotropic stress and the evolution of the gravitational potentials in a model-independent manner. Since both dark matter and dark energy affect the visible sector only through the gravitational field they produce, they are inseparable without a model for dark energy: galaxy bias cannot be measured and therefore the distribution of dark matter determined; the peculiar velocity of dark matter can be identified with that of the galaxies only when the equivalence principle holds. Given these limitations, we show how one can nonetheless build tests for classes of dark energy models which depend on making measurements at multiple scales at a particular redshift. They are null tests on the model-independent observables, do not require modeling evolution in time and do not require any parametrization of the free functions of these models, such as the sound speed. We show how one can rule out or constrain the whole class of the most-general scalar-tensor theories even without assuming the quasi-static limit.

Mariele Motta; Ignacy Sawicki; Ippocratis D. Saltas; Luca Amendola; Martin Kunz

2013-04-30T23:59:59.000Z

122

Collapsing Inhomogeneous Dust Fluid in the Background of Dark Energy  

E-Print Network (OSTI)

In the present work, gravitational collapse of an inhomogeneous spherical star model, consisting of inhomogeneous dust fluid (dark matter) in the background of dark energy is considered. The collapsing process is examined first separately for both dark matter and dark energy and then under the combined effect of dark matter and dark energy with or without interaction. The dark energy is considered in the form of perfect fluid and both marginally and non-marginally bound cases are considered for the collapsing model. Finally dark energy in the form of anisotropic fluid is investigated and it is found to be similar to ref. [12

Tanwi Bandyopadhyay; Subenoy Chakraborty

2006-05-11T23:59:59.000Z

123

Universal Forces and the Dark Energy Problem  

E-Print Network (OSTI)

The Dark Energy problem is forcing us to re-examine our models and our understanding of relativity and space-time. Here a novel idea of Fundamental Forces is introduced. This allows us to perceive the General Theory of Relativity and Einstein's Equation from a new pesrpective. In addition to providing us with an improved understanding of space and time, it will be shown how it leads to a resolution of the Dark Energy problem.

Afsar Abbas

2007-04-01T23:59:59.000Z

124

Universal Forces and the Dark Energy Problem  

E-Print Network (OSTI)

The Dark Energy problem is forcing us to re-examine our models and our understanding of relativity and space-time. Here a novel idea of Fundamental Forces is introduced. This allows us to perceive the General Theory of Relativity and Einstein's Equation from a new pesrpective. In addition to providing us with an improved understanding of space and time, it will be shown how it leads to a resolution of the Dark Energy problem.

Abbas, Afsar

2007-01-01T23:59:59.000Z

125

Towards Dark Energy from String-Theory  

E-Print Network (OSTI)

We discuss vacuum energy in string and M-theory with a focus on heterotic M-theory. In the latter theory a mechanism is described for maintaining zero vacuum energy after supersymmetry breaking. Higher-order corrections can be expected to give a sufficiently small amount of vacuum energy to possibly account for dark energy.

Axel Krause

2007-12-31T23:59:59.000Z

126

Brane-Bulk energy exchange and agegraphic dark energy  

E-Print Network (OSTI)

We consider the agegraphic models of dark energy in a braneworld scenario with brane-bulk energy exchange. We assume that the adiabatic equation for the dark matter is satisfied while it is violated for the agegraphic dark energy due to the energy exchange between the brane and the bulk. Our study shows that with the brane-bulk interaction, the equation of state parameter of agegraphic dark energy on the brane, $w_D$, can have a transition from normal state where $w_D >-1 $ to the phantom regime where $w_D energy always satisfies $w^{\\mathrm{eff}}_D\\geq-1$.

Ahmad Sheykhi

2009-08-09T23:59:59.000Z

127

The Dark Energy Survey Data Management System  

SciTech Connect

The Dark Energy Survey (DES) collaboration will study cosmic acceleration with a 5000 deg2 griZY survey in the southern sky over 525 nights from 2011-2016. The DES data management (DESDM) system will be used to process and archive these data and the resulting science ready data products. The DESDM system consists of an integrated archive, a processing framework, an ensemble of astronomy codes and a data access framework. We are developing the DESDM system for operation in the high performance computing (HPC) environments at the National Center for Supercomputing Applications (NCSA) and Fermilab. Operating the DESDM system in an HPC environment offers both speed and flexibility. We will employ it for our regular nightly processing needs, and for more compute-intensive tasks such as large scale image coaddition campaigns, extraction of weak lensing shear from the full survey dataset, and massive seasonal reprocessing of the DES data. Data products will be available to the Collaboration and later to the public through a virtual-observatory compatible web portal. Our approach leverages investments in publicly available HPC systems, greatly reducing hardware and maintenance costs to the project, which must deploy and maintain only the storage, database platforms and orchestration and web portal nodes that are specific to DESDM. In Fall 2007, we tested the current DESDM system on both simulated and real survey data. We used TeraGrid to process 10 simulated DES nights (3TB of raw data), ingesting and calibrating approximately 250 million objects into the DES Archive database. We also used DESDM to process and calibrate over 50 nights of survey data acquired with the Mosaic2 camera. Comparison to truth tables in the case of the simulated data and internal crosschecks in the case of the real data indicate that astrometric and photometric data quality is excellent.

Mohr, Joseph J.; /Illinois U., Urbana, Astron. Dept. /Illinois U., Urbana; Barkhouse, Wayne; /North Dakota U.; Beldica, Cristina; /Illinois U., Urbana; Bertin, Emmanuel; /Paris, Inst. Astrophys.; Dora Cai, Y.; /NCSA, Urbana; Nicolaci da Costa, Luiz A.; /Rio de Janeiro Observ.; Darnell, J.Anthony; /Illinois U., Urbana, Astron. Dept.; Daues, Gregory E.; /NCSA, Urbana; Jarvis, Michael; /Pennsylvania U.; Gower, Michelle; /NCSA, Urbana; Lin, Huan; /Fermilab /Rio de Janeiro Observ.

2008-07-01T23:59:59.000Z

128

The Dark Energy Survey Data Management System  

E-Print Network (OSTI)

The Dark Energy Survey collaboration will study cosmic acceleration with a 5000 deg2 griZY survey in the southern sky over 525 nights from 2011-2016. The DES data management (DESDM) system will be used to process and archive these data and the resulting science ready data products. The DESDM system consists of an integrated archive, a processing framework, an ensemble of astronomy codes and a data access framework. We are developing the DESDM system for operation in the high performance computing (HPC) environments at NCSA and Fermilab. Operating the DESDM system in an HPC environment offers both speed and flexibility. We will employ it for our regular nightly processing needs, and for more compute-intensive tasks such as large scale image coaddition campaigns, extraction of weak lensing shear from the full survey dataset, and massive seasonal reprocessing of the DES data. Data products will be available to the Collaboration and later to the public through a virtual-observatory compatible web portal. Our approach leverages investments in publicly available HPC systems, greatly reducing hardware and maintenance costs to the project, which must deploy and maintain only the storage, database platforms and orchestration and web portal nodes that are specific to DESDM. In Fall 2007, we tested the current DESDM system on both simulated and real survey data. We used Teragrid to process 10 simulated DES nights (3TB of raw data), ingesting and calibrating approximately 250 million objects into the DES Archive database. We also used DESDM to process and calibrate over 50 nights of survey data acquired with the Mosaic2 camera. Comparison to truth tables in the case of the simulated data and internal crosschecks in the case of the real data indicate that astrometric and photometric data quality is excellent.

Joseph J. Mohr; Wayne Barkhouse; Cristina Beldica; Emmanuel Bertin; Y. Dora Cai; Luiz da Costa; J. Anthony Darnell; Gregory E. Daues; Michael Jarvis; Michelle Gower; Huan Lin; leandro Martelli; Eric Neilsen; Chow-Choong Ngeow; Ricardo Ogando; Alex Parga; Erin Sheldon; Douglas Tucker; Nikolay Kuropatkin; Chris Stoughton

2008-07-16T23:59:59.000Z

129

Can dark energy be gravitational waves?  

E-Print Network (OSTI)

The idea that dark energy is gravitational waves may explain its strength and its time-evolution. A possible concept is that dark energy is the ensemble of coherent bursts (solitons) of gravitational waves originally produced when the first generation of super-massive black holes was formed. These solitons get their initial energy as well as keep up their energy density throughout the evolution of the universe by stimulating emission from a background, a process which we model by working out this energy transfer in a Boltzmann equation approach. New Planck data suggest that dark energy has increased in strength over cosmic time, supporting the concept here. The transit of these gravitational wave solitons may be detectable. Key tests include pulsar timing, clock jitter and the radio background.

Biermann, Peter L

2013-01-01T23:59:59.000Z

130

Interacting agegraphic dark energy models in non-flat universe  

E-Print Network (OSTI)

A so-called "agegraphic dark energy" was recently proposed to explain the dark energy-dominated universe. In this Letter, we generalize the agegraphic dark energy models to the universe with spatial curvature in the presence of interaction between dark matter and dark energy. We show that these models can accommodate $w_D = -1 $ crossing for the equation of state of dark energy. In the limiting case of a flat universe, i.e. $k = 0$, all previous results of agegraphic dark energy in flat universe are restored.

Ahmad Sheykhi

2009-07-29T23:59:59.000Z

131

Dark, Hypoxia, Herbicide, Other Stresses Energy Deprivation  

E-Print Network (OSTI)

Dark, Hypoxia, Herbicide, Other Stresses Energy Deprivation Upstream PKs GBF5, bZIP11, 53, 1 Glycolysis NR, SPS, HMG-CoAR Energy homeostasis, Growth, Stress response, Survival Development, Reproduction. Plants are constantly challenged by multiple types of stress that ultimately converge as an energy

Sheen, Jen

132

A Casimir approach to dark energy  

E-Print Network (OSTI)

We calculate the gravitational self-energy of vacuum quantum field fluctuations using a Casimir approach. We find that the Casimir gravitational self-energy density can account for the measured dark energy density when the SUSY-breaking energy is approximately 5 TeV, in good agreement with current estimates. Furthermore, the Casimir gravitational self-energy appears to provide a quantum mechanism for the well-know geometric relation between the Planck, SUSY and cosmological constant energy scales.

Allan Rosencwaig

2006-06-26T23:59:59.000Z

133

Braneworlds, Conformal Fields and Dark Energy  

E-Print Network (OSTI)

In the Randall-Sundrum scenario we analize the dynamics of a spherically symmetric 3-brane when matter fields propagate in the bulk. For a well defined class of conformal fields of weight -4 we determine a new set of exact 5-dimensional solutions which localize gravity in the vicinity of the brane and are stable under radion field perturbations. Geometries which describe the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy are shown to belong to this set.

Rui Neves

2006-01-06T23:59:59.000Z

134

Property:Cameras | Open Energy Information  

Open Energy Info (EERE)

Property Property Edit with form History Facebook icon Twitter icon » Property:Cameras Jump to: navigation, search Property Name Cameras Property Type Text Pages using the property "Cameras" Showing 25 pages using this property. (previous 25) (next 25) 1 1.5-ft Wave Flume Facility + None 10-ft Wave Flume Facility + None 11-ft Wave Flume Facility + None 2 2-ft Flume Facility + None 3 3-ft Wave Flume Facility + None 5 5-ft Wave Flume Facility + None 6 6-ft Wave Flume Facility + None A Alden Large Flume + Yes Alden Small Flume + Yes Alden Tow Tank + Yes Alden Wave Basin + Yes B Breakwater Research Facility + None C Carderock 2-ft Variable Pressure Cavitation Water Tunnel + None Carderock 3-ft Variable Pressure Cavitation Water Tunnel + None Carderock Circulating Water Channel + None

135

February 2006, NRAO, VA (or why H0 is the Dark Energy)  

E-Print Network (OSTI)

Wayne Hu February 2006, NRAO, VA (or why H0 is the Dark Energy) Dark Energy in Light of the CMB #12;If its not dark, it doesn't matter! · Cosmic matter-energy budget: Dark Energy Dark Matter Dark provide the high redshift cornerstone to cosmological inferences on the dark matter and dark energy WMAP

Hu, Wayne

136

Distinguishing Modified Gravity from Dark Energy  

E-Print Network (OSTI)

The acceleration of the universe can be explained either through dark energy or through the modification of gravity on large scales. In this paper we investigate modified gravity models and compare their observable predictions with dark energy models. Modifications of general relativity are expected to be scale-independent on super-horizon scales and scale-dependent on sub-horizon scales. For scale-independent modifications, utilizing the conservation of the curvature scalar and a parameterized post-Newtonian formulation of cosmological perturbations, we derive results for large scale structure growth, weak gravitational lensing, and cosmic microwave background anisotropy. For scale-dependent modifications, inspired by recent $f(R)$ theories we introduce a parameterization for the gravitational coupling $G$ and the post-Newtonian parameter $\\gamma$. These parameterizations provide a convenient formalism for testing general relativity. However, we find that if dark energy is generalized to include both entropy and shear stress perturbations, and the dynamics of dark energy is unknown a priori, then modified gravity cannot in general be distinguished from dark energy using cosmological linear perturbations.

Edmund Bertschinger; Phillip Zukin

2008-01-16T23:59:59.000Z

137

Dark Energy from Quantum Uncertainty of Simultaneity  

E-Print Network (OSTI)

The observed acceleration expansion of the universe was thought attribute to a mysterious dark energy in the framework of the classical general relativity. The dark energy behaves very similar with a vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a wrong order of the vacuum energy and leads to a severe fine-tuning, known as the cosmological constant problem. We abandon the standard interpretation that time is a global parameter in quantum mechanics, replace it by a quantum dynamical variable playing the role of an operational quantum clock system. In the framework of reinterpretation of time, we find that the synchronization of two quantum clocks distance apart can not be realized in all rigor at quantum level. Thus leading to an intrinsic quantum uncertainty of simultaneity between spatial interval, which implies a visional vacuum energy fluctuation and gives an observed dark energy density $\\rho_{de}=\\frac{6}{\\pi}L_{P}^{-2}L_{H}^{-2}$, where $L_{P}$ and $L_{H}$ are the Planck and Hubble scale cut-off. The expectation value of zero-point energy automatically vanishes under the quantum dynamical time variable. The fraction of the dark energy is precisely given by $\\Omega_{de}=\\frac{2}{\\pi}$, which does not evolve with the quantum dynamical time variable, so it is "always" comparable to the matter energy density or the critical density. This theory is consistent with current cosmic observations.

M. J. Luo

2014-01-11T23:59:59.000Z

138

Dark Energy Density in Brane World  

E-Print Network (OSTI)

We present a possible explanation to the tiny positive cosmological constant under the frame of AdS$_5$ spacetime embedded by a dS$_4$ brane. We calculate the dark energy density by summing the zero point energy of massive scalar fields in AdS$_5$ spacetime. Under the assumption that the radius of AdS$_5$ spacetime is of the same magnitude as the radius of observable universe, the dark energy density in dS$_4$ brane is obtained, which is smaller than the observational value. The reasons are also discussed.

Hai-Bao Wen; Xin-Bing Huang

2005-02-08T23:59:59.000Z

139

Inhomogeneous models of interacting dark matter and dark energy  

E-Print Network (OSTI)

We derive and analyze a class of spherically symmetric cosmological models whose source is an interactive mixture of inhomogeneous cold dark matter (DM) and a generic homogeneous dark energy (DE) fluid. If the DE fluid corresponds to a quintessense scalar field, the interaction term can be associated with a well motivated non--minimal coupling to the DM component. By constructing a suitable volume average of the DM component we obtain a Friedman evolution equation relating this average density with an average Hubble scalar, with the DE component playing the role of a repulsive and time-dependent $\\Lambda$ term. Once we select an ``equation of state'' linking the energy density ($\\mu$) and pressure ($p$) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. Considering the simple equation of state $p= (\\gamma-1) \\mu$ with $0\\leq\\gamma description of a local DM overdensity evolving in a suitable cosmic background that accurately fits current observational data. While a DE dominated scenario emerges in the asymptotic future, with total $\\Omega$ and $q$ tending respectively to 1 and -1/2 for all cosmic observers, the effects of inhomogeneity and anisotropy yield different local behavior and evolution rates for these parameters in the local overdense region. We suggest that the models presented can be directly applied to explore the effects of various DE formalisms on local DM cosmological inhomogeneities.

Roberto A Sussman; Israel Quiros; Osmel Martin Gonzalez

2005-03-29T23:59:59.000Z

140

Inhomogeneous models of interacting dark matter and dark energy  

E-Print Network (OSTI)

We derive and analyze a class of spherically symmetric cosmological models whose source is an interactive mixture of inhomogeneous cold dark matter (DM) and a generic homogeneous dark energy (DE) fluid. If the DE fluid corresponds to a quintessense scalar field, the interaction term can be associated with a well motivated non--minimal coupling to the DM component. By constructing a suitable volume average of the DM component we obtain a Friedman evolution equation relating this average density with an average Hubble scalar, with the DE component playing the role of a repulsive and time-dependent $\\Lambda$ term. Once we select an ``equation of state'' linking the energy density ($\\mu$) and pressure ($p$) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. Considering the simple equation of state $p= (\\gamma-1) \\mu$ with $0\\leq\\gamma <2/3$, we s...

Sussman, R A; Gonzalez, O M; Sussman, Roberto A; Quiros, Israel; Gonzalez, Osmel Martin

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Destiny: A Candidate Architecture for the Joint Dark Energy Mission  

E-Print Network (OSTI)

Destiny is a simple, direct, low cost mission to determine the properties of dark energy by obtaining a cosmologically deep supernova (SN) type Ia Hubble diagram. Operated at L2, its science instrument is a 1.65m space telescope, featuring a grism-fed near-infrared (NIR) (0.85-1.7micron) survey camera/spectrometer with a 0.12 square degree field of view. During its two-year primary mission, Destiny will detect, observe, and characterize ~3000 SN Ia events over the redshift interval 0.4energy equation of state from a time when it was strongly matter-dominated to the present when dark energy dominates. The grism-images simultaneously provide broad-band photometry, redshifts, and SN classification, as well as time-resolved diagnostic data for investigating additional SN luminosity diagnostics. Destiny will be used in its third year as a high resolution, wide-field imager to conduct a multicolor NIR weak lensing (WL) survey covering 1000 square degrees. The large-scale mass power spectrum derived from weak lensing distortions of field galaxies as a function of redshift will provide independent and complementary constraints on the dark energy equation of state. The combination of SN and WL is much more powerful than either technique on its own. Used together, these surveys will have more than an order of magnitude greater sensitivity than will be provided by ongoing ground-based projects. The dark energy parameters, w_0 and w_a, will be measured to a precision of 0.05 and 0.2 respectively.

Dominic J. Benford; Tod R. Lauer

2006-08-19T23:59:59.000Z

142

Holographic dark energy interacting with dark matter in a Closed Universe  

E-Print Network (OSTI)

A cosmological model of an holographic dark energy interacting with dark matter throughout a decaying term of the form $Q=3(\\lambda_1\\rho_{DE} + \\lambda_2\\rho_m) H$ is investigated. General constraint on the parameters of the model are found when accelerated expansion is imposed and we found a phantom scenarios, without any reference to a specific equation of state for the dark energy. The behavior of equation of stated for dark energy is also discussed.

Norman Cruz; Samuel Lepe; Francisco Pena; Joel Saavedra

2008-07-24T23:59:59.000Z

143

Structure formation in inhomogeneous Early Dark Energy models  

E-Print Network (OSTI)

We study the impact of Early Dark Energy fluctuations in the linear and non-linear regimes of structure formation. In these models the energy density of dark energy is non-negligible at high redshifts and the fluctuations in the dark energy component can have the same order of magnitude of dark matter fluctuations. Since two basic approximations usually taken in the standard scenario of quintessence models, that both dark energy density during the matter dominated period and dark energy fluctuations on small scales are negligible, are not valid in such models, we first study approximate analytical solutions for dark matter and dark energy perturbations in the linear regime. This study is helpful to find consistent initial conditions for the system of equations and to analytically understand the effects of Early Dark Energy and its fluctuations, which are also verified numerically. In the linear regime we compute the matter growth and variation of the gravitational potential associated with the Integrated Sach...

Batista, R C

2013-01-01T23:59:59.000Z

144

Dark Energy from Brane-world Gravity  

E-Print Network (OSTI)

Summary. Recent observations provide strong evidence that the universe is accelerating. This confronts theory with a severe challenge. Explanations of the acceleration within the framework of general relativity are plagued by difficulties. General relativistic models require a “dark energy ” field with effectively negative pressure. An alternative to dark energy is that gravity itself may behave differently from general relativity on the largest scales, in such a way as to produce acceleration. The alternative approach of modified gravity also faces severe difficulties, but does provide a new angle on the problem. This review considers an example of modified gravity, provided by brane-world models that self-accelerate at late times. 1 1

Roy Maartens

2006-01-01T23:59:59.000Z

145

A New Generalized Chaplygin Gas as a Scheme for Unification of Dark Energy and Dark Matter  

E-Print Network (OSTI)

We propose a new model for the description of unification of dark energy and dark matter, dubbed new generalized Chaplygin gas (NGCG) model. We study the cosmological scenario arising from the dynamics of this new generalized Chaplygin gas. The equation of state of the system is given by p = ?A(a)/? ?, where a is the scale factor and 0 dark matter decays to dark energy. From this scenario, the origin of the ”intermediate regime” (p = ?wX??) is clarified and the production mechanism of the acoustics is illustrated. 1 Recently, a kind of description for unification of dark energy and dark matter, the so called generalized Chaplygin gas(GCG), was proposed for understanding the observed accelerated expansion of the universe [1,2]. The scenario of this model is that dark energy and dark matter are different aspects of a single exotic substance permeated in the whole

Xin Zhang

2004-01-01T23:59:59.000Z

146

The Higgs portal and an unified model for dark energy and dark matter  

E-Print Network (OSTI)

We examine a scenario where the Higgs boson is coupled to an additional singlet scalar field which we identify with a quintessence field. We show that this results in an unified picture of dark matter and dark energy, where dark energy is the zero-mode classical field rolling the usual quintessence potential and the dark matter candidate is the quantum excitation (particle) of the field, which is produced in the universe due to its coupling to the Higgs boson.

O. Bertolami; R. Rosenfeld

2007-08-13T23:59:59.000Z

147

Viscous dark energy and generalized second law of thermodynamics  

E-Print Network (OSTI)

We examine the validity of the generalized second law of thermodynamics in a non-flat universe in the presence of viscous dark energy. At first we assume that the universe filled only with viscous dark energy. Then, we extend our study to the case where there is an interaction between viscous dark energy and pressureless dark matter. We examine the time evolution of the total entropy, including the entropy associated with the apparent horizon and the entropy of the viscous dark energy inside the apparent horizon. Our study show that the generalized second law of thermodynamics is always protected in a universe filled with interacting viscous dark energy and dark matter in a region enclosed by the apparent horizon. Finally, we show that the the generalized second law of thermodynamics is fulfilled for a universe filled with interacting viscous dark energy and dark matter in the sense that we take into account the Casimir effect.

M. R. Setare; A. Sheykhi

2011-03-05T23:59:59.000Z

148

Thermodynamical description of the interacting new agegraphic dark energy  

E-Print Network (OSTI)

We describe the thermodynamical interpretation of the interaction between new agegraphic dark energy and dark matter in a non-flat universe. When new agegraphic dark energy and dark matter evolve separately, each of them remains in thermodynamic equilibrium. As soon as an interaction between them is taken into account, their thermodynamical interpretation changes by a stable thermal fluctuation. We obtain a relation between the interaction term of the dark components and this thermal fluctuation.

A. Sheykhi; M. R. Setare

2009-12-08T23:59:59.000Z

149

arXiv:0706.2986v1[astro-ph]20Jun2007 DARK MATTER AND DARK ENERGY  

E-Print Network (OSTI)

arXiv:0706.2986v1[astro-ph]20Jun2007 DARK MATTER AND DARK ENERGY MARC KAMIONKOWSKI California, and/or the introduction of some negative-pressure "dark energy," again, the nature of which remains Press. kamion@tapir.caltech.edu 1 #12;Dark Matter and Dark Energy 2 eries may help us understand the new

Steidel, Chuck

150

A Brief History of Dark Energy  

E-Print Network (OSTI)

Gurzadyan-Xue Dark Energy was derived in 1986 (twenty years before the paper of Gurzadyan-Xue). The paper by the present author, titled The Planck Length as a Cosmological Constant, published in Astrophysics Space Science, Vol. 127, p.133-137, 1986 contains the formula claimed to have been derived by Gurzadyan-Xue (in 2003).

C Sivaram

2008-09-19T23:59:59.000Z

151

A Brief History of Dark Energy  

E-Print Network (OSTI)

Gurzadyan-Xue Dark Energy was derived in 1986 (twenty years before the paper of Gurzadyan-Xue). The paper by the present author, titled The Planck Length as a Cosmological Constant, published in Astrophysics Space Science, Vol. 127, p.133-137, 1986 contains the formula claimed to have been derived by Gurzadyan-Xue (in 2003).

Sivaram, C

2008-01-01T23:59:59.000Z

152

An introduction to the dark energy problem  

E-Print Network (OSTI)

In this work we review briefly the origin and history of the cosmological constant and its recent reincarnation in the form of the dark energy component of the universe. We also comment on the fundamental problems associated to its existence and magnitude which require and urgent solution for the sake of the internal consistency of theoretical physics.

Antonio Dobado; Antonio L. Maroto

2008-02-13T23:59:59.000Z

153

Using Newton's Law for Dark Energy  

E-Print Network (OSTI)

A model is introduced in which Newton's law is modified between matter and dark energy corpuscles (DECs). The model predicts that the DEC component is presently decelerating in its expansion at 14% of the magnitude of the matter expansion acceleration. In the future, expansion of the DEC universe will continue to decelerate.

Paul Frampton

2012-09-24T23:59:59.000Z

154

Testable and Untestable Aspects of Dark Energy  

E-Print Network (OSTI)

It has been suggested that dark energy will lead to a frequency cut-off in an experiment involving a Josephson junction. Here we show that were such a cut-off detected, it would have dramatic consequences including the possible demise of the string landscape.

Paul H. Frampton

2005-08-11T23:59:59.000Z

155

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

156

Collapse Dynamics of a Star of Dark Matter and Dark Energy  

E-Print Network (OSTI)

In this work, we study the collapse dynamics of an inhomogeneous spherically symmetric star made of dark matter (DM) and dark energy (DE). The dark matter is taken in the form of a dust cloud while anisotropic fluid is chosen as the candidate for dark energy. It is investigated how dark energy modifies the collapsing process and is examined whether dark energy has any effect on the Cosmic Censorship Conjecture. The collapsing star is assumed to be of finite radius and the space time is divided into three distinct regions $\\Sigma$ and $V^{\\pm}$, where $\\Sigma$ represents the boundary of the star and $V^{-}(V^{+})$ denotes the interior (exterior) of the star. The junction conditions for matching $V^{\\pm}$ over $\\Sigma$ are specified. Role of Dark energy in the formation of apparent horizon is studied and central singularity is analyzed.

Subenoy Chakraborty; Tanwi Bandyopadhyay

2006-09-12T23:59:59.000Z

157

Dark Energy in Perturbative String Cosmology  

E-Print Network (OSTI)

The apparent observation of dark energy poses problems for string theory. In de Sitter space, or in quintessence models, one cannot define a gauge-invariant S-matrix. We argue that eternal quintessence does not arise in weakly coupled string theory, but point out that it is difficult to define an $S$-matrix even in the presence of perturbative potentials for the moduli. The solutions of the Fischler-Susskind equations all have Big Bang or Big Crunch Singularities. We believe that an S-matrix (or S-vector) exists in this context but cannot be calculated by purely perturbative methods. We study the possibility of metastable de Sitter vacua in such weakly coupled scenarios, and conclude that the S-matrix of the extreme weak coupling region cannot probe de Sitter physics. We also consider proposed explanations of the dark energy from the perspective of string theory, and find that most are implausible. We note that it is possible that the axion constitutes both the dark matter and the dark energy.

Tom Banks; Michael Dine

2001-06-28T23:59:59.000Z

158

QED Vacuum Loops and Dark Energy  

E-Print Network (OSTI)

A QED--based "bootstrap" mechanism is suggested as an explanation for the vacuum energy that furnished the initial impulse for Inflation, and continues on to provide present day Dark Energy. Virtual vacuum fluctuations are assumed to generate effective electromagnetic fields whose average value corresponds to an effective c--number $A_{\\mu}^{\\rm vac}(x)$, which is itself equal to the vacuum expectation value of the operator $A_{\\mu}(x)$ in the presence of that $A_{\\mu}^{\\rm vac}(x)$. Lorentz invariance is manifest, as every observer would measure the same electric field in his or her own reference frame. The model has one arbitrary parameter $\\xi$, and fits the energy density of present day Dark Energy for $\\xi\\sim O(1)$.

Fried, H M

2013-01-01T23:59:59.000Z

159

On the similarity of Information Energy to Dark Energy  

E-Print Network (OSTI)

Information energy is shown here to have properties similar to those of dark energy. The energy associated with each information bit of the universe is found to be defined identically to the characteristic energy of a cosmological constant. Two independent methods are used to estimate the universe information content of ~10^91 bits, a value that provides an information energy total comparable to that of the dark energy. Information energy is also found to have a significantly negative equation of state parameter, w energy.

