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We encourage you to perform a real-time search of NLEBeta
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1

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.

2

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.

3

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.

4

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.

5

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.

6

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.

7

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.

8

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.

9

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.

10

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.

11

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.

12

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.

13

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.

14

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.

15

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.

16

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.

17

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.

18

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.

19

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.

20

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 - 29, 2005The National Science Foundation The Kavli Foundation The Theoretical Web UHE cosmic rays B

Hu, Wayne

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

Dark Matters  

ScienceCinema (OSTI)

One of the greatest mysteries in the cosmos is that it is mostly dark.  Astronomers and particle physicists today are seeking to unravel the nature of this mysterious, but pervasive dark matter which has profoundly influenced the formation of structure in the universe.  I will describe the complex interplay between galaxy formation and dark matter detectability and review recent attempts to measure particle dark matter by direct and indirect means.

Joseph Silk

2010-01-08T23:59:59.000Z

22

Dark Energy  

E-Print Network [OSTI]

We review the problem of dark energy, including a survey of theoretical models and some aspects of numerical studies.

Miao Li; Xiao-Dong Li; Shuang Wang; Yi Wang

2011-03-30T23:59:59.000Z

23

Dark matter  

Science Journals Connector (OSTI)

...just how much dark matter in baryons...have lead to the discovery that a large component of the dark mass in groups...the highest-energy photons and the...to that of the discovery of the microwave...experiments assume the dark matter in the...c) Vacuum energy and the cosmological...

1999-01-01T23:59:59.000Z

24

Dark Energy Probes of Dark Energy  

E-Print Network [OSTI]

19/12/2013 1 Dark Energy Probes of Dark Energy Probes Dark Energy Supernovae Ia probing luminosity (Betti numbers) #12;19/12/2013 2 Dark Energy Probes: Comparison Method Strengths Weaknesses Systematics

Weijgaert, Rien van de

25

Through a glass darkly  

E-Print Network [OSTI]

Closeup Through a glass darklyThrough a glass darkly James E. Hall Keywords: AKAP2; AQP0;Medicine Closeup Through a glass darkly GLUT1 Glucose

Hall, James E

2012-01-01T23:59:59.000Z

26

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

2015-01-07T23:59:59.000Z

27

Dark matter and dark energy: summary and future directions  

Science Journals Connector (OSTI)

...Brook Workshop, New York, 1979 (ed. P...Dark Matter and Dark Energy in the Universe...Dark Matter and Dark Energy in the Universe...Dark matter and dark energy 2627 Steinhardt...Cargese, 1979. New York: Plenum. Takeda...

2003-01-01T23:59:59.000Z

28

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

29

Dark Matter Theory  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Dark Matter Theory Dark Matter Theory Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email Bruce Carlsten (505)...

30

Can Dark Matter Decay in Dark Energy?  

E-Print Network [OSTI]

We analyze the interaction between Dark Energy and Dark Matter from a thermodynamical perspective. By assuming they have different temperatures, we study the possibility of occurring a decay from Dark Matter into Dark Energy, characterized by a negative parameter $Q$. We find that, if at least one of the fluids has non vanishing chemical potential, for instance $\\mu_x0$, the decay is possible, where $\\mu_x$ and $\\mu_{dm}$ are the chemical potentials of Dark Energy and Dark Matter, respectively. Using recent cosmological data, we find that, for a fairly simple interaction, the Dark Matter decay is favored with a probability of $\\sim 93%$ over the Dark Energy decay. This result comes from a likelihood analysis where only background evolution has been considered.

S. H. Pereira; J. F. Jesus

2009-02-26T23:59:59.000Z

31

Constraining Dark Matter and Dark Energy Models using Astrophysical Surveys  

E-Print Network [OSTI]

of current dark energy astrophysical surveys. Although manyMatter and Dark Energy Models using Astrophysical Surveys byMatter and Dark Energy Models using Astrophysical Surveys A

Cieplak, Agnieszka M.

32

Dark energy and dark matter with SNAP  

Science Journals Connector (OSTI)

The discovery that the expansion of the Universe is accelerating opens up new frontiers for our understanding of cosmology and particle physics. The nature of the dark energy responsible is intimately tied to the high energy theory and gravitation. Measuring the properties of the accelerating universe and studying both the dark energy and the dark matter of the Universe using supernovae and weak gravitational lensing is the primary aim of the Supernova/Acceleration Probe (SNAP). SNAP can discover and follow thousands of Type Ia supernovae at redshifts z = 0.3 ? 1.7. The resulting magnitude-redshift relation can determine the cosmological and dark energy parameters with high precision: the dark energy equation of state w to 0.05 and its time variation w? = dwdz to ±0.15. Wide area weak gravitational lensing studies will map the distribution of dark matter in the universe.

Eric V. Linder

2003-01-01T23:59:59.000Z

33

Fermilab | Science | Particle Physics | Dark matter and dark...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Dark matter and dark energy photo Visible matter makes up just 4 percent of the contents of the universe; the remaining 96 percent is made of dark matter and dark energy....

