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Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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.


1

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

2

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

3

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

4

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

5

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

6

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

7

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...

8

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Shell Storage Capacity at Operable Refineries Shell Storage Capacity at Operable Refineries Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Biomass-Based Diesel Fuel Biodiesel and other renewable diesel fuel or diesel fuel blending components derived from biomass, but excluding renewable diesel fuel coprocessed with petroleum feedstocks.

9

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Tanker and Barge Between PADDs Tanker and Barge Between PADDs Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Conventional Blendstock for Oxygenate Blending (CBOB) Motor gasoline blending components intended for blending with oxygenates to produce finished conventional motor gasoline. Conventional Gasoline Finished motor gasoline not included in the oxygenated or reformulated gasoline categories. Excludes reformulated gasoline blendstock for oxygenate blending (RBOB) as well as other blendstock.

10

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Production Production Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Butane (C4H10) A normally gaseous straight-chain or branch-chain hydrocarbon extracted from natural gas or refinery gas streams. It includes isobutane and normal butane and is designated in ASTM Specification D1835 and Gas Processors Association Specifications for commercial butane.

11

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Receipts by Pipeline, Tanker, and Barge Between PAD Districts Receipts by Pipeline, Tanker, and Barge Between PAD Districts Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Butane (C4H10) A normally gaseous straight-chain or branch-chain hydrocarbon extracted from natural gas or refinery gas streams. It includes isobutane and normal butane and is designated in ASTM Specification D1835 and Gas Processors Association Specifications for commercial butane.

12

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Exports by Destination Exports by Destination Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

13

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Area of Entry Area of Entry Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

14

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

& Blender Net Production & Blender Net Production Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Blending Plant A facility which has no refining capability but is either capable of producing finished motor gasoline through mechanical blending or blends oxygenates with motor gasoline.

15

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Total Stocks Total Stocks Definitions Key Terms Definition All Other Motor Gasoline Blending Components Naphthas (e.g. straight-run gasoline, alkylate, reformate, benzene, toluene, xylene) used for blending or compounding into finished motor gasoline. Includes receipts and inputs of Gasoline Treated as Blendstock (GTAB). Excludes conventional blendstock for oxygenate blending (CBOB), reformulated blendstock for oxygenate blending, oxygenates (e.g. fuel ethanol and methyl tertiary butyl ether), butane, and pentanes plus. Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton.

16

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Production Capacity of Operable Petroleum Refineries Production Capacity of Operable Petroleum Refineries Definitions Key Terms Definition Alkylate The product of an alkylation reaction. It usually refers to the high octane product from alkylation units. This alkylate is used in blending high octane gasoline. Aromatics Hydrocarbons characterized by unsaturated ring structures of carbon atoms. Commercial petroleum aromatics are benzene, toluene, and xylene (BTX). Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton.

17

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Stocks by Type Stocks by Type Definitions Key Terms Definition Alaskan in Transit Alaskan crude oil stocks in transit by water between Alaska and the other States, the District of Columbia, Puerto Rico, and the Virgin Islands. Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

18

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

U.S. Imports by Country of Origin U.S. Imports by Country of Origin Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

19

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Refinery Stocks Refinery Stocks Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

20

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Supply and Disposition Balance Supply and Disposition Balance Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Products Supplied Products Supplied Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

22

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Weekly Supply Estimates Weekly Supply Estimates Definitions Key Terms Definition All Other Motor Gasoline Blending Components Naphthas (e.g. straight-run gasoline, alkylate, reformate, benzene, toluene, xylene) used for blending or compounding into finished motor gasoline. Includes receipts and inputs of Gasoline Treated as Blendstock (GTAB). Excludes conventional blendstock for oxygenate blending (CBOB), reformulated blendstock for oxygenate blending, oxygenates (e.g. fuel ethanol and methyl tertiary butyl ether), butane, and pentanes plus. Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton.

23

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Working Storage Capacity at Operable Refineries Working Storage Capacity at Operable Refineries Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Biomass-Based Diesel Fuel Biodiesel and other renewable diesel fuel or diesel fuel blending components derived from biomass, but excluding renewable diesel fuel coprocessed with petroleum feedstocks.

24

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

PAD District Imports by Country of Origin PAD District Imports by Country of Origin Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

25

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Imports by Destination Imports by Destination Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Aviation Gasoline Blending Components Naphthas which will be used for blending or compounding into finished aviation gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, and xylene). Excludes oxygenates (alcohols, ethers), butane, and pentanes plus. Oxygenates are reported as other hydrocarbons, hydrogen, and oxygenates.

26

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Pipeline, Tanker, and Barge Between PADDs Pipeline, Tanker, and Barge Between PADDs Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Barrel A unit of volume equal to 42 U.S. gallons. Conventional Blendstock for Oxygenate Blending (CBOB) Motor gasoline blending components intended for blending with oxygenates to produce finished conventional motor gasoline.

27

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

28

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

29

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

30

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

31

Teleparallel Darkness  

E-Print Network (OSTI)

First a review of Teleparallel GR is done with special emphasis in the derivation of conservation equations within this theory and in particular of energy/momentum conservation. Given that we are allowed to speak about the existence of negative energy, the question is that in its interaction with matter, we need not have matter conservation: It is only the sum of both which should remain constant. This does not only lead to an accelerated expansion without the need of a cosmological constant, but it may also contribute to explain the origin of dark matter, and poses questions about the origin of inflation at earlier times.

Mariano Hermida de La Rica

2013-10-08T23:59:59.000Z

32

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

33

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

34

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

35

Exothermic dark matter  

E-Print Network (OSTI)

We propose a novel mechanism for dark matter to explain the observed annual modulation signal at DAMA/LIBRA which avoids existing constraints from every other dark matter direct detection experiment including CRESST, CDMS, ...

Graham, Peter W.

36

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

37

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

38

Search for Dark Matter  

E-Print Network (OSTI)

The search for dark matter is a very wide an active field of research, and I necessarily concentrate here only in some aspects of it. I will review the prospects for direct and indirect dark matter searches of Weakly Interacting Massive Particles in the dark halo of our galaxy and focus in particular on the data of GLAST, PAMELA and DAMA.

Graciela B. Gelmini

2008-10-21T23:59:59.000Z

39

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.

40

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Dark gravity and cosmology  

E-Print Network (OSTI)

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

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

2005-09-05T23:59:59.000Z

42

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

43

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

44

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

45

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

46

Dark matter at colliders  

SciTech Connect

We show that colliders can impose strong constraints on dark matter. We take an effective field theory approach where dark matter couples to quarks and gluons through high dimensional operators. We discuss limits on interactions of dark matter and hadronic matter from the ATLAS experiment at the Large Hadron Collider (LHC). For spin-independent scattering, the LHC limits are stronger than those from direct detection experiments for light WIMPs. For spin-dependent scattering, the LHC sets better limits over much of parameter space.

Yu Haibo [Department of Physics, University of Michigan, Ann Arbor, MI, 48109 (United States)

2013-05-23T23:59:59.000Z

47

Dark matter dynamics  

E-Print Network (OSTI)

N-body simulations have revealed a wealth of information about dark matter halos but their results are largely empirical. Here we attempt to shed light on simulation results by using a combination of analytic and numerical ...

Zukin, Phillip Gregory

2012-01-01T23:59:59.000Z

48

Explosives going dark  

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

Explosives going dark Explosives going dark 1663 Los Alamos science and technology magazine Latest Issue:November 2013 All Issues » submit Explosives going dark An enhanced biomarker developed at Los Alamos can be used in the field to detect explosives and other hazardous materials. November 25, 2013 Explosives going dark This fluorescent protein, developed at Los Alamos, is unusually stable even when briefly boiled, making it useful for unconventional applications, such as sniffing out explosives and toxins. An enhanced green fluorescent protein stops glowing when explosives are present. Nitroorganic high explosives, including TNT and RDX, as well as certain other toxins, poisons, and nerve agents, have been shown to suppress an ultraviolet excitation mechanism that causes a fluorescent biomarker to

49

Dark Matter Detectors as Dark Photon Helioscopes  

E-Print Network (OSTI)

Light new particles with masses below 10 keV, often considered as a plausible extension of the Standard Model, will be emitted from the solar interior, and can be detected on the Earth with a variety of experimental tools. Here we analyze the new "dark" vector state V, a massive vector boson mixed with the photon via an angle kappa, that in the limit of the small mass m_V has its emission spectrum strongly peaked at low energies. Thus, we utilize the constraints on the atomic ionization rate imposed by the results of the XENON10 experiment to set the limit on the parameters of this model: kappa times m_V< 3 times10^{-12} eV. This makes low-threshold Dark Matter experiments the most sensitive dark vector helioscopes, as our result not only improves current experimental bounds from other searches by several orders of magnitude, but also surpasses even the most stringent astrophysical and cosmological limits in a seven-decade-wide interval of m_V. We generalize this approach to other light exotic particles, and set the most stringent direct constraints on "mini-charged" particles.

Haipeng An; Maxim Pospelov; Josef Pradler

2013-04-11T23:59:59.000Z

50

Dark matter: Theoretical perspectives  

SciTech Connect

I both review and make the case for the current theoretical prejudice: a flat Universe whose dominant constituent is nonbaryonic dark matter, emphasizing that this is still a prejudice and not yet fact. The theoretical motivation for nonbaryonic dark matter is discussed in the context of current elementary-particle theory, stressing that: (1) there are no dark matter candidates within the standard model of particle physics; (2) there are several compelling candidates within attractive extensions of the standard model of particle physics; and (3) the motivation for these compelling candidates comes first and foremost from particle physics. The dark-matter problem is now a pressing issue in both cosmology and particle physics, and the detection of particle dark matter would provide evidence for ``new physics.`` The compelling candidates are: a very light axion ( 10{sup {minus}6} eV--10{sup {minus}4} eV); a light neutrino (20 eV--90 eV); and a heavy neutralino (10 GeV--2 TeV). The production of these particles in the early Universe and the prospects for their detection are also discussed. I briefly mention more exotic possibilities for the dark matter, including a nonzero cosmological constant, superheavy magnetic monopoles, and decaying neutrinos.

Turner, M.S. [Chicago Univ., IL (United States). Enrico Fermi Inst.]|[Fermi National Accelerator Lab., Batavia, IL (United States)

1993-01-01T23:59:59.000Z

51

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

52

The Scale of Dark QCD  

E-Print Network (OSTI)

Most of the mass of ordinary matter has its origin from quantum chromodynamics (QCD). A similar strong dynamics, dark QCD, could exist to explain the mass origin of dark matter. Using infrared fixed points of the two gauge couplings, we provide a dynamical mechanism that relates the dark QCD confinement scale to our QCD scale, and hence provides an explanation for comparable dark baryon and proton masses. Together with a mechanism that generates equal amounts of dark baryon and ordinary baryon asymmetries in the early universe, the similarity of dark matter and ordinary matter energy densities can be naturally explained. For a large class of gauge group representations, the particles charged under both QCD and dark QCD, necessary ingredients for generating the infrared fixed points, are found to have masses at one to two TeV, which sets the scale for dark matter direct detection and novel collider signatures involving visible and dark jets.

Yang Bai; Pedro Schwaller

2013-06-19T23:59:59.000Z

53

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

54

Nearly Supersymmetric Dark Atoms  

E-Print Network (OSTI)

Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.

Behbahani, Siavosh R; Rube, Tomas; Wacker, Jay G

2010-01-01T23:59:59.000Z

55

Nearly Supersymmetric Dark Atoms  

E-Print Network (OSTI)

Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.

Siavosh R. Behbahani; Martin Jankowiak; Tomas Rube; Jay G. Wacker

2010-09-17T23:59:59.000Z

56

Nearly Supersymmetric Dark Atoms  

Science Conference Proceedings (OSTI)

Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.

Behbahani, Siavosh R.; Jankowiak, Martin; /SLAC /Stanford U., ITP; Rube, Tomas; /Stanford U., ITP; Wacker, Jay G.; /SLAC /Stanford U., ITP

2011-08-12T23:59:59.000Z

57

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

58

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

59

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

60

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

62

Little Higgs Dark Matter  

E-Print Network (OSTI)

The introduction of T parity dramatically improves the consistency of Little Higgs models with precision electroweak data, and renders the lightest T-odd particle (LTP) stable. In the Littlest Higgs model with T parity, the LTP is typically the T-odd heavy photon, which is weakly interacting and can play the role of dark matter. We analyze the relic abundance of the heavy photon, including its coannihilations with other T-odd particles, and map out the regions of the parameter space where it can account for the observed dark matter. We evaluate the prospects for direct and indirect discovery of the heavy photon dark matter. The direct detection rates are quite low and a substantial improvement in experimental sensitivity would be required for observation. A substantial flux of energetic gamma rays is produced in the annihilation of the heavy photons in the galactic halo. This flux can be observed by the GLAST telescope, and, if the distribution of dark matter in the halo is favorable, by ground-based telescope arrays such as VERITAS and HESS.

Andreas Birkedal; Andrew Noble; Maxim Perelstein; Andrew Spray

2006-03-09T23:59:59.000Z

63

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

64

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

65

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

66

The First dark microhalos  

Science Conference Proceedings (OSTI)

Earth-mass dark matter halos are likely to have been the first bound structures to form in the Universe. Whether such objects have survived to the present day in galaxies depends on, among other factors, the rate of encounters with normal stars. In this letter, we estimate the amount of tidal heating and mass loss in microhalos as a result of stellar encounters. We find that while microhalos are only mildly heated in dwarf galaxies of low stellar density, and they should have been completely destroyed in bulge or M32-like regions of high stellar density. In disk galaxies, such as the Milky Way, the disruption rate depends strongly on the orbital parameters of the microhalo; while stochastic radial orbits in triaxial Galactic potential are destroyed first, systems on non-planar retrograde orbits with large pericenters survive the longest. Since many microhalos lose a significant fraction of their material to unbound tidal streams, the final dark matter distribution in the solar neighborhood is better described as a superposition of microstreams rather than as a set of discrete spherical clumps in an otherwise homogeneous medium. Different morphologies of microhalos have implications for direct and indirect dark matter detection experiments.

Zhao, HongSheng; /St. Andrews U. /Beijing Observ.; Taylor, James E.; /Caltech; Silk, Joseph; /Oxford U.; Hooper, Dan; /Oxford U. /Fermilab

2005-08-01T23:59:59.000Z

67

A dark matter scaling relation from mirror dark matter  

E-Print Network (OSTI)

Mirror dark matter, and other similar dissipative dark matter candidates, need an energy source to stabilize dark matter halos in spiral galaxies. It has been suggested previously that ordinary supernovae can potentially supply the required energy. By matching the energy supplied to the halo from supernovae to that lost due to radiative cooling, we here derive a rough scaling relation, $R_{SN} \\propto \\rho_0 r_0^2$ ($R_{SN}$ is the supernova rate and $\\rho_0, \\ r_0$ the dark matter central density and core radius). Such a relation is consistent with dark matter properties inferred from studies of spiral galaxies with halo masses larger than $3\\times 10^{11} M_\\odot$. We speculate that other observed galaxy regularities might be explained within the framework of such dissipative dark matter.

R. Foot

2013-03-07T23:59:59.000Z

68

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

69

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

70

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 photons 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

71

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

72

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

73

Heavy Flavor & Dark Sector  

E-Print Network (OSTI)

We consider some contributions to rare processes in $B$ meson decays from a Dark Sector containing 2 light unstable scalars, with large couplings to each other and small mixings with Standard Model Higgs scalars. We show that existing constraints allow for an exotic contribution to high multiplicity final states with a branching fraction as large as $\\mathcal{O}(10^{-4})$, and that exotic particles could appear as narrow resonances or long lived particles which are mainly found in high multiplicity final states from $B$ decays.

Nelson, Ann E

2013-01-01T23:59:59.000Z

74

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

75

The PICASSO Dark Matter Experiment  

Science Conference Proceedings (OSTI)

The PICASSO experiment searches for cold dark matter through the direct detection of weakly interacting massive particles (WIMPs) via their spin?dependent interactions with fluorine at SNOLAB

Ubi Wichoski; The PICASSO Collaboration

2011-01-01T23:59:59.000Z

76

Table Definitions, Sources, and Explanatory Notes  

Gasoline and Diesel Fuel Update (EIA)

Yield Yield Definitions Key Terms Definition Asphalt A dark-brown-to-black cement-like material containing bitumens as the predominant constituent obtained by petroleum processing; used primarily for road construction. It includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts. Note: The conversion factor for asphalt is 5.5 barrels per short ton. Distillate Fuel Oil A general classification for one of the petroleum fractions produced in conventional distillation operations. It includes diesel fuels and fuel oils. Products known as No. 1, No. 2, and No. 4 diesel fuel are used in on-highway diesel engines, such as those in trucks and automobiles, as well as off-highway engines, such as those in railroad locomotives and agricultural machinery. Products known as No. 1, No. 2, and No. 4 fuel oils are used primarily for space heating and electric power generation.