M. P. Gough; T. D. Carozzi; A. M. Buckley

2006-03-03T23:59:59.000Z

160

Holographic Dark Energy Model with Modified Variable Chaplygin Gas  

E-Print Network (OSTI)

In this letter we consider a correspondence between holographic dark energy and variable modified Chaplygin gas to obtain a holographic dark energy model of the universe. The corresponding potential of the scalar field has been reconstructed which describes the modified variable Chaplygin gas. The stability of the holographic dark energy in this case is also discussed.

B. C. Paul

2010-06-17T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Loop Quantum Corrections to Statefinder Parameters of Dark Energy  

E-Print Network (OSTI)

In this short letter, we presented the explicit forms of the statefinder parameters for the Friedmann-Robertson-Walker (FRW) Universe in the loop quantum cosmology (LQC) for Holographic dark energy and New-Agegraphic dark energy. Numerically we investigated cosmological implications of these parameters for models of dark energy.

Jamil, Mubasher; Myrzakulov, Ratbay

2013-01-01T23:59:59.000Z

162

Loop Quantum Corrections to Statefinder Parameters of Dark Energy  

E-Print Network (OSTI)

In this short letter, we presented the explicit forms of the statefinder parameters for the Friedmann-Robertson-Walker (FRW) Universe in the loop quantum cosmology (LQC) for Holographic dark energy and New-Agegraphic dark energy. Numerically we investigated cosmological implications of these parameters for models of dark energy.

Mubasher Jamil; D. Momeni; Ratbay Myrzakulov

2013-05-17T23:59:59.000Z

163

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.

164

Discriminating between models for the dark energy Duane A. Dicus  

E-Print Network (OSTI)

Discriminating between models for the dark energy Duane A. Dicus Center for Particle Physics a substantial dark energy component, which is usually interpreted in terms of a cosmological constant. Here we examine how much the form of this dark energy can be modified while still retaining an acceptable fit

Repko, Wayne

165

Dark Energy from Quantum Uncertainty of Simultaneity  

E-Print Network (OSTI)

The observed acceleration expansion of the universe was thought attribute to a mysterious dark energy in the framework of the classical general relativity. The dark energy behaves very similar with a vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a wrong order of the vacuum energy and leads to a severe fine-tuning, known as the cosmological constant problem. We abandon the standard interpretation that time is a global parameter in quantum mechanics, replace it by a quantum dynamical variable playing the role of an operational quantum clock system. In the framework of reinterpretation of time, we find that the synchronization of two quantum clocks distance apart can not be realized in all rigor at quantum level. Thus leading to an intrinsic quantum uncertainty of simultaneity between spatial interval, which implies a visional vacuum energy fluctuation and gives an observed dark energy density $\\rho_{de}=\\frac{6}{\\pi}L_{P}^{-2}L_{H}^{-2}$, whe...

Luo, M J

2014-01-01T23:59:59.000Z

166

Dark Matter and Dark Energy as Effects of Quantum Gravity  

E-Print Network (OSTI)

I present a theory of quantum gravity based on the principle of gravitational energy fluctuations. Gravitational energy fluctuations -- gravitons -- are responsible for elastic scattering of subatomic particles. Such scattering corresponds to complimentary force -- graviton scattering force -- arising in gravitational interaction in addition to Newtonian gravity. The strength of the graviton scattering force is proportional to the graviton scattering probability. Unlike Newtonian gravity the graviton scattering force follows the 1/r law and dominates the former on cosmological scale in the limit of low orbital accelerations. Similarly to Modified Newtonian Dynamics the quantum gravity accounts for variations in observed M/L ratios of diverse stellar systems ranging from dwarf spheroid galaxies to X-ray galaxy clusters without requiring an invisible matter (which is still required by MOND in X-Ray cluster cores). Unlike MOND the presented theory neither violates cornerstone Newton Laws nor suffers from the ambiguity of acceleration frames while enjoying vast experimental evidence usually cited in favor of MOND. To ascertain the validity of the presented theory I have examined the predictions of quantum gravity for dwarf spheroid, ordinary and giant elliptic galaxies, and X-ray clusters. In all cases quantum gravity yields M/L ratios and scaling relations consistent with observations. Quantum gravity accounts for the tilt of the Fundamental Plane of elliptical galaxies erasing the differences in M/L vs. luminosity relations for faint and bright ellipticals, which cannot be easily explained by CDM model. Lastly, by analyzing the behavior of the gravitational energy fluctuations in the limit of high matter density expected in the early Universe I show that primordial inflation and dark energy (i.e. non-zero cosmological constant) arise as natural effects of quantum gravity in the expanding Universe.

Max I. Fomitchev

2010-09-07T23:59:59.000Z

167

Statefinder Diagnostic for Dark Energy Models in Bianchi I Universe  

E-Print Network (OSTI)

In this paper, we investigate the statefinder, the deceleration and equation of state parameters when universe is composed of generalized holographic dark energy or generalized Ricci dark energy for Bianchi I universe model. These parameters are found for both interacting as well as non-interacting scenarios of generalized holographic or generalized Ricci dark energy with dark matter and generalized Chaplygin gas. We explore these parameters graphically for different situations. It is concluded that these models represent accelerated expansion of the universe.

M. Sharif; Rabia Saleem

2013-08-29T23:59:59.000Z

168

Presence of Dark Energy and Dark Matter : Does Cosmic Acceleration signifies a Weak Gravitational collapse?  

E-Print Network (OSTI)

In this work the collapsing process of a spherically symmetric star, made of dust cloud, in the background of dark energy is studied for two different gravity theories separately, i.e., DGP Brane gravity and Loop Quantum gravity. Two types of dark energy fluids, namely, Modified Chaplygin gas and Generalised Cosmic Chaplygin gas are considered for each model. Graphs are drawn to characterize the nature and the probable outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different gravity theories. It is found that in case of dark matter, there is a great possibility of collapse and consequent formation of Black hole. In case of dark energy possibility of collapse is far lesser compared to the other cases, due to the large negative pressure of dark energy component. There is an increase in mass of the cloud in case of dark matter collapse due to matter accumulation. The mass decreases considerably in case of dark energy due to dark energy accretion on the cloud. In case of collapse with a combination of dark energy and dark matter, it is found that in the absence of interaction there is a far better possibility of formation of black hole in DGP brane model compared to Loop quantum cosmology model.

Prabir Rudra; Ritabrata Biswas; Ujjal Debnath

2012-04-03T23:59:59.000Z

169

A Dynamic Dark Information Energy Consistent with Planck Data  

E-Print Network (OSTI)

The 2013 cosmology results from the European Space Agency Planck spacecraft provide new limits to the dark energy equation of state parameter. Planck data was combined with other astrophysical measurements, with two dataset combinations compatible with the cosmological constant explanation for dark energy, while another two dataset combinations show dark energy to be dynamic at the 2 sigma level. Here we show that Holographic Dark Information Energy (HDIE), a dynamic dark energy explanation, achieves a better, near optimal fit to both groups of Planck data combinations. HDIE uses Landauer's principle to account for today's dark energy value by the energy equivalence of the information, or entropy, of stellar heated gas and dust. Combining Landauer's principle with the Holographic principle yields a dark energy equation of state parameter determined solely by star formation history, allowing us to solve the 'cosmic coincidence problem'.

Gough, Michael Paul

2013-01-01T23:59:59.000Z

170

How to Distinguish Dark Energy and Modified Gravity?  

E-Print Network (OSTI)

The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification to general relativity (modified gravity). It is proposed in literature that combining the probes of cosmic expansion history and growth history can distinguish between dark energy and modified gravity. In the present work, we show that the possible interaction between dark energy and dark matter could make interacting dark energy model and modified gravity model indistinguishable. An explicit example is also given. Therefore, it is required to seek some complementary probes beyond the ones of cosmic expansion history and growth history.

Wei, Hao

2008-01-01T23:59:59.000Z

171

The physics and identity of dark energy  

E-Print Network (OSTI)

This paper may solve the dark-energy problem because our universe is not alone, and the multiverse is a powerful part of the cosmos. The decay of our aging universe is reviewed first. The accelerated expansion takes the decay debris into the inter-universal medium (IUM) of the multiverse for conservation. A prominent component of the debris and of the IUM is the enormous number of old cold photons from decaying universes. When a small central volume (apparently 6.4 percent of the total mass) of our proto-universe reached proton density, the old photons and protons became fully re-energized. Outside of that volume, the large numbers of remaining old photons continued their acceleration and the expansion of our universe. The accretion and expansion are described a second time with what we know of dark energy, particularly its acceleration of the expansion of our universe. Identical results are obtained; in fact, the two descriptions are complementary, and the conclusion is therefore made that dark energy is the acceleration energy of old photons. The model is supported by 30 observations and considerations for future work.

Tom Gehrels

2011-01-03T23:59:59.000Z

172

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

173

Virialization-induced curvature versus dark energy  

E-Print Network (OSTI)

The concordance model is successful in explaining numerous observable phenomena at the price of introducing an exotic source of unknown origin: dark energy. Dark energy dominance occurs at recent epochs, when we expect most cosmological structures to have already formed, and thus, when the error induced by forcing the homogeneous FLRW metric onto the data is expected to be the most significant. We propose a way to quantify the impact of deviations from homogeneity on the evolution of cosmological parameters. Using a multi-scale partitioning approach and the virialization fraction estimated from numerical simulations in an Einstein-de Sitter model, we obtain an observationally realistic distance modulus over redshifts 0 < z < 3 by a relativistic correction of the FLRW metric.

Ostrowski, Jan J; Buchert, Thomas

2013-01-01T23:59:59.000Z

174

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

175

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1  

E-Print Network (OSTI)

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1 Submitted March 12th , 2004 ABSTRACT I present a theory of quantum gravity based on the principle of gravitational energy fluctuations. Gravitational energy fluctuations ­ gravitons ­ are responsible for elastic scattering

Giles, C. Lee

176

New physics at low energies and dark matter-dark energy transmutation  

E-Print Network (OSTI)

A field theory is proposed where the regular fermionic matter and the dark fermionic matter can be different states of the same "primordial" fermion fields. In regime of the fermion densities typical for normal particle physics, the primordial fermions split into three families identified with regular fermions. When fermion energy density becomes comparable with dark energy density, the theory allows transition to new type of states. The possibility of such Cosmo-Low Energy Physics (CLEP) states is demonstrated by means of solutions of the field theory equations describing FRW universe filled with homogeneous scalar field and uniformly distributed nonrelativistic neutrinos. Neutrinos in CLEP state are drawn into cosmological expansion by means of dynamically changing their own parameters. One of the features of the fermions in CLEP state is that in the late time universe their masses increase as a^{3/2} (a=a(t) is the scale factor). The energy density of the cold dark matter consisting of neutrinos in CLEP state scales as a sort of dark energy; this cold dark matter possesses negative pressure and for the late time universe its equation of state approaches that of the cosmological constant. The total energy density of such universe is less than it would be in the universe free of fermionic matter at all.

E. I. Guendelman; A. B. Kaganovich

2004-04-14T23:59:59.000Z

177

Dark Energy and Search for the Generalized Second Law  

E-Print Network (OSTI)

The discovery of accelerated Hubble expansion in the SNIa data and the observed power spectrum of the microwave background radiation provide an ample support for Dark energy and Dark matter. Except for the so far well-known facts that cold dark matter (or simply dark matter) is pressureless, and dark energy has a negative pressure, the nature of these two still remains a complete mystery. The mystery facilitates different consideration. In one hand, dark matter and dark energy are assumed as distinct entities, and other interpretation is that both are different manifestation of a common structure, often referred as quartessence. Chaplygin gas, a perfect fluid also favours the second interpretation. Here, we consider modified chaplygin gas as dark energy candidate. Taking into account the existence of the observer's event horizon in accelerated universe, we find the condition where the generalized second law of gravitational thermodynamics is valid and the positivity of the temperature of the phantom fluid remains intact.

Balendra Kr. Dev Choudhury; Julie Saikia

2009-06-03T23:59:59.000Z

178

Holographic Ricci dark energy and generalized second law  

E-Print Network (OSTI)

We explore the validity of the generalized second law (GSL) of thermodynamics in flat FRW universe with apparent horizon and event horizon as the boundary. We found that in a universe with holographic Ricci dark energy and dark matter, interacting with each other, the GSL is satisfied at the apparent horizon and partially satisfied at the event horizon under thermal equilibrium conditions. We also analyses the GSL under non-equilibrium conditions and shows that the fulfillment of GSL at the apparent horizon implies that the temperature of the dark energy is greater than that of the horizon. Thus there occurs a flow of dark energy towards the apparent horizon. As a result the entropy of the dark energy decreases and that of horizon increases. This is verified by finding the evolution of the dark energy entropy and horizon entropy in a dark energy dominated universe under non-equilibrium conditions.

Titus K Mathew; P. Praseetha

2013-11-19T23:59:59.000Z

179

Observational constraints on holographic tachyonic dark energy in interaction with dark matter  

E-Print Network (OSTI)

We discuss an interacting tachyonic dark energy model in the context of the holographic principle. The potential of the holographic tachyon field in interaction with dark matter is constructed. The model results are compared with CMB shift parameter, baryonic acoustic oscilations, lookback time and the Constitution supernovae sample. The coupling constant of the model is compatible with zero, but dark energy is not given by a cosmological constant.

Sandro M. R. Micheletti

2009-12-20T23:59:59.000Z

180

Gravitational collapse due to dark matter and dark energy in the brane world scenario  

E-Print Network (OSTI)

Gravitational collapse of FRW brane world embedded in a conformaly flat bulk is considered for matter cloud consists of dark matter and dark energy with equation of state $p=\\epsilon \\rho$ $(\\epsilondark matter and dark energy is being considered first separately and then a combination of them both with and without interaction. In some cases the collapse leads to black hole in some other cases naked singularity appears.

Soma Nath; Subenoy Chakraborty; Ujjal Debnath

2005-12-21T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

A Laboratory Search for Dark Energy  

E-Print Network (OSTI)

The discovery of the accelerating universe indicates strongly the presence of a scalar field which is not only expected to solve today's version of the cosmological constant problem, or the fine-tuning and the coincidence problems, but also provides a way to understand dark energy. It has also been shown that Jordan's scalar-tensor theory is now going to be re-discovered in the new lights. In this letter we suggest a way to search for the extremely light scalar field by means of a laboratory experiment on the low-energy photon-photon interactions with the quasi-parallel incident beams.

Yasunori Fujii; Kensuke Homma

2009-12-28T23:59:59.000Z

182

The Localized Energy Distribution of Dark Energy Star Solutions  

E-Print Network (OSTI)

We examine the question of energy localization for an exact solution of Einstein's equations with a scalar field corresponding to the phantom energy interpretation of dark energy. We apply three different energy-momentum complexes, the Einstein, Papapetrou and M{\\o}ller prescriptions, to the exterior metric and determine the energy distribution for each. Comparing the results, we find that the three prescriptions yield identical energy distributions.

Paul Halpern; Michael Pecorino

2013-03-05T23:59:59.000Z

183

The Localized Energy Distribution of Dark Energy Star Solutions  

E-Print Network (OSTI)

We examine the question of energy localization for an exact solution of Einstein's equations with a scalar field corresponding to the phantom energy interpretation of dark energy. We apply three different energy-momentum complexes, the Einstein, Papapetrou and M{\\o}ller prescriptions, to the exterior metric and determine the energy distribution for each. Comparing the results, we find that the three prescriptions yield identical energy distributions.

Halpern, Paul

2013-01-01T23:59:59.000Z

184

Energy Sharing in the 2-Electron Attosecond Streak Camera  

E-Print Network (OSTI)

Using the recently developed concept of the 2-electron streak camera (see NJP 12, 103024 (2010)), we have studied the energy-sharing between the two ionizing electrons in single-photon double ionization of He(1s2s). We find that the most symmetric and asymmetric energy sharings correspond to different ionization dynamics with the ion's Coulomb potential significantly influencing the latter. This different dynamics for the two extreme energy sharings gives rise to different patterns in asymptotic observables and different time-delays between the emission of the two electrons. We show that the 2-electron streak camera resolves the time-delays between the emission of the two electrons for different energy sharings.

Price, H; Emmanouilidou, A

2011-01-01T23:59:59.000Z

185

Little Rip and Pseudo Rip Phenomena from Coupled Dark Energy  

E-Print Network (OSTI)

We consider Little Rip (LR) and Pseudo Rip (PR) cosmological models with two interacting ideal fluids, corresponding to dark energy and dark matter. The interaction between the dark energy and the dark matter fluid components is described in terms of the parameters in the equations of state for the LR and PR universes. In contrast to a model containing only a pure dark energy, the presence of the interaction term between the fluid components in the gravitational equations leads to a modification of the equation of state parameters. The properties of the early universe in this formalism are pointed out.

I. Brevik; A. V. Timoshkin; Y. Rabochaya

2013-11-21T23:59:59.000Z

186

Dark Energy as the Remnant of Inflation  

E-Print Network (OSTI)

A QED-based symmetry breaking/bootstrap mechanism, appearing at sufficiently small space-time distances, is suggested as an explanation for the vacuum energy that furnished the initial impulse for Inflation, and continues on, to the present day, to provide the "Dark Energy" which is apparently forcing our Universe apart. Very high frequency virtual vacuum currents are assumed to generate weak, effective electromagnetic fields, corresponding to the appearance of an effective 4-potential A_vac (x), which is itself equal to the vacuum expectation value of the operator A(x) in the presence of that A_vac (x). Lorentz invariance is manifest, as every observer would measure the same electric field in his or her own reference frame. Such an effective vacuum field would have no relevance to the motion of ordinary charged particules until particle energies on the order of 10^5 TeV are possible. The model is sufficiently constrained so that one parameter is needed to fit the vacuum energy densities and relevant times for the onset and end of Inflation, as well as those parameters of present day Dark Energy.

H. M. Fried; Y. Gabellini

2011-11-16T23:59:59.000Z

187

Understanding the Fundamental Properties of Dark Matter & Dark Energy in Structure formation and Cosmology  

Science Conference Proceedings (OSTI)

This program is concerned with developing and verifying the validityof observational methods for constraining the properties of dark matter and dark energy in the universe. Excellent progress has been made in comparing observational projects involving weak gravitational lensing using both ground and space-based instruments, in further constraining the nature of dark matter via precise measures of its distribution in clusters of galaxies using strong gravitational lensing, in demonstrating the possible limitations of using distant supernovae in future dark energy missions, and in investigating the requirement for ground-based surveys of baryonic acoustic oscillations.

Ellis, Richard, S.

2008-02-01T23:59:59.000Z

188

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

189

The Dark Energy and the Fate of Universe  

E-Print Network (OSTI)

Recent observations confirm that our universe is flat and consists of a dark energy component $\\Omega_{DE}\\simeq 0.7$. This dark energy is responsible for the cosmic acceleration as well as determines the feature of future evolution of the universe. In this paper, we discuss the dark energy of universe in the framework of scalar-tensor cosmology. It is shown that the dark energy is the main part of the energy density of the gravitational scalar field and the future universe will expand as $a(t)\\sim t^{1.3}$.

Mian Wang

2003-11-28T23:59:59.000Z

190

On the growth of perturbations in interacting dark energy and dark matter fluids  

E-Print Network (OSTI)

The covariant generalizations of the background dark sector coupling suggested in G. Mangano, G. Miele and V. Pettorino, Mod. Phys. Lett. A 18, 831 (2003) are considered. The evolution of perturbations is studied with detailed attention to interaction rate that is proportional to the product of dark matter and dark energy densities. It is shown that some classes of models with coupling of this type do not suffer from early time instabilities in strong coupling regime.

N. A. Koshelev

2009-12-01T23:59:59.000Z

191

Dark energy interacting with neutrinos and dark matter: a phenomenological theory  

E-Print Network (OSTI)

A model for a flat homogeneous and isotropic Universe composed of dark energy, dark matter, neutrinos, radiation and baryons is analyzed. The fields of dark matter and neutrinos are supposed to interact with the dark energy. The dark energy is considered to obey either the van der Waals or the Chaplygin equations of state. The ratio between the pressure and the energy density of the neutrinos varies with the red-shift simulating massive and non-relativistic neutrinos at small red-shifts and non-massive relativistic neutrinos at high red-shifts. The model can reproduce the expected red-shift behaviors of the deceleration parameter and of the density parameters of each constituent. The recent astronomical measurements of type-IA supernovae [1, 2, 3, 4] and the analysis of the power spectrum of the CMBR [5, 6, 7, 8, 9] provided strong evidence for a present accelerated

G. M. Kremer

2008-01-01T23:59:59.000Z

192

Can the Existence of Dark Energy be Directly Detected?  

SciTech Connect

The majority of astronomers and physicists accept the reality of dark energy and also believe that it can only be studied indirectly through observation of the motions of stars and galaxies. In this paper I open the experimental question of whether it is possible to directly detect dark energy through the presence of dark energy density. Two thirds of this paper outlines the major aspects of dark energy density as now comprehended by the astronomical and physics community. The final third summarizes various proposals for direct detection of dark energy density or its possible effects. At this time I do not have a fruitful answer to the question: Can the Existence of Dark Energy Be Directly Detected?

Perl, Martin L.; /SLAC /KIPAC, Menlo Park

2011-11-23T23:59:59.000Z

193

Conformal Higgs model of dark energy  

E-Print Network (OSTI)

Postulating conformal Weyl scaling symmetry for all fundamental fields affects both gravitational and electroweak theory. A conformal Higgs scalar field determines a modified Friedmann cosmic evolution equation. Tachyonic mass parameter $w^2$ becomes a cosmological constant in this equation. An integrated solution fits consensus Hubble expansion data within empirical error. The time derivative of gravitational Ricci scalar $R$ couples scalar and gauge fields. This determines $w^2$ while retaining the Higgs mechanism for gauge boson masses. A simplified calculation obtains dark energy Friedmann weight in order-of-magnitude agreement with its empirical value. The theory predicts variaetion of the Higgs scalar field on a cosmological time scale.

R. K. Nesbet

2010-04-28T23:59:59.000Z

194

Could Dark Matter Interactions be an Alternative to Dark Energy ?  

E-Print Network (OSTI)

We study the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, which can accommodate an accelerated expansion, equivalent to either the {\\em quintessence} or the standard $\\Lambda$ models, with the present time located after the inflection point. This is possible if there is a disequilibrium between the DM particle creation and annihilation processes with the former process dominating, which creates an effective source term with negative pressure. Comparing the predicted Hubble expansion of one of the IDM models (the simplest) with observational data we find that the effective annihilation term is quite small, as suggested by a variety of other recent experiments.

S. Basilakos; M. Plionis

2008-07-29T23:59:59.000Z

195

Interacting Dark Energy and the Cosmic Coincidence Problem  

E-Print Network (OSTI)

The introduction of an interaction for dark energy to the standard cosmology offers a potential solution to the cosmic coincidence problem. We examine the conditions on the dark energy density that must be satisfied for this scenario to be realized. Under some general conditions we find a stable attractor for the evolution of the Universe in the future. Holographic conjectures for the dark energy offer some specific examples of models with the desired properties.

Micheal S. Berger; Hamed Shojaei

2006-01-20T23:59:59.000Z

196

Ricci Dark Energy in Brans-Dicke theory  

E-Print Network (OSTI)

A holographic dark energy from Ricci scalar curvature called Ricci dark energy was proposed recently. In this model the future event horizon area is replaced by the inverse of the Ricci scalar curvature. We study the evolution of equation of state of the Ricci dark energy and the transition from decelerated to accelerated expansion of the universe in the Brans-Dicke theory, which is a natural extension of general relativity. We find that the current acceleration of our universe is well explained.

Chao-Jun Feng

2008-06-04T23:59:59.000Z

197

A Modified Generalized Chaplygin Gas as the Unified Dark Matter-Dark Energy Revisited  

E-Print Network (OSTI)

A modified generalized Chaplygin gas (MGCG) is considered as the unified dark matter-dark energy revisited. The character of MGCG is endued with the dual role, which behaves as matter at early times and as an quiessence dark energy at late times. The equation of state for MGCG is $p=-\\alpha\\rho/(1+\\alpha)-\\vartheta(z)\\rho^{-\\alpha}/(1+\\alpha) $, where $\\vartheta(z)=-[\\rho_{0c}(1+z)^{3}]^{(1+\\alpha)}(1-\\Omega_{0B})^{\\alpha}\\{\\alpha\\Omega_{0DM}+ \\Omega_{0DE}[\\omega_{DE}+\\alpha(1+\\omega_{DE})](1+z)^{3\\omega_{DE}(1+\\alpha)}\\}$. Some cosmological quantities, such as the densities of different components of the universe $\\Omega_{i}$ ($i$ respectively denotes baryons, dark matter and dark energy) and the deceleration parameter $q$, are obtained. The present deceleration parameter $q_{0}$, the transition redshift $z_{T}$ and the redshift $z_{eq}$, which describes the epoch when the densities in dark matter and dark energy are equal, are also calculated. To distinguish MGCG from others, we then apply the Statefinder diagnostic. Later on, the parameters ($\\alpha$ and $\\omega_{DE}$) of MGCG are constrained by combination of the sound speed $c^{2}_{s}$, the age of the universe $t_{0}$, the growth factor $m$ and the bias parameter $b$. It yields $\\alpha=-3.07^{+5.66}_{-4.98}\\times10^{-2}$ and $\\omega_{DE}=-1.05^{+0.06}_{-0.11}$. Through the analysis of the growth of density perturbations for MGCG, it is found that the energy will transfer from dark matter to dark energy which reach equal at $z_{eq}\\sim 0.48$ and the density fluctuations start deviating from the linear behavior at $z\\sim 0.25$ caused by the dominance of dark energy.

Xue-Mei Deng

2011-10-10T23:59:59.000Z

198

Holographic Dark Energy Model with Modified Generalized Chaplygin Gas  

E-Print Network (OSTI)

We present a holographic dark energy model of the universe considering modified generalized Chaplygin gas (GCG). The modified GCG behaves as an ordinary barotropic fluid in the early epoch when the universe was tiny but behaves subsequently as a $\\Lambda$CDM model at late epoch. An equivalent model with scalar field is obtained here by constructing the corresponding potential. The holographic dark energy is identified with the modified GCG and we determine the corresponding holographic dark energy field and its potential. The stability of the holographic dark energy in this case is also discussed.

B. C. Paul; P. Thakur; A. Saha

2007-07-31T23:59:59.000Z

199

Cosmic age problem revisited in the holographic dark energy model  

E-Print Network (OSTI)

Because of an old quasar APM 08279 + 5255 at $z=3.91$, some dark energy models face the challenge of the cosmic age problem. It has been shown by Wei and Zhang [Phys. Rev. D {\\bf 76}, 063003 (2007)] that the holographic dark energy model is also troubled with such a cosmic age problem. In order to accommodate this old quasar and solve the age problem, we propose in this paper to consider the interacting holographic dark energy in a non-flat universe. We show that the cosmic age problem can be eliminated when the interaction and spatial curvature are both involved in the holographic dark energy model.

Cui, Jinglei

2010-01-01T23:59:59.000Z

200

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...

Note: This page contains sample records for the topic "dark energy camera" 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

Parametrization of Born-Infeld Type Phantom Dark Energy Model  

E-Print Network (OSTI)

Applying the parametrization of dark energy density, we can construct directly independent-model potentials. In Born-Infeld type phantom dark energy model, we consider four special parametrization equation of state parameter. The evolutive behavior of dark energy density with respect to red-shift $z$, potentials with respect to $\\phi$ and $z$ are shown mathematically. Moreover, we investigate the effect of parameter $\\eta$ upon the evolution of the constructed potential with respect to $z$. These results show that the evolutive behavior of constructed Born-Infeld type dark energy model is quite different from those of the other models.

Z. G. Huang; H. Q. Lu; W. Fang

2009-05-07T23:59:59.000Z

202

Statefinder diagnosis and the interacting ghost model of dark energy  

E-Print Network (OSTI)

A new model of dark energy namely "ghost dark energy model" has recently been suggested to interpret the positive acceleration of cosmic expansion. The energy density of ghost dark energy is proportional to the hubble parameter. In this paper we perform the statefinder diagnostic tool for this model both in flat and non-flat universe. We discuss the dependency of the evolutionary trajectories in $s-r$ and $q-r$ planes on the interaction parameter between dark matter and dark energy as well as the spatial curvature parameter of the universe. Eventually, in the light of SNe+BAO+OHD+CMB observational data, we plot the evolutionary trajectories in $s-r$ and $q-r$ planes for the best fit values of the cosmological parameters and compare the interacting ghost model with other dynamical dark energy models. We show that the evolutionary trajectory of ghost dark energy in statefinder diagram is similar to holographic dark energy model. It has been shown that the statefinder location of $\\Lambda$CDM is in good agreement with observation and therefore the dark energy models whose current statefinder values are far from the $\\Lambda$CDM point can be ruled out.

M. Malekjani; A. Khodam-Mohammadi

2012-02-19T23:59:59.000Z

203

Optimizing New Dark Energy Experiments - Final Scientific Report  

Science Conference Proceedings (OSTI)

This is the final scientific report for the University of Pittsburgh portion of the collaborative grant, 'Optimizing New Dark Energy Experiments'

Jeffrey A. Newman

2012-06-08T23:59:59.000Z

204

Will multiple probes of dark energy find modified gravity?  

SciTech Connect

One of the most pressing issues in cosmology is whether general relativity (GR) plus a dark sector is the underlying physical theory or whether a modified gravity model is needed. Upcoming dark energy experiments designed to probe dark energy with multiple methods can address this question by comparing the results of the different methods in constraining dark energy parameters. Disagreement would signal the breakdown of the assumed model (GR plus dark energy). We study the power of this consistency test by projecting constraints in the w{sub 0}-w{sub a} plane from the four different techniques of the Dark Energy Survey in the event that the underlying true model is modified gravity. We find that the standard technique of looking for overlap has some shortcomings, and we propose an alternative, more powerful Multidimensional Consistency Test. We introduce the methodology for projecting whether a given experiment will be able to use this test to distinguish a modified gravity model from GR.

Shapiro, Charles [Institute of Cosmology and Gravitation, Portsmouth, PO1 3FX (United Kingdom); Dodelson, Scott [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637 (United States); Kavli Institute for Cosmological Physics, Chicago, Illinois 60637 (United States); Hoyle, Ben [Institut de Ciencies del Cosmos, Barcelona (Spain); Samushia, Lado [Institute of Cosmology and Gravitation, Portsmouth, PO1 3FX (United Kingdom); National Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Flaugher, Brenna [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

2010-08-15T23:59:59.000Z

205

Modified Gravitational Theory as an Alternative to Dark Energy and Dark Matter  

E-Print Network (OSTI)

The problem of explaining the acceleration of the expansion of the universe and the observational and theoretical difficulties associated with dark matter and dark energy are discussed. The possibility that Einstein gravity does not correctly describe the large-scale structure of the universe is considered and an alternative gravity theory is proposed as a possible resolution to the problems.

Moffat, J W

2004-01-01T23:59:59.000Z

206

From Dark Energy to Dark Matter via Non-Minimal Coupling  

E-Print Network (OSTI)

Toy cosmological models based on non-minimal coupling between gravity and scalar dilaton-like field are presented in the framework of Palatini formalism. They have the following property: preceding to a given cosmological epoch is a dark energy epoch with an accelerated expansion. The next (future) epoch becomes dominated by some kind of dark matter.

A. Borowiec

2008-12-23T23:59:59.000Z

207

A brief note on how to unify dark matter, dark energy, and inflation  

E-Print Network (OSTI)

A scenario in which inflation, dark energy and dark matter can be unified into a single scalar field, the inflaton field $\\phi$, is studied. The inflaton is identified with the sneutrino, the scalar partner of the heavy neutrino. We determine the conditions needed for avoiding the gravitino problem and not having negligible plasma effects and we obtain the allowed range for the sneutrino coupling.

Grigoris Panotopoulos

2007-06-15T23:59:59.000Z

208

Property:Description of Camera Types | Open Energy Information  

Open Energy Info (EERE)

Camera Types Camera Types Jump to: navigation, search Property Name Description of Camera Types Property Type Text Pages using the property "Description of Camera Types" Showing 25 pages using this property. (previous 25) (next 25) A Alden Large Flume + fully-submersible; multiplexor for four cameras; digital recording from all cameras; digital handheld Alden Small Flume + fully-submersible; multiplexor for four cameras; digital recording from all cameras; digital handheld Alden Tow Tank + Fully-submersible; multiplexor for four cameras; digital recording from all cameras; digital handheld Alden Wave Basin + Fully-submersible; multiplexor for four cameras; digital recording from all cameras; digital handheld C Conte Large Flume + Conventional underwater video, 4; high speed (1000 fps), 1

209

The Casimir effect as a candidate of dark energy  

E-Print Network (OSTI)

It is known that the simply evaluated value of the zero point energy of quantum fields is extremely deviated from the observed value of dark energy density. In this paper, we consider whether the Casimir energy, which is the zero point energy brought from boundary conditions, can cause the accelerated expansion of the Universe by using proper renormalization method and introducing the fermions of finite temperature living in $3+n+1$ space-time. We show that the zero temperature Casimir energy and the finite temperature Casimir energy can explain dark energy and dark matter, respectively.

Matsumoto, Jiro

2013-01-01T23:59:59.000Z

210

Statefinder Diagnostic for Born-Infeld Type Dark Energy Model  

E-Print Network (OSTI)

Using a new method--statefinder diagnostic which can differ one dark energy model from the others, we investigate in this letter the dynamics of Born-Infeld(B-I) type dark energy model. The evolutive trajectory of B-I type dark energy with Mexican hat potential model with respect to $e-folding$ time $N$ is shown in the $r(s)$ diagram. When the parameter of noncanonical kinetic energy term $\\eta\\to0$ or kinetic energy $\\dot{\\phi}^2\\to0$, B-I type dark energy(K-essence) model reduces to Quintessence model or $\\Lambda$CDM model corresponding to the statefinder pair $\\{r, s\\}$=$\\{1, 0\\}$ respectively. As a result, the the evolutive trajectory of our model in the $r(s)$ diagram in Mexican hat potential is quite different from those of other dark energy models.

Z. G. Huang; H. Q. Lu

2008-02-16T23:59:59.000Z

211

In the OSTI Collections: Dark Matter and Dark Energy | OSTI, US Dept of  

Office of Scientific and Technical Information (OSTI)

Dark Matter and Dark Energy Dark Matter and Dark Energy Recent observations of the universe, combined with Einstein's theory of general relativity, indicate that most of the universe consists of entities very different from the matter and energy long familiar to us. These previously unknown entities are beginning to be explored on several fronts, many through Department of Energy sponsorship. Albert Einstein's theory of relativity describes space and time as observer-dependent aspects of a single absolute entity (spacetime). According to the theory, just as a two-dimensional surface can be curved, four-dimensional spacetime is also curved, with the curvature at different places and times being partly determined by how matter (or equivalently, energy) is distributed within it. Where curvature is lacking, matter will

212

Generalized holographic dark energy model described at the Hubble length  

E-Print Network (OSTI)

We generalize the holographic dark energy model described in Hubble length IR cutoff by assuming a slowly time varying function for holographic parameter $c^2$. We calculate the evolution of EoS parameter and the deceleration parameter as well as the evolution of dark energy density in this generalized model. We show that the phantom line is crossed from quintessence regime to phantom regime which is in agreement with observation. The evolution of deceleration parameter indicates the transition from decelerated to accelerated expansion. Eventually, we show that the GHDE with HIR cutoff can interpret the pressureless dark matter era at the early time and dark energy dominated phase later.

M. Malekjani

2012-09-25T23:59:59.000Z

213

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

214

Dark Matter and Dark Energy from the solution of the strong CP problem  

E-Print Network (OSTI)

The Peccei Quinn (PQ) solution of the strong CP problem requires the existence of axions, which are a viable candidate for Dark Matter. Here we show that, if the Nambu Goldstone potential of the PQ model is replaced by a potential V(|\\Phi|) admitting a tracker solution, the scalar field |\\Phi| can account for Dark Energy, while the phase of \\Phi yields axion Dark Matter. Such Dark Matter and Dark Energy turn out to be weakly coupled. If V is a SUGRA potential, the model essentially depends on a single parameter, the energy scale \\Lambda. Once we set \\Lambda \\simeq 10^{10} GeV, at the quark--hadron transition, |\\Phi| naturally passes through values suitable to solve the strong CP problem, later growing to values providing fair amounts of Dark Matter and Dark Energy. In this model, the linear growth factor, from recombination to now, is quite close to \\LambdaCDM. The selected \\Lambda value can be an indication of the scale where the soft breaking of SUSY occurred.

Roberto Mainini; Silvio A. Bonometto

2004-06-04T23:59:59.000Z

215

Constraints on Dark Energy Models from Weak Gravity Conjecture  

E-Print Network (OSTI)

We study the constraints on the dark energy model with constant equation of state parameter $w=p/\\rho$ and the holographic dark energy model by using the weak gravity conjecture. The combination of weak gravity conjecture and the observational data gives $wenergy model realized by a scalar field is in swampland.

Chen, Ximing; Gong, Yungui

2008-01-01T23:59:59.000Z

216

Constraints on Dark Energy Models from Weak Gravity Conjecture  

E-Print Network (OSTI)

We study the constraints on the dark energy model with constant equation of state parameter $w=p/\\rho$ and the holographic dark energy model by using the weak gravity conjecture. The combination of weak gravity conjecture and the observational data gives $wenergy model realized by a scalar field is in swampland.

Ximing Chen; Jie Liu; Yungui Gong

2008-06-15T23:59:59.000Z

217

Evolution of the horizons for dark energy universe  

E-Print Network (OSTI)

Recent observational evidences of accelerating phase of the universe strongly demand that the dominating matter in the universe is in the form of dark energy. In this work, we study the evolution of the apparent and event horizons for various dark energy models and examine their behavior across phantom barrier line.

Ritabrata Biswas; Nairwita Mazumder; Subenoy Chakraborty

2011-06-12T23:59:59.000Z

218

Constraints on the interacting holographic dark energy model  

E-Print Network (OSTI)

We examined the interacting holographic dark energy model in a universe with spatial curvature. Using the near-flatness condition and requiring that the universe is experiencing an accelerated expansion, we have constrained the parameter space of the model and found that the model can accommodate a transition of the dark energy from $\\omega_D>-1$ to $\\omega_D<-1$.

Bin Wang; Chi-Yong Lin; Elcio Abdalla

2005-09-14T23:59:59.000Z

219

Reconstructing f(R) theory according to holographic dark energy  

E-Print Network (OSTI)

In this paper a connection between the holographic dark energy model and the $f(R)$ theory is established. We treat the $f(R)$ theory as an effective description for the holographic dark energy and reconstruct the function $f(R)$ with the parameter $c>1$, $c=1$ and $cR)$ theory, especially for the future evolution.

Xing Wu; Zong-Hong Zhu

2007-12-21T23:59:59.000Z

220

9/24/09 2:12 PMErasing Dark Energy SEEDMAGAZINE.COM Page 1 of 23http://seedmagazine.com/content/article/erasing_dark_energy/  

E-Print Network (OSTI)

9/24/09 2:12 PMErasing Dark Energy § SEEDMAGAZINE.COM Page 1 of 23http://seedmagazine.com/content/article/erasing_dark_energy » Follow us on Twitter » Erasing Dark Energy Wide Angle / by Veronique Greenwood / September 24, 2009 Why do we need dark energy to explain the observable universe? Two mathematicians propose an alternate

Temple, Blake

Note: This page contains sample records for the topic "dark energy camera" 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.


221

A Compact High Energy Camera for the Cherenkov Telescope Array  

E-Print Network (OSTI)

The Compact High Energy Camera (CHEC) is a camera-development project involving UK, US, Japanese and Dutch institutes for the dual-mirror Small-Sized Telescopes (SST-2M) of the Cherenkov Telescope Array (CTA). Two CHEC prototypes, based on different photosensors are funded and will be assembled and tested in the UK over the next ~18 months. CHEC is designed to record flashes of Cherenkov light lasting from a few to a hundred nanoseconds, with typical RMS image width and length of ~0.2 x 1.0 degrees, and has a 9 degree field of view. The physical camera geometry is dictated by the telescope optics: a curved focal surface with radius of curvature 1m and diameter ~35cm is required. CHEC is designed to work with both the ASTRI and GATE SST-2M telescope structures and will include an internal LED flasher system for calibration. The first CHEC prototype will be based on multi-anode photomultipliers (MAPMs) and the second on silicon photomultipliers (SiPMs or MPPCs). The first prototype will soon be installed on the...

Daniel, M K; Berge, D; Buckley, J; Chadwick, P M; Cotter, G; Funk, S; Greenshaw, T; Hidaka, N; Hinton, J; Lapington, J; Markoff, S; Moore, P; Nolan, S; Ohm, S; Okumura, A; Ross, D; Sapozhnikov, L; Schmoll, J; Sutcliffe, P; Sykes, J; Tajima, H; Varner, G S; Vandenbroucke, J; Vink, J; Williams, D

2013-01-01T23:59:59.000Z

222

Dark energy as an elastic strain fluid  

E-Print Network (OSTI)

The origin of the accelerated expansion of the universe is still unclear and new physics is needed on cosmological scales. We propose and test a novel interpretation of dark energy as originated by an elastic strain due to a cosmic defect in an otherwise Euclidean space-time. The strain modifies the expansion history of the universe. This new effective contribution tracks radiation at early times and mimics a cosmological constant at late times. The theory is tested against observations, from nucleosynthesis to the cosmic microwave background and formation and evolution of large scale structure to supernovae. Data are very well reproduced with Lam\\'e parameters of the order of 10^{-52} m^{-2}.

N. Radicella; M. Sereno; A. Tartaglia

2012-11-13T23:59:59.000Z

223

Thermodynamical picture of the interacting holographic dark energy model  

E-Print Network (OSTI)

In the present paper, we provide a thermodynamical interpretation for the holographic dark energy model in a non-flat universe. For this case, the characteristic length is no more the radius of the event horizon ($R_E$) but the event horizon radius as measured from the sphere of the horizon ($L$). Furthermore, when interaction between the dark components of the holographic dark energy model in the non-flat universe is present its thermodynamical interpretation changes by a stable thermal fluctuation. A relation between the interaction term of the dark components and this thermal fluctuation is obtained.

M R Setare

2009-02-24T23:59:59.000Z

224

Interacting holographic dark energy in Brans-Dicke theory  

E-Print Network (OSTI)

We study cosmological application of interacting holographic energy density in the framework of Brans-Dicke cosmology. We obtain the equation of state and the deceleration parameter of the holographic dark energy in a non-flat universe. As system's IR cutoff we choose the radius of the event horizon measured on the sphere of the horizon, defined as $L=ar(t)$. We find that the combination of Brans-Dicke field and holographic dark energy can accommodate $w_D = -1 $ crossing for the equation of state of \\textit{noninteracting} holographic dark energy. When an interaction between dark energy and dark matter is taken into account, the transition of $w_D$ to phantom regime can be more easily accounted for than when resort to the Einstein field equations is made.

Ahmad Sheykhi

2009-07-31T23:59:59.000Z

225

NASA and DOE Collaborate on Dark Energy Research | Department of Energy  

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

NASA and DOE Collaborate on Dark Energy Research NASA and DOE Collaborate on Dark Energy Research NASA and DOE Collaborate on Dark Energy Research November 19, 2008 - 4:58pm Addthis WASHINGTON, DC -- NASA and the U.S. Department of Energy (DOE) have signed a memorandum of understanding for the implementation of the Joint Dark Energy Mission, or JDEM. The mission will feature the first space-based observatory designed specifically to understand the nature of dark energy. Dark energy is a form of energy that pervades and dominates the universe. The mission will measure with high precision the universe's expansion rate and growth structure. Data from the mission could help scientists determine the properties of dark energy, fundamentally advancing physics and astronomy. "Understanding the nature of dark energy is the biggest challenge in

226

hep-th/0411025 Cosmology with Interaction between Phantom Dark Energy and Dark Matter and the Coincidence Problem  

E-Print Network (OSTI)

We study a cosmological model in which phantom dark energy has an interaction with dark matter by introducing a term in the equations of motion of dark energy and dark matter. Such a term is parameterized by a product of a dimensionless coupling function ?, Hubble parameter and the energy density of dark matter, and it manifests an energy flow between the dark energy and dark matter. We discuss two cases, one is that the state parameter ?e of the dark energy keeps as a constant; the other is that the dimensionless coupling function ? remains as a constant. We investigate the effect of the interaction on the evolution of the universe, the total lifetime of the universe, and the ratio of the period when the universe is in the coincidence state to its total lifetime. It turns out the interaction will produce significant deviation from the case without the interaction.

Rong-gen Cai; Anzhong Wang

2004-01-01T23:59:59.000Z

227

Reconstructing $f(R,T)$ gravity from holographic dark energy  

E-Print Network (OSTI)

We numerically reconstruct those $f(R,T)$ theories of gravity (where $T$ is the trace of the energy-momentum tensor) which are able to reproduce holographic dark energy models.

Houndjo, M J S

2011-01-01T23:59:59.000Z

228

Interacting holographic dark energy model in non-flat universe  

E-Print Network (OSTI)

We employ the holographic model of interacting dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named $L$.

M R Setare

2006-09-11T23:59:59.000Z

229

Holographic Dark Energy Like in $f(R)$ Gravity  

E-Print Network (OSTI)

We investigate the corresponding relation between $f(R)$ gravity and holographic dark energy. We introduce a kind of energy density from $f(R)$ which has role of the same as holographic dark energy. We obtain the differential equation that specify the evolution of the introduced energy density parameter based on varying gravitational constant. We find out a relation for the equation of state parameter to low redshifts which containing varying $G$ correction.

Saaidi, Kh

2010-01-01T23:59:59.000Z

230

Non-flat time-variable dark energy cosmology  

E-Print Network (OSTI)

We generalize the time-variable dark energy scalar field $\\Phi$ model ($\\Phi$CDM) to non-flat space. We show that even in the space-curvature-dominated epoch the scalar field solution is a time-dependent fixed point or attractor, with scalar field energy density that grows relative to the energy density in spatial curvature. This is the first example of a physically consistent and complete model of dynamical dark energy in a non-flat geometry.

Pavlov, Anatoly; Saaidi, Khaled; Ratra, Bharat

2013-01-01T23:59:59.000Z

231

Holographic Dark Energy Like in $f(R)$ Gravity  

E-Print Network (OSTI)

We investigate the corresponding relation between $f(R)$ gravity and holographic dark energy. We introduce a kind of energy density from $f(R)$ which has role of the same as holographic dark energy. We obtain the differential equation that specify the evolution of the introduced energy density parameter based on varying gravitational constant. We find out a relation for the equation of state parameter to low redshifts which containing varying $G$ correction.

Kh. Saaidi; A. Aghamohammadi

2010-10-12T23:59:59.000Z

232

Co-existence of Gravity and Antigravity: The Unification of Dark Matter and Dark Energy  

E-Print Network (OSTI)

Massive gravity with second and fourth derivatives is shown to give both attractive and repulsive gravities. In contrast to the attractive gravity correlated with the energy-momentum tensor, the repulsive gravity is related to a fixed mass $m_x$, which equals a spin-dependent factor $f_\\sigma$ times the graviton mass. Therefore, particles with energy below $m_x$ are both dark matter and dark energy: Their overall gravity is attractive with normal matter but repulsive among themselves. Detailed analyses reveal that this unified dark scenario can properly account for the observed dark matter/energy phenomena: galaxy rotation curves, transition from early cosmic deceleration to recent acceleration; and naturally overcome other dark scenarios' difficulties: the substructure and cuspy core problems, the difference of dark halo distributions in galaxies and clusters, and the cosmic coincidence. Very interestingly, Dirac particles have $f_\\sigma=1/\\sqrt 2$, all bosonic matter particles have $f_\\sigma=0$, and the only exceptional boson is the graviton itself, which may have $f_\\sigma>1$.

Xiang-Song Chen

2005-06-03T23:59:59.000Z

233

The Unified Equation of State for Dark Matter and Dark Energy  

E-Print Network (OSTI)

We assume that dark matter and dark energy satisfy the unified equation of state: p = B(z)?, with p = pdE, ? = ?dm + ?dE, where the pressure of dark matter pdm = 0 has been taken into account. A special function B = ? A (1+z) ? is presented, which can well describe the evolution of the universe. In this model, the universe will end up with a Big Rip. By further simple analysis, we know other choices of the function B can also describe the universe but lead to a different doomsday.

Wei Wang; Yuanxing Gui; Suhong Zhang; Guanghai Guo; Ying Shao

2005-01-01T23:59:59.000Z

234

Seeking Answers in the Darkness | Department of Energy  

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

Seeking Answers in the Darkness Seeking Answers in the Darkness Seeking Answers in the Darkness November 19, 2010 - 12:56pm Addthis John Schueler John Schueler Former New Media Specialist, Office of Public Affairs What are the key facts? Fermilab is leading construction of a 570-megapixel camera, which attached to the Bianco 4-meter telescope, will survey the deepest reaches of the universe to answer questions on the behavior of gravity. In 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. This flies in the face of Einstein's theory of general relativity, which states that gravity should naturally lead to a slowing of the expansion, since over time it causes mass to attract other mass. Theorists offer two

235

Darke County, Ohio: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

Darke County, Ohio: Energy Resources Darke County, Ohio: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 40.1056572°, -84.6897495° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":40.1056572,"lon":-84.6897495,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

236

Dark River, Minnesota: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

Dark River, Minnesota: Energy Resources Dark River, Minnesota: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 47.6691447°, -92.8564089° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":47.6691447,"lon":-92.8564089,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

237

New Agegraphic Dark Energy in $f(R)$ Gravity  

E-Print Network (OSTI)

In this paper we study cosmological application of new agegraphic dark energy density in the $f(R)$ gravity framework. We employ the new agegraphic model of dark energy to obtain the equation of state for the new agegraphic energy density in spatially flat universe. Our calculation show, taking $nenergy model in flat universe in the modified gravity cosmology framework. Also we develop a reconstruction scheme for the modified gravity with $f(R)$ action.

Setare, M R

2009-01-01T23:59:59.000Z

238

New Agegraphic Dark Energy in $f(R)$ Gravity  

E-Print Network (OSTI)

In this paper we study cosmological application of new agegraphic dark energy density in the $f(R)$ gravity framework. We employ the new agegraphic model of dark energy to obtain the equation of state for the new agegraphic energy density in spatially flat universe. Our calculation show, taking $nenergy model in flat universe in the modified gravity cosmology framework. Also we develop a reconstruction scheme for the modified gravity with $f(R)$ action.

M. R. Setare

2009-08-03T23:59:59.000Z

239

Fine Structure of Dark Energy and New Physics  

E-Print Network (OSTI)

Following our recent work on the cosmological constant problem, in this letter we make a specific proposal regarding the fine structure (i.e., the spectrum) of dark energy. The proposal is motivated by a deep analogy between the blackbody radiation problem, which led to the development of quantum theory, and the cosmological constant problem, which we have recently argued calls for a conceptual extension of the quantum theory. We argue that the fine structure of dark energy is governed by a Wien distribution, indicating its dual quantum and classical nature. We discuss a few observational consequences of such a picture of dark energy.

Vishnu Jejjala; Michael Kavic; Djordje Minic

2007-05-31T23:59:59.000Z

240

Interacting Ghost Dark Energy in Brans-Dicke Theory  

E-Print Network (OSTI)

We investigate the QCD ghost model of dark energy in the framework of Brans-Dicke cosmology. First, we study the non-interacting ghost dark energy in a flat Brans-Dicke theory. In this case we obtain the EoS and the deceleration parameters and a differential equation governing the evolution of ghost energy density. Interestingly enough, we find that the EoS parameter of the non-interacting ghost dark energy can cross the phantom line ($w_D=-1$) provided the parameters of the model are chosen suitably. Then, we generalize the study to the interacting ghost dark energy in both flat and non-flat Brans-Dicke framework and find out that the transition of $w_D$ to phantom regime can be more easily achieved for than when resort to the Einstein field equations is made.

Esmaeil Ebrahimi; Ahmad Sheykhi

2011-05-28T23:59:59.000Z

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


241

Dark energy, chaotic fields, and fundamental constants  

E-Print Network (OSTI)

To explain the currently observed accelerated expansion of the universe, a large number of different theoretical models are presently being discussed. In one way or another, all of these contain `new physics', though at different levels. The big question is how to select out of infinitely many possible models the right one. Here we discuss a possibility that has so far been somewhat neglected, namely that the new physics underlying dark energy arises out of a gravitationally active amendment of the electroweak and strong sector of the standard model. This amendment basically consists of a rapidly fluctuating gravitationally active dynamics of vacuum fluctuations with a cutoff of the order of the neutrino mass scale. We consider a concrete model for this based on second-quantized self-interacting scalar fields, which evolve in a chaotic way. It is shown that expectations with respect to the chaotic dynamics yield statements on the observed numerical values of the electroweak coupling constants with amazing precision, thus providing evidence for the physical relevance of this model.

Christian Beck

2005-02-10T23:59:59.000Z

242

Gravitational Collapse With Dark Energy And Dark Matter In Ho?ava-Lifshitz Gravity  

E-Print Network (OSTI)

In this work, the collapsing process of a spherically symmetric star, made of dust cloud, is studied in Ho\\v{r}ava Lifshitz gravity in the background of Chaplygin gas dark energy. Two different classes of Chaplygin gas, namely, New variable modified Chaplygin gas and generalized cosmic Chaplygin gas are considered for the collapse study. Graphs are drawn to characterize the nature and to determine the possible outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different dark energy models. It is found that for open and closed universe, collapse proceeds with an increase in black hole mass, the only constraint being that, relatively smaller values of $\\Lambda$ has to be considered in comparison to $\\lambda$. But in case of flat universe, possibility of the star undergoing a collapse in highly unlikely. Moreover it is seen that the most favourable environment for collapse is achieved when a combination of dark energy and dark matter is considered, both in the presence and absence of interaction. Finally, it is to be seen that, contrary to our expectations, the presence of dark energy does not really hinder the collapsing process in case of Ho\\v{r}ava-Lifshitz gravity.

Prabir Rudra; Ujjal Debnath

2013-07-12T23:59:59.000Z

243

Press Pass - Press Release - September 3, 2013: Dark Energy Survey...  

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

find out why the expansion of the universe is speeding up, instead of slowing down due to gravity, and to probe the mystery of dark energy, the force believed to be causing that...

244

Growth Diagnostics for Dark Energy models and EUCLID forecast  

E-Print Network (OSTI)

In this work we introduce a new set of parameters $(r_{g}, s_{g})$ involving the linear growth of matter perturbation that can distinguish and constrain different dark energy models very efficiently. Interestingly, for $\\Lambda$CDM model these parameters take exact value $(1,1)$ at all red shifts whereas for models different from $\\Lambda$CDM, they follow different trajectories in the $(r_{g}, s_{g})$ phase plane. By considering the parametrization for the dark energy equation of state ($w$) and for the linear growth rate ($f_{g}$), we show that different dark energy behaviours with similar evolution of the linear density contrast, can produce distinguishable trajectories in the $(r_{g}, s_{g})$ phase plane. Moreover, one can put stringent constraint on these phase plane using future measurements like EUCLID ruling out some of the dark energy behaviours.

Sampurnanand; Anjan A. Sen

2013-01-06T23:59:59.000Z

245

Stable dark energy stars: An alternative to black holes?  

E-Print Network (OSTI)

In this work, a generalization of the Mazur-Mottola gravastar model is explored, by considering a matching of an interior solution governed by the dark energy equation of state, $\\omega\\equiv p/ \\rhoenergy is a possible candidate.

Francisco S. N. Lobo

2006-12-05T23:59:59.000Z

246

Sensorcam: an energy-efficient smart wireless camera for environmental monitoring  

Science Conference Proceedings (OSTI)

Reducing energy cost is crucial for energy-constrained smart wireless cameras. Existing platforms impose two main challenges: First, most commercial smart phones have a closed platform, which makes it impossible to manage low-level circuits. Since the ... Keywords: energy profile, environmental monitoring, smart wireless camera, video coding

Zichong Chen; Paolo Prandoni; Guillermo Barrenetxea; Martin Vetterli

2012-04-01T23:59:59.000Z

247

About the Geometric Solution to the Problems of Dark Energy  

E-Print Network (OSTI)

In this paper is proposed a geometric solution to the dark energy, assuming that the space can be divided into regions of size $\\sim L_{p}$ and energy $\\sim E_{p}$. Significantly this assumption generate a energy density similar to the energy density observed for the vaccum energy, the correct solution for the coincidence problem and the state equation characteristic of quintessence in the comoving coordinates. Similarly is studied the ultraviolet and infrarred limits and the amount of dark energy in the Universe.

Miguel Angel García-Aspeitia

2010-11-19T23:59:59.000Z

248

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

249

Gravity assisted dark energy dominance and cosmic acceleration  

E-Print Network (OSTI)

It is proposed that dark energy may become dominant over standard matter due to universe expansion (curvature decrease). Two models: non-linear gravity-matter system and modified gravity may provide the effective phantom or effective quintessence dark energy which complies with the conjecture. It is interesting that future of such universe is not necessary finite time singularity (Big Rip). The effective quintessence naturally describes current cosmic speed-up.

Nojiri, S; Nojiri, Shin'ichi; Odintsov, Sergei D.

2004-01-01T23:59:59.000Z

250

Large Synoptic Survey Telescope: Dark Energy Science Collaboration  

E-Print Network (OSTI)

This white paper describes the LSST Dark Energy Science Collaboration (DESC), whose goal is the study of dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST). It provides an overview of dark energy science and describes the current and anticipated state of the field. It makes the case for the DESC by laying out a robust analytical framework for dark energy science that has been defined by its members and the comprehensive three-year work plan they have developed for implementing that framework. The analysis working groups cover five key probes of dark energy: weak lensing, large scale structure, galaxy clusters, Type Ia supernovae, and strong lensing. The computing working groups span cosmological simulations, galaxy catalogs, photon simulations and a systematic software and computational framework for LSST dark energy data analysis. The technical working groups make the connection between dark energy science and the LSST system. The working groups have close linkages, especially through the use of the photon simulations to study the impact of instrument design and survey strategy on analysis methodology and cosmological parameter estimation. The white paper describes several high priority tasks identified by each of the 16 working groups. Over the next three years these tasks will help prepare for LSST analysis, make synergistic connections with ongoing cosmological surveys and provide the dark energy community with state of the art analysis tools. Members of the community are invited to join the LSST DESC, according to the membership policies described in the white paper. Applications to sign up for associate membership may be made by submitting the Web form at http://www.slac.stanford.edu/exp/lsst/desc/signup.html with a short statement of the work they wish to pursue that is relevant to the LSST DESC.