77

DARK ENERGY AND NONLINEAR PERTURBATIONS  

E-Print Network (OSTI)

Dark energy might have an influence on the formation of nonlinear structures during the cosmic history. For example, in models in which dark energy couples to dark matter, it will be nonhomogeneous 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

78

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

79

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

80

Turning off the lights: How dark is dark matter?  

SciTech Connect

We consider current observational constraints on the electromagnetic charge of dark matter. The velocity dependence of the scattering cross section through the photon gives rise to qualitatively different constraints than standard dark matter scattering through massive force carriers. In particular, recombination epoch observations of dark matter density perturbations require that {epsilon}, the ratio of the dark matter to electronic charge, is less than 10{sup -6} for m{sub X}=1 GeV, rising to {epsilon}<10{sup -4} for m{sub X}=10 TeV. Though naively one would expect that dark matter carrying a charge well below this constraint could still give rise to large scattering in current direct detection experiments, we show that charged dark matter particles that could be detected with upcoming experiments are expected to be evacuated from the Galactic disk by the Galactic magnetic fields and supernova shock waves and hence will not give rise to a signal. Thus dark matter with a small charge is likely not a source of a signal in current or upcoming dark matter direct detection experiments.

McDermott, Samuel D.; Yu Haibo; Zurek, Kathryn M. [Michigan Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2011-03-15T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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81

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

82

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.

83

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

84

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

85

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

86

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

87

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

88

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

89

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

90

Cold Dark Matter Resuscitated?  

E-Print Network (OSTI)

The Cold Dark Matter (CDM) model has an elegant simplicitly which makes it very predictive, but when its parameters are fixed at their `canonical' values its predictions are in conflict with observational data. There is, however, much leeway in the initial conditions within the CDM framework. We advocate a re-examination of the CDM model, taking into account modest variation of parameters from their canonical values. We find that CDM models with $n=0.8$--0.9 and $h=0.45$--0.50 can fit the available data. Our ``best fit'' CDM model has $n=0.9$, $h=0.45$ and $C_2^{T}/C_2^{S}=0.7$. We discuss the current state of observations which could definitely rule out this model.

Martin White; Douglas Scott; Joe Silk; Marc Davis

1995-08-02T23:59:59.000Z

91

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

92

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

93

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

94

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

95

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

96

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 Khler 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; Jrme Martin; et al.

2009-01-01T23:59:59.000Z

97

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

98

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

99

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

100

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

102

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

103

Fake Dark Matter at Colliders  

E-Print Network (OSTI)

If the dark matter (DM) consists of a weakly interacting massive particle (WIMP), it can be produced and studied at future collider experiments like those at the LHC. The production of collider-stable WIMPs is characterized by hard scattering events with large missing transverse energy. Here we point out that the discovery of this well-characterized DM signal may turn out to be a red herring. We explore an alternative explanation -- fake dark matter -- where the only sources of missing transverse energy are standard model neutrinos. We present examples of such models, focusing on supersymmetric models with R-parity violation. We also briefly discuss means of differentiating fake dark matter from the production of new collider-stable particles.

Chang, Spencer

2009-01-01T23:59:59.000Z

104

Fake Dark Matter at Colliders  

E-Print Network (OSTI)

If the dark matter (DM) consists of a weakly interacting massive particle (WIMP), it can be produced and studied at future collider experiments like those at the LHC. The production of collider-stable WIMPs is characterized by hard scattering events with large missing transverse energy. Here we point out that the discovery of this well-characterized DM signal may turn out to be a red herring. We explore an alternative explanation -- fake dark matter -- where the only sources of missing transverse energy are standard model neutrinos. We present examples of such models, focusing on supersymmetric models with R-parity violation. We also briefly discuss means of differentiating fake dark matter from the production of new collider-stable particles.

Spencer Chang; Andre de Gouvea

2009-01-30T23:59:59.000Z

105

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) G? = ?8?GT? (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

106

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

107

Baryonic Dark Matter in Galaxies  

E-Print Network (OSTI)

Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in the discs or halos of galaxies. If they were in the form of compact objects, they would then be natural MACHO candidates, in which case they are likely to be the remnants of a first generation of pregalactic or protogalactic Population III stars. Various candidates have been proposed for such remnants - brown dwarfs, red dwarfs, white dwarfs, neutron stars or black holes - and we review the many types of observations (including microlensing searches) which can be used to constrain or exclude them.

B. J. Carr

2000-08-01T23:59:59.000Z

108

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

109

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

110

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

111

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

112

Semi-annihilation of dark matter  

E-Print Network (OSTI)

We show that the thermal relic abundance of dark matter can be affected by a new type of reaction: semi-annihilation. Semi-annihilation takes the schematic form ..., where psi i are stable dark matter particles and phi is ...

DEramo, Francesco

113

Dark matter axions and caustic rings  

SciTech Connect

This report contains discussions on the following topics: the strong CP problem; dark matter axions; the cavity detector of galactic halo axions; and caustic rings in the density distribution of cold dark matter halos.

Sikivie, P.

1997-11-01T23:59:59.000Z

114

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

115

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

116

A Search for Dark Higgs Bosons  

SciTech Connect

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb{sup -1} of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the Standard Model-dark sector mixing angle and the dark sector coupling constant.

Lees, J.P.

2012-06-08T23:59:59.000Z

117

"Dark Web: Exploring and Min-ing the Dark Side of the Web"  

E-Print Network (OSTI)

Title: "Dark Web: Exploring and Min- ing the Dark Side of the Web" Speaker: Director, Prof will review the emerging research in Terrorism Informatics based on a web mining perspective. Recent progress in the internationally re- nowned Dark Web project will be reviewed, including: deep/dark web spider- ing (web sites

Michelsen, Claus

118

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

119

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

120

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 brown-to-black cement-like" 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

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

122

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

123

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

124

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

125

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

126

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

127

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

128

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

129

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

130

Dark matter chaos in the Solar System  

E-Print Network (OSTI)

We study the capture of galactic dark matter particles in the Solar System produced by rotation of Jupiter. It is shown that the capture cross section is much larger than the area of Jupiter orbit being inversely diverging at small particle energy. We show that the dynamics of captured particles is chaotic and is well described by a simple symplectic dark map. This dark map description allows to simulate the scattering and dynamics of $10^{14}$ dark matter particles during the life time of the Solar System and to determine dark matter density profile as a function of distance from the Sun. The mass of captured dark matter in the radius of Neptune orbit is estimated to be $2 \\cdot 10^{15} g$. The radial density of captured dark matter is found to be approximately constant behind Jupiter orbit being similar to the density profile found in galaxies.

J. Lages; D. L. Shepelyansky

2012-11-05T23:59:59.000Z

131

Baryon destruction by asymmetric dark matter  

SciTech Connect

We investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number, as may occur when the dark matter abundance is linked to the baryon abundance. Antibaryonic dark matter can cause induced nucleon decay by annihilating visible baryons through inelastic scattering. These processes lead to an effective nucleon lifetime of 10{sup 29}-10{sup 32} yrs in terrestrial nucleon decay experiments, if baryon number transfer between visible and dark sectors arises through new physics at the weak scale. The possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments. Monojet searches (and related signatures) at hadron colliders also provide a complementary probe of weak-scale dark-matter-induced baryon number violation. Finally, we discuss the effects of baryon-destroying dark matter on stellar systems and show that it can be consistent with existing observations.

Davoudiasl, Hooman [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States); Morrissey, David E.; Tulin, Sean [Theory Group, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3 (Canada); Sigurdson, Kris [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

2011-11-01T23:59:59.000Z

132

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

133

The Cosmology of Composite Inelastic Dark Matter  

SciTech Connect

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

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

2011-08-19T23:59:59.000Z

134

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

135

DARK-FIELD ILLUMINATION SYSTEM  

DOE Patents (OSTI)

A means was developed for viewing objects against a dark background from a viewing point close to the light which illuminates the objects and under conditions where the back scattering of light by the objects is minimal. A broad light retro-directing member on the opposite side of the objects from the light returns direct light back towards the source while directing other light away from the viewing point. The viewing point is offset from the light and thus receives only light which is forwardly scattered by an object while returning towards the source. The object is seen, at its true location, against a dark background. The invention is particularly adapted for illuminating and viewing nuclear particle tracks in a liquid hydrogen bubble chamber through a single chamber window. (AEC)

Norgren, D.U.

1962-07-24T23:59:59.000Z

136

EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS  

SciTech Connect

Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

Baushev, A. N., E-mail: baushev@gmail.com [DESY, D-15738 Zeuthen (Germany); Institut fuer Physik und Astronomie, Universitaet Potsdam, D-14476 Potsdam-Golm (Germany)

2013-07-10T23:59:59.000Z

137

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

138

TASI 2008 Lectures on Dark Matter  

SciTech Connect

Based on lectures given at the 2008 Theoretical Advanced Study Institute (TASI), I review here some aspects of the phenomenology of particle dark matter, including the process of thermal freeze-out in the early universe, and the direct and indirect detection of WIMPs. I also describe some of the most popular particle candidates for dark matter and summarize the current status of the quest to discover dark matter's particle identity.

Hooper, Dan; /Fermilab /Chicago U., Astron. Astrophys. Ctr.

2009-01-01T23:59:59.000Z

139

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

140

Dark Matter Jets at the LHC  

SciTech Connect

We argue that dark matter particles which have strong interactions with the Standard Model particles are not excluded by current astrophysical constraints. These dark matter particles have unique signatures at colliders; instead of missing energy, the dark matter particles produce jets. We propose a new search strategy for such strongly interacting particles by looking for a signal of two trackless jets. We show that suitable cuts can plausibly allow us to find these signals at the LHC even in early data.

Bai, Yang; /SLAC; Rajaraman, Arvind; /UC, Irvine

2012-03-28T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

142

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

143

Dark algae, life on Mars?  

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

Dark algae, life on Mars? Dark algae, life on Mars? Name: Jungle Fever Location: N/A Country: N/A Date: N/A Question: I'm probably writing this is vain since my numerous other notes weren't answered, but here goes. Does anyone out there know anything about the dark algae found in Siberia (or Antarctica, I don't remember which) or the primitive microbes found by Chris McKay that were revived by a drop of water? Also, can this concept be applied to the possibility of life on Mars? I'd also appreciate any information on extraterrestrial microorganisms or life forms. Much thanks. Replies: I don't know specifically about the algae that you mention. However, I do know that there are several kinds of algae that go into a sexual reproductive state in response to adverse conditions often including high temperatures or lack of moisture. This sexual phase results in formation of a fertilized zygote which becomes dormant until conditions are optimum for growth. This usually involves water - so a drop of water could initiate growth of the new alga, and it could reproduce asexually quite rapidly, until conditions trigger the sexual phase again. I see no reason why such a growth pattern couldn't apply to life on Mars or anywhere else. There isn't much information, as far as I'm aware, regarding extraterrestrial life. So far, none has been found, but it is likely, statistically, that there is some out there, somewhere. The SETI program (Search for extraterrestrial intelligence), funded in part by the Planetary Society, is trying to find higher forms of life by doing radio searches.

144

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

145

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

146

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

147

Some Practical Applications of Dark Matter Research  

E-Print Network (OSTI)

Two practical spin-offs from the development of cryogenic dark matter detectors are presented. One in materials research, the other in biology.

Stodolsky, L

2008-01-01T23:59:59.000Z

148

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

149

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

150

A dark matter model with non-Abelian gauge symmetry.  

SciTech Connect

We propose a dark-matter model in which the dark sector is gauged under a new SU(2) group. The dark sector consists of SU(2) dark gauge fields, two triplet dark Higgs fields, and two dark fermion doublets (dark-matter candidates in this model). The dark sector interacts with the standard model sector through kinetic and mass mixing operators. The model explains both PAMELA and Fermi LAT data very well and also satisfies constraints from both the dark-matter relic density and standard model precision observables. The phenomenology of the model at the LHC is also explored.

Zhang, H.; Li, C. S.; Cao, Q.-H.; Li, Z.; High Energy Physics; Univ. of Chicago; Peking Univ.; Michigan State Univ.

2010-10-07T23:59:59.000Z

151

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.

152

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

153

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

154

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

155

MSU Extension Publication Archive Archive copy of publication, do not use for current recommendations. Up-to-date  

E-Print Network (OSTI)

corn rootworm beetle (Fig. B) is yellow or red and usually has three black stripes down its back. The size of the stripes varies from small spots at the base of the wing to stripes nearly covering the whole wing. The hind tibia (shins) of the · western corn rootworms are dark brown to black. Two species

156

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

157

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

158

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

159

Dark degeneracy and interacting cosmic components  

SciTech Connect

We study some properties of the dark degeneracy, which is the fact that what we measure in gravitational experiments is the energy-momentum tensor of the total dark sector, and any split into components (as in dark matter and dark energy) is arbitrary. In fact, just one dark fluid is necessary to obtain exactly the same cosmological and astrophysical phenomenology as the {Lambda}CDM model. We work explicitly the first-order perturbation theory and show that beyond the linear order the dark degeneracy is preserved under some general assumptions. Then we construct the dark fluid from a collection of interacting fluids. Finally, we try to break the degeneracy with a general class of couplings to baryonic matter. Nonetheless, we show that these interactions can also be understood in the context of the {Lambda}CDM model as between dark matter and baryons. For this last investigation we choose two independent parametrizations for the interactions, one inspired by electromagnetism and the other by chameleon theories. Then, we constrain them with a joint analysis of CMB and supernovae observational data.

Aviles, Alejandro [Instituto de Ciencias Nucleares, UNAM (Mexico); Cervantes-Cota, Jorge L. [Depto. de Fisica, Instituto Nacional de Investigaciones Nucleares (Mexico)

2011-10-15T23:59:59.000Z

160

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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161

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

162

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

163

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

164

Dark Matter Studies Entrain Nuclear Physics  

E-Print Network (OSTI)

We review theoretically well-motivated dark-matter candidates, and pathways to their discovery, in the light of recent results from collider physics, astrophysics, and cosmology. Taken in aggregate, these encourage broader thinking in regards to possible dark-matter candidates --- dark-matter need not be made of "WIMPs," i.e., elementary particles with weak-scale masses and interactions. Facilities dedicated to nuclear physics are well-poised to investigate certain non-WIMP models. In parallel to this, developments in observational cosmology permit probes of the relativistic energy density at early epochs and thus provide new ways to constrain dark-matter models, provided nuclear physics inputs are sufficiently well-known. The emerging confluence of accelerator, astrophysical, and cosmological constraints permit searches for dark-matter candidates in a greater range of masses and interaction strengths than heretofore possible.

Susan Gardner; George Fuller

2013-03-19T23:59:59.000Z

165

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

166

The XENON Dark Matter Search  

SciTech Connect

The XENON experiment will search for Weakly Interacting Massive Particles (WIMPS), a leading candidate for the dark matter content of the Universe. The XENON detector uses the simultaneous measurement of ionization and scintillation in liquid xenon to distinguish between nuclear recoils and background electronic interactions. Ionization electrons are extracted into the xenon vapor where they produce a large proportional scintillation signal in a grid assembly. Both prompt and proportional scintillation light are detected by PMT arrays on the top and bottom of the active liquid xenon volume. The distribution of proportional scintillation light in the top PMT array can be used to achieve xy position resolution, while the ionization drift time gives position resolution in the z direction. This allows the definition of a low-background fiducial volume. I describe the results of the R and D phase of this project before providing a status update on the XENON10 phase.

McKinsey, D. N. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2006-11-17T23:59:59.000Z

167

Singlet-Doublet Dark Matter  

Science Conference Proceedings (OSTI)

In light of recent data from direct detection experiments and the Large Hadron Collider, we explore models of dark matter in which an SU(2){sub L} doublet is mixed with a Standard Model singlet. We impose a thermal history. If the new particles are fermions, this model is already constrained due to null results from XENON100. We comment on remaining regions of parameter space and assess prospects for future discovery. We do the same for the model where the new particles are scalars, which at present is less constrained. Much of the remaining parameter space for both models will be probed by the next generation of direct detection experiments. For the fermion model, DeepCore may also play an important role.

Cohen, Timothy; /SLAC /Michigan U., MCTP; Kearney, John; Pierce, Aaron; /Michigan U., MCTP; Tucker-Smith, David; /Williams Coll.

2012-02-15T23:59:59.000Z

168

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

169

Cosmic Structure Probes of the Dark Universe | Argonne Leadership...  

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

Hours at ALCF: 150 Million Year: 2010 to 2013 Research Domain: Physics Dark matter and dark energy are the dominant components of the Universe. Their ultimate nature, however,...

170

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

171

#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.

172

Dark Matter in the Private Higgs Model  

E-Print Network (OSTI)

The extremely large hierarchy observed in the fermion mass spectrum remains as one of the most puzzling and unresolved issues in particle physics. In a recent proposal, however, it was demonstrated that by introducing one Higgs doublet (or Private Higgs) per fermion this hierarchy could be made natural by making the Yukawa couplings between each fermion and its respective Higgs boson of order unity. Among the interesting predictions of the Private Higgs scenario is a variety of scalars which could be probed at future collider experiments and a possible dark matter candidate. In this paper, we study in some detail the dark matter sector of the Private Higgs model. We first calculate the annihilation cross sections of dark matter in this model and find that one can easily account for the observed density of dark matter in the Universe with relatively natural values of the model's parameters. Finally, we investigate the possibility of detecting Private Higgs dark matter indirectly via the observation of anomalous gamma rays originating from the galactic halo. We show that a substantial flux of photons can be produced from the annihilation of Private Higgs dark matter such that, if there is considerable clumping of dark matter in the galactic halo, the flux of these gamma rays could be observed by ground-based telescope arrays such as VERITAS and HESS.