LSST Dark Energy Science Collaboration

2012-11-01T23:59:59.000Z

251

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

252

A model of a varying Ghost Dark energy  

E-Print Network (OSTI)

Motivated by recent developments in Cosmology we would like to assume a possibility of the existence of varying Ghost Dark energy. Ghost Dark energy like other models was introduced recently as a model of dark energy. As accepted in general, in GR dark energy is a possible way to explain accelerated expansion of the Universe reported from different experimental data. From the beginning we would like to stress the fact, that proposed modifications are based on our believe and probably for this reason there is not a well establish physical theory behind the models. Concerning to the origin of varying Ghost dark energy, we can assume an existence of some interaction (and unknown physics behind it), between Ghost Dark energy and a fluid and last component during interaction evaporated completely making sense of the proposed effect. Moreover, we can assume that this was in epochs and scales which are unreachable by nowadays experiments. The same assumptions could be accepted or proposed for the interaction terms.

Martiros Khurshudyan; Amalya Khurshudyan

2013-07-30T23:59:59.000Z

253

BOSS: THE BARYON OSCILLATION SPECTROSCOPIC SURVEY Probing the Physics of Dark Energy with Baryon Acoustic Oscillations  

E-Print Network (OSTI)

BOSS: THE BARYON OSCILLATION SPECTROSCOPIC SURVEY Probing the Physics of Dark Energy with Baryon demand the existence of a pervasive new component of the Universe ("dark energy") with exotic physical on cosmological scales. Because of the fundamental importance of the dark energy problem, the Dark Energy Task

Knowles, David William

254

arXiv:astro-ph/0703364v227Aug2007 Electromagnetic dark energy  

E-Print Network (OSTI)

arXiv:astro-ph/0703364v227Aug2007 Electromagnetic dark energy Christian Beck School of MathematicalGill University, Montreal, Quebec, Canada (Dated: August 28, 2007) We introduce a new model for dark energy equations, or more generally with the existence of dark energy. The dark energy density consistent

Low, Robert

255

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

256

Dynamics of Quintessence Models of Dark Energy with Exponential Coupling to the Dark Matter  

E-Print Network (OSTI)

We explore quintessence models of dark energy which exhibit non-minimal coupling between the dark matter and the dark energy components of the cosmic fluid. The kind of coupling chosen is inspired in scalar-tensor theories of gravity. We impose a suitable dynamics of the expansion allowing to derive exact Friedmann-Robertson-Walker solutions once the coupling function is given as input. Self-interaction potentials of single and double exponential types emerge as result of our choice of the coupling function. The stability and existence of the solutions is discussed in some detail. Although, in general, models with appropriated interaction between the components of the cosmic mixture are useful to handle the coincidence problem, in the present study the coincidence can not be evaded due to the choice of the solution generating ansatz.

Tame Gonzalez; Genly Leon; Israel Quiros

2007-02-08T23:59:59.000Z

257

Vacuum quantum fluctuation energy in expanding universe and dark energy  

E-Print Network (OSTI)

This article is based on the Planckon densely piled vacuum model and the principle of cosmology. With Planck era as initial conditions and including early inflation, we have solved the Einstein-Friedmann equations to describe the evolution of the universe, a reasonable relation between dark energy density and vacuum quantum fluctuation energy density is obtained. The main results are : 1) the solution of Einstein-Friedmann equations has yielded the result $\\frac{{{\\rho}_{de}}}{{{\\rho}_{vac}}}\\sim{{(\\frac{{{t}_{P}}}{{{T}_{0}}})}^{2}}\\sim{{10}^{-122}} $ (Planck time ${{t}_{P}}={{10}^{-43}}s$ and universe age ${{T}_{0}}={{10}^{18}}s$);2) at inflation time ${{t}_{\\inf}}={{10}^{-35}}s$, the calculated universe radiation energy density is $\\rho ({{t}_{\\inf}})\\sim{{10}^{-16}}{{\\rho}_{vac}}$ and the corresponding temperature is ${{E}_{c}}\\sim{{10}^{15}}GeV$ consistent with GUT phase transition temperature;3) it is showed that the expanding universe is a non-equilibrium open system constantly exchanging energy with vacuum; during its expanding, the Planckons in universe lose quantum fluctuation energy and create cosmic expansion quanta-cosmons, the energy of cosmons is the lost part of vacuum quantum fluctuation energy and contributes to the total energy of the universe with the calculated value ${{E}_{\\cos mos}}={{10}^{22}}{{M}_{\\otimes}}{{c}^{2}}$ (${{M}_{\\otimes}}$ is solar mass) agreed with astronomic data; 4) the gravity potential and gravity acceleration of cosmons are derived with the nature of repulsive force, indicating that the cosmon may be the candidate of dark energy quantum; 5) solution to three well known cosmic problems of Big Bang model is presented.

Shun-Jin Wang

2013-01-02T23:59:59.000Z

258

Dark energy of the Universe as a field of particles with spin 3  

E-Print Network (OSTI)

A hypothesis is presented for explanation of the dark matter and dark energy properties in terms of a new interaction field with spin 3.

B. A. Trubnikov

2008-12-09T23:59:59.000Z

259

DarkStar VI | Open Energy Information  

Open Energy Info (EERE)

DarkStar VI DarkStar VI Jump to: navigation, search Name DarkStar VI Place Collinsville, Illinois Zip 62234-2022 Sector Services Product Manufacturer of biodiesel processing equipment and supplier of accessories, information and services. Coordinates 36.720014°, -79.91284° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":36.720014,"lon":-79.91284,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

260

Constraining the interacting dark energy models from weak gravity conjecture and recent observations  

E-Print Network (OSTI)

We examine the effectiveness of the weak gravity conjecture in constraining the dark energy by comparing with observations. For general dark energy models with plausible phenomenological interactions between dark sectors, we find that although the weak gravity conjecture can constrain the dark energy, the constraint is looser than that from the observations.

Chen, Ximing; Pan, Nana; Gong, Yungui

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Mapping and Embedding of Two Metrics Associated with Dark Matter, Dark Energy, and Ordinary Matter  

E-Print Network (OSTI)

In this paper we build a mapping between two different metrics and embed them in a flat manifold. One of the metrics represents the ordinary matter, and the other describes the dark matter, the dark energy, and the particle-antiparticle asymmetry. The latter was obtained in a recent paper. For the mapping and embedding, we use two new formalisms developed and presented in two previous papers, Mapping Among Manifolds and, Conformal Form of Pseudo-Riemannian Metrics by Normal Coordinate Transformations, which was a generalization of the Cartan's approach of Riemannian normal coordinates.

de Siqueira, A C V V

2010-01-01T23:59:59.000Z

262

Mapping and Embedding of Two Metrics Associated with Dark Matter, Dark Energy, and Ordinary Matter  

E-Print Network (OSTI)

In this paper we build a mapping between two different metrics and embed them in a flat manifold. One of the metrics represents the ordinary matter, and the other describes the dark matter, the dark energy, and the particle-antiparticle asymmetry. The latter was obtained in a recent paper. For the mapping and embedding, we use two new formalisms developed and presented in two previous papers, Mapping Among Manifolds and, Conformal Form of Pseudo-Riemannian Metrics by Normal Coordinate Transformations, which was a generalization of the Cartan's approach of Riemannian normal coordinates.

A. C. V. V. de Siqueira

2010-10-29T23:59:59.000Z

263

Dark Energy, Expansion History of the Universe, and SNAP  

E-Print Network (OSTI)

This talk presents a pedagogical discussion of how precision distance-redshift observations can map out the recent expansion history of the universe, including the present acceleration and the transition to matter dominated deceleration. The proposed Supernova/Acceleration Probe (SNAP) will carry out observations determining the components and equations of state of the energy density, providing insights into the cosmological model, the nature of the accelerating dark energy, and potentially clues to fundamental high energy physics theories and gravitation. This includes the ability to distinguish between various dynamical scalar field models for the dark energy, as well as higher dimension and alternate gravity theories. A new, advantageous parametrization for the study of dark energy to high redshift is also presented.

Eric V. Linder

2003-02-03T23:59:59.000Z

264

Bulk-Brane Interaction and Holographic Dark Energy  

E-Print Network (OSTI)

In this paper we consider the bulk-brane interaction to obtain the equation of state for the holographic energy density in non-flat universe enclosed by the event horizon measured from the sphere of horizon named $L$. We assumes that the cold dark matter energy density on the brane is conserved, but the holographic dark energy density on the brane is not conserved due to brane-bulk energy exchange. Our calculation show, taking $\\Omega_{\\Lambda}=0.73$ for the present time, the lower bound of $w_{\\rm \\Lambda}^{eff}$ is -0.9. This implies that one can not generate phantom-like equation of state from an interacting holographic dark energy model in non-flat universe.

M R Setare

2006-09-14T23:59:59.000Z

265

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

266

Testing the Cosmic Coincidence Problem and the Nature of Dark Energy  

E-Print Network (OSTI)

Dark energy models which alter the relative scaling behavior of dark energy and matter could provide a natural solution to the cosmic coincidence problem - why the densities of dark energy and dark matter are comparable today. A generalized class of dark energy models is introduced which allows non-canonical scaling of the ratio of dark matter and dark energy with the Robertson-Walker scale factor a(t). Upcoming observations, such as a high redshift supernova survey, application of the Alcock-Paczynski test to quasar pairs, and cluster evolution, will strongly constrain the relative scaling of dark matter and dark energy as well as the equation of state of the dark energy. Thus, whether there actually is a coincidence problem, and the extent of cosmic coincidence in the universe's recent past can be answered observationally in the near future. Determining whether today is a special time in the history of the universe will be a SNAP.

Neal Dalal; Kevork Abazajian; Elizabeth Jenkins; Aneesh V. Manohar

2001-05-18T23:59:59.000Z

267

Ghost dark energy in $f(R)$ model of gravity  

E-Print Network (OSTI)

We study a correspondence between $f(R)$ model of gravity and a phenomenological kind of dark energy (DE), which is known as QCD ghost dark energy. Since this kind of dark energy is not stable in the context of Einsteinian theory of gravity and Brans-Dicke model of gravity, we consider two kinds of correspondence between modified gravity and DE. By studding the dynamical evolution of model and finding relevant quantities such as, equation of state parameter, deceleration parameter, dimensionless density parameter, we show that the model can describe the present Universe and also the EoS parameter can cross the phantom divide line without needs to any kinetic energy with negative sign. Furthermore, by obtaining the adiabatic squared sound speed of the model for different cases of interaction, we show that this model is stable.

Saaidi, Kh; Sabet, B

2012-01-01T23:59:59.000Z

268

A Dark Energy model combining DGP gravity and Chaplygin gas  

E-Print Network (OSTI)

The expansion of the Universe is accelerating, as testified by observations of supernovae of type Ia as a function of redshift. Explanations are of two types: modifications of Einstein gravity or new forms of energy, coined dark energy.The accelerated expansion is explained here by a combination of Dvali-Gabadadze-Porrati (DGP) model gravity and Chaplygin gas dark energy. Both models are characterized by a length scale L which may be the same. The continuity equation for the combined model is derived in flat geometry, and solved by numerical methods. The solution is shown to have the expected properties: at very small scales (aenergy density behaves as pressureless dust, at very large scales (a>>L) as a cosmological constant. The modifications to the DGP model and the Chaplygin gas model occur for values of a L. The results show an increase in the present dark energy density relative to the plain DGP model.

Matts Roos

2007-04-06T23:59:59.000Z

269

A dark energy model alternative to generalized Chaplygin gas  

E-Print Network (OSTI)

We propose a new fluid model of dark energy for $-1 \\leq \\omega_{\\text{eff}} \\leq 0$ as an alternative to the generalized Chaplygin gas models. The energy density of dark energy fluid is severely suppressed during barotropic matter dominant epochs, and it dominates the universe evolution only for eras of small redshift. From the perspective of fundamental physics, the fluid is a tachyon field with a scalar potential flatter than that of power-law decelerated expansion. Different from the standard $\\Lambda\\text{CDM}$ model, the suggested dark energy model claims that the cosmic acceleration at present epoch can not continue forever but will cease in the near future and a decelerated cosmic expansion will recover afterwards.

Hova, Hoavo

2010-01-01T23:59:59.000Z

270

The issue of Dark Energy in String Theory  

E-Print Network (OSTI)

Recent astrophysical observations, pertaining to either high-redshift supernovae or cosmic microwave background temperature fluctuations, as those measured recently by the WMAP satellite, provide us with data of unprecedented accuracy, pointing towards two (related) facts: (i) our Universe is accelerated at present, and (ii) more than 70 % of its energy content consists of an unknown substance, termed dark energy, which is believed responsible for its current acceleration. Both of these facts are a challenge to String theory. In this review I outline briefly the challenges, the problems and possible avenues for research towards a resolution of the Dark Energy issue in string theory.

Nick E. Mavromatos

2006-07-01T23:59:59.000Z

271

Dark energy model with higher derivative of Hubble parameter  

E-Print Network (OSTI)

In this letter we consider a dark energy model in which the energy density is a function of the Hubble parameter $H$ and its derivative with respect to time $\\rho_{de}=3\\alpha \\ddot{H}H^{-1}+3\\beta\\dot{H}+3\\gamma H^2$. The behavior of the dark energy and the expansion history of the Universe depend heavily on the parameters of the model $\\alpha$, $\\beta$ and $\\gamma$. It is very interesting that the age problem of the well-known three old objects can be alleviated in this models.

Songbai Chen; Jiliang Jing

2009-04-20T23:59:59.000Z

272

High Energy Positrons From Annihilating Dark Matter  

E-Print Network (OSTI)

Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmic ray positrons above 10 GeV. In this letter, we consider possibility that this signal is the result of dark matter annihilations taking place in the halo of the Milky Way. Rather than focusing on a specific particle physics model, we take a phenomenological approach and consider a variety of masses and two-body annihilation modes, including W+W-, ZZ, b bbar, tau+ tau-, mu+ mu-, and e+e. We also consider a range of diffusion parameters consistent with current cosmic ray data. We find that a significant upturn in the positron fraction above 10 GeV is compatible with a wide range of dark matter annihilation modes, although very large annihilation cross sections and/or boost factors arising from inhomogeneities in the local dark matter distribution are required to produce the observed intensity of the signal. We comment on constraints from gamma rays, synchrotron emission, and cosmic ray antiproton measurements.

Ilias Cholis; Lisa Goodenough; Dan Hooper; Melanie Simet; Neal Weiner

2008-09-10T23:59:59.000Z

273

Shining Light on Dark Energy and Modifications of Gravity  

E-Print Network (OSTI)

Many theories of dark energy and modified gravity give rise to scalar fields that couple derivatively to the energy momentum tensor of matter. This is known as disformal coupling. I will show that laboratory searches for axions are ideally suited to search for and constrain disformal scalar fields.

Burrage, Clare

2013-01-01T23:59:59.000Z

274

Shining Light on Dark Energy and Modifications of Gravity  

E-Print Network (OSTI)

Many theories of dark energy and modified gravity give rise to scalar fields that couple derivatively to the energy momentum tensor of matter. This is known as disformal coupling. I will show that laboratory searches for axions are ideally suited to search for and constrain disformal scalar fields.

Clare Burrage

2013-01-08T23:59:59.000Z

275

Property:Number of Color Cameras | Open Energy Information  

Open Energy Info (EERE)

Color Cameras Color Cameras Jump to: navigation, search Property Name Number of Color Cameras Property Type Number Pages using the property "Number of Color Cameras" Showing 25 pages using this property. (previous 25) (next 25) A Alden Large Flume + 2 + Alden Small Flume + 2 + Alden Tow Tank + 2 + Alden Wave Basin + 2 + C Chase Tow Tank + 1 + Conte Large Flume + 5 + Conte Small Flume + 5 + D Davidson Laboratory Tow Tank + 2 + DeFrees Flume 1 + 5 + DeFrees Flume 2 + 5 + DeFrees Flume 3 + 5 + DeFrees Flume 4 + 5 + DeFrees Large Wave Basin + 5 + DeFrees Small Wave Basin + 5 + F Flood Fighting Research Facility + 1 + H Haynes Tow Tank + 6 + Haynes Wave Basin + 6 + Hinsdale Wave Basin 1 + 20 + Hinsdale Wave Basin 2 + 20 + M MIT Tow Tank + 1 + MMA Tugboat/ Barge/ Vessel + 1 +

276

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

277

Dark energy: Q&A with Steve Kuhlmann | Argonne National Laboratory  

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

energy: Q&A with Steve Kuhlmann Dark energy: Q&A with Steve Kuhlmann By Jared Sagoff * September 17, 2012 Tweet EmailPrint Why do we care about dark energy in the first place? One...

278

Role of Modified Chaplygin Gas as a Dark Energy Model in Collapsing Spherically Symmetric Cloud  

E-Print Network (OSTI)

In this work, gravitational collapse of a spherical cloud, consists of both dark matter and dark energy in the form of modified Chaplygin gas is studied. It is found that dark energy alone in the form of modified Chaplygin gas forms black hole. Also when both components of the fluid are present then the collapse favors the formation of black hole in cases the dark energy dominates over dark matter. The conclusion is totally opposite to the usually known results.

Ujjal Debnath; Subenoy Chakraborty

2006-01-12T23:59:59.000Z

279

Reconstruction of modified gravity with ghost dark energy models  

E-Print Network (OSTI)

In this work, we reconstruct the $f(R)$ modified gravity for different ghost and generalized ghost dark energy models in FRW flat universe, which describe the accelerated expansion of the universe. The equation of state of reconstructed $f(R)$ - gravity has been calculated. We show that the corresponding $f(R)$ gravity of ghost dark energy model can behave like phantom or quintessence. We also show that the equation of state of reconstructed $f(R)$ gravity for generalized ghost model can transit from quintessence regime to the phantom regime as indicated by recent observations.

Khodam-Mohammadi, A

2012-01-01T23:59:59.000Z

280

A single model of interacting dark energy: generalized phantom energy or generalized Chaplygin gas  

E-Print Network (OSTI)

I present a model in which dark energy interacts with matter. The former is represented by a variable equation of state. It is shown that the phantom crossing takes place at zero redshift, moreover, stable scaling solution of the Friedmann equations is obtained. I show that dark energy is most probably be either generalized phantom energy or the generalized Chaplygin gas.

Mubasher Jamil

2009-12-22T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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

Model Independent Early Expansion History and Dark Energy  

E-Print Network (OSTI)

We examine model independent constraints on the high redshift and prerecombination expansion history from cosmic microwave background observations, using a combination of principal component analysis and other techniques. This can be translated to model independent limits on early dark energy and the number of relativistic species $N_{\\rm eff}$. Models such as scaling (Doran-Robbers), dark radiation ($\\Delta N_{\\rm eff}$), and barotropic aether fall into distinct regions of eigenspace and can be easily distinguished from each other. Incoming CMB data will map the expansion history from $z=0$--$10^5$, achieving subpercent precision around recombination, and enable determination of the amount of early dark energy and valuable guidance to its nature.

Samsing, Johan; Smith, Tristan L

2012-01-01T23:59:59.000Z

282

Thermodynamics of viscous dark energy in an RSII braneworld  

E-Print Network (OSTI)

We show that for an RSII braneworld filled with interacting viscous dark energy and dark matter, one can always rewrite the Friedmann equation in the form of the first law of thermodynamics, $dE=T_hdS_h+WdV$, at apparent horizon. In addition, the generalized second law of thermodynamics can fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time variable 5-dynamical Newton's constant $G_5$. These results hold regardless of the specific form of the dark energy. Our study further support that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.

M. R. Setare; A. Sheykhi

2011-03-05T23:59:59.000Z

283

Ghost dark energy in $f(R)$ model of gravity  

E-Print Network (OSTI)

We study a correspondence between $f(R)$ model of gravity and a phenomenological kind of dark energy (DE), which is known as QCD ghost dark energy. Since this kind of dark energy is not stable in the context of Einsteinian theory of gravity and Brans-Dicke model of gravity, we consider two kinds of correspondence between modified gravity and DE. By studding the dynamical evolution of model and finding relevant quantities such as, equation of state parameter, deceleration parameter, dimensionless density parameter, we show that the model can describe the present Universe and also the EoS parameter can cross the phantom divide line without needs to any kinetic energy with negative sign. Furthermore, by obtaining the adiabatic squared sound speed of the model for different cases of interaction, we show that this model is stable. Finally, we fit this model with supernova observational data in a non interaction case and we find the best values of parameter at $1\\sigma$ confidence interval as; $f_0=0.958^{+0.07}_{-0.25}$, $\\beta=-0,256^{+0.2}_{-0.1}$, and $\\Om_{m_0} = 0.23^{+0.3}_{-0.15}$. These best-fit values show that dark energy equation of state parameter, $\\om_{d_0}$, can cross the phantom divide line at the present time.

Kh. Saaidi; Ali. Aghamohammadi; B. Sabet; O. Farooq

2012-03-17T23:59:59.000Z

284

Bright and dark exciton energy and excitonic effect of single wall carbon  

E-Print Network (OSTI)

Bright and dark exciton energy and excitonic effect of single wall carbon nanotubes Kentaro Sato1-inactive (dark) exciton energy of single wall carbon nanotubes (SWNTs). The bright and dark exciton energy of SWNTs is calculated by solving the Bethe-Salpeter equation in which the one particle energies are given

Maruyama, Shigeo

285

Dark Universe II  

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

Uncertainty Principle Uncertainty Principle Quantum fluctuations? Vacuum Energy Dark Energy? Quintessence Gravity and pressure Properties of Dark Energy Concordance Model...

286

Dark Energy Function in Modified Gravity and Supergravity  

E-Print Network (OSTI)

We propose new theoretical constraints on the dynamical dark energy function in f(R) gravity and F(R) supergravity theories by demanding the effective scalar potential to be (i) renormalizable and (ii) supersymmetrizable. A model of the hidden sector responsible for spontaneous supersymmetry breaking is also proposed.

Ketov, Sergei V

2012-01-01T23:59:59.000Z

287

Dark Matter, Quantum Gravity, Vacuum Energy, and Lorentz Invariance  

E-Print Network (OSTI)

We discuss the problems of dark matter, quantum gravity, and vacuum energy within the context of a theory for which Lorentz invariance is not postulated, but instead emerges as a natural consequence in the physical regimes where it has been tested.

Roland E. Allen

2001-10-23T23:59:59.000Z

288

The Graviton and the Nature of Dark Energy  

E-Print Network (OSTI)

I discuss various thoughts, old and new, about the cosmological constant (or dark energy) paradox. In particular, I suggest the possibility that the cosmological ``constant'' may decay as $\\Lambda \\sim \\alpha^2 m_N^3 / \\tau$, where $\\tau$ is the age of the universe.

A. Zee

2004-03-05T23:59:59.000Z

289

Phantom dark energy with tachyonic instability: metric perturbations  

E-Print Network (OSTI)

We study the behavior of metric perturbations in a recently proposed model of phantom dark energy with tachyonic instability at long wavelengths. We find that metric perturbations exponentially grow in time, starting from very small values determined by vacuum fluctuations, and may become sizeable at late times. This property may be of interest for phenomenology.

S. Sergienko; V. Rubakov

2008-03-21T23:59:59.000Z

290

Features of holographic dark energy under the combined cosmological constraints  

E-Print Network (OSTI)

The holographic dark energy model is an important attempt to probe the nature of dark energy which is based on the holographic principle. In this paper, we present the key equations of the holographic dark energy with and without interaction, then using several recent observational data, including 182 selected high-quality type Ia supernovae ($\\rm SN_{sel}$), the baryon acoustic oscillation (BAO) measurement from SDSS, 42 latest X-rays gas mass fraction ($\\rm f_{gas}$) in the clusters and 27 high-redshift gamma-ray burst (GRB) samples, to give reliable and tighter constraints on the holographic dark energy models. The results of our constraints for the $\\rm SN_{sel}+BAO+f_{gas}+GRB$ data set without (with) interaction are c=0.735^{+0.134}_{-0.103}$ and $\\Omega_{\\mathrm{m0}}=0.271^{+0.022}_{-0.019}$, ($c=0.542^{+0.146}_{-0.083}$, $\\Omega_{\\mathrm{m0}}=0.273^{+0.020}_{-0.021}$ and $\\alpha=-0.112^{+0.126}_{-0.008}$, $\\alpha$ is an interacting parameter). We also utilize the Bayesian evidence as a model selection...

Ma, Yin-Zhe

2007-01-01T23:59:59.000Z

291

A preliminary analysis of the energy transfer between the dark sectors of the Universe  

E-Print Network (OSTI)

We study the mutual interaction between the dark sectors (dark matter and dark energy) of the Universe by resorting to the extended thermodynamics of irreversible processes and constrain the former with supernova type Ia data. As a byproduct, the present dark matter temperature results in good agreement with independent estimates of the temperature of the gas of sterile neutrinos.

Jia Zhou; Bin Wang; Diego Pavon; Elcio Abdalla

2008-07-20T23:59:59.000Z

292

On the Origin of Gravity, Dark Energy and Matter.  

E-Print Network (OSTI)

Insights from black hole physics and developments in string theory strongly indicate that the gravity is derived from an underlying microscopic description in which it has no a priori meaning. Starting from first principles we argue that inertia and gravity are caused by the fact that phase space volume (or entropy) associated with the underlying microscopic system is influenced by the positions of material objects. Application of these ideas to cosmology leads to surprising new insights into the nature of dark energy and dark matter.

CERN. Geneva

2011-01-01T23:59:59.000Z

293

Bright Lights From Dark Places | Department of Energy  

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

Bright Lights From Dark Places Bright Lights From Dark Places Bright Lights From Dark Places May 23, 2011 - 2:09pm Addthis Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science What are the key facts? Scientists used the illumination of some 14,000 quasars -- powered by gigantic black holes at the heart of galaxies -- about 10 to 12 billion light years away to create the new map. Scientists at the Energy Department's national labs are using black holes to illuminate the distant parts of the universe in detail. Specifically, scientists from the Sloan Digital Sky Survey (SDSS-III), of which the Department's Lawrence Berkley and Brookhaven National Labs are both a part, have used quasars to construct the largest three-dimensional map of the universe ever made. Quasars are one of the most brilliant beacons in

294

Entropy-Corrected New Agegraphic Dark Energy Model in Horava-Lifshitz Gravity  

E-Print Network (OSTI)

In this work, we have considered the entropy-corrected new agegraphic dark energy (ECNADE) model in Horava-Lifshitz gravity in FRW universe. We have discussed the correspondence between ECNADE and other dark energy models such as DBI-essence,Yang-Mills dark energy, Chameleon field, Non-linear electrodynamics field and hessence dark energy in the context of Horava-Lifshitz gravity and reconstructed the potentials and the dynamics of the scalar field theory which describe the ECNADE.

Piyali Bagchi Khatua; Shuvendu Chakraborty; Ujjal Debnath

2011-05-08T23:59:59.000Z

295

Entropy-Corrected New Agegraphic Dark Energy Model in Horava-Lifshitz Gravity  

E-Print Network (OSTI)

In this work, we have considered the entropy-corrected new agegraphic dark energy (ECNADE) model in Horava-Lifshitz gravity in FRW universe. We have discussed the correspondence between ECNADE and other dark energy models such as DBI-essence,Yang-Mills dark energy, Chameleon field, Non-linear electrodynamics field and hessence dark energy in the context of Horava-Lifshitz gravity and reconstructed the potentials and the dynamics of the scalar field theory which describe the ECNADE.

Khatua, Piyali Bagchi; Debnath, Ujjal

2011-01-01T23:59:59.000Z

296

Renormalization Group Flow and the Dark Energy Problem  

E-Print Network (OSTI)

Casimir energy is calculated for 5D scalar theory in the {\\it warped} geometry. A new regularization, called {\\it sphere lattice regularization}, is taken. The regularized configuration is {\\it closed-string like}. We numerically evaluate $\\La$(4D UV-cutoff), $\\om$(5D bulk curvature, extra space UV-boundary parameter) and $T$(extra space IR-boundary parameter) dependence of Casimir energy. 5D Casimir energy is {\\it finitely} obtained after the {\\it proper renormalization procedure.} The {\\it warp parameter} $\\om$ suffers from the {\\it renormalization effect}. Regarding Casimir energy as the main contribution to the cosmological term, we examine the dark energy problem.

Ichinose, Shoichi

2011-01-01T23:59:59.000Z

297

Holographic Dark Energy Scenario and Variable Modified Chaplygin Gas  

E-Print Network (OSTI)

In this letter, we have considered that the universe is filled with normal matter and variable modified Chaplygin gas. Also we have considered the interaction between normal matter and variable modified Chaplygin gas in FRW universe. Then we have considered a correspondence between the holographic dark energy density and interacting variable modified Chaplygin gas energy density. Then we have reconstructed the potential of the scalar field which describes the variable modified Chaplygin cosmology.

Surajit Chattopadhyay; Ujjal Debnath

2009-01-15T23:59:59.000Z

298

March 18, 2010 James Webb Space Telescope Studies of Dark Energy  

E-Print Network (OSTI)

March 18, 2010 James Webb Space Telescope Studies of Dark Energy Jonathan P. Gardner (NASA. Introduction The Hubble Space Telescope (HST) has contributed significantly to studies of dark energy) was due to dark energy rather than observational or astrophysical effects such as systematic errors

Sirianni, Marco

299

Interacting new agegraphic Phantom model of dark energy in non-flat universe  

E-Print Network (OSTI)

In this paper we consider the new agegraphic model of interacting dark energy in non-flat universe. We show that the interacting agegraphic dark energy can be described by a phantom scalar field. Then we show this phantomic description of the agegraphic dark energy and reconstruct the potential of the phantom scalar field.