C. B. Jackson

2008-04-23T23:59:59.000Z

173

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

174

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

175

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

176

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

177

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

178

SOLAR CONSTRAINTS ON ASYMMETRIC DARK MATTER  

SciTech Connect

The dark matter content of the universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freezeout depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels) of particles and antiparticles. In these {eta}-parameterized asymmetric dark matter ({eta}ADM) models, the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of dark matter asymmetry {eta} close to the baryon asymmetry {eta}{sub B}. Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT, and CRESST experiments. Here, we constrain {eta}ADM by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an {eta}-asymmetry with a value in the interval 10{sup -12}-10{sup -10}, would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. This result is also confirmed by helioseismology data. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological {eta}ADM scenarios that we discuss have a relic dark matter density {Omega}h {sup 2} and baryon asymmetry {eta}{sub B} in agreement with the current WMAP measured values, {Omega}{sub DM} h {sup 2} = 0.1109 {+-} 0.0056 and {eta}{sub B} = 0.88 Multiplication-Sign 10{sup -10}.

Lopes, Ilidio [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Silk, Joseph, E-mail: ilidio.lopes@ist.utl.pt, E-mail: silk@astro.ox.ac.uk [Institut d'Astrophysique de Paris, F-75014 Paris (France)

2012-10-01T23:59:59.000Z

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 brown-to-black cement-like" 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

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

182

Dark Photon Search at BABAR  

SciTech Connect

Presented is the current progress of a search for the signature of a dark photon or new particle using the BaBar data set. We search for the processes e{sup +}e{sup -} {yields} {gamma}{sub ISR}A{prime},A{prime} {yields} e{sup +}e{sup -} and e{sup +}e{sup -} {yields} {gamma}{sub ISR}{gamma}, {gamma} {yields} A{prime},A{prime} {yields} e{sup +}e{sup -}, where {gamma}{sub ISR} is an initial state radiated photon of energy E{sub {gamma}} >= 1 GeV. Twenty-five sets of Monte Carlo, simulating e{sup +}e{sup -} collisions at an energy of 10.58 GeV, were produced with different values of the A{prime} mass ranging from 100 MeV to 9.5 GeV. The mass resolution is calculated based on Monte Carlo simulations. We implement ROOT's Toolkit for Multivariate Analysis (TMVA), a machine learning tool that allows us to evaluate the signal character of events based on many of discriminating variables. TMVA training is conducted with samples of Monte Carlo as signal and a small portion of Run 6 as background. The multivariate analysis produces additional cuts to separate signal and background. The signal efficiency and sensitivity are calculated. The analysis will move forward to fit the background and scan the residuals for the narrow resonance peak of a new particle.

Greenwood, Ross N; /MIT /SLAC

2012-09-07T23:59:59.000Z

183

Chance and Chandra (and repulsive dark matter)  

E-Print Network (OSTI)

A few examples are given of Chandra's work on statistical and stochastic problems that relate to open questions in astrophysics, in particular his theory of dynamical relaxation in systems with inverse-square interparticle forces. The roles of chaos and integrability in this theory require clarification, especially for systems having a dominant central mass. After this prelude, a hypothetical form of repulsive bosonic dark matter is discussed. The repulsion leads to nontrivial thermodynamic behavior, including superfluidity, and would tend to suppress dynamical friction, greatly reducing the drag exerted on rotating galactic bars. However, this form of dark matter can probably be ruled out, at least for parameters that allow halos to reach thermal equilibria within a Hubble time. One combination of the particle mass and interparticle repulsion determines the minimum core radius of dark halos. Bounds on dark-matter collisionality inferred from the Bullet Cluster constrain a second combination. It is possible t...

Goodman, Jeremy

2011-01-01T23:59:59.000Z

184

Light Dark Matter Annihilations into Two Photons  

E-Print Network (OSTI)

We compute the pair annihilation cross section of light (spin-0) dark matter particles into two photons and discuss the detectability of the monochromatic line associated with these annihilations.

C. Boehm; J. Orloff; P. Salati

2006-07-19T23:59:59.000Z

185

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

186

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

187

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

188

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

189

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

190

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

191

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

192

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

193

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

194

Hierarchical phase space structure of dark matter haloes: Tidal debris, caustics, and dark matter annihilation  

E-Print Network (OSTI)

Most of the mass content of dark matter haloes is expected to be in the form of tidal debris. The density

Bertschinger, Edmund

195

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

196

The C-4 Dark Matter Experiment  

Science Conference Proceedings (OSTI)

Abstract We describe the experimental design of C-4, an expansion of the CoGeNT dark matter search to four identical detectors each approximately three times the mass of the p-type point contact (PPC) germanium diode presently taking data at the Soudan Underground Laboratory. Expected reductions of radioactive backgrounds and energy threshold are discussed, including an estimate of the additional sensitivity to low-mass dark matter candidates to be obtained with this search.

Bonicalzi, Ricco; Collar, J. I.; Colaresi, J.; Fast, James E.; Fields, N.; Fuller, Erin S.; Hai, M.; Hossbach, Todd W.; Kos, Marek S.; Orrell, John L.; Overman, Cory T.; Reid, Douglas J.; VanDevender, Brent A.; Wiseman, Clinton G.; Yocum, K. M.

2013-06-01T23:59:59.000Z

197

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

198

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

199

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

200

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Measuring the dark matter equation of state  

E-Print Network (OSTI)

The nature of the dominant component of galaxies and clusters remains unknown. While the astrophysics community supports the cold dark matter (CDM) paradigm as a clue factor in the current cosmological model, no direct CDM detections have been performed. Faber and Visser 2006 have suggested a simple method for measuring the dark matter equation of state that combines kinematic and gravitational lensing data to test the widely adopted assumption of pressureless dark matter. Following this formalism, we have measured the dark matter equation of state for first time using improved techniques. We have found that the value of the equation of state parameter is consistent with pressureless dark matter within the errors. Nevertheless, the measured value is lower than expected because typically the masses determined with lensing are larger than those obtained through kinematic methods. We have tested our techniques using simulations and we have also analyzed possible sources of error that could invalidate or mimic our results. In the light of this result, we can now suggest that the understanding of the nature of dark matter requires a complete general relativistic analysis.

Ana Laura Serra; Mariano Javier de Len Domnguez Romero

2011-03-28T23:59:59.000Z

202

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

203

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

204

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

205

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

206

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

207

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

208

Dark atoms of dark matter from new stable quarks and leptons  

SciTech Connect

The nonbaryonic dark matter of the Universe can consist of new stable charged leptons and quarks, if they are hidden in elusive 'dark atoms' of composite dark matter. Such possibility can be compatible with the severe constraints on anomalous isotopes, if there exist stable particles with charge -2 and there are no stable particles with charges +1 and -1. These conditions cannot be realized in supersymmetric models, but can be satisfied in several recently developed alternative scenarios. The excessive -2 charged particles are bound with primordial helium in O-helium 'atoms', maintaining specific nuclear-interacting form of the Warmer than Cold Dark Matter. The puzzles of direct dark matter searches appear in this case as a reflection of nontrivial nuclear physics of O-helium.

Khlopov, Maxim Yu. [APC laboratory 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France)

2012-06-20T23:59:59.000Z

209

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

210

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

211

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

212

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

213

Direct Detection of Dark Matter Debris Flows  

E-Print Network (OSTI)

Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended "debris flows" in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earth's location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments. At Earth-frame speeds greater than 450 km/s, debris flow comprises more than half of the dark matter at the Sun's location, and up to 80% at even higher speeds. Therefore, debris flow is most important for experiments that are particularly sensitive to the high speed tail of the dark matter distribution, such as searches for light or inelastic dark matter or experiments with directional sensitivity. We show that debris flow yields a distinctive recoil energy spectrum and a broadening of the distribution of incidence direction.

Michael Kuhlen; Mariangela Lisanti; David N. Spergel

2012-01-31T23:59:59.000Z

214

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":""}]}

215

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

216

MODELING OBSERVATIONAL CONSTRAINTS FOR DARK MATTER HALOS  

SciTech Connect

Observations show that the underlying rotation curves at intermediate radii in spiral and low-surface-brightness galaxies are nearly universal. Further, in these same galaxies, the product of the central density and the core radius ({rho}{sub 0} r{sub 0}) is constant. An empirically motivated model for dark matter halos that incorporates these observational constraints is presented and shown to be in accord with the observations. A model fit to the observations of the galaxy cluster A611 shows that {rho}{sub 0} r{sub 0} for the dark matter halo in this more massive structure is larger by a factor of {approx}20 over that assumed for the galaxies. The model maintains the successful Navarro-Frenk-White form in the outer regions, although the well-defined differences in the inner regions suggest that modifications to the standard cold dark matter picture are required.

Hartwick, F. D. A. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada)

2012-12-01T23:59:59.000Z

217

The Top Window for dark matter  

E-Print Network (OSTI)

We investigate a scenario that the top quark is the only window to the dark matter particle. We use the effective Lagrangian approach to write down the interaction between the top quark and the dark matter particle. Requiring the dark matter satisfying the relic density we obtain the size of the effective interaction. We show that the scenario can be made consistent with the direct and indirect detection experiments by adjusting the size of the effective coupling. Finally, we calculate the production cross section for $t\\bar t + \\chi \\bar \\chi$ at the Large Hadron Collider (LHC), which will give rise to an interesting signature of a top-pair plus large missing energy.

Kingman Cheung; Kentarou Mawatari; Eibun Senaha; Po-Yan Tseng; Tzu-Chiang Yuan

2010-09-03T23:59:59.000Z

218

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

219

Traveling dark solitons in superfluid Fermi gases  

SciTech Connect

Families of dark solitons exist in superfluid Fermi gases. The energy-velocity dispersion and number of depleted particles completely determine the dynamics of dark solitons on a slowly varying background density. For the unitary Fermi gas, we determine these relations from general scaling arguments and conservation of local particle number. We find solitons to oscillate sinusoidally at the trap frequency reduced by a factor of 1/{radical}(3). Numerical integration of the time-dependent Bogoliubov-de Gennes equation determines spatial profiles and soliton-dispersion relations across the BEC-BCS crossover, and proves consistent with the scaling relations at unitarity.

Liao Renyuan; Brand, Joachim [New Zealand Institute for Advanced Study and Centre for Theoretical Chemistry and Physics, Massey University, Private Bag 102904 NSMC, Auckland 0745 (New Zealand)

2011-04-15T23:59:59.000Z

220

A New Dark Matter Model for Galaxies  

E-Print Network (OSTI)

In this paper a new theory of Dark Matter is proposed. Experimental analysis of several Galaxies show how the non-gravitational contribution to galactic Velocity Rotation Curves can be interpreted as that due to the Cosmological Constant ?. The experimentally determined values for ? are found to be consistent with those expected from Cosmological Constraints. The Cosmological Constant is interpreted as leading to a constant energy density which in turn can be used to partly address the energy deficit problem (Dark Energy) of the Universe. The work presented here supports the proposal for an accelerating universe and that we live in a quasi de-Sitter universe.

George Kraniotis; Steven Whitehouse

2000-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Black Hole Remnants and Dark Matter  

DOE Green Energy (OSTI)

We argue that, when the gravity effect is included, the generalized uncertainty principle (GUP) may prevent black holes from total evaporation in a similar way that the standard uncertainty principle prevents the hydrogen atom from total collapse. Specifically we invoke the GUP to obtain a modified Hawking temperature, which indicates that there should exist non-radiating remnants (BHR) of about Planck mass. BHRs are an attractive candidate for cold dark matter. We investigate an alternative cosmology in which primordial BHRs are the primary source of dark matter.

Chen, Pisin

2002-07-31T23:59:59.000Z

222

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

223

A Critique of Drexler Dark Matter  

E-Print Network (OSTI)

Drexler dark matter is an alternate approach to dark matter that assumes that highly relativistic protons trapped in the halo of the galaxies could account for the missing mass. We look at various energetics involved in such a scenario such as the energy required to produce such particles and the corresponding lifetimes. Also we look at the energy losses from synchrotron and inverse Compton scattering and their signatures. The Coulomb repulsive instability due to the excess charge around the galaxies is also calculated. The above results lead us to conclude that such a model for DM is unfeasible.

C. Sivaram; Kenath Arun; R. Nagaraja

2010-11-26T23:59:59.000Z

224

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

225

Dipole Moment Bounds on Dark Matter Annihilation  

E-Print Network (OSTI)

We consider constraints on simplified models in which scalar dark matter annihilates to light charged leptons through the exchange of charged mediators. We find that loop diagrams will contribute corrections to the magnetic and electric dipole moments of the light charged leptons, and experimental constraints on these corrections place significant bounds on the dark matter annihilation cross section. In particular, annihilation to electrons with an observable cross section would be ruled out, while annihilation to muons is only permitted if the dominant contributions arise from CP-violating interactions.

Keita Fukushima; Jason Kumar

2013-07-26T23:59:59.000Z

226

Might Dark Matter be Actually Black?  

DOE Green Energy (OSTI)

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. We argue here first that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. Secondly we note that the hybrid inflation model provides a plausible mechanism for production of large numbers of small black holes. Combining these we suggest that the dark matter might be composed of Planck-size BHRs and discuss the possible constraints and signatures associated with this notion.

Chen, Pisin

2003-08-06T23:59:59.000Z

227

Generalized Uncertainty Principle and Dark Matter  

DOE Green Energy (OSTI)

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. Recently we argued that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. We further noted that the hybrid inflation model provides a plausible mechanism for production of large numbers of small black holes. Combining these we suggested that the dark matter might be composed of Planck-size BHRs. In this paper we briefly review these arguments, and discuss the reheating temperature as a result of black hole evaporation.

Chen, P

2004-01-13T23:59:59.000Z

228

Dark Matter in the Light of COBE  

E-Print Network (OSTI)

The observations of all three COBE instruments are examined for the effects of dark matter. The anisotropy measured by the DMR, and especially the degree-scale ground- and balloon-based experiments, is only compatible with large-scale structure formation by gravity if the Universe is dominated by non-baryonic dark matter. The FIRAS instrument measures the total power radiated by cold dust, and thus places tight limits on the absorption of starlight by very cold gas and dust in the outer Milky Way. The DIRBE instrument measures the infrared background, and will place tight limits on the emission by low mass stars in the Galactic halo.

Edward L. Wright

1994-08-01T23:59:59.000Z

229

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

230

Search for Low-Mass Dark-Sector Higgs Bosons  

E-Print Network (OSTI)

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516??fb[superscript ...

Cowan, Ray Franklin

231

PICO-LON project to search for cosmic dark matter  

Science Conference Proceedings (OSTI)

The dark matter search project PICO-LON has been started. Thin and wide area NaI(Tl) scintillator is the promising detector system to study the properties of dark matter particle.

Fushimi, K.; Harada, K.; Kameda, Y.; Nakayama, S. [Department of Physics, University of Tokushima, 1-1 Minami Josanjimacho Tokushima city, 770-8502 Tokushima (Japan); Ejiri, H.; Shima, T. [Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka Ibaraki city, 567-0047 Osaka (Japan); Hazama, R. [Department of Engineering, Hiroshima University, 1-4-1 Higashi Kagamiyama Higashi Hiroshima city, 739-8527 Hiroshima (Japan); Imagawa, K.; Matsumoto, E. [Horiba Ltd., 2 Minami-ku Kisshoin Miyanohigashimachi Kyoto city, 601-8510 Kyoto (Japan)

2010-08-12T23:59:59.000Z

232

BABAR Constrains Dark-Matter Photon and Higgs  

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

Constrains Dark-Matter Photon and Higgs The majority of matter in the universe is "dark matter" that does not interact with light. Since it cannot be seen directly, its existence...

233

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

234

Determining Supersymmetric Parameters With Dark Matter Experiments  

Science Conference Proceedings (OSTI)

In this article, we explore the ability of direct and indirect dark matter experiments to not only detect neutralino dark matter, but to constrain and measure the parameters of supersymmetry. In particular, we explore the relationship between the phenomenological quantities relevant to dark matter experiments, such as the neutralino annihilation and elastic scattering cross sections, and the underlying characteristics of the supersymmetric model, such as the values of {mu} (and the composition of the lightest neutralino), m{sub A} and tan {beta}. We explore a broad range of supersymmetric models and then focus on a smaller set of benchmark models. We find that by combining astrophysical observations with collider measurements, {mu} can often be constrained far more tightly than it can be from LHC data alone. In models in the A-funnel region of parameter space, we find that dark matter experiments can potentially determine m{sub A} to roughly {+-}100 GeV, even when heavy neutral MSSM Higgs bosons (A, H{sub 1}) cannot be observed at the LHC. The information provided by astrophysical experiments is often highly complementary to the information most easily ascertained at colliders.

Hooper, Dan; /Fermilab; Taylor, Andrew M.; /Oxford U.

2006-07-01T23:59:59.000Z

235

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

236

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

237

Explorations of the Bright and Dark Universe  

E-Print Network (OSTI)

have light bulbs: SUPERNOVAE ! #12;ExpansionoftheUniverse Time Present10 billion years ago #12;Dark 965965 #12;2 Million Light Years Andromeda Galaxy Observed as it was 2 million years ago. 12 Billion Light Years Distant galax observed as i serving distant objects _Looking into the p #12;Microwave

Leka, K. D .

238

Direct search for WIMP dark matter  

E-Print Network (OSTI)

We will review the experimental aspects of the direct search for WIMP dark matter. In thin search, one looks in a terrestrial target for nuclear recoils produced by the impacts with WIMPs from the galatic halo. After describing the different search strategies and review the currently running experiments and the prospects of future experiments

J. Gascon

2005-04-11T23:59:59.000Z

239

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

240

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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 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

242

ON THE LOCAL DARK MATTER DENSITY  

SciTech Connect

An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic midplane by Moni Bidin et al. has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights. We substitute the assumption, supported by data, that the circular speed is independent of radius in the midplane. We demonstrate that the assumption of constant mean azimuthal velocity is implausible by showing that it requires the circular velocity to drop more steeply than allowed by any plausible mass model, with or without dark matter, at large heights above the midplane. Using the approximation that the circular-velocity curve is flat in the midplane, we find that the data imply a local dark matter density of 0.008 {+-} 0.003 M{sub Sun} pc{sup -3} = 0.3 {+-} 0.1 GeV cm{sup -3}, fully consistent with standard estimates of this quantity. This is the most robust direct measurement of the local dark matter density to date.

Bovy, Jo; Tremaine, Scott [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

2012-09-01T23:59:59.000Z

243

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

244

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

245

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

246

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

247

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

248

Welcome to the jungle: HCI after dark  

Science Conference Proceedings (OSTI)

The transformation of urban spaces that occurs once darkness falls is simultaneously exhilarating and menacing, and over the past 20 months we have investigated the potential for mobile technology to help users manage their personal safety concerns in ... Keywords: city, convergence, disasters, fear, mobile artifacts, night, personal safety artifacts

Christine Satchell; Marcus Foth

2011-05-01T23:59:59.000Z

249

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

250

MoNDian Dark Matter, Entropic Gravity, and Infinite Statistics  

E-Print Network (OSTI)

We propose the concept of MoNDian dark matter which behaves like cold dark matter at cluster and cosmic scales but emulates modified Newtonian dynamics at the galactic scale. The connection between global physics and local galactic dynamics is implemented via entropic gravity. We also give an alternative formulation of MoNDian dark matter by using an effective gravitational Born-Infeld theory. In the latter approach, we show that the quanta of MoNDian dark matter obey infinite statistics.

Y. Jack Ng

2012-12-27T23:59:59.000Z

251

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

252

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

253

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

254

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

255

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

256

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.

257

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

258

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

259

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

260

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

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261

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

262

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

263

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

264

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

265

Experiment Profile: DAMIC NAME: Dark Matter In CCDs, or DAMIC  

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

DAMIC DAMIC NAME: Dark Matter In CCDs, or DAMIC ThE ORIGIN OF ThE NAME: DAMIC searches for dark matter using Charge Coupled Devices. These digital chips register light that gets converted into a digital value a computer can store. WHAT WILL THIS TELL? Everything you see, visible matter, makes up 4 percent of the universe. Dark matter and dark energy make up the rest of the universe. Physicists understand that dark matter acts as an invisible source of gravity, but little more. DAMIC seeks to pinpoint what particles make up dark matter, which will help explain how the universe came to exist. Without the added gravitational attraction of dark matter, stars and galaxies would have never formed. The expansion of the universe after the Big Bang would have dispersed visible

266

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

267

The Universe Adventure - The Search for Dark Matter  

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

Search for Dark Matter Search for Dark Matter Large Hadron Collider Particle accelerators, such as the newly constructed LHC (Large Hadron Collider) at CERN in Geneva, Switzerland, use powerful magnets to accelerate particles to velocities near that of light and collide them into target beams. Physicists analyze the spray of particles created by the collisions which may contain clues about the properties of elusive dark matter particles. Today the search for dark matter is carried out in labs, observatories, and particle accelerators around the world. Scientists hope that the next generation of experiments will finally uncover the identity of dark matter. Alternatives to Dark Matter Some cosmologists are looking for alternative theories that explain these phenomena without relying on unobservable dark matter. Most of these

268

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

269

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

270

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

271

The physics and identity of dark matter  

E-Print Network (OSTI)

This paper follows "The physics and identity of Dark Energy", which is the acceleration energy of old photons. The present paper considers everything else in the decay of our universe; it is an ensemble called "old protons, etc."; the ensemble will be listed. The accelerated expansion of our universe brings the decay debris into the inter-universal medium (IUM) of the multiverse, where it is conserved during long times. Debris clouds eventually accrete from the IUM and grow into proto-universes. The protons, etc. are involved as much as are the photons; they are the receivers of the kinetic energy of photon acceleration. Dark matter is therefore the matter of "old protons,etc." mentioned before.

Tom Gehrels

2010-12-30T23:59:59.000Z

272

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

273

Dark side of the Higgs boson.  

Science Conference Proceedings (OSTI)

Current limits from the Large Hadron Collider exclude a standard model-like Higgs mass above 150 GeV, by placing an upper bound on the Higgs production rate. We emphasize that, alternatively, the limit could be interpreted as a lower bound on the total decay width of the Higgs boson. If the invisible decay width of the Higgs is of the same order as the visible decay width, a heavy Higgs boson could be consistent with null results from current searches. We propose a method to infer the invisible decay of the Higgs by using the width of the measured h {yields} ZZ {yields} 4 {ell} line shape, and study the effect on the width extraction due to a reduced signal strength. Assuming the invisible decay product is the dark matter, we show that minimal models are tightly constrained by limits from Higgs searches at the LHC and direct detection experiments of dark matter, unless the relic density constraint is relaxed.

Low, I.; Schwaller, P.; Shaughnessy, G.; Wagner, C. E. M. (High Energy Physics); (Northwestern University); (University of Illinois); (University of Wisconsin); (University of Chicago); (University of Chicago)

2012-01-01T23:59:59.000Z

274

Supersymmetry, Dark Matter and the LHC  

Science Conference Proceedings (OSTI)

The conceptually simplest scenario for dark matter (DM) is that it is a stable thermal relic from standard Big Bang cosmology, in many SUSY models the lightest neutralino. The relic density determination selects special regions in SUSY model parameter space with concomitant implications for collider physics, dark matter searches and low energy measurements. By studying various one-parameter extensions of the much-studied mSUGRA model (where we relax the untested universality assumptions) constructed to be in accord with the measured relic density, we show that these implications are in general model-dependent, so that LHC and DM measurements will provide clues to how sparticles acquire their masses. We point out some relatively robust implications for LHC and DM searches and conclude with an outlook for the future.

Tata, Xerxes [Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96825 (United States) and Physics Department, University of Wisconsin, Madison, WI 53705 (United States)

2010-02-10T23:59:59.000Z

275

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

276

DMTPC: Dark matter detection with directional sensitivity  

E-Print Network (OSTI)

The Dark Matter Time Projection Chamber (DMTPC) experiment uses CF_4 gas at low pressure (0.1 atm) to search for the directional signature of Galactic WIMP dark matter. We describe the DMTPC apparatus and summarize recent results from a 35.7 g-day exposure surface run at MIT. After nuclear recoil cuts are applied to the data, we find 105 candidate events in the energy range 80 - 200 keV, which is consistent with the expected cosmogenic neutron background. Using this data, we obtain a limit on the spin-dependent WIMP-proton cross-section of 2.0 \\times 10^{-33} cm^2 at a WIMP mass of 115 GeV/c^2. This detector is currently deployed underground at the Waste Isolation Pilot Plant in New Mexico.

Battat, J B R; Caldwell, T; Deaconu, C; Dujmic, D; Fedus, W; Fisher, P; Golub, F; Henderson, S; Inglis, A; Kaboth, A; Kohse, G; Lanza, R; Lee, A; Lopez, J; Monroe, J; Sahin, T; Sciolla, G; Skvorodnev, N; Tomita, H; Wellenstein, H; Wolfe, I; Yamamoto, R; Yegoryan, H

2010-01-01T23:59:59.000Z

277

The XENON100 Dark Matter Experiment  

SciTech Connect

The XENON100 experiment is searching for WIMPs, which are particles that may consist dark matter. It is located in the underground laboratory of Gran Sasso (LNGS) in Italy at a depth of {approx}3600 m.w.e.. The experiment description, its performance and the expected background based on Monte Carlo simulations and material screening along with the projected sensitivities of the experiment are presented. In addition, a brief description of the upgrade XENON100 detector is given.

Tziaferi, E. [Physics Institute, University of Zuerich, Winterthurerstr. 190, Zuerich (Switzerland)

2010-06-23T23:59:59.000Z

278

Have Atmospheric Cerenkov Telescopes Observed Dark Matter?  

E-Print Network (OSTI)

Two ground-based experiments have recently independently detected TeV $\\gamma$-rays from the direction of the Galactic center. The observations made by the VERITAS and CANGAROO collaborations are unexpected, although not impossible to interpret in terms of astrophysical sources. Here we examine in detail whether the observed $\\gamma$-rays may arise from the more exotic alternative of annihilations of dark matter particles clustered in the center of the Galaxy.

Dan Hooper; Ignacio de la Calle Perez; Joseph Silk; Francesc Ferrer; Subir Sarkar

2004-04-09T23:59:59.000Z

279

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

280

Death of Stellar Baryonic Dark Matter Candidates  

E-Print Network (OSTI)

The nature of the dark matter in the Universe is one of the outstanding questions in astrophysics. In this talk, I address possible stellar baryonic contributions to the 50-90% of our Galaxy that is made of unknown dark matter. First I show that faint stars and brown dwarfs constitute only a few percent of the mass of the Galaxy. Next, I show that stellar remnants, including white dwarfs and neutron stars, are also insufficient in abundance to explain all the dark matter of the Galaxy. High energy gamma-rays observed in HEGRA data place the most robust constraints, $\\Omega_{WD} < 3 \\times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km s$^{-1}$ Mpc$^{-1}$. Overproduction of chemical abundances (carbon, nitrogen, and helium) provide the most stringent constraints, $\\Omega_{WD} < 2 \\times 10^{-4} h^{-1}$. Comparison with recent updates of microlensing data are also made. According to the gamma-ray limit, all Massive Compact Halo Objects seen by the experiments (Machos) can be white dwarfs if one takes the extreme numbers; however, from chemical overproduction limits, NOT all Machos can be white dwarfs. Comments on recent observations of the infrared background and of white dwarfs are also made. In conclusion, a nonbaryonic component in the Halo seems to be required.

Katherine Freese; Brian Fields; David Graff

2000-07-28T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

282

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

283

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

284

A Quantum Approach to Dark Matter  

E-Print Network (OSTI)

This work develops and explores a quantum-based theory which enables the nature and origin of cold dark matter (CDM) to be understood without need to introduce exotic particles. The quantum approach predicts the existence of certain macroscopic quantum structures that are WIMP-like even when occupied by traditional baryonic particles. These structures function as dark matter candidates for CDM theory on large scales where it has been most successful, and retain the potential to yield observationally compliant predictions on galactic cluster and sub-cluster scales. Relatively pure, high angular momentum, eigenstate solutions obtained from Schrodinger's equation in weak gravity form the structural basis. They have no classical analogue, and properties radically different from those of traditional localised matter (whose eigenstate spectra contain negligible quantities of such states). Salient features include radiative lifetimes that can exceed the age of the universe, energies and 'sizes' consistent with galactic halos, and negligible interaction rates with radiation and macroscopic galactic objects. This facilitates the formation of sparsely populated macroscopic quantum structures that are invisible and stable. Viable structure formation scenarios are based on the seed potential wells of primordial black holes formed at the e+/e- phase transition. The structures can potentially produce suitable internal density distributions and have capacity to accommodate the required amount of halo dark matter. The formation scenarios show that it is possible to incorporate structures into universal evolutionary scenarios without significantly compromising the results of WMAP or the measurements of elemental BBN ratios.

A. D. Ernest

2004-06-06T23:59:59.000Z

285

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

286

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

287

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

288

Indistinguishability of Warm Dark Matter, Modified Gravity, and Coupled Cold Dark Matter  

E-Print Network (OSTI)

The current accelerated expansion of our universe could be due to an unknown energy component with negative pressure (dark energy) or a modification to general relativity (modified gravity). On the other hand, recently warm dark matter (WDM) remarkably rose as an alternative of cold dark energy (CDM). Obviously, it is of interest to distinguish these different types of models. In fact, many attempts have been made in the literature. However, in this work we show that WDM, modified gravity and coupled CDM form a trinity, namely, they are indistinguishable by using the cosmological observations of both cosmic expansion history and growth history. Therefore, to break the degeneracy, the other complementary probes beyond the ones of cosmic expansion history and growth history are required.

Wei, Hao; Chen, Zu-Cheng; Yan, Xiao-Peng

2013-01-01T23:59:59.000Z

289

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

290

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

291

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

292

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

293

Constraints on inelastic dark matter from XENON10  

SciTech Connect

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E{sub nr} = 75 keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses m{sub x} {approx}> 150 GeV are disfavored.

Angle, J; Aprile, E; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Coelho, L C; Dahl, C E; DeViveiros, L; Ferella, A D; Fernandes, L P; Fiorucci, S; Gaitskell, R J; Giboni, K L; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, J M; Madden, N; Manalaysay, A; Manzur, A; McKinsey, D N; Monzani, M E; Ni, K; Oberlack, U; Orboeck, J; Plante, G; Santorelli, R; dos Santos, J; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Winant, C; Yamashita, M

2009-11-23T23:59:59.000Z

294

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

295

Search for Low-Mass Dark Matter at BABAR  

E-Print Network (OSTI)

This review briefly describes light dark matter searches performed by the BABAR experiment. Although dark matter candidates have traditionally been associated with heavy particles appearing in extensions of the Standard Model, a lighter component remains a well motivated alternative, and many scenarios of light dark matter have been recently proposed. Thanks to their large luminosities, B factories offer an ideal environment to probe these possibilities, complementing searches from direct detection and satellite experiments.

Echenard, B

2012-01-01T23:59:59.000Z

296

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

297

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

298

Dark Matter Stabilization Symmetries from Spontaneous Symmetry Breaking  

E-Print Network (OSTI)

We present a class of models in which the dark matter stabilization symmetry is generated by spontaneous symmetry breaking. These models naturally correlate the dark and electroweak symmetry breaking scales. The result is a generic mechanism linking the annihilation cross section for thermally populated dark matter with the weak scale. The thermal relic abundance, sensitivity to major precision electroweak observables and additional LHC signatures are also presented.

Walker, Devin G E

2009-01-01T23:59:59.000Z

299

Dark Matter Stabilization Symmetries from Spontaneous Symmetry Breaking  

E-Print Network (OSTI)

We present a class of models in which the dark matter stabilization symmetry is generated by spontaneous symmetry breaking. These models naturally correlate the dark and electroweak symmetry breaking scales. The result is a generic mechanism linking the annihilation cross section for thermally populated dark matter with the weak scale. The thermal relic abundance, sensitivity to major precision electroweak observables and additional LHC signatures are also presented.

Devin G. E. Walker

2009-07-20T23:59:59.000Z

300

Measuring Dark Matter Distribution in Directional Direct Detection  

E-Print Network (OSTI)

Direct detection of dark matter with directional sensitivity offers not only measurement of both recoil energy and direction of dark matter, but also a way to understand dark matter distribution in the Galaxy. Maxwell distribution is usually supposed as the distribution near the Earth, however, deviation from that, caused by tidal streams in the Galaxy, has been suggested. We explore the possibility of distinguishing the distribution by direct detection using nuclear emulsions.

Keiko I. Nagao

2013-12-11T23:59:59.000Z

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301

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

302

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

303

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

304

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

305

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

306

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

307

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

308

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...

309

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

310

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

311

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

312

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

313

OBSERVATIONAL EVIDENCE FOR DARK MATTER INTERACTING THROUGH A YUKAWA POTENTIAL  

SciTech Connect

Recent observations in galaxies and clusters indicate that dark matter density profiles exhibit core-like structures which contradict the numerical simulation results of collisionless cold dark matter (CDM). On the other hand, it has been shown that CDM particles interacting through a Yukawa potential could naturally explain the cores in dwarf galaxies. In this Letter, I use the Yukawa potential interacting dark matter model to derive two simple scaling relations on the galactic and cluster scales, respectively, which give excellent agreements with observations. Also, in our model, the masses of the force carrier and dark matter particle can be constrained by the observational data.