M. R. Setare

2009-07-28T23:59:59.000Z

300

Freezing in the dark: Energy security and heating emergencies in Nova Scotia  

E-Print Network (OSTI)

Freezing in the dark: Energy security and heating emergencies in Nova Scotia Larry Hughes, Ph://lh.ece.dal.ca/enen Presented to Freezing in the dark: Energy security, heating emergencies, and electricity supply in Nova Scotia Saint Mary's University, Halifax 10 March 2009 ERG/200903 #12;Freezing in the dark: Energy

Hughes, Larry

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


301

A Comment or two on Holographic Dark Energy  

E-Print Network (OSTI)

It has, quite recently, become fashionable to study a certain class of holographic-inspired models for the dark energy. These investigations have, indeed, managed to make some significant advances towards explaining the empirical data. Nonetheless, surprisingly little thought has been given to conceptual issues such as the composition and the very nature of the implicated energy source. In the current discourse, we attempt to fill this gap by the way of some speculative yet logically self-consistent arguments. Our construction takes us along a path that begins with an entanglement entropy and ends up at a Hubble-sized gas of exotic particles. Moreover, our interpretation of the dark energy turns out to be suggestive of a natural resolution to the cosmic-coincidence problem.

A. J. M. Medved

2008-02-13T23:59:59.000Z

302

The Coincidence Problem and Interacting Holographic Dark Energy  

E-Print Network (OSTI)

We study the dynamical behaviour of the interacting holographic dark energy model whose interaction term is $Q=3H(\\lam_d\\rho_d + \\lam_c\\rho_c)$, where $\\rho_d$ and $\\rho_c$ are the energy density of dark energy and CDM respectively. To satisfy the observational constraints from SNIa, CMB shift parameter and BAO measurement, if $\\lam_c = \\lam_d$ or $\\lam_d, \\lam_c >0$, the cosmic evolution will only reach the attractor in the future and the ratio $\\rho_c/\\rho_d$ cannot be slowly varying at present. Since the cosmic attractor can be reached in the future even when the present values of the cosmological parameters do not satisfy the observational constraints, the coincidence problem is not really alleviated in this case. However, if $\\lam_c \

Khamphee Karwan

2008-01-11T23:59:59.000Z

303

Inflation and dark energy from three-forms  

E-Print Network (OSTI)

Three-forms can give rise to viable cosmological scenarios of inflation and dark energy with potentially observable signatures distinct from standard single scalar field models. In this study, the background dynamics and linear perturbations of self-interacting three-form cosmology are investigated. The phase space of cosmological solutions possesses (super)-inflating attractors and saddle points which can describe three-form driven inflation or dark energy. The quantum generation and the classical evolution of perturbations is considered. The scalar and tensor spectra from a three-form inflation and the impact from the presence of a three-form on matter perturbations are computed. Stability properties and equivalence of the model with alternative formulations are discussed.

Nunes, Tomi S Koivisto Nelson J

2009-01-01T23:59:59.000Z

304

Phantom dark energy as an effect of bulk viscosity  

E-Print Network (OSTI)

In a homogeneous and isotropic universe bulk viscosity is the unique viscous effect capable to modify the background dynamics. Effects like shear viscosity or heat conduction can only change the evolution of the perturbations. The existence of a bulk viscous pressure in a fluid, which in order to obey to the second law of thermodynamics is negative, reduces its effective pressure. We discuss in this study the degeneracy in bulk viscous cosmologies and address the possibility that phantom dark energy cosmology could be caused by the existence of non-equilibrium pressure in any cosmic component. We establish the conditions under which either matter or radiation viscous cosmologies can be mapped into the phantom dark energy scenario with constraints from multiple observational data-sets

Hermano Velten; Jiaxin Wang; Xinhe Meng

2013-07-16T23:59:59.000Z

305

Dynamics of Bianchi I Universe with Magnetized Anisotropic Dark Energy  

E-Print Network (OSTI)

We study Bianchi type $I$ cosmological model in the presence of magnetized anisotropic dark energy. The energy-momentum tensor consists of anisotropic fluid with anisotropic EoS $p=\\omega{\\rho}$ and a uniform magnetic field of energy density $\\rho_B$. We obtain exact solutions to the field equations using the condition that expansion is proportional to the shear scalar. The physical behavior of the model is discussed with and without magnetic field. We conclude that universe model as well as anisotropic fluid do not approach isotropy through the evolution of the universe.

M. Sharif; M. Zubair

2010-05-25T23:59:59.000Z

306

Dynamics of Bianchi I Universe with Magnetized Anisotropic Dark Energy  

E-Print Network (OSTI)

We study Bianchi type $I$ cosmological model in the presence of magnetized anisotropic dark energy. The energy-momentum tensor consists of anisotropic fluid with anisotropic EoS $p=\\omega{\\rho}$ and a uniform magnetic field of energy density $\\rho_B$. We obtain exact solutions to the field equations using the condition that expansion is proportional to the shear scalar. The physical behavior of the model is discussed with and without magnetic field. We conclude that universe model as well as anisotropic fluid do not approach isotropy through the evolution of the universe.

Sharif, M

2010-01-01T23:59:59.000Z

307

Dark Energy, Induced Gravity and Broken Scale Invariance  

E-Print Network (OSTI)

We study the cosmological evolution of an induced gravity model with a self-interacting scalar field $\\sigma$ and in the presence of matter and radiation. Such model leads to Einstein Gravity plus a cosmological constant as a stable attractor among homogeneous cosmologies and is therefore a viable dark-energy (DE) model for a wide range of scalar field initial conditions and values for its positive $\\gamma$ coupling to the Ricci curvature $\\gamma \\sigma^{2}R$.

Finelli, F; Venturi, G

2008-01-01T23:59:59.000Z

308

Solar System Constraints on Gauss-Bonnet Dark Energy  

E-Print Network (OSTI)

Quadratic curvature Gauss-Bonnet gravity may be the solution to the dark energy problem, but a large coupling strength is required. This can lead to conflict with laboratory and planetary tests of Newton's law, as well as light bending. The corresponding constraints are derived. If applied directly to cosmological scales, the resulting bound on the density fraction is |Omega_GB| < 3.6 x 10^-32.

Stephen C. Davis

2007-08-15T23:59:59.000Z

309

Holographic dark energy with non-minimal coupling  

E-Print Network (OSTI)

We study a scalar field non-minimally coupled to the curvature, in the framework of holographic dark energy. We obtain a relation between the coupling of the scalar field and the holographic DE parameters. In the model without potential we found the EOS parameter in different regions of the parameters, giving rise to accelerated expansion. For some restrictions on the parameters, the model presents quintom behavior.

L. N. Granda; L. D. Escobar

2009-10-03T23:59:59.000Z

310

9/18/09 2:07 PMSPACE.com --'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 8http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html  

E-Print Network (OSTI)

9/18/09 2:07 PMSPACE.com -- 'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 8http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html What is Dark Energy? Universe Might Be Bigger and Older Than Expected In New? Register: Join Now! 'Big Wave' Theory Offers Alternative to Dark Energy By Clara Moskowitz Staff

Temple, Blake

311

The Energy Density of the Quaternionic Field as Dark Energy in the Universe  

E-Print Network (OSTI)

In this article we describe a model of the universe consisting of a mixture of the ordinary matter and a so-called cosmic quaternionic field. The basic idea here consists in an attempt to interpret $\\Lambda$ as the energy density of the quaternionic field whose source is any form of energy including the proper energy density of this field. We set the energy density of this field to $\\Lambda$ and show that the ratio of ordinary dark matter energy density assigned to $\\Lambda$ is constant during the cosmic evolution. We investigate the interaction of the quaternionic field with the ordinary dark matter and show that this field exerts a force on the moving dark matter which might possible create the dark matter in the early universe. Such determined $\\Lambda$ fulfils the requirements asked from the dark energy. In this model of the universe, the cosmical constant, the fine-tuning and the age problems might be solved. Finally, we sketch the evolution of the universe with the cosmic quaternionic field and show that the energy density of the cosmic quaternionic field might be a possible candidate for the dark energy.

V. Majernik

2003-11-05T23:59:59.000Z

312

Method for Reducing Background Clutter in a Camera Image - Energy ...  

Energy Analysis; Energy Storage; Geothermal; Hydrogen and Fuel Cell; Hydropower, Wave and Tidal; ... and any other scenario which requires accurate 3D mapping. ...

313

Shedding Light on Dark Matter and Dark Energy | Argonne National Laboratory  

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

Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Shedding Light on Dark Matter and Dark Energy By Gail Pieper * March 6, 2013 Tweet EmailPrint Cosmology is currently in one of its most scientifically exciting phases.

314

A Terrestrial Search for Dark Contents of the Vacuum, Such as Dark Energy, Using Atom Interferometry  

SciTech Connect

We describe the theory and first experimental work on our concept for searching on earth for the presence of dark contents of the vacuum (DCV) using atom interferometry. Specifically, we have in mind any DCV that has not yet been detected on a laboratory scale, but which might manifest itself as dark energy on the cosmological scale. The experimental method uses two atom interferometers to cancel the effect of earth's gravity and diverse noise sources. It depends upon two assumptions: first, that the DCV possesses some space inhomogeneity in density, and second that it exerts a sufficiently strong nongravitational force on matter. The motion of the apparatus through the DCV should then lead to an irregular variation in the detected matter-wave phase shift. We discuss the nature of this signal and note the problem of distinguishing it from instrumental noise. We also discuss the relation of our experiment to what might be learned by studying the noise in gravitational wave detectors such as LIGO. The paper concludes with a projection that a future search of this nature might be carried out using an atom interferometer in an orbiting satellite. The laboratory apparatus is now being constructed.

Adler, Ronald J.; /Stanford U., HEPL /San Francisco State U.; Muller, Holger; /UC, Berkeley; Perl, Martin L.; /KIPAC, Menlo Park /SLAC

2012-06-11T23:59:59.000Z

315

Galactic cluster winds in presence of a dark energy  

E-Print Network (OSTI)

We obtain a solution for the hydrodynamic outflow of the polytropic gas from the gravitating center, in presence of the uniform Dark Energy (DE). The antigravity of DE is enlightening the outflow and make the outflow possible at smaller initial temperature, at the same density. The main property of the wind in presence of DE is its unlimited acceleration after passing the critical point. In application of this solution to the winds from galaxy clusters we suggest that collision of the strongly accelerated wind with another galaxy cluster, or with another galactic cluster wind could lead to the formation of a highest energy cosmic rays.

Bisnovatyi-Kogan, G S

2013-01-01T23:59:59.000Z

316

arXiv:astro-ph/0208093v327Nov2002 Dark Energy and Matter Evolution from Lensing Tomography  

E-Print Network (OSTI)

arXiv:astro-ph/0208093v327Nov2002 Dark Energy and Matter Evolution from Lensing Tomography Wayne Hu on the growth function of structure and the evolution of the dark energy density. We examine this potential tests for the existence of multiple dark matter components or a dark energy component

Hu, Wayne

317

Generalized LTB model with Inhomogeneous Isotropic Dark Energy: Observational Constraints  

E-Print Network (OSTI)

We consider on-center and off-center observers in an inhomogeneous, spherically symmetric, isocurvature (flat) concentration of dark energy with typical size of a few Gpc. Such a concentration could be produced e.g. by a recently formed global monopole with core size that approaches the Hubble scale. In this case we would have what may be called `topological quintessence' in analogy with the well-known topological inflation. We show that the minimum comoving radius r_{0min} of such a dark energy inhomogeneity that is consistent with the Union2 Type Ia supernovae (SnIa) data at the 3\\sigma level is r_{0min}\\simeq 1.8 Gpc. As expected, the best-fit fractional dark energy density at the center, \\Omega_X,in, approaches the corresponding LCDM value \\Omega_X,in =0.73 for large enough values of the inhomogeneity radius r_0 (r_0 > 4Gpc). Using the Union2 data, we show that the maximum allowed shift r_{obs-max} of the observer from the center of the inhomogeneity is about 0.7 r_0 which respects the Copernican principle. The model naturally predicts the existence of a preferred axis and alignment of the low CMB multipoles. However, the constraints on r_{obs-max} coming from the magnitude of the CMB dipole remain a severe challenge to the Copernican principle and lead to r_{obs-max}< 110 Mpc even for an inhomogeneity radius as large as r_0=7 Gpc.

J. Grande; L. Perivolaropoulos

2011-03-21T23:59:59.000Z

318

Interacting new agegraphic dark energy in non-flat Brans-Dicke cosmology  

E-Print Network (OSTI)

We construct a cosmological model of late acceleration based on the new agegraphic dark energy model in the framework of Brans-Dicke cosmology where the new agegraphic energy density $\\rho_{D}= 3n^2 m^2_p /\\eta^{2}$ is replaced with $\\rho_{D}= {3n^2\\phi^2}/({4\\omega \\eta^2}$). We show that the combination of Brans-Dicke field and agegraphic dark energy can accommodate $w_D = -1 $ crossing for the equation of state of \\textit{noninteracting} dark energy. When an interaction between dark energy and dark matter is taken into account, the transition of $w_D $ to phantom regime can be more easily accounted for than when resort to the Einstein field equations is made. In the limiting case $\\alpha = 0$ $(\\omega\\to \\infty)$, all previous results of the new agegraphic dark energy in Einstein gravity are restored.

Ahmad Sheykhi

2009-08-05T23:59:59.000Z

319

Limits from Weak Gravity Conjecture on Dark Energy Models  

E-Print Network (OSTI)

The weak gravity conjecture has been proposed as a criterion to distinguish the landscape from the swampland in string theory. As an application in cosmology of this conjecture, we use it to impose theoretical constraint on parameters of two types of dark energy models. Our analysis indicates that the Chaplygin-gas-type models realized in quintessence field are in the swampland, whereas the $a$ power-low decay model of the variable cosmological constant can be viable but the parameters are tightly constrained by the conjecture.

Xing Wu; Zong-Hong Zhu

2007-10-07T23:59:59.000Z

320

Modified GBIG Scenario as a Successful Alternative for Dark Energy  

E-Print Network (OSTI)

We construct a DGP-inspired braneworld model where induced gravity on the brane is modified in the spirit of $f(R)$ gravity and stringy effects are taken into account by incorporation of the Gauss-Bonnet term in the bulk action. We explore cosmological dynamics of this model and we show that this scenario is a successful alternative for dark energy proposal. Interestingly, it realizes the phantom-like behavior without introduction of any phantom field on the brane and the effective equation of state parameter crosses the cosmological constant line naturally in the same way as observational data suggest.

Nozari, Kourosh

2009-01-01T23:59:59.000Z

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


321

Modified GBIG Scenario as an Alternative for Dark Energy  

E-Print Network (OSTI)

We construct a DGP-inspired braneworld model where induced gravity on the brane is modified in the spirit of $f(R)$ gravity and stringy effects are taken into account by incorporation of the Gauss-Bonnet term in the bulk action. We explore cosmological dynamics of this model and we show that this scenario is a successful alternative for dark energy proposal. Interestingly, it realizes the phantom-like behavior without introduction of any phantom field on the brane and the effective equation of state parameter crosses the cosmological constant line naturally in the same way as observational data suggest.

Kourosh Nozari; Narges Rashidi

2009-06-23T23:59:59.000Z

322

Dark Energy from holographic theories with hyperscaling violation  

E-Print Network (OSTI)

We show that analytical continuation maps scalar solitonic solutions of Einstein-scalar gravity, interpolating between an hyperscaling violating and an Anti de Sitter (AdS) region, in flat FLRW cosmological solutions sourced by a scalar field. We generate in this way exact FLRW solutions that can be used to model cosmological evolution driven by dark energy (a quintessence field) and usual matter. In absence of matter, the flow from the hyperscaling violating regime to the conformal AdS fixed point in holographic models corresponds to cosmological evolution from power-law expansion at early cosmic times to a de Sitter (dS) stable fixed point at late times. In presence of matter, we have a scaling regime at early times, followed by an intermediate regime in which dark energy tracks matter. At late times the solution exits the scaling regime with a sharp transition to a dS spacetime. The phase transition between hyperscaling violation and conformal fixed point observed in holographic gravity has a cosmological counterpart in the transition between a scaling era and a dS era dominated by the energy of the vacuum.

Mariano Cadoni; Matteo Ciulu

2013-11-16T23:59:59.000Z

323

Magnetized dark energy and the late time acceleration  

E-Print Network (OSTI)

In the present work we have searched the existence of the late time acceleration of the Universe. The matter source that is responsible for the late time acceleration of the Universe consists of cosmic fluid with the equation of state parameter $\\omega =\\frac{p}{\\rho}$ and uniform magnetic field of energy density $\\rho_{B}$. The study is done here under the framework of spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-I cosmological model in the presence of magnetized dark energy. To get the deterministic model of the Universe, we assume that the shear scalar $(\\sigma)$ in the model is proportional to expansion scalar $(\\theta)$. This condition leads to $A=B^{n}$, where $A$ and $B$ are metric functions and $n$ is a positive constant giving the proportionality condition between shear and expansion scalar. It has been found that the isotropic distribution of magnetized dark energy leads to the present accelerated expansion of the Universe and the derived model is in good agreement with the recent astrophysical observations. The physical behavior of the Universe has been discussed in details.

Anil Kumar Yadav; Farook Rahaman; Saibal Ray; G. K. Goswami

2012-02-03T23:59:59.000Z

324

An Interacting Dark Energy Model for the Expansion History of the Universe  

E-Print Network (OSTI)

We explore a model of interacting dark energy where the dark energy density is related by the holographic principle to the Hubble parameter, and the decay of the dark energy into matter occurs at a rate comparable to the current value of the Hubble parameter. We find this gives a good fit to the observational data supporting an accelerating Universe, and the model represents a possible alternative interpretation of the expansion history of the Universe.

Micheal S. Berger; Hamed Shojaei

2006-06-16T23:59:59.000Z

325

Holographic dark energy with varying gravitational constant in Horava-Lifshitz cosmology  

E-Print Network (OSTI)

We investigate the holographic dark energy scenario with a varying gravitational constant in a flat background in the context of Ho\\v{r}ava-Lifshitz gravity. We extract the exact differential equation determining the evolution of the dark energy density parameter, which includes $G$ variation term. Also we discuss a cosmological implication of our work by evaluating the dark energy equation of state for low redshifts containing varying $G$ corrections.

M. R. Setare; Mubasher Jamil

2010-01-08T23:59:59.000Z

326

Hydro-Gravitational-Dynamics of Planets and Dark Energy  

E-Print Network (OSTI)

Self-gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition from plasma to gas. Linear protogalaxyclusters fragment at 0.003 Mpc viscous-inertial scales along turbulent vortex lines or in spirals, as observed. The plasma protogalaxies fragment on transition into white-hot planet-mass gas clouds (PFPs) in million-solar-mass clumps (PGCs) that become globular-star-clusters (GCs) from tidal forces or dark matter (PGCs) by freezing and diffusion into 0.3 Mpc halos with 97% of the galaxy mass. The weakly collisional non-baryonic dark matter diffuses to > Mpc scales and frag-ments to form galaxy cluster halos. Stars and larger planets form by binary mergers of the trillion PFPs per PGC on 0.03 Mpc galaxy accretion disks. Star deaths depend on rates of planet accretion and internal star mixing. Moderate accretion rates produce white dwarfs that evaporate surrounding gas planets by spin-radiation to form planetary nebulae before Supernova Ia events, dimming some events to give systematic distance errors misinterpreted as the dark energy hypothesis and overestimates of the universe age. Failures of standard LCDM cosmological models reflect not only obsolete Jeans 1902 fluid mechanical assumptions, but also failures of standard turbulence models that claim the cascade of turbulent kinetic energy is from large scales to small. Because turbulence is always driven at all scales by inertial-vortex forces the turbulence cascade is always from small scales to large.

Carl H. Gibson; Rudolph E. Schild

2008-08-24T23:59:59.000Z

327

Interacting model of new agegraphic dark energy: observational constraints and age problem  

E-Print Network (OSTI)

Many dark energy models fail to pass the cosmic age test because of the old quasar APM 08279+5255 at redshift $z=3.91$, the $\\Lambda$CDM model and holographic dark energy models being no exception. In this paper, we focus on the topic of age problem in the new agegraphic dark energy (NADE) model. We determine the age of the universe in the NADE model by fitting the observational data, including type Ia supernovae (SNIa), baryon acoustic oscillations (BAO) and the cosmic microwave background (CMB). We find that the NADE model also faces the challenge of the age problem caused by the old quasar APM 08279+5255. In order to overcome such a difficulty, we consider the possible interaction between dark energy and dark matter. We show that this quasar can be successfully accommodated in the interacting new agegraphic dark energy (INADE) model at the $2\\sigma$ level under the current observational constraints.

Yun-He Li; Jing-Zhe Ma; Jing-Lei Cui; Zhuo Wang; Xin Zhang

2010-11-29T23:59:59.000Z

328

Dark Energy Models and Laws of Thermodynamics in Bianchi I Model  

E-Print Network (OSTI)

This paper is devoted to check validity of the laws of thermodynamics for LRS Bianchi type I universe model which is filled with combination of dark matter and dark energy. We take two types of dark energy models, i.e., generalized holographic dark energy and generalized Ricci dark energy. It is proved that the first and generalized second law of thermodynamics are valid on the apparent horizon for both the models. Further, we take fixed radius $L$ of the apparent horizon with original holographic or Ricci dark energy. We conclude that the first and generalized second laws of thermodynamics do not hold on the horizon of fixed radius $L$ for both the models.

Sharif, M

2013-01-01T23:59:59.000Z

329

Dark Energy Models and Laws of Thermodynamics in Bianchi I Model  

E-Print Network (OSTI)

This paper is devoted to check validity of the laws of thermodynamics for LRS Bianchi type I universe model which is filled with combination of dark matter and dark energy. We take two types of dark energy models, i.e., generalized holographic dark energy and generalized Ricci dark energy. It is proved that the first and generalized second law of thermodynamics are valid on the apparent horizon for both the models. Further, we take fixed radius $L$ of the apparent horizon with original holographic or Ricci dark energy. We conclude that the first and generalized second laws of thermodynamics do not hold on the horizon of fixed radius $L$ for both the models.

M. Sharif; Rabia Saleem

2013-02-20T23:59:59.000Z

330

Astro2010 White Paper Coronal "Dark Energy" and Solar/Stellar Activity  

E-Print Network (OSTI)

Astro2010 White Paper Coronal "Dark Energy" and Solar/Stellar Activity Stephen White, University activity. Solar activity is intrinsically tied to its magnetic field, the "dark energy" of the Sun's atmo efficient energy conversion takes place must be small. In the solar corona this scale is of order tens

331

Interacting polytropic gas model of phantom dark energy in non-flat universe  

E-Print Network (OSTI)

By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for even polytropic index by choosing $K>Ba^{\\frac{3}{n}}$, one can obtain $\\omega^{\\rm eff}_{\\Lambda}dark energy.

K. Karami; S. Ghaffari; J. Fehri

2009-11-25T23:59:59.000Z

332

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

333

Testing Loop Quantum Gravity and Electromagnetic Dark Energy in Superconductors  

E-Print Network (OSTI)

In 1989 Cabrera and Tate reported an anomalous excess of mass of the Cooper pairs in rotating thin Niobium rings. So far, this experimental result never received a proper theoretical explanation in the context of superconductor's physics. In the present work we argue that what Cabrera and Tate interpreted as an anomalous excess of mass can also be associated with a deviation from the classical gravitomagnetic Larmor theorem due to the presence of dark energy in the superconductor, as well as with the discrete structure of the area of the superconducting Niobium ring as predicted by Loop Quantum Gravity. From Cabrera and Tate measurements we deduce that the quantization of spacetime in superconducting circular rings occurs at the Planck-Einstein scale $l_{PE} = (\\hbar G/c^3 \\Lambda)^{1/4}\\sim 3.77\\times 10 ^{-5} m$, instead of the Planck scale $l_{P} =(\\hbar G / c^3)^{1/2}=1.61 \\times 10 ^{-35} m$, with an Immirzi parameter which depends on the specific critical temperature of the superconducting material and on the area of the ring. The stephan-Boltzmann law for quantized areas delimited by superconducting rings is predicted, and an experimental concept based on the electromagnetic black-body radiation emitted by this surfaces, is proposed to test loop quantum gravity and electromagnetic dark energy in superconductors.

Clovis Jacinto de Matos

2008-12-30T23:59:59.000Z

334

Reconciling dark energy models with f(R) theories  

E-Print Network (OSTI)

Higher order theories of gravity have recently attracted a lot of interest as alternative candidates to explain the observed cosmic acceleration without the need of introducing any scalar field. A critical ingredient is the choice of the function f(R) of the Ricci scalar curvature entering the gravity Lagrangian and determining the dynamics of the universe. We describe an efficient procedure to reconstruct f(R) from the Hubble parameter $H$ depending on the redshift z. Using the metric formulation of f(R) theories, we derive a third order linear differential equation for f(R(z)) which can be numerically solved after setting the boundary conditions on the basis of physical considerations. Since H(z) can be reconstructed from the astrophysical data, the method we present makes it possible to determine, in principle, what is the f(R) theory which best reproduces the observed cosmological dynamics. Moreover, the method allows to reconcile dark energy models with f(R) theories finding out what is the expression of f(R) which leads to the same H(z) of the given quintessence model. As interesting examples, we consider "quiessence" (dark energy with constant equation of state) and the Chaplygin gas.

S. Capozziello; V. F. Cardone; A. Troisi

2005-01-20T23:59:59.000Z

335

NASA and DOE Collaborate on Dark Energy Research | U.S. DOE Office of  

Office of Science (SC) Website

8 » NASA and DOE 8 » NASA and DOE Collaborate on Dark Energy Research News Featured Articles 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 Science Headlines Presentations & Testimony News Archives Contact Information Office of Science U.S. Department of Energy 1000 Independence Ave., SW Washington, DC 20585 P: (202) 586-5430 11.19.08 NASA and DOE Collaborate on Dark Energy Research Print Text Size: A A A Subscribe FeedbackShare Page WASHINGTON, DC -- NASA and the U.S. Department of Energy (DOE) have signed a memorandum of understanding for the implementation of the Joint Dark Energy Mission, or JDEM. The mission will feature the first space-based observatory designed specifically to understand the nature of dark energy. Dark energy is a form of energy that pervades and dominates the universe.

336

Effective Dark Energy Models and Dark Energy Models with Bounce in frames of $F(T)$ Gravity  

E-Print Network (OSTI)

Various cosmological models in frames of $F(T)$ gravity are considered. The general scheme of constructing effective dark energy models with various evolution is presented. It is showed that these models in principle are compatible with $\\Lambda$CDM model. The dynamics of universe governed by $F(T)$ gravity can mimics $\\Lambda$CDM evolution in past but declines from it in a future. We also construct some dark energy models with the "real" (non-effective) equation-of-state parameter $w$ such that $w\\leq-1$. It is showed that in $F(T)$ gravity the Universe filled phantom field not necessarily ends its existence in singularity. There are two possible mechanisms permitting the final singularity. Firstly due to the nonlinear dependence between energy density and $H^{2}$ ($H$ is the Hubble parameter) the universe can expands not so fast as in the general relativity and in fact Little Rip regime take place instead Big Rip. We also considered the models with possible bounce in future. In these models the universe expansion can mimics the dynamics with future singularity but due to bounce in future universe begin contracts.

Artyom V. Astashenok

2013-08-02T23:59:59.000Z

337

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

338

Statefinder diagnostic and $w-w^{\\prime}$ analysis for interacting polytropic gas dark energy model  

E-Print Network (OSTI)

The interacting polytropic gas dark energy model is investigated from the viewpoint of statefinder diagnostic tool and $w-w^{\\prime}$ analysis. The dependency of the statefinder parameters on the parameter of the model as well as the interaction parameter between dark matter and dark energy is calculated. We show that different values of the parameters of model and different values of interaction parameter result different evolutionary trajectories in $s-r$ and $w-w^{\\prime}$ planes. The polytropic gas model of dark energy mimics the standard $\\Lambda$CDM model at the early time.

M. Malekjani; A. Khodam-Mohammadi

2012-01-03T23:59:59.000Z

339

Modified Holographic Dark Energy in Non-flat Kaluza-Klein Universe with Varying G  

E-Print Network (OSTI)

The purpose of this paper is to discuss the evolution of modified holographic dark energy with variable $G$ in non-flat Kaluza$-$Klein universe. We consider the non-interacting and interacting scenarios of the modified holographic dark energy with dark matter and obtain the equation of state parameter through logarithmic approach. It turns out that the universe remains in different dark energy eras for both cases. Further, we study the validity of the generalized second law of thermodynamics in this scenario. We also justify that the statefinder parameters satisfy the limit of $\\Lambda$CDM model.