Chan, M. H., E-mail: mhchan@phy.cuhk.edu.hk [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (Hong Kong)

2013-05-20T23:59:59.000Z

314

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

315

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

316

Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation  

E-Print Network (OSTI)

Most of the mass content of dark matter haloes is expected to be in the form of tidal debris. The density of debris is not constant, but rather can grow due to formation of caustics at the apocenters and pericenters of the orbit, or decay as a result of phase mixing. In the phase space, the debris assemble in a hierarchy which is truncated by the primordial temperature of dark matter. Understanding this phase structure can be of significant importance for the interpretation of many astrophysical observations and in particular dark matter detection experiments. With this purpose in mind, we develop a general theoretical framework to describe the hierarchical structure of the phase space of cold dark matter haloes. We do not make any assumption of spherical symmetry and/or smooth and continuous accretion. Instead, working with correlation functions in the action-angle space, we can fully account for the hierarchical structure (predicting a two-point correlation function ~ (\\Delta J)^{-1.6} in the action space), as well as the primordial discreteness of the phase space. As an application, we estimate the boost to the dark matter annihilation signal due to the structure of the phase space within virial radius: the boost due to the hierarchical tidal debris is of order unity, whereas the primordial discreteness of the phase structure can boost the total annihilation signal by up to an order of magnitude. The latter is dominated by the regions beyond 20% of the virial radius, and is largest for the recently formed haloes with the least degree of phase mixing.

Niayesh Afshordi; Roya Mohayaee; Edmund Bertschinger

2008-11-10T23:59:59.000Z

317

Warped Unification, Proton Stability and Dark Matter  

E-Print Network (OSTI)

Many extensions of the Standard Model have to face the problem of new unsuppressed baryon-number violating interactions. In supersymmetry, the simplest way to solve this problem is to assume R-parity conservation. As a result, the lightest supersymmetric particle becomes stable and a well-motivated dark matter candidate. In this paper, we show that solving the problem of baryon number violation in non supersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza-Klein particle. This exotic particle has gauge quantum numbers of a right-handed neutrino, but carries fractional baryon-number and is related to the top quark within the higher-dimensional GUT. A combination of baryon-number and SU(3) color ensures its stability. Its relic density can easily be of the right value for masses in the 10 GeV--few TeV range. An exciting aspect of these models is that the entire parameter space will be tested at near future dark matter direct detection experiments. Other exotic GUT partners of the top quark are also light and can be produced at high energy colliders with distinctive signatures.

Kaustubh Agashe; Geraldine Servant

2004-03-15T23:59:59.000Z

318

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

319

The bias field of dark matter haloes  

E-Print Network (OSTI)

This paper presents a stochastic approach to the clustering evolution of dark matter haloes in the Universe. Haloes, identified by a Press-Schechter-type algorithm in Lagrangian space, are described in terms of `counting fields', acting as non-linear operators on the underlying Gaussian density fluctuations. By ensemble averaging these counting fields, the standard Press-Schechter mass function as well as analytic expressions for the halo correlation function and corresponding bias factors of linear theory are obtained, thereby extending the recent results by Mo and White. The non-linear evolution of our halo population is then followed by solving the continuity equation, under the sole hypothesis that haloes move by the action of gravity. This leads to an exact and general formula for the bias field of dark matter haloes, defined as the local ratio between their number density contrast and the mass density fluctuation. Besides being a function of position and `observation' redshift, this random field depends upon the mass and formation epoch of the objects and is both non-linear and non-local. The latter features are expected to leave a detectable imprint on the spatial clustering of galaxies, as described, for instance, by statistics like bispectrum and skewness. Our algorithm may have several interesting applications, among which the possibility of generating mock halo catalogues from low-resolution N-body simulations.

P. Catelan; F. Lucchin; S. Matarrese; C. Porciani

1997-08-07T23:59:59.000Z

320

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Gas and Dark Matter Spherical Dynamics  

E-Print Network (OSTI)

We investigate the formation of spherical cosmological structures following both dark matter and gas components. We focus on the dynamical aspect of the collapse assuming an adiabatic, $\\gamma = 5/3$, fully ionized primordial plasma. We use for that purpose a fully Lagrangian hydrodynamical code designed to describe highly compressible flows in spherical geometry. We investigate also a "fluid approach" to describe the mean physical quantities of the dark matter flow. We test its validity for a wide range of initial density contrast. We show that an homogeneous isentropic core forms in the gas distribution, surrounded by a self-similar hydrostatic halo, with much higher entropy generated by shock dissipation. We derive analytical expressions for the size, density and temperature of the core, as well as for the surrounding halo. We show that, unless very efficient heating processes occur in the intergalactic medium, we are unable to reproduce within adiabatic models the typical core sizes in X-ray clusters. We also show that, for dynamical reasons only, the gas distribution is naturally antibiased relative to the total mass distribution, without invoking any reheating processes. This could explain why the gas fraction increases with radius in very large X-ray clusters. As a preparation for the next study devoted to the thermodynamical aspect of the collapse, we investigate the initial entropy level required to solve the core problem in X-ray clusters.

Jean-Pierre CHIEZE; Romain Teyssier; Jean-Michel Alimi

1997-04-03T23:59:59.000Z

322

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

323

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

324

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

325

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

326

Exact cosmological solutions of models with an interacting dark sector  

E-Print Network (OSTI)

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

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

2011-01-01T23:59:59.000Z

327

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

328

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

329

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

330

Indirect Search for Dark Matter with the ANTARES Neutrino Telescope  

Science Conference Proceedings (OSTI)

One of the goals of the ANTARES underwater neutrino telescope is the search for dark matter in the universe. In this paper the first results on the search for dark matter in the Sun with ANTARES in its 5 line configuration, as well as sensitivity studies with the full ANTARES detector are presented.

Loucatos, S. [IRFU-SPP, CEA-Saclay, 91191 Gif sur Yvette (France)

2010-02-10T23:59:59.000Z

331

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

332

Search for Dark Matter Satellites of the Milky Way with the Fermi LAT  

E-Print Network (OSTI)

Results and discussion 4.1 Search for Dark Matter SatellitesNeutrino Ob- servatory IV: Searches for Dark Matter andFermi-LAT Collaboration], Search for Dark Matter Satellites

Zalewski, Sheridan Henryk

2013-01-01T23:59:59.000Z

333

Dark spot formation relative to ITO surface roughness for polyfluorene  

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

Dark spot formation relative to ITO surface roughness for polyfluorene Dark spot formation relative to ITO surface roughness for polyfluorene devices Title Dark spot formation relative to ITO surface roughness for polyfluorene devices Publication Type Journal Article Year of Publication 2004 Authors Liu, Gao, John B. Kerr, and Stephen G. Johnson Journal Synthetic Metals Volume 144 Pagination 1-6 Keywords dark spot, failure mechanism, interface, ito surface, oled Abstract The failure behaviors of ITO/PEDOT;PSS/polyfluorene/Al devices are different depending on the surface roughness of the sputtered ITO anode film. The spikes on ITO surface are responsible for the initial local shorts of the device, which develop into dark spots very quickly. Indium adsorption is observed on the polymer and Al cathode interface. A chemical etching procedure is used to smoothen the ITO surface without changing the ITO thickness and the sheet resistance. Devices made out of smooth ITO show minimum changes at polymer-cathode interface during operation.

334

Galactic structure explained with dissipative mirror dark matter  

E-Print Network (OSTI)

Dissipative dark matter, such as mirror dark matter and related hidden sector dark matter candidates, requires an energy source to stabilize dark matter halos in spiral galaxies. It has been proposed previously that supernovae could be the source of this energy. Recently, it has been argued that this mechanism might explain two galactic scaling relations inferred from observations of spiral galaxies. One of which is that $\\rho_0 r_0$ is roughly constant, and another relates the galactic luminosity to $r_0$. [$\\rho_0$ is the dark matter central density and $r_0$ is the core radius.] Here we derive equations for the heating of the halo via supernova energy, and the cooling of the halo via thermal bremsstrahlung. These equations are numerically solved to obtain constraints on the $\\rho_0, \\ r_0$ parameters appropriate for spiral galaxies. These constraints are in remarkable agreement with the aforementioned scaling relations.

R. Foot

2013-04-17T23:59:59.000Z

335

DARK MATTER POWERED STARS: CONSTRAINTS FROM THE EXTRAGALACTIC BACKGROUND LIGHT  

SciTech Connect

The existence of predominantly cold non-baryonic dark matter is unambiguously demonstrated by several observations (e.g., structure formation, big bang nucleosynthesis, gravitational lensing, and rotational curves of spiral galaxies). A candidate well motivated by particle physics is a weakly interacting massive particle (WIMP). Self-annihilating WIMPs would affect the stellar evolution especially in the early universe. Stars powered by self-annihilating WIMP dark matter should possess different properties compared with standard stars. While a direct detection of such dark matter powered stars seems very challenging, their cumulative emission might leave an imprint in the diffuse metagalactic radiation fields, in particular in the mid-infrared part of the electromagnetic spectrum. In this work, the possible contributions of dark matter powered stars (dark stars, DSs) to the extragalactic background light (EBL) are calculated. It is shown that existing data and limits of the EBL intensity can already be used to rule out some DS parameter sets.

Maurer, A.; Raue, M.; Kneiske, T.; Horns, D. [Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Elsaesser, D. [Institut fuer Theoretische Physik und Astrophysik, Am Hubland, D-97074 Wuerzburg (Germany); Hauschildt, P. H., E-mail: andreas.maurer@physik.uni-hamburg.de [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)

2012-02-01T23:59:59.000Z

336

DARK MATTER SUBHALOS IN THE URSA MINOR DWARF GALAXY  

SciTech Connect

Through numerical simulations, we study the dissolution timescale of the Ursa Minor cold stellar clump, due to the combination of phase-mixing and gravitational encounters with compact dark substructures in the halo of Ursa Minor. We compare two scenarios: one where the dark halo is made up by a smooth mass distribution of light particles and one where the halo contains 10% of its mass in the form of substructures (subhalos). In a smooth halo, the stellar clump survives for a Hubble time provided that the dark matter halo has a large core. In contrast, when the point-mass dark substructures are added, the clump survives for barely {approx}1.5 Gyr. These results suggest a strong test of the {Lambda}-cold dark matter scenario at dwarf galaxy scale.

Lora, V.; Just, A.; Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Sanchez-Salcedo, F. J., E-mail: vlora@ari.uni-heidelberg.de [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, AP 70-264, 04510 D.F. (Mexico)

2012-09-20T23:59:59.000Z

337

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

338

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

339

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

340

Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence  

E-Print Network (OSTI)

Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter which is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has galactic origins.

C. Jess Riedel

2012-12-13T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Longevity Problem of Sterile Neutrino Dark Matter  

E-Print Network (OSTI)

Sterile neutrino dark matter of mass O(1-10) keV decays into an active neutrino and an X-ray photon, and the non-observation of the corresponding X-ray line requires the sterile neutrino to be more long-lived than estimated based on the seesaw formula : the longevity problem. We show that, if one or more of the B-L Higgs fields are charged under a flavor symmetry (or discrete R symmetry), the split mass spectrum for the right-handed neutrinos as well as the required longevity is naturally realized. We provide several examples in which the predicted the X-ray flux is just below the current bound.

Hiroyuki Ishida; Kwang Sik Jeong; Fuminobu Takahashi

2013-09-12T23:59:59.000Z

342

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

343

"Jordan's Scalar Stars" and Dark Matter  

E-Print Network (OSTI)

Here we are starting the study of the field equations of relativistic scalar tensor theories in the spherically symmetric gravitational field. In the present article we shall consider as an example only the simplest Jordan-Brans-Dicke (JBD) one. To illustrate the property of the spherically symmetric JBD configuration we exhibit a new representation of the well-known four dimensional solutions. In this model, a suitable segment of Brans solution is chosen for the interior of the object while the outer region consists of a Schwarzschild vacuum. We have constructed "Jordan's scalar stars" model consisting of three parts: a homogeneous inner core with linear equation of state; an envelope of Brans spacetime matching the core and the exterior Schwarzschild spacetime. We have also showed that this toy model can explain the intergalactic effects without the dark matter hypothesis.

S. M. Kozyrev

2008-08-25T23:59:59.000Z

344

Mini Little Higgs and Dark Matter  

E-Print Network (OSTI)

We construct a little Higgs model with the most minimal extension of the standard model gauge group by an extra U(1) gauge symmetry. For specific charge assignments of scalars, an approximate U(3) global symmetry appears in the cutoff-squared scalar mass terms generated from gauge bosons at one-loop level. Hence, the Higgs boson, identified as a pseudo-Goldstone boson of the broken global symmetry, has its mass radiatively protected up to scales of 5-10 TeV. In this model, a Z2 symmetry, ensuring the two U(1) gauge groups to be identical, also makes the extra massive neutral gauge boson stable and a viable dark matter candidate with a promising prospect of direct detection.

Yang Bai

2008-01-10T23:59:59.000Z

345

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

346

Dark spreads measure returns over fuel costs of coal-fired ...  

U.S. Energy Information Administration (EIA)

The dark spread is a common metric used to estimate returns over fuel costs of coal-fired electric generators. A dark spread is the difference between ...

347

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

348

Axionic Co-genesis of Baryon, Dark Matter and Dark Radiation  

E-Print Network (OSTI)

We argue that coherent oscillations of the axion field excited by the misalignment mechanism and non-thermal leptogenesis by the saxion decay can naturally explain the observed abundance of dark matter and baryon asymmetry, thus providing a solution to the baryon-dark matter coincidence problem. The successful axionic co-genesis requires a supersymmetry breaking scale of O(10^{6-7}) GeV, which is consistent with the recently discovered standard-model like Higgs boson of mass about 126 GeV. Although the saxion generically decays into a pair of axions, their abundance sensitively depends on the saxion stabilization mechanism as well as couplings with the Higgs field. We discuss various ways to make the saxion dominantly decay into the right-handed neutrinos rather than into axions, and show that the abundance of axion dark radiation can be naturally as small as \\Delta N_{\\rm eff} \\lesssim {\\cal O}(0.1), which is allowed by the Planck data.

Kwang Sik Jeong; Fuminobu Takahashi

2013-02-06T23:59:59.000Z

349

Composite dark matter from a model with composite Higgs boson  

E-Print Network (OSTI)

In a previous paper \\cite{Khlopov:2007ic}, we showed how the minimal walking technicolor model (WTC) can provide a composite dark matter candidate, by forming bound states between a -2 electrically charged techniparticle and a $^4He^{++}$. We studied the properties of these \\emph{techni-O-helium} $tOHe$ "atoms", which behave as warmer dark matter rather than cold. In this paper we extend our work on several different aspects. We study the possibility of a mixed scenario where both $tOHe$ and bound states between +2 and -2 electrically charged techniparticles coexist in the dark matter density. We argue that these newly proposed bound states solely made of techniparticles, although they behave as Weakly Interacting Massive Particles (WIMPs), due to their large elastic cross section with nuclei, can only account for a small percentage of the dark matter density. Therefore we conclude that within the minimal WTC, composite dark matter should be mostly composed of $tOHe$. Moreover in this paper, we put cosmological bounds in the masses of the techniparticles, if they compose the dark matter density. Finally we propose within this setup, a possible explanation of the discrepancy between the DAMA/NaI and DAMA/LIBRA findings and the negative results of CDMS and other direct dark matter searches that imply nuclear recoil measurement, which should accompany ionization.

Maxim Yu. Khlopov; Chris Kouvaris

2008-06-06T23:59:59.000Z

350

Gamma-Ray Lines from Radiative Dark Matter Decay  

E-Print Network (OSTI)

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Mathias Garny; Alejandro Ibarra; David Tran; Christoph Weniger

2010-11-16T23:59:59.000Z

351

Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant  

E-Print Network (OSTI)

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

Aharon Davidson

2004-09-15T23:59:59.000Z

352

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

353

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

354

An Overview of Dark Matter Experiments at Jefferson Lab  

Science Conference Proceedings (OSTI)

Dark Matter research at Jefferson Lab started in 2006 with the LIght Pseudoscalar and Scalar Search (LIPSS) collaboration to check the validity of results reported by the PVLAS collaboration. In the intervening years interest in dark matter laboratory experiments has grown at Jefferson Lab. Current research underway or in planning stages probe various mass regions covering 14 orders of magnitude: from 10{sup -6} eV to 100 MeV. This presentation will be an overview of our dark matter efforts, three of which focus on the hypothesized A' gauge boson.

James Boyce

2012-09-01T23:59:59.000Z

355

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

356

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

357

Bremsstrahlung gamma rays from light Dark Matter  

E-Print Network (OSTI)

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the inner Galaxy gas distribution as well as to compute self-consistently the gamma emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully gamma-ray map `residuals' in terms of (light) DM annihilations.

Marco Cirelli; Pasquale D. Serpico; Gabrijela Zaharijas

2013-07-26T23:59:59.000Z

358

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

359

Spontaneously Induced Gravity: From Rippled Dark Matter to Einstein Corpuscles  

E-Print Network (OSTI)

Suppose General Relativity, provocatively governed by a dimensional coupling constant, is a spontaneously induced theory of Gravity. Invoking Zee's mechanism, we represent the reciprocal Newton constant by a Brans Dicke scalar field, and let it damped oscillating towards its General Relativistic VEV. The corresponding cosmological evolution, in the Jordan frame, averagely resembles the familiar dark radiation -> dark matter -> dark energy domination sequence. The fingerprints of the theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the strict General Relativity limit. Also derived is the spherically symmetric static configuration associated with spontaneously induced General Relativity. At the stiff scalar potential limit, the exterior Schwarzschild solution is recovered. However, due to level crossing at the would have been horizon, it now connects with a novel dark core characterized by a locally varying Newton constant. The theory further predicts light Einstein-style gravitational corpuscles (elementary particles?) which become point-like at the GR-limit.

Aharon Davidson; Ilya Gurwich

2006-06-13T23:59:59.000Z

360

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...

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Neutrino dark matter candidate in fourth generation scenarios  

E-Print Network (OSTI)

We overview the constraints on the 4th-generation neutrino dark matter candidate and investigate a possible way to make it a viable dark matter candidate. Given the LEP constraints tell us that the 4th-generation neutrino has to be rather heavy (> M_Z/2), in sharp contrast to the other three neutrinos, the underlying nature of the 4th-generation neutrino is expected to be different. We suggest that an additional gauge symmetry B-4L_4 distinguishes it from the Standard Model's three lighter neutrinos and this also facilitates promotion of the 4th-generation predominantly right-handed neutrino to a good cold dark matter candidate. It provides distinguishable predictions for the dark matter direct detection and the Large Hadron Collider experiments.

Hye-Sung Lee; Zuowei Liu; Amarjit Soni

2011-05-17T23:59:59.000Z

362

Neutrino Backgrounds to Dark Matter Searches and Directionality  

E-Print Network (OSTI)

Neutrino-nucleus coherent scattering cross sections can be as large as 10[superscript ?39] cm[superscript 2], while current dark matter experiments have sensitivities to WIMP coherent scattering cross sections several ...

Monroe, Jocelyn

363

DMTPC: A dark matter detector with directional sensitivity  

E-Print Network (OSTI)

By correlating nuclear recoil directions with the Earth's direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence ...

Battat, James

364

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...

365

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

366

Study of alpha background in a dark matter detector  

E-Print Network (OSTI)

Alpha background, specifically from radon and its progeny in the uranium and thorium chains, has been a major issue in dark matter detectors. This work focuses on alpha background presence in the DMTPC experiment by examining ...

Yegoryan, Hayk

2010-01-01T23:59:59.000Z

367

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

368

Search for Dark Matter Satellites Using the FERMI-LAT  

SciTech Connect

Numerical simulations based on the {Lambda}CDM model of cosmology predict a large number of as yet unobserved Galactic dark matter satellites. We report the results of a Large Area Telescope (LAT) search for these satellites via the {gamma}-ray emission expected from the annihilation of weakly interacting massive particle (WIMP) dark matter. Some dark matter satellites are expected to have hard {gamma}-ray spectra, finite angular extents, and a lack of counterparts at other wavelengths. We sought to identify LAT sources with these characteristics, focusing on {gamma}-ray spectra consistent with WIMP annihilation through the b{bar b} channel. We found no viable dark matter satellite candidates using one year of data, and we present a framework for interpreting this result in the context of numerical simulations to constrain the velocity-averaged annihilation cross section for a conventional 100 GeV WIMP annihilating through the b{bar b} channel.

Ackermann, M.; /DESY; Albert, A.; /Ohio State U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bottacini, E.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Brandt, T.J.; /IRAP, Toulouse /Toulouse III U.; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Burnett, T.H.; /Washington U., Seattle; Caliandro, G.A.; /ICE, Bellaterra; Cameron, R.A.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /ASDC, Frascati /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stockholm U. /Stockholm U., OKC /ASDC, Frascati /Bari U. /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari /INFN, Perugia /Perugia U. /Bari U. /INFN, Bari /Bari U. /INFN, Bari /Bologna Observ. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

2012-08-16T23:59:59.000Z

369

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

370

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

371

Direct Detection of Sub-GeV Dark Matter  

SciTech Connect

Direct detection strategies are proposed for dark matter particles with MeV to GeV mass. In this largely unexplored mass range, dark matter scattering with electrons can cause single-electron ionization signals, which are detectable with current technology. Ultraviolet photons, individual ions, and heat are interesting alternative signals. Focusing on ionization, we calculate the expected dark matter scattering rates and estimate the sensitivity of possible experiments. Backgrounds that may be relevant are discussed. Theoretically interesting models can be probed with existing technologies, and may even be within reach using ongoing direct detection experiments. Significant improvements in sensitivity should be possible with dedicated experiments, opening up a window to new regions in dark matter parameter space.

Essig, Rouven; Mardon, Jeremy; Volansky, Tomer

2012-03-20T23:59:59.000Z

372

Design and Construction of Prototype Dark Matter Detectors  

SciTech Connect

The Lepton Quark Studies (LQS) group is engaged in searching for dark matter using the Dark Matter Time Projection Chamber (DMTPC) at the Waste Isolation Pilot Plant (WIPP) (Carlsbad, NM). DMTPC is a direction-sensitive dark matter detector designed to measure the recoil direction and energy deposited by fluorine nuclei recoiling from the interaction with incident WIMPs. In the past year, the major areas of progress have been: #15; to publish the #12;first dark matter search results from a surface run of the DMTPC prototype detector, #15; to build and install the 10L prototype in the underground laboratory at WIPP which will house the 1 m{sup 3} detector, and #15; to demonstrate charge and PMT readout of the TPC using prototype detectors, which allow triggering and #1;{Delta}z measurement to be used in the 1 m{sup 3} detector under development.

Peter Fisher

2012-03-23T23:59:59.000Z

373

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

374

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

375

Effects of dark matter annihilation on the first stars  

E-Print Network (OSTI)

We study the evolution of the first stars in the universe (Population III) from the early pre-Main Sequence until the end of helium burning in the presence of WIMP dark matter annihilation inside the stellar structure. The two different mechanisms that can provide this energy source are the contemporary contraction of baryons and dark matter, and the capture of WIMPs by scattering off the gas with subsequent accumulation inside the star. We find that the first mechanism can generate an equilibrium phase, previously known as a "dark star", which is transient and present in the very early stages of pre-MS evolution. The mechanism of scattering and capture acts later, and can support the star virtually forever, depending on environmental characteristic of the dark matter halo and on the specific WIMP model.

F. Iocco; A. Bressan; E. Ripamonti; R. Schneider; A. Ferrara; P. Marigo

2008-09-14T23:59:59.000Z

376

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

377

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

378

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

379

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

380

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

382

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

383

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

384

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

385

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

386

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

387

The Unification and Cogeneration of Dark Matter and Baryonic Matter  

E-Print Network (OSTI)

In grand unified theories with gauge groups larger than SU(5), the multiplets that contain the known quarks and leptons also contain fermions that are singlets under the Standard Model gauge group. Some of these could be the dark matter of the universe. Grand unified theories can also have accidental U(1) global symmetries (analogous to B-L in minimal SU(5)) that can stabilize dark matter. These ideas are illustrated in an SU(6) model.

S. M. Barr

2011-09-12T23:59:59.000Z

388

The Unification and Cogeneration of Dark Matter and Baryonic Matter  

E-Print Network (OSTI)

In grand unified theories with gauge groups larger than SU(5), the multiplets that contain the known quarks and leptons also contain fermions that are singlets under the Standard Model gauge group. Some of these could be the dark matter of the universe. Grand unified theories can also have accidental U(1) global symmetries (analogous to B-L in minimal SU(5)) that can stabilize dark matter. These ideas are illustrated in an SU(6) model.

Barr, S M

2011-01-01T23:59:59.000Z

389

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

390

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

391

Linear and nonlinear interactions in the dark sector  

E-Print Network (OSTI)

We investigate models of interacting dark matter and dark energy for the universe in a spatially flat Friedmann-Robertson-Walker (FRW) space-time. We find the "source equation" for the total energy density and determine the energy density of each dark component. We introduce an effective one-fluid description to evidence that interacting and unified models are related with each other, analyze the effective model and obtain the attractor solutions. We study linear and nonlinear interactions, the former comprises a linear combination of the dark matter and dark energy densities, their first derivatives, the total energy density, its first and second derivatives and a function of the scale factor. The latter is a possible generalization of the linear interaction consisting of an aggregate of the above linear combination and a significant nonlinear term built with a rational function of the dark matter and dark energy densities homogeneous of degree one. We solve the evolution equations of the dark components for both interactions and examine exhaustively several examples. There exist cases where the effective one-fluid description produces different alternatives to the $\\La$CDM model and cases where the problem of coincidence is alleviated. In addition, we find that some nonlinear interactions yield an effective one-fluid model with a Chaplygin gas equation of state, whereas others generate cosmological models with de Sitter and power-law expansions. We show that a generic nonlinear interaction induces an effective equation of state which depends on the scale factor in the same way that the variable modified Chaplygin gas model, giving rise to the "relaxed Chaplygin gas model".

Luis P. Chimento

2009-11-30T23:59:59.000Z

392

Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond  

E-Print Network (OSTI)

In this Report we discuss the four complementary searches for the identity of dark matter: direct detection experiments that look for dark matter interacting in the lab, indirect detection experiments that connect lab signals to dark matter in our own and other galaxies, collider experiments that elucidate the particle properties of dark matter, and astrophysical probes sensitive to non-gravitational interactions of dark matter. The complementarity among the different dark matter searches is discussed qualitatively and illustrated quantitatively in several theoretical scenarios. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program based on all four of those approaches.

Sebastian Arrenberg; Howard Baer; Vernon Barger; Laura Baudis; Daniel Bauer; James Buckley; Matthew Cahill-Rowley; Randel Cotta; Alex Drlica-Wagner; Jonathan L. Feng; Stefan Funk; JoAnne Hewett; Dan Hooper; Ahmed Ismail; Manoj Kaplinghat; Kyoungchul Kong; Alexander Kusenko; Konstantin Matchev; Mathew McCaskey; Daniel McKinsey; Dan Mickelson; Tom Rizzo; David Sanford; Gabe Shaughnessy; William Shepherd; Tim M. P. Tait; Xerxes Tata; Sean Tulin; Alexander M. Wijangco; Matthew Wood; Jonghee Yoo; Hai-Bo Yu

2013-10-31T23:59:59.000Z

393

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

394

Astrophysical manifestations of clumps of cold dark matter  

SciTech Connect

Small-scale structures (clumps) of dark matter may manifest themselves owing to the annihilation of dark-matter particles in them as pointlike gamma-ray sources. In view of this, investigation into respective effects on the basis of data on unidentified pointlike gamma-ray sources is of importance. It is shown that the existing uncertainties in the description of physical properties of dark-matter particles (their annihilation cross section) and in the distribution of their density in the clumps are of crucial importance; therefore, an analysis of data from the observation of pointlike gamma-ray sources makes it possible to impose constraints on the values of respective uncertain parameters (that is, to single out preferable ones). It is considered that the rate of annihilation of dark-matter particles in the clumps may be enhanced both owing to a higher density and owing to the growth of the cross section at low relative velocities of dark-matter particles in the clumps. In particular, dark-matter particles may have self-interaction of the Coulomb type, and this leads to the enhancement of the annihilation rate because of the Sommerfeld-Sakharov effect. It is shown that the heavy-neutrino model featuring an extra interaction can explain partly Fermi and EGRET data on unidentified pointlike gamma-ray sources. It is indicated that the motion of gamma-ray sources over the celestial sphere can be noticed for several clumps within several years of observations.

Belotsky, K. M., E-mail: k-belotsky@yandex.ru; Kirillov, A. A., E-mail: kirillov-aa@yandex.ru; Khlopov, M. Yu., E-mail: khlopov@apc.univ-paris7.fr [National Research Nuclear University MEPhI (Russian Federation)

2013-04-15T23:59:59.000Z

395

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

396

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

397

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.

398

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

399

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

400

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

Merger Rates of Dark-Matter Haloes  

E-Print Network (OSTI)

We derive analytic merger rates for dark-matter haloes within the framework of the Extended Press-Schechter (EPS) formalism. These rates become self-consistent within EPS once we realize that the typical merger in the limit of a small time-step involves more than two progenitors, contrary to the assumption of binary mergers adopted in earlier studies. We present a general method for computing merger rates that span the range of solutions permitted by the EPS conditional mass function, and focus on a specific solution that attempts to match the merger rates in N-body simulations. The corrected EPS merger rates are more accurate than the earlier estimates of Lacey & Cole, by ~20% for major mergers and by up to a factor of ~3 for minor mergers of mass ratio 1:10^4. Based on the revised merger rates, we provide a new algorithm for constructing Monte-Carlo EPS merger trees, that could be useful in Semi-Analytic Modeling. We provide analytic expressions and plot numerical results for several quantities that are very useful in studies of galaxy formation. This includes (a) the rate of mergers of a given mass ratio per given final halo, (b) the fraction of mass added by mergers to a halo, and (c) the rate of mergers per given main progenitor. The creation and destruction rates of haloes serve for a self-consistency check. Our method for computing merger rates can be applied to conditional mass functions beyond EPS, such as those obtained by the ellipsoidal collapse model or extracted from $N$-body simulations.

Eyal Neistein; Avishai Dekel

2008-02-04T23:59:59.000Z

402

Dark matter growth and baryon bias in an accelerating universe  

E-Print Network (OSTI)

We investigate the exact analytic solutions for the growths of the dark matter and the baryon in sub-horizon scale. The growth of the dark matter $\\delta_{\\DM}$ is related to that of the halos. Thus, the exact solution for the growth of the dark matter is important to obtain the proper properties of dark matter halos. However, the dark energy model dependence of $\\delta_{\\DM}$ is confused with the $\\delta_{\\DM}$ dependence on $\\Omega_{m}^{0}$. Thus, the careful investigation is necessary for the $\\delta_{\\DM}$ dependence on dark energy models. We also obtain the exact solution of the growth of the baryon $\\delta_{\\B}$ which can be used to obtain the baryon bias factor $b(a)$. This might be able to be observed in intracluster gas or in Lyman-$\\alpha$ clouds. However, $b(a)$ is quite model independent. Recently, we obtained the exact analytic solution for the growing mode solution of the matter linear density perturbation $\\delta$ on sub-horizon scale for general dark energy model \\cite{SK}. This solution is not same as the well known approximate analytic solution \\cite{Waga}. The exact analytic solution shows the same evolution behavior of the growth factor obtained numerically. However, the exact solution is simple and useful for the extension to other models including modified gravity theories. Furthermore, it guides to the fact that the growth index parameter depends on both models $\\omega_{\\de}$ and $\\Omega_{m}^{0}$ and thus we need to be careful for applying the fitting formulae to the general models \\cite{WS}. The exact analytic solutions for the growth factor will provide the more accurate tools for the weak lensing, the number density of clusters, their mass and etc.

Seokcheon Lee

2009-06-17T23:59:59.000Z

403

Non-relativistic effective theory of dark matter direct detection  

E-Print Network (OSTI)

Dark matter direct detection searches for signals coming from dark matter scattering against nuclei at a very low recoil energy scale ~ 10 keV. In this paper, a simple non-relativistic effective theory is constructed to describe interactions between dark matter and nuclei without referring to any underlying high energy models. It contains the minimal set of operators that will be tested by direct detection. The effective theory approach highlights the set of distinguishable recoil spectra that could arise from different theoretical models. If dark matter is discovered in the near future in direct detection experiments, a measurement of the shape of the recoil spectrum will provide valuable information on the underlying dynamics. We bound the coefficients of the operators in our non-relativistic effective theory by the null results of current dark matter direct detection experiments. We also discuss the mapping between the non-relativistic effective theory and field theory models or operators, including aspects of the matching of quark and gluon operators to nuclear form factors.

JiJi Fan; Matthew Reece; Lian-Tao Wang

2010-08-09T23:59:59.000Z

404

DARK MATTER AS AN ACTIVE GRAVITATIONAL AGENT IN CLOUD COMPLEXES  

SciTech Connect

We study the effect that the dark matter background (DMB) has on the gravitational energy content and, in general, on the star formation efficiency (SFE) of a molecular cloud (MC). We first analyze the effect that a dark matter halo, described by the Navarro-Frenk-White density profile, has on the energy budget of a spherical, homogeneous cloud located at different distances from the halo center. We found that MCs located in the innermost regions of a massive galaxy can feel a contraction force greater than their self-gravity due to the incorporation of the potential of the galaxy's dark matter halo. We also calculated analytically the gravitational perturbation that an MC produces over a uniform DMB (uniform at the scales of an MC) and how this perturbation will affect the evolution of the MC itself. The study shows that the star formation in an MC will be considerably enhanced if the cloud is located in a dense and low velocity dark matter environment. We confirm our results by measuring the SFE in numerical simulations of the formation and evolution of MCs within different DMBs. Our study indicates that there are situations where the dark matter's gravitational contribution to the evolution of the MCs should not be neglected.