M. Sharif; A. Jawad

2012-04-30T23:59:59.000Z

340

A model of accelerating dark energy in decelerating gravity  

E-Print Network (OSTI)

The expansion of the Universe is accelerated as testified by observations of SNeIa at varying redshifts. Explanations of this acceleration are of two kinds: modifications of Einstein gravity or new forms of energy. An example of modified gravity is the braneworld Dvali-Gabadadze-Porrati (DGP) model, an example of dark energy is Chaplygin gas. Both are characterized by a cross-over length scale $r_c$ which marks the transition between physics occurring on our four-dimensional brane, and in a five-dimensional bulk space. Assuming that the scales $r_c$ in the two models are the same, we study Chaplygin gas dark energy in flat DGP geometries. The self-accelerating branch does not give a viable model, it causes too much acceleration. We derive the Hubble function and the luminosity distance for the self-decelerating branch, and then fit a compilation of 192 SNeIa magnitudes and redshifts in the space of the three parameters of the model. Our model with the self-decelerating branch fits the supernova data as successfully as does the $\\Lambda CDM$ model, and with only one additional parameter. In contrast to the $\\Lambda CDM$ model, this model needs no fine-tuning, and it can explain the coincidence problem. It is unique in the sense that it cannot be reduced to a cosmological constant model in any other limit of the parameter space than in the distant future. If later tests with other cosmological data are successful, we have here a first indication that we live in a five-dimensional braneworld.

M. Roos

2007-07-07T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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 holographic dark energy in non-flat Brans-Dicke cosmology  

E-Print Network (OSTI)

In this paper we study cosmological application of holographic dark energy density in the Brans-Dicke framework. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named $L$. Our calculation show, taking $\\Omega_{\\Lambda}=0.73$ for the present time, the lower bound of $w_{\\rm \\Lambda}$ is -0.9. Therefore it is impossible to have $w_{\\rm \\Lambda}$ crossing -1. This implies that one can not generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans-Dicke cosmology framework. In the other hand, we suggest a correspondence between the holographic dark energy scenario in flat universe and the phantom dark energy model in framework of Brans-Dicke theory with potential.

M R Setare

2006-10-17T23:59:59.000Z

342

Thermodynamical properties of interacting holographic dark energy model with apparent horizon  

E-Print Network (OSTI)

We have investigated the thermodynamical properties of the universe with dark energy. It is demonstrated that in a universe with spacial curvature the natural choice for IR cutoff could be the apparent horizon radius. We shown that any interaction of pressureless dark matter with holographic dark energy, whose infrared cutoff is set by the apparent horizon radius, implying a constant effective equation of state of dark component in a universe. In addition we found that for the static observer in space, the comoving distance has a faster expansion than the apparent horizon radius with any spatial curvature. We also verify that in some conditions the modified first law of thermodynamics could return to the classic form at apparent horizon for a universe filled with dark energy and dark matter. Besides, the generalized second law of thermodynamics is discussed in a region enclosed by the apparent horizon.

Bin Liu; Xian-Ru Hu; Jian-Bo Deng

2011-07-01T23:59:59.000Z

343

Is the Interacting Dark Matter Scenario an Alternative to Dark Energy ?  

E-Print Network (OSTI)

We study the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, which can accommodate an accelerated expansion, equivalent to either the {\\em quintessence} or the standard $\\Lambda$ models. We also find realistic solutions in which the present time is located after the inflection point.

Basilakos, S

2008-01-01T23:59:59.000Z

344

Dark flash photography  

Science Conference Proceedings (OSTI)

Camera flashes produce intrusive bursts of light that disturb or dazzle. We present a prototype camera and flash that uses infra-red and ultra-violet light mostly outside the visible range to capture pictures in low-light conditions. This "dark" flash ... Keywords: computational photography, dark flash, multi-spectral imaging, spectral image correlations

Dilip Krishnan; Rob Fergus

2009-07-01T23:59:59.000Z

345

CDF Note 10709 A Search For Dark Matter in the Monojet + Missing Transverse Energy  

E-Print Network (OSTI)

CDF Note 10709 A Search For Dark Matter in the Monojet + Missing Transverse Energy Signature in 6: November 23, 2011) We present the results of a search for dark matter production in the monojet + missing transverse energy signature. We analyze a sample of Tevatron pp collisions at s=1.96 TeV, recorded

Quigg, Chris

346

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

347

Dark energy: a quantum fossil from the inflationary Universe?  

E-Print Network (OSTI)

The discovery of dark energy (DE) as the physical cause for the accelerated expansion of the Universe is the most remarkable experimental finding of modern cosmology. However, it leads to insurmountable theoretical difficulties from the point of view of fundamental physics. Inflation, on the other hand, constitutes another crucial ingredient, which seems necessary to solve other cosmological conundrums and provides the primeval quantum seeds for structure formation. One may wonder if there is any deep relationship between these two paradigms. In this work, we suggest that the existence of the DE in the present Universe could be linked to the quantum field theoretical mechanism that may have triggered primordial inflation in the early Universe. This mechanism, based on quantum conformal symmetry, induces a logarithmic, asymptotically-free, running of the gravitational coupling. If this evolution persists in the present Universe, and if matter is conserved, the general covariance of Einstein's equations demands...

Sola, Joan

2007-01-01T23:59:59.000Z

348

Do primordial Lithium abundances imply there's no Dark Energy?  

E-Print Network (OSTI)

Explaining the well established observation that the expansion rate of the universe is apparently accelerating is one of the defining scientific problems of our age. Within the standard model of cosmology, the repulsive 'dark energy' supposedly responsible has no explanation at a fundamental level, despite many varied attempts. A further important dilemma in the standard model is the Lithium problem, which is the substantial mismatch between the theoretical prediction for 7-Li from Big Bang Nucleosynthesis and the value that we observe today. This observation is one of the very few we have from along our past worldline as opposed to our past lightcone. By releasing the untested assumption that the universe is homogeneous on very large scales, both apparent acceleration and the Lithium problem can be easily accounted for as different aspects of cosmic inhomogeneity, without causing problems for other cosmological phenomena such as the cosmic microwave background. We illustrate this in the context of a void model.

Marco Regis; Chris Clarkson

2010-03-04T23:59:59.000Z

349

Energy from the Center of the Milky Way May Be the Remnant of Dark Matter |  

Office of Science (SC) Website

Energy from Energy from the Center of the Milky Way May Be the Remnant of Dark Matter News Featured Articles 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 Science Headlines Presentations & Testimony News Archives Contact Information Office of Science U.S. Department of Energy 1000 Independence Ave., SW Washington, DC 20585 P: (202) 586-5430 11.17.10 Energy from the Center of the Milky Way May Be the Remnant of Dark Matter Dark matter particles continue to hide, but they release energy when they collide: evidence shows that gamma rays from the center of our galaxy may come from dark matter collisions. Print Text Size: A A A Subscribe FeedbackShare Page From the center of the Milky Way, dark matter particles may be sending signals of their existence. Astrophysicists analyzing data from the center

350

Cosmological Coincidence and Dark Mass Problems in Einstein Universe and Friedman Dust Universe with Einstein's Lambda Quantum Cosmology Dark Energy Schroedinger Wave Motion  

E-Print Network (OSTI)

In this paper, it is shown that the cosmological model that was introduced in a sequence of three earlier papers under the title, A Dust Universe Solution to the Dark Energy Problem can be used to analyse and solve the Cosmological Coincidence Problem. The generic coincidence problem that appears in the original Einstein universe model is shown to arise from a misunderstanding about the magnitude of dark energy density and the epoch time governing the appearance of the integer relation between dark energy and normal energy density. The solution to the generic case then clearly points to the source of the time coincidence integer problem in the Friedman dust universe model. It is then possible to eliminate this coincidence by removing a degeneracy between different measurement epoch times. In this paper's first appendix, a fundamental time dependent relation between dark mass and dark energy is derived with suggestions how this relation could explain cosmological voids and the clumping of dark mass to become visible matter. In this paper's second appendix, it is shown that that dark energy is a conserved with time substance that is everywhere and for all time permeable to the dark mass and visible mass of which the contracting or expanding universe is composed. The last two appendices involve detailed studies of cosmology, quantum dark energy related issues. There are more detailed abstracts given with all four appendices.

James G. Gilson

2007-05-20T23:59:59.000Z

351

9/18/09 2:43 PM'Big Wave' Theory Offers Alternative to Dark Energy // Current Page 1 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy.htm  

E-Print Network (OSTI)

9/18/09 2:43 PM'Big Wave' Theory Offers Alternative to Dark Energy // Current Page 1 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy.htm login | register |home tv shows schedule to Dark Energy // Current Page 2 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy

Temple, Blake

352

Problems of antimatter after Big Bang, dark energy and dark matter. Solutions in the frame of non-local physics  

E-Print Network (OSTI)

Quantum solitons are discovered with the help of generalized quantum hydrodynamics. The solitons have the character of the stable quantum objects in the self consistent electric field. The delivered theory demonstrates the great possibilities of the generalized quantum hydrodynamics in investigation of the quantum solitons. The theory leads to solitons as typical formations in the generalized quantum hydrodynamics. The principle of universal antigravitation is considered from positions of the Newtonian theory of gravitation and non-local kinetic theory. It is found that explanation of Hubble effect in the Universe and peculiar features of the rotational speeds of galaxies need not in introduction of new essence like dark matter and dark energy. Problems of antimatter after Big Bang are considered from positions of non-local physics. The origin of difficulties consists in total Oversimplification following from principles of local physics and reflects the general shortenings of the local kinetic transport theory. Keywords: Foundations of the theory of transport processes; generalized Boltzmann physical kinetics; plasma - gravitational analogy; antigravitation; dark energy; dark matter; the theory of solitons; antimatter after Big Bang. PACS: 67.55.Fa, 67.55.Hc

Boris V. Alexeev

2010-12-22T23:59:59.000Z

353

9/18/09 2:09 PM'Big Wave' Theory Offers Alternative to Dark Energy -Physical Science Page 1 of 3http://scienceblips.dailyradar.com/story/big_wave_theory_offers_alternative_to_dark_energy/  

E-Print Network (OSTI)

9/18/09 2:09 PM'Big Wave' Theory Offers Alternative to Dark Energy - Physical Science Page 1 of 3http://scienceblips.dailyradar.com/story/big_wave_theory_offers_alternative_to_dark_energy/ Gadget working my way through a preprint of a paper arguing that dark energy is not what many scientists think

Temple, Blake

354

9/18/09 2:12 PM'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 4http://digg.com/general_sciences/Big_Wave_Theory_Offers_Alternative_to_Dark_Energy  

E-Print Network (OSTI)

9/18/09 2:12 PM'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 4http://digg.com/general_sciences/Big_Wave_Theory_Offers_Alternative_to_Dark_Energy show profanity settings Digg is a place Offers Alternative to Dark Energy space.com -- Mathematicians have proposed an alternative explanation

Temple, Blake

355

Behaviour of interacting Ricci dark energy in logarithmic f(T) gravity  

E-Print Network (OSTI)

In the present work we have considered a modified gravity dubbed as "logarithmic $f(T)$ gravity" and investigated the behavior of Ricci dark energy interacting with pressureless dark matter. We have chosen the interaction term in the form $Q\\propto H\\delta\\rho_{m}$ and investigated the behavior of the Hubble parameter $H$ as a function of the redshift $z$. For this reconstructed $H$ we have investigated the behavior of the density of the Ricci dark energy $\\rho_{RDE}$ and density contribution due to torsion $\\rho_{T}$. All of the said cosmological parameters are seen to have increasing behavior from higher to lower redshifts for all values of $c^{2}$ pertaining to the Ricci dark energy. Subsequently, we observed the equation of state parameter $w_{RDE}$ in this situation. The equation of state parameter is found to behave like phantom for all choices of $c^{2}$ in the Ricci dark energy.

Rahul Ghosh; Surajit Chattopadhyay

2012-10-07T23:59:59.000Z

356

Interacting holographic dark energy in the scalar-Gauss-Bonnet gravity  

E-Print Network (OSTI)

In this paper we study cosmological application of interacting holographic dark energy density in the scalar-Gauss-Bonnet framework. We employ the interacting holographic model of dark energy to obtain the equation of state for the interacting holographic energy density in spatially flat universe. Our calculation show, taking $\\Omega_{\\Lambda}=0.73$ for the present time, it is possible to have $w_{\\rm \\Lambda}^{eff}$ crossing -1. This implies that one can generate phantom-like equation of state from the interacting holographic dark energy model in flat universe in the scalar-Gauss-Bonnet cosmology framework. Then we reconstruct the potential of the scalar field.

M. R. Setare

2007-08-24T23:59:59.000Z

357

arXiv:astro-ph/0410680v227Jan2005 Crossing the Phantom Divide: Dark Energy Internal Degrees of Freedom  

E-Print Network (OSTI)

arXiv:astro-ph/0410680v227Jan2005 Crossing the Phantom Divide: Dark Energy Internal Degrees Fermi Institute, University of Chicago, Chicago IL 60637 Dark energy constraints have forced viable that evolves across the phantom divide set by . Naively, crossing this divide makes the dark energy

Hu, Wayne

358

arXiv:astro-ph/0407158v17Jul2004 Dark Energy Probes in Light of the CMB  

E-Print Network (OSTI)

arXiv:astro-ph/0407158v17Jul2004 Dark Energy Probes in Light of the CMB Wayne Hu Kavli Institute regime and provided two self-calibrated absolute standards for dark energy studies: the sound horizon redshift range or depth. The single most important complement to the CMB for measuring the dark energy

Hu, Wayne

359

arXiv:astro-ph/0408456v21Dec2004 Measuring Dark Energy Clustering with CMB-Galaxy Correlations  

E-Print Network (OSTI)

arXiv:astro-ph/0408456v21Dec2004 Measuring Dark Energy Clustering with CMB-Galaxy Correlations opportunity to study the dynamics of the dark energy through its large scale clustering properties. Ultimately 3% changes in the gravitational potential or total density fluctuation due to dark energy clustering

Hu, Wayne

360

arXiv:astro-ph/0406496v122Jun2004 A Low CMB Quadrupole from Dark Energy Isocurvature Perturbations  

E-Print Network (OSTI)

arXiv:astro-ph/0406496v122Jun2004 A Low CMB Quadrupole from Dark Energy Isocurvature Perturbations, Chicago IL 60637 We explicate the origin of the temperature quadrupole in the adiabatic dark energy model and explore the mechanism by which scale invariant isocurvature dark energy perturbations can lead to its

Hu, Wayne

Note: This page contains sample records for the topic "dark energy camera" 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

10/14/09 2:35 PMMathematicians' Alternate Model of the Universe Explains Away the Need For Dark Energy | Popular Science Page 1 of 13http://www.popsci.com/military-aviation-amp-space/article/2009-09/mathematicians-seek-explain-away-dark-energy-universe  

E-Print Network (OSTI)

-09/mathematicians-seek-explain-away-dark-energy-universe Mathematicians' Alternate Model of the Universe Explains Away the Need For Dark Energy By Jeremy Hsu Posted 09.25.2009 at 2:15 pm RELATED ARTICLES Most Convincing Sign of Dark Energy's Presence Yet? Dark Energy Hits Tenth Birthday, Still a Mystery Dark Energy

Temple, Blake

362

Interacting Holographic Dark Energy Model as a Dynamical system and the Coincidence Problem  

E-Print Network (OSTI)

We examine the evolution of a holographic cosmological model with future event horizon as the infrared cut-off and dark matter and dark energy do not evolve independently $-$ there is interaction between them. The basic evolution equations are reduced to an autonomous system and corresponding phase space is analyzed.

Ritabrata Biswas; Nairwita Mazumder; Subenoy Chakraborty

2011-06-23T23:59:59.000Z

363

Entropy In The Present And Early Universe: New Small Parameters And Dark Energy Problem  

E-Print Network (OSTI)

It is demonstrated that entropy and its density play a significant role in solving the problem of the vacuum energy density (cosmological constant) of the Universe and hence the dark energy problem. Taking this in mind, two most popular models for dark energy - Holographic Dark Energy Model and Agegraphic Dark Energy Model - are analyzed. It is shown that the fundamental quantities in the first of these models may be expressed in terms of a new small dimensionless parameter. It is revealed that this parameter is naturally occurring in High Energy Gravitational Thermodynamics and Gravitational Holography (UV-limit). On this basis the possibility of a new approach to the problem of Quantum Gravity is discussed. Besides, the results obtained on the uncertainty relation of the pair "cosmological constant - volume of space-time", where the cosmological constant is a dynamic quantity, are reconsidered and generalized up to the Generalized Uncertainty Relation.

A. E. Shalyt-Margolin

2009-11-30T23:59:59.000Z

364

Entropy In The Present And Early Universe, New Small Parameters And Dark Energy Problem  

E-Print Network (OSTI)

It is demonstrated that entropy and its density play a significant role in solving the problem of the vacuum energy density (cosmological constant) of the Universe and hence the dark energy problem. Taking this in mind, two most popular models for dark energy - Holographic Dark Energy Model and Agegraphic Dark Energy Model - are analyzed. It is shown that the fundamental quantities in the first of these models may be expressed in terms of a new small dimensionless parameter. It is revealed that this parameter is naturally occurring in High Energy Gravitational Thermodynamics and Gravitational Holography (UV-limit). On this basis the possibility of a new approach to the problem of Quantum Gravity is discussed. Besides, the results obtained on the uncertainty relation of the pair "cosmological constant - volume of space-time", where the cosmological constant is a dynamic quantity, are reconsidered and generalized up to the Generalized Uncertainty Relation

Shalyt-Margolin, A E

2009-01-01T23:59:59.000Z

365

Low Energy INTEGRAL Positrons from eXciting Dark Matter  

E-Print Network (OSTI)

The origin of the e^+e^- 511 keV line observed by INTEGRAL remains unclear. The rate and morphology of the signal have prompted questions as to whether dark matter could play a role. We explore the case of dark matter upscattering in the framework of eXciting Dark Matter (XDM), where WIMPs \\chi, interacting through a new dark force, scatter into excited states \\chi*, which subsequently emit e^+e^- pairs when they de-excite. We numerically compute the cross sections for two Yukawa-coupled DM particles upscattering into excited states, specifically considering variations motivated by recent N-body simulations with additional baryonic physics. We find that that l>0 components of the partial-wave decomposition are often significant contributions to the total cross section and that for reasonable ranges of parameters dark matter can produce the ~10^43 e^+/s observed by INTEGRAL.

Rob Morris; Neal Weiner

2011-09-17T23:59:59.000Z

366

Extremely High Energy Neutrinos, Neutrino Hot Dark Matter, and the Highest Energy Cosmic Rays  

E-Print Network (OSTI)

Extremely high energy (up to 10**(22) eV) cosmic neutrino beams initiate high energy particle cascades in the background of relic neutrinos from the Big Bang. We perform numerical calculations to show that such cascades could contribute more than 10% to the observed cosmic ray flux above 10**(19) eV if neutrinos have masses in the electron volt range. The required intensity of primary neutrinos could be consistent with astrophysical models for their production if the maximum neutrino energy reaches to 10**(22) eV and the massive neutrino dark matter is locally clustered. Future observations of ultra high energy cosmic rays will lead to an indirect but practical search for neutrino dark matter.

Shigeru Yoshida; Guenter Sigl; Sangjin Lee

1998-08-14T23:59:59.000Z

367

Energy of string loops and thermodynamics of dark energy  

Science Conference Proceedings (OSTI)

We discuss the thermodynamic aspects of a simple model of cosmic string loops, whose energy is nonlinearly related to their lengths. We obtain in a direct way an equation of state having the form p=-(1+{alpha}){rho}/3, with {rho} the energy density and 1+{alpha} the exponent which relates the energy u{sub l} of a loop with its length l as u{sub l}{approx}l{sup 1+{alpha}}. In the linear situation ({alpha}=0) one has p=-{rho}/3, in the quadratic one ({alpha}=1) p=-2{rho}/3, and in the cubic case ({alpha}=2) p=-{rho}. For all values of {alpha} the entropy goes as S{approx}(2-{alpha})L{sup 3/2} (L being the string length density). The expression of S is useful to explore the behavior of such string loops under adiabatic expansion of the Universe. Thermodynamic stability suggests that the gas of string loops must coexist with several long strings, longer than the horizon radius.

Jou, D. [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Mongiovi, M. S.; Sciacca, M. [Dipartimento di Metodi e Modelli Matematici, Universita di Palermo, Viale delle Scienze, 90128, Palermo (Italy)

2011-02-15T23:59:59.000Z

368

Weak Gravity Conjecture and Holographic Dark Energy Model with Interaction and Spatial Curvature  

E-Print Network (OSTI)

In the paper, we apply the weak gravity conjecture to the holographic quintessence model of dark energy. Three different holographic dark energy models are considered: without the interaction in the non-flat universe; with interaction in the flat universe; with interaction in the non-flat universe. We find that only in the models with the spatial curvature and interaction term proportional to the energy density of matter, it is possible for the weak gravity conjecture to be satisfied.

Cheng-Yi Sun

2010-07-09T23:59:59.000Z

369

Interacting Entropy-Corrected Holographic Dark Energy and IR Cut-Off Length  

E-Print Network (OSTI)

In this paper we consider holographic dark energy model with corrected holographic energy density and show that this model may be equivalent to the modified Chaplygin gas model. Then we obtain relation between entropy corrected holographic dark energy model and scalar field models. We do these works by using choices of IR cut-off length proportional to the Hubble radius, the event horizon radius, the Ricci length, and the Granda-Oliveros length.

J. Sadeghi; B. Pourhassan; Z. Abbaspour Moghaddam

2013-06-09T23:59:59.000Z

370

Acceleressence: Dark energy from a phase transition at the seesawscale  

Science Conference Proceedings (OSTI)

Simple models are constructed for ''acceleressence'' dark energy: the latent heat of a phase transition occurring in a hidden sector governed by the seesaw mass scale v{sup 2}/M{sub Pl}, where v is the electroweak scale and M{sub Pl} the gravitational mass scale. In our models, the seesaw scale is stabilized by supersymmetry, implying that the LHC must discover superpartners with a spectrum that reflects a low scale of fundamental supersymmetry breaking. Newtonian gravity may be modified by effects arising from the exchange of fields in the acceleressence sector whose Compton wavelengths are typically of order the millimeter scale. There are two classes of models. In the first class the universe is presently in a metastable vacuum and will continue to inflate until tunneling processes eventually induce a first order transition. In the simplest such model, the range of the new force is bounded to be larger than 25 {micro}m in the absence of fine-tuning of parameters, and for couplings of order unity it is expected to be {approx} 100 {micro}m. In the second class of models thermal effects maintain the present vacuum energy of the universe, but on further cooling, the universe will ''soon'' smoothly relax to a matter dominated era. In this case, the range of the new force is also expected to be of order the millimeter scale or larger, although its strength is uncertain. A firm prediction of this class of models is the existence of additional energy density in radiation at the eV era, which can potentially be probed in precision measurements of the cosmic microwave background. An interesting possibility is that the transition towards a matter dominated era has occurred in the very recent past, with the consequence that the universe is currently decelerating.

Chacko, Z.; Hall, Lawrence J.; Nomura, Yasunori

2004-10-05T23:59:59.000Z

371

End User Computing: The Dark Matter and Dark Energy of Corporate IT  

Science Conference Proceedings (OSTI)

End user computing EUC is like dark matter in physics. EUC is enormous in quantity and importance yet has been largely invisible to corporate IT departments, information systems IS researchers, and corporate management. EUC applications, especially spreadsheet ... Keywords: Base Error Rate, Cell Error Rate, Descriptive Research, End User Computing, Fourth Generation Languages 4GLs, Human Error, Mission-Critical, Primary Descriptive Research, Spreadsheet, Spreadsheet Error, Third Generation Languages 3GLs, Use And User Studies, User Studies

Raymond R. Panko, Daniel N. Port

2013-07-01T23:59:59.000Z

372

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics  

E-Print Network (OSTI)

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.

Maity, Sayani; Debnath, Ujjal

2011-01-01T23:59:59.000Z

373

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics  

E-Print Network (OSTI)

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.

Sayani Maity; Shuvendu Chakraborty; Ujjal Debnath

2011-04-12T23:59:59.000Z

374

On model selection forecasting, Dark Energy and modified gravity  

E-Print Network (OSTI)

The Fisher matrix approach (Fisher 1935) allows one to calculate in advance how well a given experiment will be able to estimate model parameters, and has been an invaluable tool in experimental design. In the same spirit, we present here a method to predict how well a given experiment can distinguish between different models, regardless of their parameters. From a Bayesian viewpoint, this involves computation of the Bayesian evidence. In this paper, we generalise the Fisher matrix approach from the context of parameter fitting to that of model testing, and show how the expected evidence can be computed under the same simplifying assumption of a gaussian likelihood as the Fisher matrix approach for parameter estimation. With this `Laplace approximation' all that is needed to compute the expected evidence is the Fisher matrix itself. We illustrate the method with a study of how well upcoming and planned experiments should perform at distinguishing between Dark Energy models and modified gravity theories. In particular we consider the combination of 3D weak lensing, for which planned and proposed wide-field multi-band imaging surveys will provide suitable data, and probes of the expansion history of the Universe, such as proposed supernova and baryonic acoustic oscillations surveys. We find that proposed large-scale weak lensing surveys from space should be able readily to distinguish General Relativity from modified gravity models.

A. F. Heavens; T. D. Kitching; L. Verde

2007-03-08T23:59:59.000Z

375

Dark energy: a quantum fossil from the inflationary Universe?  

E-Print Network (OSTI)

The discovery of dark energy (DE) as the physical cause for the accelerated expansion of the Universe is the most remarkable experimental finding of modern cosmology. However, it leads to insurmountable theoretical difficulties from the point of view of fundamental physics. Inflation, on the other hand, constitutes another crucial ingredient, which seems necessary to solve other cosmological conundrums and provides the primeval quantum seeds for structure formation. One may wonder if there is any deep relationship between these two paradigms. In this work, we suggest that the existence of the DE in the present Universe could be linked to the quantum field theoretical mechanism that may have triggered primordial inflation in the early Universe. This mechanism, based on quantum conformal symmetry, induces a logarithmic, asymptotically-free, running of the gravitational coupling. If this evolution persists in the present Universe, and if matter is conserved, the general covariance of Einstein's equations demands the existence of dynamical DE in the form of a running cosmological term whose variation follows a power law of the redshift.

Joan Sola

2007-10-22T23:59:59.000Z

376

Thermodynamics of interacting holographic dark energy with apparent horizon as an IR cutoff  

E-Print Network (OSTI)

As soon as an interaction between holographic dark energy and dark matter is taken into account, the identification of IR cutoff with Hubble radius $H^{-1}$, in flat universe, can simultaneously drive accelerated expansion and solve the coincidence problem. Based on this, we demonstrate that in a non-flat universe the natural choice for IR cutoff could be the apparent horizon radius, $\\tilde{r}_A={1}/{\\sqrt{H^2+k/a^2}}$. We show that any interaction of dark matter with holographic dark energy, whose infrared cutoff is set by the apparent horizon radius, implies an accelerated expansion and a constant ratio of the energy densities of both components thus solving the coincidence problem. We also verify that for a universe filled with dark energy and dark matter the Friedmann equation can be written in the form of the modified first law of thermodynamics, $dE=T_hdS_h+WdV$, at apparent horizon. In addition, the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. These results hold regardless of the specific form of dark energy and interaction term. Our study might reveal that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.

Ahmad Sheykhi

2009-10-03T23:59:59.000Z

377

Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts  

E-Print Network (OSTI)

We study the range of consistency of a model based on a nonlinear scalar field Dirac-Born-Infeld action for the unification of dark matter and dark energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59 high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this analysis, we also include the CMB7-year data and the baryonic acoustic peak BAO. Besides, it is calculated the parameter of the equation of state $w$, the deceleration parameter $q_0$ and the redshift of the transition to the decelerate-accelerated phase $z_t$.

Ariadna Montiel; Nora Bretón

2012-02-14T23:59:59.000Z

378

Dark energy, integrated Sachs-Wolfe effect and large-scale magnetic fields  

E-Print Network (OSTI)

The impact of large-scale magnetic fields on the interplay between the ordinary and integrated Sachs-Wolfe effects is investigated in the presence of a fluctuating dark energy component. The modified initial conditions of the Einstein-Boltzmann hierarchy allow for the simultaneous inclusion of dark energy perturbations and of large-scale magnetic fields. The temperature and polarization angular power spectra are compared with the results obtained in the magnetized version of the (minimal) concordance model. Purported compensation effects arising at large scales are specifically investigated. The fluctuating dark energy component modifies, in a computable manner, the shapes of the 1- and 2-$\\sigma$ contours in the parameter space of the magnetized background. The allowed spectral indices and magnetic field intensities turn out to be slightly larger than those determined in the framework of the magnetized concordance model where the dark energy fluctuations are absent.

Massimo Giovannini

2009-07-18T23:59:59.000Z

379

NASA and DOE Collaborate on Dark Energy Research | U.S. DOE Office...  

Office of Science (SC) Website

8 NASA and DOE Collaborate on Dark Energy Research News In the News In Focus 2013 2012 2011 2010 2009 2008 2007 2006 2005 Presentations & Testimony Recovery Act Contact...

380

Modified Chaplygin Gas as Scalar Field and Holographic Dark Energy Model  

E-Print Network (OSTI)

We study the correspondence between field theoretic and holographic dark energy density of the universe with the modified Chaplygin gas (MCG) respectively both in a flat and non-flat FRW universe. We present an equivalent representation of the MCG with a homogeneous minimally coupled scalar field by constructing the corresponding potential. A new scalar field potential is obtained here which is physically realistic and important for cosmological model building. In addition we also present holographic dark energy model described by the MCG. The dynamics of the corresponding holographic dark energy field is determined by reconstructing the potential in a non-flat universe. The stability of the holographic dark energy in this case in a non-flat universe is also discussed.