Suarez-Madrigal, Andres; Ballesteros-Paredes, Javier; Colin, Pedro; D'Alessio, Paola, E-mail: a.suarez@crya.unam.mx [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 72-3 (Xangari), Morelia, Michocan, Mexico C.P. 58089 (Mexico)

2012-04-01T23:59:59.000Z

405

Dynamics and constraints of the unified dark matter flat cosmologies  

SciTech Connect

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

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

2008-10-15T23:59:59.000Z

406

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

407

Boldly Illuminating Biology's "Dark Matter"  

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

14, 2013 14, 2013 Boldly Illuminating Biology's "Dark Matter" Is space really the final frontier, or are the greatest mysteries closer to home? In cosmology, dark matter is said to account for the majority of mass in the universe, however its presence is inferred by indirect effects rather than detected through telescopes. The biological equivalent is "microbial dark matter," that pervasive yet practically invisible infrastructure of life on the planet, which can have profound influences on the most significant environmental processes from plant growth and health, to nutrient cycles in terrestrial and marine environments, the global carbon cycle, and possibly even climate processes. By employing next generation DNA sequencing of genomes isolated from single cells, great

408

Keeping terrorists from putting us in the dark  

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

Keeping terrorists from putting us in the dark Keeping terrorists from putting us in the dark Community Connections: Our link to Northern New Mexico Communities Latest Issue:Dec. 2013 - Jan. 2014 All Issues » submit Keeping terrorists from putting us in the dark Lab research helps keep electrical grid secure. April 1, 2013 Power lines Lab research helps protect the grid. Contact Editor Linda Anderman Email Community Programs Office Kurt Steinhaus Email While there is potential that terrorists could target the nation's electric grid, Los Alamos scientists are minimizing that risk through the application of quantum cryptography. A successful, realistic demonstration of the new technology recently took place within the Trustworthy Cyber Infrastructure for the Power Grid project operated by the University of Illinois.

409

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

410

Stable Higgs Bosons - new candidate for cold dark matter -  

E-Print Network (OSTI)

The Higgs boson is in the backbone of the standard model of electroweak interactions. It must exist in some form for achieving unification of interactions. In the gauge-Higgs unification scenario the Higgs boson becomes a part of the extra-dimensional component of gauge fields. The Higgs boson becomes absolutely stable in a class of the gauge-Higgs unification models, serving as a promising candidate for cold dark matter in the universe. The observed relic abundance of cold dark matter is obtained with the Higgs mass around 70 GeV. The Higgs-nucleon scattering cross section is found to be close to the recent CDMS II and XENON10 bounds in the direct detection of dark matter. In collider experiments stable Higgs bosons are produced in a pair, appearing as missing energies and momenta so that the way of detecting Higgs bosons must be altered.

Yutaka Hosotani

2010-03-31T23:59:59.000Z

411

Stable Higgs Bosons - new candidate for cold dark matter  

SciTech Connect

The Higgs boson is in the backbone of the standard model of electroweak interactions. It must exist in some form for achieving unification of interactions. In the gauge-Higgs unification scenario the Higgs boson becomes a part of the extra-dimensional component of gauge fields. The Higgs boson becomes absolutely stable in a class of the gauge-Higgs unification models, serving as a promising candidate for cold dark matter in the universe. The observed relic abundance of cold dark matter is obtained with the Higgs mass around 70 GeV. The Higgs-nucleon scattering cross section is found to be close to the recent CDMS II XENON10 bounds in the direct detection of dark matter. In collider experiments stable Higgs bosons are produced in a pair, appearing as missing energies momenta so that the way of detecting Higgs bosons must be altered.

Hosotani, Yutaka [Department of Physics, Osaka University, Toyonaka Osaka 560-0043 (Japan)

2010-08-12T23:59:59.000Z

412

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

413

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

414

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

415

(Lack of) lensing constraints on cluster dark matter profiles  

E-Print Network (OSTI)

Using stellar dynamics and strong gravitational lensing as complementary probes, Sand et al. (2002, 2003) have recently claimed strong evidence for shallow dark matter density profiles in several lensing clusters, which may conflict with predictions of the Cold Dark Matter paradigm. However, systematic uncertainties in the analysis weaken the constraints. By re-analyzing their data, we argue that the tight constraints claimed by Sand et al., were driven by prior assumptions. Relaxing the assumptions, we find that no strong constraints may be derived on the dark matter inner profile from the Sand et al. data; we find satisfactory fits (with reasonable parameters) for a wide range of inner slopes 0 < beta < 1.4. Useful constraints on the mass distributions of lensing clusters can still be obtained, but they require moving beyond mere measurements of lensing critical radii into the realm of detailed lens modeling.

Neal Dalal; Charles R. Keeton

2003-12-02T23:59:59.000Z

416

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

417

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

418

Nonextensive theory of dark matter and gas density profiles  

E-Print Network (OSTI)

Pronounced core-halo patterns of dark matter and gas density profiles, observed in relaxed galaxies and clusters, were hitherto fitted by empirical power-laws. On the other hand, similar features are well known from astrophysical plasma environments, subject to long-range interactions, modeled in the context of nonextensive entropy generalization. We link nonextensive statistics to the problem of density distributions in large-scale structures and provide fundamentally derived density profiles, representing accurately the characteristics of both, dark matter and hot plasma distributions, as observed or generated in simulations. The bifurcation of the density distribution into a kinetic dark matter and thermodynamic gas branch turns out as natural consequence of the theory and is controlled by a single parameter kappa, measuring physically the degree of coupling within the system. Consequently, it is proposed to favor nonextensive distributions, derived from the fundamental physical context of entropy generali...

Leubner, M P

2005-01-01T23:59:59.000Z

419

Distribution of annihilation luminosities in dark matter substructure  

SciTech Connect

We calculate the probability distribution function (PDF) of the expected annihilation luminosities of dark matter subhalos as a function of subhalo mass and distance from the Galactic center using a semianalytical model of halo evolution. We find that the PDF of luminosities is relatively broad, exhibiting a spread of as much as an order of magnitude at fixed subhalo mass and halo-centric distance. The luminosity PDF allows for simple construction of mock samples of {gamma}-ray luminous subhalos and assessment of the variance in the predicted {gamma}-ray signals from dark matter annihilation. Other applications include quantifying the variance among the expected luminosities of dwarf spheroidal galaxies, assessing the level at which dark matter annihilation can be a contaminant in the expected {gamma}-ray signal from other astrophysical sources, as well as estimating the level at which nearby subhalos can contribute to the antimatter flux.

Koushiappas, Savvas M. [Department of Physics, Brown University, 182 Hope Street, Providence, Rhode Island 02912 (United States); Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Kravtsov, Andrey V. [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637 (United States); Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60605 (United States)

2010-10-15T23:59:59.000Z

420

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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

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

422

A DERIVATION OF (HALF) THE DARK MATTER DISTRIBUTION FUNCTION  

SciTech Connect

All dark matter structures appear to follow a set of universalities, such as phase-space density or velocity anisotropy profiles; however, the origin of these universalities remains a mystery. Any equilibrated dark matter structure can be fully described by two functions, namely the radial and tangential velocity distribution functions (VDFs), and once these two are understood we will understand all the observed universalities. Here, we demonstrate that if we know the radial VDF then we can derive and understand the tangential VDF. This is based on simple dynamical arguments about properties of collisionless systems. We use a range of controlled numerical simulations to demonstrate the accuracy of this result. We therefore boil the question of the dark matter structural properties down to understanding the radial VDF.

Hansen, Steen H.; Sparre, Martin, E-mail: hansen@dark-cosmology.dk, E-mail: sparre@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

2012-09-01T23:59:59.000Z

423

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

424

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

425

Dark/visible parallel universes and Big Bang nucleosynthesis  

Science Conference Proceedings (OSTI)

We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated.

Bertulani, C. A.; Frederico, T.; Fuqua, J.; Hussein, M. S.; Oliveira, O.; Paula, W. de [Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce TX 75429 (United States); Departamento de Fisica, Instituto Tecnologico de Aeronautica, DCTA 12.228-900, Sao Jose dos Campos, SP (Brazil); Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce TX 75429 (United States); Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05314-970 Sao Paulo, SP (Brazil); Departamento de Fisica, Instituto Tecnologico de Aeronautica, DCTA 12.228-900, Sao Jose dos Campos, SP, Brazil and Departamento de Fisica, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Departamento de Fisica, Instituto Tecnologico de Aeronautica, DCTA 12.228-900, Sao Jose dos Campos, SP (Brazil)

2012-11-20T23:59:59.000Z

426

Isospin-Violating Dark Matter and Neutrinos From the Sun  

E-Print Network (OSTI)

We study the indirect detection of dark matter through neutrino flux from their annihilation in the center of the Sun, in a class of theories where the dark matter-nucleon spin-independent interactions break the isospin symmetry. We point out that, while the direct detection bounds with heavy targets like Xenon are weakened and reconciled with the positive signals in DAMA and CoGeNT experiments, the indirect detection using neutrino telescopes can impose a relatively stronger constraint and brings tension to such explanation, if the annihilation is dominated by heavy quark or $\\tau$-lepton final states. As a consequence, the qualified isospin violating dark matter candidate has to preferably annihilate into light flavors.

Shao-Long Chen; Yue Zhang

2011-06-20T23:59:59.000Z

427

Declarative Modeling and Bayesian Inference of Dark Matter Halos  

E-Print Network (OSTI)

Probabilistic programming allows specification of probabilistic models in a declarative manner. Recently, several new software systems and languages for probabilistic programming have been developed on the basis of newly developed and improved methods for approximate inference in probabilistic models. In this contribution a probabilistic model for an idealized dark matter localization problem is described. We first derive the probabilistic model for the inference of dark matter locations and masses, and then show how this model can be implemented using BUGS and Infer.NET, two software systems for probabilistic programming. Finally, the different capabilities of both systems are discussed. The presented dark matter model includes mainly non-conjugate factors, thus, it is difficult to implement this model with Infer.NET.

Kronberger, Gabriel

2013-01-01T23:59:59.000Z

428

The Dark Side of the Solar Neutrino Parameter Space  

E-Print Network (OSTI)

Results of neutrino oscillation experiments have always been presented on the(sin^2 2theta, Delta m^2) parameter space for the case of two-flavoroscillations. We point out, however, that this parameterization misses the halfof the parameter space pi/4 < theta <= pi/2 (``the dark side''), which isphysically inequivalent to the region 0 <= theta <= pi/4 (``the light side'')in the presence of matter effects. The MSW solutions to the solar neutrinoproblem can extend to the dark side, especially if we take the conservativeattitude to allow higher confidence levels, ignore some of the experimentalresults in the fits, or relax theoretical predictions. Furthermore even theso-called ``vacuum oscillation'' solution distinguishes the dark and the lightsides. We urge experimental collaborations to present their results on theentire parameter space.

De Gouva, A; Murayama, H; Gouvea, Andre de; Friedland, Alexander; Murayama, Hitoshi

2000-01-01T23:59:59.000Z

429

A new test of the light dark matter hypothesis  

E-Print Network (OSTI)

Detection of a surprisingly high flux of positron annihilation radiation from the inner galaxy has motivated the proposal that dark matter is made of weakly interacting light particles (possibly as light as the electron). This scenario is extremely hard to test in current high energy physics experiments. Here, however, we demonstrate that the current value of the electron anomalous magnetic moment already has the required precision to unambiguously test the light dark matter hypothesis. If confirmed, the implications for astrophysics are far-reaching.

Celine Boehm; Joseph Silk

2007-08-21T23:59:59.000Z

430

ENVIRONMENT DEPENDENCE OF DARK MATTER HALOS IN SYMMETRON MODIFIED GRAVITY  

Science Conference Proceedings (OSTI)

We investigate the environment dependence of dark matter halos in the symmetron modified gravity scenario. The symmetron is one of three known mechanisms for screening a fifth force and thereby recovering general relativity in dense environments. The effectiveness of the screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations we find a significant difference, which depends on the halo's mass and environment, between the lensing and dynamical masses of dark matter halos similar to the f(R) modified gravity. The symmetron can however yield stronger signatures due to a freedom in the strength of coupling to matter.

Winther, Hans A.; Mota, David F. [Institute of Theoretical Astrophysics, University of Oslo, NO-0315 Oslo (Norway); Li Baojiu [ICC, Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)

2012-09-10T23:59:59.000Z

431

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

432

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

433

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

434

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

435

Standard model Higgs boson-inflaton and dark matter  

Science Conference Proceedings (OSTI)

The standard model Higgs boson can serve as the inflaton field of slow roll inflationary models provided it exhibits a large nonminimal coupling with the gravitational scalar curvature. The Higgs boson self interactions and its couplings with a standard model singlet scalar serving as the source of dark matter are then subject to cosmological constraints. These bounds, which can be more stringent than those arising from vacuum stability and perturbative triviality alone, still allow values for the Higgs boson mass which should be accessible at the LHC. As the Higgs boson coupling to the dark matter strengthens, lower values of the Higgs boson mass consistent with the cosmological data are allowed.

Clark, T. E.; Liu Boyang; Love, S. T.; Veldhuis, T. ter [Department of Physics, Purdue University, West Lafayette, Indiana 47907-2036 (United States); Department of Physics and Astronomy, Macalester College, Saint Paul, Minnesota 55105-1899 (United States)

2009-10-01T23:59:59.000Z

436

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 Garca-Aspeitia

2010-11-19T23:59:59.000Z

437

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

438

Photonic portal to the sterile world of cold dark matter  

E-Print Network (OSTI)

We assume that the cold dark matter consists of spin-1/2 and spin-0 particles described by a bispinor field \\psi and a scalar field \\phi, sterile from all Standard Model charges (in contrast, neutralinos, supersymmetric candidates for cold dark matter, are not sterile from weak Standard Model charges). We propose, however, that such a sterile world can contact with our Standard Model world not only through gravity but also through a portal provided by photons coupled to sterile particles by means of two very weak effective interactions -(f/M^2)\\phi F^{\\mu\

Wojciech Krolikowski

2007-12-04T23:59:59.000Z

439

DMTPC: A dark matter detector with directional sensitivity  

E-Print Network (OSTI)

By correlating nuclear recoil directions with the Earth's direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence of backgrounds. Here, we describe the Dark Matter Time-Projection Chamber (DMTPC) detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this detector, we have measured the vector direction (head-tail) of nuclear recoils down to energies of 100 keV with an angular resolution of Mexico.

Battat, J B R; Caldwell, T; Dujmic, D; Dushkin, A; Fisher, P; Golub, F; Goyal, S; Henderson, S; Inglis, A; Lanza, R; Lpez, J; Kaboth, A; Kohse, G; Monroe, J; Sciolla, G; Skvorodnev, B N; Tomita, H; Vanderspek, R; Wellenstein, H; Yamamoto, R

2009-01-01T23:59:59.000Z

440

Limits on Stellar Objects as the Dark Matter of Our Halo: Nonbaryonic Dark Matter Seems to be Required  

E-Print Network (OSTI)

The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that the dark matter does not consist of ordinary stellar or substellar objects, i.e., the dark matter is not made of faint stars, brown dwarfs, white dwarfs, or neutron stars. In fact, faint stars and brown dwarfs constitute no more than a few percent of the mass of our Galaxy, and stellar remnants must satisfy $\\Omega_{WD} \\leq 3 \\times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km/s Mpc^{-1}. On theoretical grounds one is then pushed to more exotic explanations. Indeed a nonbaryonic component in the Halo seems to be required.

Katherine Freese; Brian Fields; David Graff

1999-04-28T23:59:59.000Z

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441

Heart of Darkness: Modeling Public-Private Funding Interactions Inside the R&D Black Box  

E-Print Network (OSTI)

of Darkness: Modeling Public-Private Funding InteractionsT O F DARKNESS: MODELING PUBLIC-PRIVATE FUNDING INTERACTIONSAndrew A. Toole. "Are Public and Private R&D Expenditures

David, Paul A.; Hall, Bronwyn H.

2000-01-01T23:59:59.000Z

442

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

443

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...

444

The case for a directional dark matter detector and the status of current experimental efforts  

E-Print Network (OSTI)

We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and ...

Battat, James

445

Constraints on Bosonic Dark Matter From Observations of Old Neutron Stars  

E-Print Network (OSTI)

Baryon interactions with bosonic dark matter are constrained by the potential for dark matter-rich neutron stars to collapse into black holes. We consider the effect of dark matter self-interactions and dark matter annihilation on these bounds, and treat the evolution of the black hole after formation. We show that, for non-annihilating dark matter, these bounds extend up to $m_X \\sim 10^{5-7}$ GeV, depending on the strength of self-interactions. However, these bounds are completely unconstraining for annihilating bosonic dark matter with an annihilation cross-section of $ \\gtrsim 10^{-38} {\\rm cm^3 /s}$. Dark matter decay does not significantly affect these bounds. We thus show that bosonic dark matter accessible to near-future direct detection experiments must participate in an annihilation or self-interaction process to avoid black hole collapse constraints from very old neutron stars.