B. C. Paul; P. Thakur; A. Saha

2008-09-20T23:59:59.000Z

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


381

Testing of Dark Energy and a Solution of the Cosmological Constant Problem  

E-Print Network (OSTI)

A probable solution of the cosmological constant problem was recently found. We propose that dark energy of the Universe is vacuum energy. Our Universe during its expansion is spending its vacuum energy for creation of new quantum states, but in the quantum regime phase transitions were more effective in reducing the vacuum energy than creation of new quantum states. Here we show how the 123 crisis orders of the vacuum energy are reduced by conventional physical processes in both the quantum and classical regimes of the Universe evolution. Numeral estimates of dark energy evolution are also presented.

Burdyuzha, Vladimir

2014-01-01T23:59:59.000Z

382

Testing of Dark Energy and a Solution of the Cosmological Constant Problem  

E-Print Network (OSTI)

A probable solution of the cosmological constant problem was recently found. We propose that dark energy of the Universe is vacuum energy. Our Universe during its expansion is spending its vacuum energy for creation of new quantum states, but in the quantum regime phase transitions were more effective in reducing the vacuum energy than creation of new quantum states. Here we show how the 123 crisis orders of the vacuum energy are reduced by conventional physical processes in both the quantum and classical regimes of the Universe evolution. Numeral estimates of dark energy evolution are also presented.

Vladimir Burdyuzha

2014-01-19T23:59:59.000Z

383

A Universe with a Ghost Dark Energy and van der Waals fluid interacting with a Fluid  

E-Print Network (OSTI)

We consider a model of a Universe with Ghost Dark Energy and van der Waals fluid interacting with a fluid which was born as a result of interaction between original fluid and some other fluid existing in Universe. We suppose that Ghost Dark energy has its contribution to the model by an interaction term $Q$ and we suppose that $Q=3Hb(\\rho_{\\small{tot}}-\\rho_{GDe})$.

Martiros Khurshudyan

2013-01-26T23:59:59.000Z

384

Statefinder diagnostic and stability of modified gravity consistent with holographic and new agegraphic dark energy  

E-Print Network (OSTI)

Recently one of us derived the action of modified gravity consistent with the holographic and new-agegraphic dark energy. In this paper, we investigate the stability of the Lagrangians of the modified gravity as discussed in [M. R. Setare, Int. J. Mod. Phys. D 17 (2008) 2219; M. R. Setare, Astrophys. Space Sci. 326 (2010) 27]. We also calculate the statefinder parameters which classify our dark energy model.

M. R. Setare; Mubasher Jamil

2010-08-27T23:59:59.000Z

385

Space-time curvature due to quantum vacuum fluctuations: An alternative to dark energy?  

E-Print Network (OSTI)

It is pointed out that quantum vacuum fluctuations may give rise to a curvature of space-time equivalent to the curvature currently attributed to dark energy. A simple calculation is made, which suggests that the value of the dark energy density is roughly given by the product of Newton constant time the quantity m^6 c^4 h^-4, m being a typical mass of elementary particles. The estimate is compatible with observations.

Santos, Emilio

2010-01-01T23:59:59.000Z

386

Covariance of dark energy parameters and sound speed constraints from large HI surveys  

E-Print Network (OSTI)

An interesting probe of the nature of dark energy is the measure of its sound speed, $c_s$. We review the significance for constraining sound speed models of dark energy using large neutral hydrogen (HI) surveys with the Square Kilometre Array (SKA). Our analysis considers the effect on the sound speed measurement that arises from the covariance of $c_s$ with the dark energy density, $\\Omega_\\LLambda$, and a time-varying equation of state, $w(a)=w_0+(1-a)w_a$. We find that the approximate degeneracy between dark energy parameters that arises in power spectrum observations is lifted through redshift tomography of the HI-galaxy angular power spectrum, resulting in sound speed constraints that are not severely degraded. The cross-correlation of the galaxy and the integrated Sachs-Wolfe (ISW) effect spectra contributes approximately 10 percent of the information that is needed to distinguish variations in the dark energy parameters, and most of the discriminating signal comes from the galaxy auto-correlation spectrum. We also find that the sound speed constraints are weakly sensitive to the HI bias model. These constraints do not improve substantially for a significantly deeper HI survey since most of the clustering sensitivity to sound speed variations arises from $z \\lsim 1.5$. A detection of models with sound speeds close to zero, $c_s \\lsim 0.01,$ is possible for dark energy models with $w\\gsim -0.9$.

A. Torres-Rodriguez; C. M. Cress; K. Moodley

2008-04-15T23:59:59.000Z

387

Astrophysical and cosmological problems of invisible mass and dark energy in the Universe  

E-Print Network (OSTI)

The Workshop on results of the Project Kosmomikrofizyka-2 (Astroparticle Physics) of the National Academy of Sciences (NAS) of Ukraine "Astrophysical and cosmological problems of invisible mass and dark energy in the Universe" was held on November 21-22, 2012 in the Institute for Nuclear Research, Kyiv, Ukraine (http://lpd.kinr.kiev.ua/kmf12). This Project was carried out during three years (2010-2012) by scientists from various universities and institutes of the National Academy of Sciences of Ukraine; it was a logical continuation of the previous scientific program of the NAS of Ukraine "Researches of structure and composition of the Universe, hidden mass and dark energy (Kosmomikrofizyka)" in 2007-2009. These programs were devoted to theoretical and experimental investigations in astronomy, astrophysics, cosmology, physics of atomic nuclei and particle physics, which are related with the problems of dark matter and dark energy in the Universe.

P. Belli; L. A. Berdina; R. Bernabei; A. Bogdan; R. S. Boiko; A. Yu. Burgazli; F. Cappella; R. Cerulli; D. M. Chernyak; F. A. Danevich; A. d'Angelo; M. V. Eingorn; S. H. Fakhr; E. Fedorova; E. N. Galashov; A. Giuliani; B. I. Hnatyk; A. Incicchitti; G. Ivashchenko; V. V. Kobychev; O. O. Kobzar; H. Kraus; B. N. Kropivyansky; A. V. Kudinova; Yu. A. Kulinich; M. Laubenstein; V. V. Marchenko; S. Marnieros; V. B. Mikhailik; A. A. Minakov; V. M. Mokina; L. L. Nagornaya; A. S. Nikolaiko; C. Nones; B. S. Novosyadlyj; E. Olivieri; V. O. Pelykh; D. V. Poda; R. B. Podviyanuk; O. G. Polischuk; O. N. Sergijenko; V. N. Shlegel; V. M. Shulga; V. M. Sliusar; O. B. Sushchov; Y. V. Taistra; M. Tenconi; O. Torbaniuk; V. I. Tretyak; V. S. Tsvetkova; V. G. Vakulik; Ya. V. Vasiliev; A. Vasylenko; O. Vasylenko; V. I. Zhdanov; A. I. Zhuk

2013-04-16T23:59:59.000Z

388

Reconciliation of Zero-Point and Dark Energies in a Friedman Dust Universe with Einstein's Lambda  

E-Print Network (OSTI)

In this paper, it is shown that the cosmological model that was introduced in a sequence of three earlier papers under the title, A Dust Universe Solution to the Dark Energy Problem, can be used to resolve the problem of the great mismatch of numerical values between dark energy from cosmology and zero point energy from quantum theory. It is shown that, if the zero point energies for the cosmic microwave background and for all the rest of the universe that is not cosmic microwave background are introduced into this model as two entities, their separate values appear within this theory in the form of a numerical difference. It is this difference that gives the numerical value for the zero point value of Einstein's dark energy density. Consequently, although the two zero point energies may be large, their difference can give the known small dark energy value from cosmology for dark energy density. Issues relating to interpretation, calculation and measurement associated with this result and an interpretation of dark energy as a measure of polarisation of the vacuum are discussed. In the first appendix to this paper, problems associated with the standard model of cosmology are solved by redefining temperature in the dust universe model. In the second appendix of this paper, an examination of the dark matter problem in relation to a general relativistic generalisation of Newton's inverse square law is undertaken. In the third appendix to this paper, the formalism is used to derive a formula that gives a possible value for the mass of the universe in terms of Newton's gravitation constant, Einstein's Lambda and the velocity of light. All three appendices have their own detailed abstracts.

James G. Gilson

2007-04-23T23:59:59.000Z

389

Is there Correlation between Fine Structure and Dark Energy Cosmic Dipoles?  

E-Print Network (OSTI)

We present a detailed analysis (including redshift tomography) of the cosmic dipoles in the Keck+VLT quasar absorber and in the Union2 SnIa samples. We show that the fine structure constant cosmic dipole obtained through the Keck+VLT quasar absorber sample at $4.1\\sigma$ level is anomalously aligned with the corresponding dark energy dipole obtained through the Union2 sample at $2\\sigma$ level. The angular separation between the two dipole directions is $11.3^\\circ \\pm 11.8^\\circ$. We use Monte Carlo simulations to find the probability of obtaining the observed dipole magnitudes with the observed alignment, in the context of an isotropic cosmological model with no correlation between dark energy and fine structure constant $\\alpha$. We find that this probability is less than one part in $10^6$. We propose a simple physical model (extended topological quintessence) which naturally predicts a spherical inhomogeneous distribution for both dark energy density and fine structure constant values. The model is based on the existence of a recently formed giant global monopole with Hubble scale core which also couples non-minimally to electromagnetism. Aligned dipole anisotropies would naturally emerge for an off-centre observer for both the fine structure constant and for dark energy density. This model smoothly reduces to \\lcdm for proper limits of its parameters. Two predictions of this model are (a) a correlation between the existence of strong cosmic electromagnetic fields and the value of $\\alpha$ and (b) the existence of a dark flow on Hubble scales due to the repulsive gravity of the global defect core (`Great Repulser') aligned with the dark energy and $\\alpha$ dipoles. The direction of the dark flow is predicted to be towards the spatial region of lower accelerating expansion. Existing data about the dark flow are consistent with this prediction.

Antonio Mariano; Leandros Perivolaropoulos

2012-06-18T23:59:59.000Z

390

A Short History of the Missing Mass and Dark Energy Paradigms  

E-Print Network (OSTI)

In 1900 it was believed that almost 100% of the mass of the Universe resided in stars. Now, in the year 2000, such stars (and cold gas) are known to account for only ~1% its mass. The remaining mass of the Universe is thought to reside in hot baryons (~3%), cold dark matter (~30%) and dark energy (~66%). The present paper traces the evolution of our thinking about the density of the Universe during the Twentieth Century, with special emphasis on the of the discovery of cold dark matter.

Sidney van den Bergh

2000-05-15T23:59:59.000Z

391

UT tower goes dark to conserve energy by KVUE.com  

E-Print Network (OSTI)

UT tower goes dark to conserve energy by KVUE.com Posted on November 22, 2013 at 5:12 PM Updated, but the first time the tower turned off its lights for the initiative. In previous initiatives, the UT Energy) assisted with turning off lights and electronics across campus to conserve energy. While the clock faces

392

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

393

CMB bounds on dark matter annihilation: nucleon energy-losses after recombination  

E-Print Network (OSTI)

We consider the propagation and energy losses of protons and anti-protons produced by dark matter annihilation at redshifts 100energy injected into e^\\pm and \\gamma's, but their interactions are normally neglected when deriving CMB bounds from altered recombination histories. Here, we follow numerically the energy-loss history of typical protons/antiprotons in the cosmological medium. We show that about half of their energy is channeled into photons and e^\\pm, and we present a simple prescription to estimate the corresponding strengthening of the CMB bounds on the dark matter annihilation cross section.

Weniger, Christoph; Iocco, Fabio; Bertone, Gianfranco

2013-01-01T23:59:59.000Z

394

arXiv:1004.0236v1[astro-ph.CO]1Apr2010 Figures of merit for present and future dark energy probes  

E-Print Network (OSTI)

arXiv:1004.0236v1[astro-ph.CO]1Apr2010 Figures of merit for present and future dark energy probes constraints on dynamical dark energy models from Type Ia supernovae and the cosmic microwave background using figures of merit based on the volume of the allowed dark energy parameter space. For a two-parameter dark

Hu, Wayne

395

On using the WMAP distance priors in constraining the time evolving equation of state of dark energy  

E-Print Network (OSTI)

Recently, the WMAP group has published their five-year data and considered the constraints on the time evolving equation of state of dark energy for the first time from the WMAP distance information. In this paper, we study the effectiveness of the usage of these distance information and find that these compressed CMB information can give similar constraints on dark energy parameters compared with the full CMB power spectrum if dark energy perturbations are included, however, once incorrectly neglecting the dark energy perturbations, the difference of the results are sizable.

Hong Li; Jun-Qing Xia; Gong-Bo Zhao; Zu-Hui Fan; Xinmin Zhang

2008-05-08T23:59:59.000Z

396

On using the WMAP distance priors in constraining the time evolving equation of state of dark energy  

E-Print Network (OSTI)

Recently, the WMAP group has published their five-year data and considered the constraints on the time evolving equation of state of dark energy for the first time from the "WMAP distance priors". In this paper, we study the effectiveness of the usage of these distance priors and find that these compressed CMB information can give similar constraints on dark energy parameters compared with the full CMB power spectrum if dark energy perturbation is included, however, once incorrectly neglecting the dark energy perturbation, the difference of the results is sizable.

Li, Hong; Zhao, Gong-Bo; Fan, Zu-Hui; Zhang, Xinmin

2008-01-01T23:59:59.000Z

397

A Dark Energy Model with Generalized Uncertainty Principle in the Emergent, Intermediate and Logamediate Scenarios of the Universe  

E-Print Network (OSTI)

This work is motivated by the work of Kim et al (2008), which considered the equation of state parameter for the new agegraphic dark energy based on generalized uncertainty principle coexisting with dark matter without interaction. In this work, we have considered the same dark energy inter- acting with dark matter in emergent, intermediate and logamediate scenarios of the universe. Also, we have investigated the statefinder, kerk and lerk parameters in all three scenarios under this inter- action. The energy density and pressure for the new agegraphic dark energy based on generalized uncertainty principle have been calculated and their behaviors have been investigated. The evolu- tion of the equation of state parameter has been analyzed in the interacting and non-interacting situations in all the three scenarios. The graphical analysis shows that the dark energy behaves like quintessence era for logamediate expansion and phantom era for emergent and intermediate expansions of the universe.

Rahul Ghosh; Surajit Chattopadhyay; Ujjal Debnath

2011-05-23T23:59:59.000Z

398

High Energy Electron Signals from Dark Matter Annihilation in the Sun  

Science Conference Proceedings (OSTI)

In this paper we discuss two mechanisms by which high energy electrons resulting from dark matter annihilations in or near the Sun can arrive at the Earth. Specifically, electrons can escape the sun if DM annihilates into long-lived states, or if dark matter scatters inelastically, which would leave a halo of dark matter outside of the sun. Such a localized source of electrons may affect the spectra observed by experiments with narrower fields of view oriented towards the sun, such as ATIC, differently from those with larger fields of view such as Fermi. We suggest a simple test of these possibilities with existing Fermi data that is more sensitive than limits from final state radiation. If observed, such a signal will constitute an unequivocal signature of dark matter.

Schuster, Philip; /SLAC; Toro, Natalia; /Stanford U., ITP; Weiner, Neal; Yavin, Itay; /New York U., CCPP

2012-04-09T23:59:59.000Z

399

Higher Order Curvature Theories of Gravity Matched with Observations: a Bridge Between Dark Energy and Dark Matter Problems  

E-Print Network (OSTI)

Higher order curvature gravity has recently received a lot of attention due to the fact that it gives rise to cosmological models which seem capable of solving dark energy and quintessence issues without using "ad hoc" scalar fields. Such an approach is naturally related to fundamental theories of quantum gravity which predict higher order terms for loop expansions of quantum fields in curved spacetimes. In this framework, we obtain a class of cosmological solutions which are fitted against cosmological data. We reproduce reliable models able to fit high redshift supernovae and WMAP observations. The age of the universe and other cosmological parameters are recovered in this context. Furthermore, in the weak field limit, we obtain gravitational potentials which differ from the Newtonian one because of repulsive corrections increasing with distance. We evaluate the rotation curve of our Galaxy and compare it with the observed data in order to test the viability of these theories and to estimate the scale-length of the correction. It is remarkable that the Milky Way rotation curve is well fitted without the need of any dark matter halo and similar results hold also for other galaxies.

S. Capozziello; V. F. Cardone; S. Carloni; A. Troisi

2004-11-04T23:59:59.000Z

400

Comparison of Frames: Jordan vs Einstein Frame for a Non-minimal Dark Energy Model  

E-Print Network (OSTI)

We construct a dark energy model where a scalar field non-minimally coupled to gravity plays the role of the dark component. We compare cosmological consequences of this non-minimal coupling of the scalar field and gravity in the spirit of the dark energy paradigm in Jordan and Einstein frames. Some important issues such as phantom divide line crossing, existence of the bouncing solutions and the stability of the solutions are compared in these two frames. We show that while a non-minimally coupled scalar field in the Jordan frame is a suitable dark energy component with capability to realize phantom divide line crossing, its conformal transformation in the Einstein frame has not this capability. The conformal transformation from Jordan frame to Einstein frame transforms the equation of state parameter of the dark energy component to its minimal form with a redefined scalar field and in this case it is impossible to realize a phantom phase with possible crossing of the phantom divide line.

Kourosh Nozari; S. Davood Sadatian

2009-05-03T23:59:59.000Z

Note: This page contains sample records for the topic "dark energy camera" 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.


401

Discovery of Dark Energy Ushered in a New Era in Computational Cosmology  

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

Discovery of Dark Discovery of Dark Energy Ushered in a New Era in Computational Cosmology Discovery of Dark Energy Ushered in a New Era in Computational Cosmology October 4, 2011 | Tags: Astrophysics, Awards John Hules, JAHules@lbl.gov, +1 510 486 6008 "If NERSC does not enable a major scientific discovery every few years, then we're not doing our job." That was the challenge issued by Bill McCurdy, then Lawrence Berkeley National Laboratory's Associate Laboratory Director for Computing Sciences, at the first all-hands meeting for staff of the National Energy Research Scientific Computing Center (NERSC) when the center reopened after moving to Berkeley Lab in spring of 1996. No one at that meeting could have guessed that the first major breakthrough enabled by NERSC would be a startling discovery in cosmology-that the

402

The effect of the recoil energy window on the results of direct dark matter experiments  

E-Print Network (OSTI)

The effect of the chosen analysis energy window on the results of a dark matter experiment is exemplified by the curious intersection of the exclusion plots of the XENON10 and the CDMS experiments. After proving that the narrow energy window XENON10 chose to analyze is indeed the cause of such intersection, a method to determine the high-energy extreme of the recoil energy window an experiment should use is obtained.

F. Giuliani

2009-10-09T23:59:59.000Z

403

Reconstruction of f(T) gravity from the Holographic dark energy  

E-Print Network (OSTI)

Among different candidates to play the role of Dark Energy (DE), modified gravity has emerged as offering a possible unification of Dark Matter (DM) and DE. The purpose of this work is to develop a reconstruction scheme for the modified gravity with $f(T)$ action using holographic energy density. In the framework of the said modified gravity we have considered the equation of state of the Holographic DE (HDE) density. Subsequently we have developed a reconstruction scheme for modified gravity with $f(T)$ action. Finally we have obtained a modified gravity action consistent with the HDE scenario.

Chattopadhyay, Surajit

2012-01-01T23:59:59.000Z

404

Reconstruction of f(T) gravity from the Holographic dark energy  

E-Print Network (OSTI)

Among different candidates to play the role of Dark Energy (DE), modified gravity has emerged as offering a possible unification of Dark Matter (DM) and DE. The purpose of this work is to develop a reconstruction scheme for the modified gravity with $f(T)$ action using holographic energy density. In the framework of the said modified gravity we have considered the equation of state of the Holographic DE (HDE) density. Subsequently we have developed a reconstruction scheme for modified gravity with $f(T)$ action. Finally we have obtained a modified gravity action consistent with the HDE scenario.

Surajit Chattopadhyay; Antonio Pasqua

2012-11-09T23:59:59.000Z

405

A Note on the Local Cosmological Constant and the Dark Energy Coincidence Problem  

E-Print Network (OSTI)

It has been suggested that the Dark Energy Coincidence Problem could be interpreted as a possible link between the cosmological constant and a massive graviton. We show that by using that link and models for the graviton mass a dark energy density can be obtained that is indeed very close to measurements by WMAP. As a consequence of the models, the cosmological constant was found to depend on the density of matter. A brief outline of the cosmological consequences such as the effect on the black hole solution is given.

M. Tajmar

2006-07-20T23:59:59.000Z

406

Feasibility of Probing Dark Energy with Strong Gravitational Lensing Systems -- Fisher-Matrix Approach --  

E-Print Network (OSTI)

We assess the feasibility of probing dark energy with strong gravitational lensing systems. The capability of the method, which depends on the accuracy with which the lensing systems are modeled, is quantitatively investigated using the Fisher-matrix formalism. We show that this method might place useful constraints on the density parameter and the redshift evolution of the dark energy by combining it with a constraint from supernova measurements. For this purpose, the lens potential needs to be precisely reconstructed. We determine the required quality of data. We also briefly discuss the optimal strategy to constrain the cosmological parameters using gravitational lensing systems.

Kazuhiro Yamamoto; Yasufum Kadoya; Tsukasa Murata; Toshifumi Futamase

2001-10-29T23:59:59.000Z

407

Hydro-Gravitational-Dynamics of Planets and Dark Energy  

E-Print Network (OSTI)

Self-gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition from plasma to gas. Linear protogalaxyclusters fragment at 0.003 Mpc viscous-inertial scales along turbulent vortex lines or in spirals, as observed. The plasma protogalaxies fragment on transition into white-hot planet-mass gas clouds (PFPs) in million-solar-mass clumps (PGCs) that become globular-star-clusters (GCs) from tidal forces or dark matter (PGCs) by freezing and diffusion into 0.3 Mpc halos with 97% of the galaxy mass. The weakly collisional non-baryonic dark matter diffuses to > Mpc scales and frag-ments to form galaxy cluster halos. Stars and larger planets form by binary mergers of the trillion PFPs per PGC on 0.03 Mpc galaxy accretion disks. Star deaths depend on rates of planet accretion and internal star mixing. Moderate accretion rates p...

Gibson, Carl H

2008-01-01T23:59:59.000Z

408

The coincidence problem in the scenario of dark energy interacting with two fluids  

E-Print Network (OSTI)

A cosmological model of dark energy interacting with dark matter and another general component of the universe is considered. The evolution equations for coincidence parameters r and s, which represent the ratios between the dark energy and the matter and the other cosmic fluid, respectively, are analyzed in terms of the stability of stationary solutions. The obtained general results allow to shed some light on the coincidence problem and in the equations of state of the three interacting fluids, due to the constraints imposes by the stability of the solutions. We found that for an interaction proportional to the sum of the DE density and the third fluid density, the hypothetical fluid must have positive pressure, which leads naturally to a cosmological scenario with radiation, unparticle or even some form of warm DM as the third interacting fluid.

Norman Cruz; Samuel Lepe; Francisco Pena

2009-10-07T23:59:59.000Z

409

Matter density perturbations and effective gravitational constant in modified gravity models of dark energy  

E-Print Network (OSTI)

We derive the equation of matter density perturbations on sub-horizon scales for a general Lagrangian density f(R, phi, X) that is a function of a Ricci scalar R, a scalar field phi and a kinetic term X=-(nabla phi)^2/2. This is useful to constrain modified gravity dark energy models from observations of large-scale structure and weak lensing. We obtain the solutions for the matter perturbation delta_m as well as the gravitational potential Phi for some analytically solvable models. In a f(R) dark energy model with the Lagrangian density f(R)=alpha R^{1+m}-Lambda, the growth rates of perturbations exhibit notable differences from those in the standard Einstein gravity unless m is very close to 0. In scalar-tensor models with the Lagrangian density f=F(phi)R+2p(phi,X) we relate the models with coupled dark energy scenarios in the Einstein frame and reproduce the equations of perturbations known in the current literature by making a conformal transformation. We also estimate the evolution of perturbations in both Jordan and Einstein frames when the energy fraction of dark energy is constant during the matter-dominated epoch.

Shinji Tsujikawa

2007-05-08T23:59:59.000Z

410

Reconstructing $f(R)$-gravity from the ordinary and entropy-corrected versions of the holographic and agegraphic dark energy  

E-Print Network (OSTI)

Here we peruse cosmological usage of the most promising candidates of dark energy in the framework of $f(R)$-gravity. We reconstruct the $f(R)$ theory in the spatially-flat FRW universe according to the ordinary and entropy-corrected versions of the holographic and new agegraphic dark energy models, which describe accelerated expansion of the universe.

Karami, K

2010-01-01T23:59:59.000Z

411

arXiv:0808.3125v1[astro-ph]22Aug2008 Crossing the Phantom Divide with Parameterized Post-Friedmann Dark Energy  

E-Print Network (OSTI)

-Friedmann Dark Energy Wenjuan Fang,1 Wayne Hu,2 and Antony Lewis3 1 Department of Physics, Columbia University, Cambridge, CB3 0HA, UK. (Dated: August 22, 2008) Dark energy models with a single scalar field cannot cross of "smooth" dark energy models. It conserves energy and momentum and is exact in the metric evolution

Hu, Wayne

412

Self-Calibration of Cluster Dark Energy Studies: Observable-Mass Distribution  

E-Print Network (OSTI)

The exponential sensitivity of cluster number counts to the properties of the dark energy implies a comparable sensitivity to not only the mean but also the actual_distribution_ of an observable mass proxy given the true cluster mass. For example a 25% scatter in mass can provide a ~50% change in the number counts at z~2 for the upcoming SPT survey. Uncertainty in the scatter of this amount would degrade dark energy constraints to uninteresting levels. Given the shape of the actual mass function, the properties of the distribution may be internally monitored by the shape of the_observable_ mass function. An arbitrary evolution of the scatter of a mass-independent Gaussian distribution may be self-calibrated to allow a measurement of the dark energy equation of state of Delta w ~0.1. External constraints on the mass_variance_ of the distribution that are more accurate than Delta var distribution that will protect against misinterpretation of the dark energy constraints.

Marcos Lima; Wayne Hu

2005-03-16T23:59:59.000Z

413

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

414

Rip Singularity Scenario and Bouncing Universe in a Chaplygin Gas Dark Energy Model  

E-Print Network (OSTI)

We choose a modified Chaplygin Gas Dark energy model for considering some its cosmological behaviors. In this regards, we study different Rip singularity scenarios and bouncing model of the universe in context of this model. We show that by using suitable parameters can explain some cosmological aspects of the model.

S. Davood Sadatian

2013-09-28T23:59:59.000Z

415

On coincidence problem and attractor solutions in ELKO dark energy model  

E-Print Network (OSTI)

We study the critical points of a Universe dominated by ELKO spinor field dark energy and a barotropic matter in an almost general case. The coincidence problem and attractor solutions are discussed and it is shown the coincidence problem can not be alleviated in this model.

Sadjadi, H Mohseni

2011-01-01T23:59:59.000Z

416

Modified Hubble law, the time-varying Hubble parameter and the problem of dark energy  

E-Print Network (OSTI)

In the framework of the solvable model of cosmology constructed in the Earth-related coordinate system, we derive the modified Hubble law. This law carries the slowly time-varying Hubble parameter. The modified Hubble law eliminates the need for dark energy.

Jian-Miin Liu

2005-07-04T23:59:59.000Z

417

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

Science Conference Proceedings (OSTI)

The final technical report from the project "Discovering the Nature of Dark Energy: Towards Better Distances from Type Ia Supernovae" led at Rutgers the State University of New Jersey by Prof. Saurabh W. Jha is presented, including all publications resulting from this award.

Saurabh W. Jha

2012-10-03T23:59:59.000Z

418

A new perspective in the dark energy puzzle from particle mixing phenomenon  

E-Print Network (OSTI)

We report on recent results on particle mixing and oscillations in quantum field theory. We discuss the role played in cosmology by the vacuum condensate induced by the neutrino mixing phenomenon. We show that it can contribute to the dark energy of the universe.

M. Blasone; A. Capolupo; S. Capozziello; G. Vitiello

2008-08-30T23:59:59.000Z

419

A Non-minimally Coupled Quintom Dark Energy Model on the Warped DGP Brane  

E-Print Network (OSTI)

We study dynamics of equation of state parameter for a non-minimally coupled quintom dark energy component on the warped DGP brane. We investigate crossing of the cosmological constant line in this scenario. This crossing occurs in both DGP$^{\\pm}$ branches of the model.

Kourosh Nozari; M. R. Setare; Tahereh Azizi; Noushin Behrouz

2008-10-08T23:59:59.000Z

420

Does Unruh radiation accelerate the universe? A novel approach to dark energy  

E-Print Network (OSTI)

In braneworld scenario, the brane accelerates in the bulk, and hence it perceives a thermal bulk filled with Unruh radiation. We put forward that there may be an energy exchange between Unruh radiation in the bulk and the dark matter confined to the brane, which accelerates the universe.

Hongsheng Zhang; Zong-Hong Zhu

2006-07-24T23:59:59.000Z

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


421

Testing the phenomenological interacting dark energy with observational $H(z)$ data  

E-Print Network (OSTI)

In order to test the possible interaction between dark energy and dark matter, we investigate observational constraints on a phenomenological scenario, in which the ratio between the dark energy and matter energy densities is proportional to the pow law case of the scale factor, $r\\equiv (\\rho_X/\\rho_m)\\propto a^{\\xi}$. With the newly revised $H(z)$ data, as well as the cosmic microwave background (CMB) observation from the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) results, the baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release and the type Ia supernovae (SNe Ia) from Union2 set, by using the Markov Chain Monte Carlo (MCMC) method, we obtain $\\Omega_{m0}=0.253_{-0.018}^{+0.020}$ and $\\xi=3.07_{-0.11}^{+0.12}$ for the phenomenological $\\Lambda$CDM scenario; and $\\Omega_{m0}=0.276_{-0.028}^{+0.028}$, $\\xi=3.41_{-0.52}^{+0.61}$, and $w_X=-1.07_{-0.13}^{+0.12}$ for the phenomenological $w$CDM scenario with a constant EoS of dark energy. Th...

Cao, Shuo

2010-01-01T23:59:59.000Z

422

A reconstruction of modified holographic Ricci dark energy in $f(R,T)$ gravity  

E-Print Network (OSTI)

In this paper, we consider a recently proposed model of Dark Energy (DE) know as Modified Holographic Ricci DE (MHRDE) (which is function of the Hubble parameter and its first derivative with respect to the cosmic time $t$) in the light of the $f(R,T)$ model of modified gravity, considering the particular model $f(R,T) = \\mu R + \

Antonio Pasqua; Surajit Chattopadhyay; Iuliia Khomenko

2013-03-20T23:59:59.000Z

423

Search for a dark matter particle in high energy cosmic rays  

E-Print Network (OSTI)

Existing data hints that high energy cosmic ray experiments may offer the most promissing shot at finding a dark matter particle. A search in the PeV mass range is suggested, where the discovery of such a particle might help explain the GZK cutoff violation data.

Yukio Tomozawa

2008-04-09T23:59:59.000Z

424

Constraints on Dark Energy from the Observed Expansion of our Cosmic Horizon  

E-Print Network (OSTI)

Within the context of standard cosmology, an accelerating universe requires the presence of a third `dark' component of energy, beyond matter and radiation. The available data, however, are still deemed insufficient to distinguish between an evolving dark energy component and the simplest model of a time-independent cosmological constant. In this paper, we examine the cosmological expansion in terms of observer-dependent coordinates, in addition to the more conventional co-moving coordinates. This procedure explicitly reveals the role played by the radius R_h of our cosmic horizon in the interrogation of the data. (In Rindler's notation, R_h coincides with the `event horizon' in the case of de Sitter, but changes in time for other cosmologies that also contain matter and/or radiation.) With this approach, we show that the interpretation of dark energy as a cosmological constant is clearly disfavored by the observations. Within the framework of standard Friedman-Robertson-Walker cosmology, we derive an equation describing the evolution of R_h, and solve it using the WMAP and Type Ia supernova data. In particular, we consider the meaning of the observed equality (or near equality) R_h(t_0) ~ ct_0, where t_0 is the age of the Universe. This empirical result is far from trivial, for a cosmological constant would drive R_h(t) towards ct (where t is the cosmic time) only once--and that would have to occur right now. Though we are not here espousing any particular alternative model of dark energy, for comparison we also consider scenarios in which dark energy is given by scaling solutions, which simultaneously eliminate several conundrums in the standard model, including the `coincidence' and `flatness' problems, and account very well for the fact that R_h(t_0) ~ ct_0.

Fulvio Melia

2008-12-27T23:59:59.000Z

425

Cosmic microwave background constraints on dark energy dynamics: analysis beyond the power spectrum  

E-Print Network (OSTI)

We consider the distribution of the non-Gaussian signal induced by weak lensing on the primary total intensity cosmic microwave background (CMB) anisotropies. Our study focuses on the three point statistics exploiting an harmonic analysis based on the CMB bispectrum. By considering the three multipoles as independent variables, we reveal a complex structure of peaks and valleys determined by the re-projection of the primordial acoustic oscillations through the lensing mechanism. We study the dependence of this system on the expansion rate at the epoch in which the weak lensing power injection is relevant, probing the dark energy equation of state at redshift corresponding to the equivalence with matter or higher ($w_\\infty$). We evaluate the impact of the bispectrum observable on the CMB capability of constraining the dark energy dynamics. We perform a maximum likelihood analysis by varying the dark energy abundance, the present equation of state $w_0$ and $w_\\infty$. We show that the projection degeneracy affecting a pure power spectrum analysis in total intensity is broken if the bispectrum is taken into account. For a Planck-like experiment, assuming nominal performance, no foregrounds or systematics, and fixing all the parameters except $w_0$, $w_\\infty$ and the dark energy abundance, a percent and ten percent precision measure of $w_0$ and $w_\\infty$ is achievable from CMB data only. These results indicate that the detection of the weak lensing signal by the forthcoming CMB probes may be relevant to gain insight into the dark energy dynamics at the onset of cosmic acceleration.

Fabio Giovi; Carlo Baccigalupi; Francesca Perrotta

2004-11-25T23:59:59.000Z

426

Testing the "Dark-Energy"-Dominated Cosmology via the Solar-System Experiments  

E-Print Network (OSTI)

The effect of "dark energy" (i.e. the Lambda-term in Einstein equations) is sought for at the interplanetary scales by comparing the rates of secular increase in the lunar orbit obtained by two different ways: (1) measured immediately by the laser ranging and (2) estimated independently from the deceleration of the Earth's proper rotation. The first quantity involves both the well-known effect of geophysical tides and the Kottler effect of Lambda-term (i.e. a kind of the "local" Hubble expansion), while the second quantity is associated only with the tidal influence. The difference between them, 2.2 +/- 0.3 cm/yr, can be attributed just to the local Hubble expansion with rate H_0^(loc) = 56 +/- 8 km/s/Mpc. Assuming that Hubble expansion is formed locally only by the uniformly distributed dark energy (Lambda-term), while globally also by a clumped substance (for the most part, the cold dark matter), the total (large-scale) Hubble constant should be H_0 = 65 +/- 9 km/s/Mpc. This is in reasonable agreement both with the commonly-accepted WMAP result, H_0 = 71 +/- 3.5 km/s/Mpc, and with the data on supernovae Ia distribution. The above coincidence can serve as one more argument in favor of the dark energy.

Yu. V. Dumin

2005-07-16T23:59:59.000Z

427

Measuring Dark Energy with the Wide-Field Multi-Object Spectrograph (WFMOS)  

E-Print Network (OSTI)

Dark energy is one of the greatest scientific challenges of the 21st century. One of the key questions facing cosmologists is whether dark energy is either a breakdown of General Relativity on large scales or a new form of matter in the Universe with a negative effective pressure. This question can only be answered through a suite of different observations as a function of redshift. In this paper, I briefly review various dark energy reports published in the last year, which all highlight the importance of the baryon acoustic oscillations (BAO) for probing the "dark physics" of the Universe. I also summarize the recent measurements of the BAO in large galaxy redshift surveys. I then look forward to a new instrument planned by the Subaru and Gemini communities called the "Wide-Field Multi-Object Spectrograph" (WFMOS) for the Subaru telescope. The baseline design of this facility includes ~4500 spectroscopic fibers over a field-of-view of 1.5 degree diameter, covering a wavelength range of 0.39 to 1 microns. The instrument is schedule for first-light early next decade and will perform massive spectroscopic surveys of both distant galaxies and faint stars in our own Galaxy. The WFMOS dark energy surveys will deliver ~1% errors on the angular-diameter distance and Hubble parameter to high redshift. WFMOS will also be a unique user-facility allowing astronomers to address a host of astrophysical problems like galaxy evolution, the intergalactic medium and calibrate photometric redshifts. The WFMOS archive will also provide a rich resource for further ancillary science much like the present-day SDSS archive.

Robert Nichol

2006-11-27T23:59:59.000Z

428

arXiv:astro-ph/0503363v116Mar2005 Self-Calibration of Cluster Dark Energy Studies: Observable-Mass Distribution  

E-Print Network (OSTI)

of the observable-mass distribution that will protect against misinterpretation of the dark energy constraints. I, uncertainties in the distribution directly translate into uncertainties in the dark energy inferences that must-mass distribution on high redshift cluster counts. Previous work on fore- casting prospects for dark energy

Hu, Wayne

429

arXiv:0912.3816v1[astro-ph.CO]18Dec2009 Testable dark energy predictions from current data  

E-Print Network (OSTI)

arXiv:0912.3816v1[astro-ph.CO]18Dec2009 Testable dark energy predictions from current data Michael a class of dark energy models, constraints from one set of cosmic acceleration observables make, and the Hubble constant. With a cosmological constant as the dark energy and assuming near-minimal neutrino

Hu, Wayne

430

Dark Energy and How to Find It: The SNAP Experiment  

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

Energy and How to Find It: The SNAP Experiment PowerPoint Presentation Slide 3 Slide 4 Slide 5 Slide 6 Slide 7 Slide 8 Slide 9 Slide 10 Slide 11 Slide 12 Slide 13 Slide 14 Slide 15...

431

3.2B Pixel Camera to Shed Light on Southern Sky | Department of Energy  

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

3.2B Pixel Camera to Shed Light on Southern Sky 3.2B Pixel Camera to Shed Light on Southern Sky 3.2B Pixel Camera to Shed Light on Southern Sky July 24, 2012 - 10:56am Addthis This is an artist's rendering of the Large Synoptic Survey Telescope (LSST), the 8.4 meter wide-field telescope that the National Science Board recently approved to advance to its final design stage. Construction is expected to begin in 2014 and take about five years. | Photo courtesy of LSST Corporation. This is an artist's rendering of the Large Synoptic Survey Telescope (LSST), the 8.4 meter wide-field telescope that the National Science Board recently approved to advance to its final design stage. Construction is expected to begin in 2014 and take about five years. | Photo courtesy of LSST Corporation. Charles Rousseaux Charles Rousseaux

432

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

433

Dilaton Dark Energy Model in f(R), f(T) and Horava-Lifshitz Gravities  

E-Print Network (OSTI)

In this work, we have considered dilaton dark energy model in Weyl-scaled induced gravitational theory in presence of barotropic fluid. It is to be noted that the dilaton field behaves as a quintessence. Here we have discussed the role of dilaton dark energy in modified gravity theories namely, f(R); f(T) and Horava-Lifshitz gravities and analyzed the behaviour of the dilaton field and the corresponding potential in respect to these modified gravity theories instead of Einstein's gravity. In f(R) and f(T) gravities, we have considered some particular forms of f(R) and f(T) and we have shown that the potentials always increase with the dilaton fields. But in Horava-Lifshitz gravity, it has been seen that the potential always decreases as dilation field increases.

Khatua, Piyali Bagchi; Debnath, Ujjal

2011-01-01T23:59:59.000Z

434

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

435

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter  

SciTech Connect

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

Sorensen, P; Dahl, C E

2011-02-14T23:59:59.000Z

436

Reconstructing f(T)-gravity from the polytropic and different Chaplygin gas dark energy models  

E-Print Network (OSTI)

Motivated by a recent work of us [1], we reconstruct the different f(T)-gravity models corresponding to a set of dark energy scenarios containing the polytropic, the standard Chaplygin, the generalized Chaplygin and the modified Chaplygin gas models. We also derive the equation of state parameter of the selected f(T)-gravity models and obtain the necessary conditions for crossing the phantom-divide line.

Karami, K

2010-01-01T23:59:59.000Z

437

Dark Energy: the equation of state description versus scalar-tensor or modified gravity  

E-Print Network (OSTI)

Dark energy dynamics of the universe can be achieved by equivalent mathematical descriptions taking into account generalized fluid equations of state in General Relativity, scalar-tensor theories or modified F(R) gravity in Einstein or Jordan frames. The corresponding technique transforming equation of state description to scalar-tensor or modified gravity is explicitly presented. We show that such equivalent pictures can be discriminated by matching solutions with data capable of selecting the true physical frame.

S. Capozziello; S. Nojiri; S. D. Odintsov

2005-12-10T23:59:59.000Z

438

Optimizing future imaging survey of galaxies to confront dark energy and modified gravity models  

E-Print Network (OSTI)

We consider the extent to which future imaging surveys of galaxies can distinguish between dark energy and modified gravity models for the origin of the cosmic acceleration. Dynamical dark energy models may have similar expansion rates as models of modified gravity, yet predict different growth of structure histories. We parameterize the cosmic expansion by the two parameters, $w_0$ and $w_a$, and the linear growth rate of density fluctuations by Linder's $\\gamma$, independently. Dark energy models generically predict $\\gamma \\approx 0.55$, while the DGP model $\\gamma \\approx 0.68$. To determine if future imaging surveys can constrain $\\gamma$ within 20 percent (or $\\Delta\\gamma<0.1$), we perform the Fisher matrix analysis for a weak lensing survey such as the on-going Hyper Suprime-Cam (HSC) project. Under the condition that the total observation time is fixed, we compute the Figure of Merit (FoM) as a function of the exposure time $\\texp$. We find that the tomography technique effectively improves the FoM, which has a broad peak around $\\texp\\simeq {\\rm several}\\sim 10$ minutes; a shallow and wide survey is preferred to constrain the $\\gamma$ parameter. While $\\Delta\\gamma < 0.1$ cannot be achieved by the HSC weak-lensing survey alone, one can improve the constraints by combining with a follow-up spectroscopic survey like WFMOS and/or future CMB observations.

Kazuhiro Yamamoto; David Parkinson; Takashi Hamana; Robert C. Nichol; Yasushi Suto

2007-04-23T23:59:59.000Z

439

Testing the "dark-energy"-dominated cosmology via the solar-system experiments  

E-Print Network (OSTI)

According to the recent astronomical data, the most part of energy density in the Universe (73%) is in the "dark" form (such as the so-called "quintessence", inflaton potential, polarization of vacuum, and so on), which is effectively described by Lambda-term in the Einstein equations. All arguments in favor of the dark energy were obtained so far from the observational data related to very large (intergalactic) scales. The present letter shows that Lambda-dominated cosmology can be efficiently tested via the solar-system experiments, seeking for the effect of local Hubble expansion: if the dark energy really exists, it should increase the mean Earth-Moon distance by 2-3 cm per year, which is comparable with the effect of geophysical tides and well measurable by the lunar laser ranging. As follows from our analysis, the "local" Hubble constant should be H_0^(loc) = 56 +/- 8 (km/s)/Mpc, implying that either the total Hubble constant is H_0 = 59 +/- 8 (km/s)/Mpc (i.e. a bit less than the commonly-accepted value...

Dumin, Y V

2005-01-01T23:59:59.000Z

440

The Joint Efficient Dark-energy Investigation (JEDI): Measuring the cosmic expansion history from type Ia supernovae  

E-Print Network (OSTI)

JEDI (Joint Efficient Dark-energy Investigation) is a candidate implementation of the NASA-DOE Joint Dark Energy Mission (JDEM). JEDI will probe dark energy in three independent methods: (1) type Ia supernovae, (2) baryon acoustic oscillations, and (3) weak gravitational lensing. In an accompanying paper, an overall summary of the JEDI mission is given. In this paper, we present further details of the supernova component of JEDI. To derive model-independent constraints on dark energy, it is important to precisely measure the cosmic expansion history, H(z), in continuous redshift bins from z \\~ 0-2 (the redshift range in which dark energy is important). SNe Ia at z > 1 are not readily accessible from the ground because the bulk of their light has shifted into the near-infrared where the sky background is overwhelming; hence a space mission is required to probe dark energy using SNe. Because of its unique near-infrared wavelength coverage (0.8-4.2 microns), JEDI has the advantage of observing SNe Ia in the rest frame J band for the entire redshift range of 0 energy are discussed, with special emphasis on the improved precision afforded by the rest frame near-infrared data.

M. M. Phillips; Peter Garnavich; Yun Wang; David Branch; Edward Baron; Arlin Crotts; J. Craig Wheeler; Edward Cheng; Mario Hamuy; for the JEDI Team

2006-06-28T23:59:59.000Z

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


441

Solar System Constraints on Gauss-Bonnet Mediated Dark Energy  

E-Print Network (OSTI)

Although the Gauss-Bonnet term is a topological invariant for general relativity, it couples naturally to a quintessence scalar field, modifying gravity at solar system scales. We determine the solar system constraints due to this term by evaluating the post-Newtonian metric for a distributional source. We find a mass dependent, 1/r^7 correction to the Newtonian potential, and also deviations from the Einstein gravity prediction for light-bending. We constrain the parameters of the theory using planetary orbits, the Cassini spacecraft data, and a laboratory test of Newton's law, always finding extremely tight bounds on the energy associated to the Gauss-Bonnet term. We discuss the relevance of these constraints to late-time cosmological acceleration.

Luca Amendola; Christos Charmousis; Stephen C. Davis

2007-04-02T23:59:59.000Z

442

A quantized frequency reference in the short-ranged gravity potential and its application for dark matter and dark energy searches  

E-Print Network (OSTI)

The evidence for the observation of the Higgs spin-0-boson as a manifestation of a scalar field provides the missing corner stone for the standard model of particles (SM). However, the SM fails to explain the non-visible but gravitationally active part of the universe. Its nature is unknown but the confirmation of a scalar Higgs is giving a boost to scalar-field-theories. So far gravity experiments and observations performed at different distances find no deviation from Newton's gravity law. Therefore dark energy must possess a screening mechanism which suppresses the scalar-mediated fifth force. Our line of attack is a novel gravity experiment with neutrons based on a quantum interference technique. The spectroscopic measurement of quantum states on resonances with an external coupling makes this a powerful search for dark matter and dark energy contributions in the universe. Quantum states in the gravity potential are intimately related to other scalar field or spin-0-bosons if they exist. If the reason is that some undiscovered particle interact with a neutron, this results in a measurable energy shift of quantum states in the gravity potential, because for neutrons the screening effect is absent. We use Gravity Resonance Spectroscopy to measure the energy splitting at the highest level of precision, providing a constraint on any possible new interaction. We obtain a sensitivity of 10^-14 eV. We set an experimental limit on any fifth force, in particular on parameter \\betagravity is understood at this improved level of precision.

T. Jenke; G. Cronenberg; P. Geltenbort; A. N. Ivanov; T. Lauer; T. Lins; U. Schmidt; H. Saul; H. Abele

2012-08-19T23:59:59.000Z

443

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

444

High accuracy power spectra including baryonic physics in dynamical Dark Energy models  

E-Print Network (OSTI)

The next generation mass probes will obtain information on non--linear power spectra P(k,z) and their evolution, allowing us to investigate the nature of Dark Energy. To exploit such data we need high precision simulations, extending at least up to scales of k\\simeq 10 h^-1 Mpc, where the effects of baryons can no longer be neglected. In this paper, we present a series of large scale hydrodynamical simulations for LCDM and dynamical Dark Energy (dDE) models, in which the equation of state parameter is z-dependent. The simulations include gas cooling, star formation and Supernovae feedback. They closely approximate the observed star formation rate and the observationally derived star/Dark Matter mass ratio in collapsed systems. Baryon dynamics cause spectral shifts exceeding 1% at k > 2-3 hMpc^-1 compared to pure n-body simulations in the LCDM simulations. This agrees with previous studies, although we find a smaller effect (~50%) on the power spectrum amplitude at higher k's. dDE exhibits similar behavior, ev...

Casarini, Luciano; Bonometto, Silvio A; Stinson, Greg S

2010-01-01T23:59:59.000Z

445

9/18/09 2:49 PM`Dark Energy' reminds us: consensus has no place in real science -Telegraph Blogs Page 1 of 42http://blogs.telegraph.co.uk/news/jamesdelingpole/100006809/dark-energy-reminds-us-consensus-has-no-place-in-real-science/  

E-Print Network (OSTI)

9/18/09 2:49 PM`Dark Energy' reminds us: consensus has no place in real science - Telegraph Blogs Page 1 of 42http://blogs.telegraph.co.uk/news/jamesdelingpole/100006809/dark-energy Lifestyle Comment Travel Culture Technology Fashion #12;9/18/09 2:49 PM`Dark Energy' reminds us: consensus

Temple, Blake

446

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

447

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

448

Suppression of energy-relaxation-induced decoherence in -type three-level SQUID flux qubits: A dark-state approach  

E-Print Network (OSTI)

Suppression of energy-relaxation-induced decoherence in -type three-level SQUID flux qubits: A dark) We report a theoretical investigation of decoherence induced by energy relaxation of the auxiliary level in the -type three-level SQUID flux qubits. We show that the energy-relaxation-induced decoherence

Chu, Shih-I

449

Casimir Energy Density at Planck Time: Cosmic Coincidence or Double Solution to the Cosmological Dark Energy Problem?  

E-Print Network (OSTI)

The Casimir energy density calculated for a spherical shell of radius equal to the size of the Universe projected back to the Planck time is almost equal to the present day critical density. Is it just a coincidence, or is it a solution to the ‘cosmic dark energy ’ and the ‘cosmic coincidence ’ problems? The correspondence is too close to be ignored as a coincidence, especially since this solution fits the conceptual and numerical ideas about the dark energy, and also answers why this energy is starting to dominate at the present era in the evolution of the Universe. It is startling to notice that the Casimir energy density of a spherical bounded space with its radius equal to the size of our present Universe scaled back to its size at the Planck time is almost exactly the critical energy density. It is perhaps not reasonable to discard this as a coincidence, since it solves the two important current problems in cosmology with vacuum energy [1], namely the problem of the smallness of the cosmological vacuum energy

C. S. Unnikrishnan

2002-01-01T23:59:59.000Z

450

On Dark Energy, Weyl Geometry and Brans-Dicke-Jordan Scalar Field  

E-Print Network (OSTI)

We review firstly why Weyl’s Geometry, within the context of Friedman-Lemaitre-Robertson-Walker cosmological models, can account for both the origins and the value of the observed vacuum energy density (dark energy). The source of dark energy is just the dilaton-like Jordan-Brans-Dicke scalar field that is required to implement Weyl invariance of the most simple of all possible actions. A nonvanishing value of the vacuum energy density of the order of 10 ?123 M 4 P lanck is derived in agreement with the experimental observations. Next, a Jordan-Brans-Dicke gravity model within the context of ordinary Riemannian geometry, yields also the observed vacuum energy density (cosmological constant) to very high precision. One finds that the temporal flow of the scalar field ?(t) in ordinary Riemannian geometry, from t = 0 to t = to, has the same numerical effects (as far as the vacuum energy density is concerned) as if there were Weyl scalings from the field configuration ?(t), to the constant field configuration ?o, in Weyl geometry. Hence, Weyl scalings in Weyl geometry can recapture the flow of time which is consistent with Segal’s Conformal Cosmology, in such a fashion that an expanding universe may be visualized as Weyl scalings of a static universe. The main novel result of this work is that one is able to reproduce the observed vacuum energy density to such a degree of precision 10 ?123 M 4 P lanck, while still having a Big-Bang singularity at t = 0 when the vacuum energy density blows up. This temporal flow of the vacuum energy density, from very high values in the past, to very small values today, is not a numerical coincidence but is the signal of an underlying Weyl geometry (conformal invariance) operating in cosmology, combined with the dynamics of a Brans-Dicke-Jordan scalar field.

Carlos Castro

2008-01-01T23:59:59.000Z

451

Dark energy model with variable $q$ and $?$ in LRS Bianchi-II space-time  

E-Print Network (OSTI)

The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein's field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\\sigma^{1}_{1})$ and expansion scalar $(\\vartheta)$, which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.

Bijan Saha; Anil Kumar Yadav

2011-10-21T23:59:59.000Z

452

CCD Camera  

DOE Patents (OSTI)

A CCD camera capable of observing a moving object which has varying intensities of radiation emanating therefrom and which may move at varying speeds is shown wherein there is substantially no overlapping of successive images and wherein the exposure times and scan times may be varied independently of each other. 7 figs.

Roth, R.R.

1983-08-02T23:59:59.000Z

453

arXiv:astro-ph/0401559v126Jan2004 Self-Calibration of Cluster Dark Energy Studies: Counts in Cells  

E-Print Network (OSTI)

arXiv:astro-ph/0401559v126Jan2004 Self-Calibration of Cluster Dark Energy Studies: Counts in Cells of Chicago, Chicago IL 60637 Cluster number counts can constrain the properties of dark energy if and only constraints on the dark energy equation of state by a factor of 2 or more to (w) = 0.06 for a deep 4000 deg2

Hu, Wayne

454

Transmission electron microscope CCD camera  

DOE Patents (OSTI)

In order to improve the performance of a CCD camera on a high voltage electron microscope, an electron decelerator is inserted between the microscope column and the CCD. This arrangement optimizes the interaction of the electron beam with the scintillator of the CCD camera while retaining optimization of the microscope optics and of the interaction of the beam with the specimen. Changing the electron beam energy between the specimen and camera allows both to be optimized.

Downing, Kenneth H. (Lafayette, CA)

1999-01-01T23:59:59.000Z

455

Quantum Theory at Planck Scale, Limiting Values, Deformed Gravity and Dark Energy Problem  

E-Print Network (OSTI)

Within a theory of the existing fundamental length on the order of Planck's a high-energy deformation of the General Relativity for the space with horizon has been constructed. On this basis, Markov's work of the early eighties of the last century has been given a new interpretation to show that the heuristic model considered by him may be placed on a fundamental footing. The obtained results have been applied to solving of the dark energy problem, making it possible to frame the following hypothesis: a dynamic cosmological term is a measure of deviation from a thermodynamic identity (the first law of thermodynamics) of the high-energy (Planck's) deformation of Einstein equations for horizon spaces in their thermodynamic interpretation.

A. E. Shalyt-Margolin

2011-02-24T23:59:59.000Z

456

Interacting non-minimally coupled canonical, phantom and quintom models of holographic dark energy in non-flat universe  

E-Print Network (OSTI)

Motivated by our recent work \\cite{set1}, we generalize this work to the interacting non-flat case. Therefore in this paper we deal with canonical, phantom and quintom models, with the various fields being non-minimally coupled to gravity, within the framework of interacting holographic dark energy. We employ the holographic model of interacting dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named $L$.

M R Setare; Alberto Rozas-Fernández

2009-06-10T23:59:59.000Z

457

Alternative High-z Cosmic Tracers and the Dark Energy Equation of State  

E-Print Network (OSTI)

We propose to use alternative cosmic tracers to measure the dark energy equation of state and the matter content of the Universe [w(z) & \\Omega_m]. Our proposed method consists of two components: (a) tracing the Hubble relation using HII-like starburst galaxies, as an alternative to SNIa, which can be detected up to very large redshifts, z~4, and (b) measuring the clustering pattern of X-ray selected AGN at a median redshift of ~1. Each component of the method can in itself provide interesting constraints on the cosmological parameters, especially under our anticipation that we will reduce the corresponding random and systematic errors significantly. However, by joining their likelihood functions we will be able to put stringent cosmological constraints and break the known degeneracies between the dark energy equation of state (whether it is constant or variable) and the matter content of the universe and provide a powerful and alternative rute to measure the contribution to the global dynamics, and the e...

Plionis, M; Basilakos, S; Bresolin, F; Terlevich, E; Melnick, J; Georgantopoulos, I

2009-01-01T23:59:59.000Z

458

Constraining the Dark Energy Equation of State using Alternative High-z Cosmic Tracers  

E-Print Network (OSTI)

We propose to use alternative cosmic tracers to measure the dark energy equation of state and the matter content of the Universe [w(z) & Omega_m]. Our proposed method consists of two components: (a) tracing the Hubble relation using HII galaxies which can be detected up to very large redshifts, z~4, as an alternative to supernovae type Ia, and (b) measuring the clustering pattern of X-ray selected AGN at a median redshift of z~1. Each component of the method can in itself provide interesting constraints on the cosmological parameters, especially under our anticipation that we will reduce the corresponding random and systematic errors significantly. However, by joining their likelihood functions we will be able to put stringent cosmological constraints and break the known degeneracies between the dark energy equation of state (whether it is constant or variable) and the matter content of the universe and provide a powerful and alternative route to measure the contribution to the global dynamics and the equ...

Plionis, M; Basilakos, S; Bressolin, F; Terlevich, E; Melnick, J; Chavez, R

2009-01-01T23:59:59.000Z

459

Correspondence between $f(G)$ Gravity and Holographic Dark Energy via Power-law Solution  

E-Print Network (OSTI)

In this paper, we discuss cosmological application of holographic Dark Energy (HDE) in the framework of $f(G)$ modified gravity. For this purpose, we construct $f(G)$ model with the inclusion of HDE and a well-known power law form of the scale factor $a(t)$. The reconstructed $f(G)$ is found to satisfy a sufficient condition for a realistic modified gravity model. We find quintessence behavior of effective equation of state (EoS) parameter $\\omega_{DE}$ through energy conditions in this context. Also, we observe that the squared speed of sound $v_s^2$ remains negative which shows the instability of HDE $f(G)$ model.

Abdul Jawad; Antonio Pasqua; Surajit Chattopadhyay

2012-11-22T23:59:59.000Z

460

Reconstruction of f(T) and f(R) gravity according to (m,n)-type holographic dark energy  

E-Print Network (OSTI)

Motivated by earlier works on reconstruction of modified gravity models with dark energy components, we extend them by considering a newly proposed model of (m, n)- type of holographic dark energy for two models of modified gravity, f(R) and f(T) theories, where R and T represent Ricci scalar and torsion scalar respectively. Specifically we reconstruct the two later gravity models and discuss their viability and cosmography. The obtained gravity models are ghost free, compatible with local solar system tests and describe effective positive gravitational constant.

Farooq, M Umar; Momeni, Davood; Myrzakulov, Ratbay

2013-01-01T23:59:59.000Z

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