Joseph Bramante; Keita Fukushima; Jason Kumar

2013-01-01T23:59:59.000Z

446

THE COLD AND DARK PROCESS AT THE SAVANNAH RIVER SITE  

Science Conference Proceedings (OSTI)

The deactivation and decommissioning (D&D) of a facility exposes D&D workers to numerous hazards. One of the more serious hazards is coming into contact to hazardous energy sources (e.g. electrical, pressurized steam). At the Savannah River Site (SRS) a formal process for identifying and eliminating sources of hazardous energy was developed and is called ''Cold & Dark''. Several ''near miss'' events involving cutting of energized conductors during D&D work in buildings thought to be isolated identified the need to have a formal process to identify and isolate these potentially hazardous systems. This process was developed using lessons learned from D&D activities at the Rocky Flats Environmental Technology Site (Rocky Flats) in Colorado. The Cold & Dark process defines an isolation boundary (usually a building perimeter) and then systematically identifies all of the penetrations through this boundary. All penetrations that involve hazardous energy sources are then physically air-gapped. The final product is a documented declaration of isolation performed by a team involving operations, engineering, and project management. Once the Cold & Dark declaration is made for a building work can proceed without the usual controls used in an operational facility (e.g. lockout/tagout, arc flash PPE). It is important to note that the Cold & Dark process does not remove all hazards from a facility. Work planning and controls still need to address hazards that can be present from such things as chemicals, radiological contamination, residual liquids, etc., as well as standard industrial hazards.

Gilmour, J; William Austin, W; Cathy Sizemore, C

2007-01-31T23:59:59.000Z

447

LHC constraints on light neutralino dark matter in the MSSM  

E-Print Network (OSTI)

Light neutralino dark matter can be achieved in the Minimal Supersymmetric Standard Model if staus are rather light, with mass around 100 GeV. We perform a detailed analysis of the relevant supersymmetric parameter space, including also the possibility of light selectons and smuons, and of light higgsino- or wino-like charginos. In addition to the latest limits from direct and indirect detection of dark matter, ATLAS and CMS constraints on electroweak-inos and on sleptons are taken into account using a "simplified models" framework. Measurements of the properties of the Higgs boson at 125 GeV, which constrain amongst others the invisible decay of the Higgs boson into a pair of neutralinos, are also implemented in the analysis. We show that viable neutralino dark matter can be achieved for masses as low as 15 GeV. In this case, light charginos close to the LEP bound are required in addition to light right-chiral staus. Significant deviations are observed in the couplings of the 125 GeV Higgs boson. These constitute a promising way to probe the light neutralino dark matter scenario in the next run of the LHC.

Genevieve Belanger; Guillaume Drieu La Rochelle; Beranger Dumont; Rohini M. Godbole; Sabine Kraml; Suchita Kulkarni

2013-08-16T23:59:59.000Z

448

The necessity of dark matter in MOND within galactic scales  

E-Print Network (OSTI)

To further test MOdified Newtonian Dynamics (MOND) on galactic scales -- originally proposed to explain the rotation curves of disk galaxies without dark matter -- we study a sample of six strong gravitational lensing early-type galaxies from the CASTLES database. To determine whether dark matter is present in these galaxies, we compare the total mass (from lensing) with the stellar mass content (from a comparison of photometry and stellar population synthesis). We find that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain this excess matter -- in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MONDian scale of $\\sim 10^{-10}$m/s$^2$. This is a serious challenge to MOND unless the proper treatment of lensing is qualitatively different (possibly to be developed within a consistent theory such as TeVeS).

Ignacio Ferreras; Mairi Sakellariadou; Muhammad Furqaan Yusaf

2007-09-20T23:59:59.000Z

449

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

450

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

451

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

452

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

453

TeV Dark Matter detection by Atmospheric Cerenkov Telescopes  

E-Print Network (OSTI)

Ground based Atmospheric Cerenkov Telescopes have recently unveiled a TeV gamma-ray signal from the direction of the Galactic Centre. We examine whether these gamma-rays, observed by the VERITAS, CANGAROO-II and HESS collaborations, may arise from annihilations of dark matter particles. Emission from nearby dwarf spheroidals, such as Sagittarius, could provide a test of this scenario.

Francesc Ferrer

2005-05-19T23:59:59.000Z

454

DARK SATELLITES AND THE MORPHOLOGY OF DWARF GALAXIES  

SciTech Connect

One of the strongest predictions of the {Lambda}CDM cosmological model is the presence of dark satellites orbiting all types of galaxies. We focus here on the dynamical effects of such satellites on disky dwarf galaxies, and demonstrate that these encounters can be dramatic. Although mergers with M{sub sat} > M{sub d} are not very common, because of the lower baryonic content they occur much more frequently on the dwarf scale than for L{sub *} galaxies. As an example, we present a numerical simulation of a 20% (virial) mass ratio merger between a dark satellite and a disky dwarf (akin to the Fornax dwarf galaxy in luminosity) that shows that the merger remnant has a spheroidal morphology. Perturbations by dark satellites thus provide a plausible path for the formation of dSph systems. The transition from disky to the often amorphous, irregular, or spheroidal morphologies of dwarfs could be a natural consequence of the dynamical heating of hitherto unobservable dark satellites.

Helmi, Amina; Starkenburg, E.; Starkenburg, T. K.; Vera-Ciro, C. A. [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Sales, L. V. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); De Lucia, G. [INAF-Astronomical Observatory of Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Li, Y.-S., E-mail: ahelmi@astro.rug.nl [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2012-10-10T23:59:59.000Z

455

COSMIC MICROWAVE BACKGROUND CONSTRAINTS OF DECAYING DARK MATTER PARTICLE PROPERTIES  

SciTech Connect

If a component of cosmological dark matter is made up of massive particles-such as sterile neutrinos-that decay with cosmological lifetime to emit photons, the reionization history of the universe would be affected, and cosmic microwave background anisotropies can be used to constrain such a decaying particle model of dark matter. The optical depth depends rather sensitively on the decaying dark matter particle mass m{sub dm}, lifetime {tau}{sub dm}, and the mass fraction of cold dark matter f that they account for in this model. Assuming that there are no other sources of reionization and using the Wilkinson Microwave Anisotropy Probe 7-year data, we find that 250 eV {approx}< m{sub dm} {approx}< 1 MeV, whereas 2.23 Multiplication-Sign 10{sup 3} yr {approx}< {tau}{sub dm}/f {approx}< 1.23 Multiplication-Sign 10{sup 18} yr. The best-fit values for m{sub dm} and {tau}{sub dm}/f are 17.3 keV and 2.03 Multiplication-Sign 10{sup 16} yr, respectively.

Yeung, S.; Chan, M. H.; Chu, M.-C., E-mail: mcchu@phy.cuhk.edu.hk [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Shatin, New Territories (Hong Kong)

2012-08-20T23:59:59.000Z

456

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

457

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

458

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

459

Dark Matter Constraints from a Cosmic Index of Refraction  

E-Print Network (OSTI)

The dark-matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects in the propagation and attenuation of light. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter and a new possibility for its direct detection. As a first application we use the time delay determined from radio afterglow observations of distant gamma-ray bursts to realize a direct limit on the electric-charge-to-mass ratio of dark matter of |varepsilon|/M < 1 x 10^{-5} eV^{-1} at 95% CL.

S. Gardner; D. C. Latimer

2009-04-10T23:59:59.000Z

460

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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461

Probing EWSB Naturalness in Unified SUSY Models with Dark Matter  

E-Print Network (OSTI)

We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos, $\\Omega_{\

Amsel, Stephen; Sandick, Pearl

2011-01-01T23:59:59.000Z

462

Dark matter constraints from a cosmic index of refraction  

SciTech Connect

The dark matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects in the propagation and attenuation of light. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter and a new possibility for its direct detection. As a first application we use the time delay determined from radio afterglow observations of distant gamma-ray bursts to realize a direct limit on the electric charge-to-mass ratio of dark matter of |{epsilon}|/M<1x10{sup -5} eV{sup -1} at 95% C.L.

Gardner, Susan [Center for Particle Astrophysics and Theoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States); Latimer, David C. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)

2010-09-15T23:59:59.000Z

463

The dark side of the Internet: Attacks, costs and responses  

Science Conference Proceedings (OSTI)

The Internet and Web technologies have originally been developed assuming an ideal world where all users are honorable. However, the dark side has emerged and bedeviled the world. This includes spam, malware, hacking, phishing, denial of service attacks, ... Keywords: Click fraud, Cyber warfare, Denial of service attack, Digital rights management, Hacking, Malware, Online frauds, Online gambling, Online piracy, Phishing, Spam

Won Kim; Ok-Ran Jeong; Chulyun Kim; Jungmin So

2011-05-01T23:59:59.000Z

464

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

465

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

466

Visible and dark matter in M 31 - II. A dynamical model and dark matter density distribution  

E-Print Network (OSTI)

In the present paper we derive the density distribution of dark matter (DM) in a well-observed nearby disc galaxy, the Andromeda galaxy. From photometrical and chemical evolution models constructed in the first part of the study (Tamm, Tempel & Tenjes 2007 (arXiv:0707.4375), hereafter Paper I) we can calculate the mass distribution of visible components. In the dynamical model we calculate stellar rotation velocities along the major axis and velocity dispersions along the major, minor and intermediate axes of the galaxy. Comparing the calculated values with the collected observational data, we find the amount of DM, which must be added to reach an agreement with the observed rotation and dispersion data. We conclude that within the uncertainties, the DM distributions by Moore, Burkert, isothermal, Navarro, Frenk & White (NFW) and Navarro et al. 2004 (N04) fit with observations. The NFW and N04 density distributions give the best fit with observations. The total mass of M 31 with the NFW DM distributio...

Tempel, Elmo; Tenjes, Peeter

2007-01-01T23:59:59.000Z

467

The Cold and Dark Process at the Savannah River Site  

SciTech Connect

The deactivation and decommissioning (D and D) of a facility exposes D and D workers to numerous hazards. One of the more serious hazards is coming into contact to hazardous energy sources (e.g. electrical, pressurized steam). At the Savannah River Site (SRS) a formal process for identifying and eliminating sources of hazardous energy was developed and is called 'Cold and Dark'. Several 'near miss' events involving cutting of energized conductors during D and D work in buildings thought to be isolated identified the need to have a formal process to identify and isolate these potentially hazardous systems. This process was developed using lessons learned from D and D activities at the Rocky Flats Environmental Technology Site (Rocky Flats) in Colorado. The Cold and Dark process defines an isolation boundary (usually a building perimeter) and then systematically identifies all of the penetrations through this boundary. All penetrations that involve hazardous energy sources are then physically air-gapped. The final product is a documented declaration of isolation performed by a team involving operations, engineering, and project management. Once the Cold and Dark declaration is made for a building work can proceed without the usual controls used in an operational facility (e.g. lockout/tag-out, arc flash PPE). It is important to note that the Cold and Dark process does not remove all hazards from a facility. Work planning and controls still need to address hazards that can be present from such things as chemicals, radiological contamination, residual liquids, etc., as well as standard industrial hazards. Savannah River Site experienced 6 electrical events prior to declaring a facility 'cold and dark' and has had zero electrical events after 'cold and dark' declaration (263 facilities to date). The formal Cold and Dark process developed at SRS has eliminated D and D worker exposures to hazardous energy sources. Since the implementation of the process there have been no incidents involving energized conductors or pressurized liquids/gases. During this time SRS has demolished over 200 facilities. The ability to perform intrusive D and D activities without the normal controls such as lock outs results in shorter schedule durations and lower overall costs for a facility D and D.

Gilmour, John C. [CH2SRC, Savannah River Site, Aiken, SC 29808 (United States); Willis, Michael L. [Washington Savannah River Company, Aiken, SC 29808 (United States)

2008-01-15T23:59:59.000Z

468

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

469

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

470

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

471

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

472

Dark matter searches with cosmic antideuterons: status and perspectives  

E-Print Network (OSTI)

The search for antideuterons in cosmic rays has been proposed as a promising channel for dark matter indirect detection, especially for dark matter particles with a low or intermediate mass. With the current operational phase of the AMS-02 experiment and the ongoing development of a future dedicated experiment, the General Antiparticle Spectrometer (GAPS), there are exciting prospects for a dark matter detection in the near future. In this paper we develop a detailed and complete re-analysis of the cosmic-ray antideuteron signal, by discussing the main relevant issues related to antideuteron production and propagation through the interstellar medium and the heliosphere. In particular, we first critically revisit the coalescence mechanism for antideuteron production in dark matter annihilation processes. Then, since antideuteron searches have their best prospects of detection at low kinetic energies where the effect of the solar wind and magnetic field are most relevant, we address the impact of solar modulation modeling on the antideuteron flux at the Earth by developing a full numerical 4D solution of cosmic rays transport in the heliosphere. We finally use these improved predictions to provide updated estimates of the reaching capabilities for AMS-02 and GAPS, compatible with the current constraints imposed by the antiprotons measurements of PAMELA. After the antiproton bound is applied, prospects of detection of up to about 15 events in GAPS LDB+ and AMS-02 missions are found, depending on the dark matter mass, annihilation rate and production channel from one side, and on the coalescence process, galactic and solar transport parameters on the other.

N. Fornengo; L. Maccione; A. Vittino

2013-06-18T23:59:59.000Z

473

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

474

Statistical Physics of Dark and Normal Matter Distribution in Galaxy Formation : Dark Matter Lumps and Black Holes in Core and Halo of Galaxy  

E-Print Network (OSTI)

In unified field theory the cosmological model of the universe has supersymmetric fields. Supersymmetric particles as dark and normal matter in galaxy clusters have a phase separation. Dark matter in halos have a statistical physics equation of state. Neutralino particle gas with gravitation can have a collapse of dark matter lumps. A condensate phase due to boson creation by annhillation and exchange can occur at high densities. The collapse of the boson condensate, including neutralinos, into the Schwarzschild radius creates dark matter black holes. Microscopic dark matter black holes can evaporate with Hawking effect giving gamma ray bursts and create a spectrum of normal particles. The phase separation of normal and dark matter in galaxy clusters and inside galaxies is given by statistical physics.

Ajay Patwardhan

2008-05-15T23:59:59.000Z

475

Visible and dark matter in M 31 - II. A dynamical model and dark matter density distribution  

E-Print Network (OSTI)

In the present paper we derive the density distribution of dark matter (DM) in a well-observed nearby disc galaxy, the Andromeda galaxy. From photometrical and chemical evolution models constructed in the first part of the study (Tamm, Tempel & Tenjes 2007 (arXiv:0707.4375), hereafter Paper I) we can calculate the mass distribution of visible components (the bulge, the disc, the stellar halo, the outer diffuse stellar halo). In the dynamical model we calculate stellar rotation velocities along the major axis and velocity dispersions along the major, minor and intermediate axes of the galaxy assuming triaxial velocity dispersion ellipsoid. Comparing the calculated values with the collected observational data, we find the amount of DM, which must be added to reach an agreement with the observed rotation and dispersion data. We conclude that within the uncertainties, the DM distributions by Moore, Burkert, Navarro, Frenk & White (NFW) and the Einasto fit with observations nearly at all distances. The NFW and Einasto density distributions give the best fit with observations. The total mass of M 31 with the NFW DM distribution is 1.19*10^12 M_sun, the ratio of the DM mass to the visible mass is 10.0. For the Einasto DM distribution, these values are 1.28*10^12 M_sun and 10.8. The ratio of the DM mass to the visible mass inside the Holmberg radius is 1.75 for the NFW and the Einasto distributions. For different cuspy DM distributions, the virial mass is in a range 6.9-7.9*10^11 M_sun and the virial radius is ~150 kpc. The DM mean densities inside 10 pc for cusped models are 33 and 16 M_sun pc^-3 for the NFW and the Einasto profiles, respectively. For the cored Burkert profile, this value is 0.06 M_sun pc^-3.

Elmo Tempel; Antti Tamm; Peeter Tenjes

2007-07-30T23:59:59.000Z

476

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

477

Effect of dark matter annihilation on gas cooling and star formation  

E-Print Network (OSTI)

In the current paradigm of cosmic structure formation, dark matter plays a key role on the formation and evolution of galaxies through its gravitational influence. On microscopic scales, dark matter particles are expected to annihilate amongst themselves into different products, with some fraction of the energy being transferred to the baryonic component. It is the aim of the present work to show that, in the innermost regions of dark matter halos, heating by dark matter annihilation may be comparable to the cooling rate of the gas. We use analytical models of the dark matter and gas distributions in order to estimate the heating and cooling rates, as well as the energy available from supernova explosions. Depending on the model parameters and the precise nature of dark matter particles, the injected energy may be enough to balance radiative cooling in the cores of galaxy clusters. On galactic scales, it would inhibit star formation more efficiently than supernova feedback. Our results suggest that dark matte...

Ascasibar, Y

2006-01-01T23:59:59.000Z

478

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

479

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":""}]}

480

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

Note: This page contains sample records for the topic "dark brown-to-black cement-like" 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 res