34

UNIFIED THEORY OF DARK ENERGY AND DARK SHOUHONG WANG 2  

E-Print Network [OSTI]

UNIFIED THEORY OF DARK ENERGY AND DARK MATTER TIAN MA, 1 SHOUHONG WANG 2 Abstract. The aim of this research report is to derive a uni- fied theory for dark matter and dark energy. Due to the presence of dark energy and dark matter, we postulate that the energy- momentum tensor of the normal matter

Wang, Shouhong

35

Dark Fiber Testbed  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

US) 1 510-486-7600 (Globally) 1 510-486-7607 (Globally) Report Network Problems: trouble@es.net Provide Web Site Feedback: info@es.net Dark Fiber Testbed Info on dark fiber testbed...

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

2014-12-30T23:59:59.000Z

37

Dark Soliton Fiber Laser  

E-Print Network [OSTI]

We report on the experimental observation of stable dark solitons in an all normal dispersion fiber laser. We found experimentally that dark soliton formation is a generic feature of the fiber laser under strong continuous wave (CW) emission. However, only under appropriate pump strength and negative cavity feedback, stable single or multiple dark soliton could be achieved. Furthermore, we show that the features of the observed dark solitons could be well understood based on the nonlinear Schrodinger equation (NLSE).

H. Zhang; D. Y. Tang; L. M. Zhao; X. Wu; Q. L. Bao; K. P. Loh

2009-05-08T23:59:59.000Z

38

Dark Energy Phenomenology  

E-Print Network [OSTI]

We discuss the phenomenology of the dark energy in first order perturbation theory, demonstrating that the dark energy cannot be fully constrained unless the dark matter is found, and that there are two functions that characterise the observational properties of the dark sector for cosmological probes. We argue that measuring these two functions should be an important goal for observational cosmology in the next decades.

Martin Kunz; Luca Amendola; Domenico Sapone

2008-06-08T23:59:59.000Z

39

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

2006-04-11T23:59:59.000Z

40

Surveying the dark side  

Science Journals Connector (OSTI)

......next generation of imaging surveys driven by dark-energy science typically feature...specifications for both the Dark Energy Survey (DES, see Abbott et al...References Abbott T et al. 2005 Dark Energy Survey Collaboration arXiv:astro-ph......

Roberto Trotta; Richard Bower

2006-08-01T23:59:59.000Z

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.


41

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.

42

Natural Dark Energy  

E-Print Network [OSTI]

It is now well accepted that both Dark Matter and Dark Energy are required in any successful cosmological model. Although there is ample evidence that both Dark components are necessary, the conventional theories make no prediction for the contributions from each of them. Moreover, there is usually no intrinsic relationship between the two components, and no understanding of the nature of the mysteries of the Dark Sector. Here we suggest that if the Dark Side is so seductive then we should not be restricted to just 2 components. We further suggest that the most natural model has 5 distinct forms of Dark Energy in addition to the usual Dark Matter, each contributing precisely equally to the cosmic energy density budget.

Douglas Scott; Ali Frolop

2007-03-30T23:59:59.000Z

43

Atomic dark matter  

SciTech Connect (OSTI)

We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Weak-scale dark atoms can accommodate hyperfine splittings of order 100 keV, consistent with the inelastic dark matter interpretation of the DAMA data while naturally evading direct detection bounds. Moreover, protohalo formation can be suppressed below M{sub proto} ? 10{sup 3}–10{sup 6}M{sub s}un for weak scale dark matter due to Ion-Radiation and Ion-Atom interactions in the dark sector.

Kaplan, David E.; Krnjaic, Gordan Z.; Rehermann, Keith R.; Wells, Christopher M., E-mail: dkaplan@pha.jhu.edu, E-mail: gordan@pha.jhu.edu, E-mail: keith@pha.jhu.edu, E-mail: cwells13@pha.jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686 (United States)

2010-05-01T23:59:59.000Z

44

Correspondence Accountforthe`dark  

E-Print Network [OSTI]

and dark energy actually dominate many key processes. Likewise, it is time for more biologists to ventureCorrespondence Accountforthe`dark matter' of biology Philip Ball correctly opines of DNA that "we biological systems. Ball makes an apt analogy to the 1998 discovery that the expansion of the Universe

Hadly, Elizabeth

45

Dark Energy, or Worse  

SciTech Connect (OSTI)

General relativity is inconsistent with cosmological observations unless we invoke components of dark matter and dark energy that dominate the universe. While it seems likely that these exotic substances really do exist, the alternative is worth considering: that Einstein's general relativity breaks down on cosmological scales. I will discuss models of modified gravity, tests in the solar system and elsewhere, and consequences for cosmology.

Carroll, Sean (CalTech) [CalTech

2006-11-13T23:59:59.000Z

46

Dark Energy, or Worse  

ScienceCinema (OSTI)

General relativity is inconsistent with cosmological observations unless we invoke components of dark matter and dark energy that dominate the universe. While it seems likely that these exotic substances really do exist, the alternative is worth considering: that Einstein's general relativity breaks down on cosmological scales. I will discuss models of modified gravity, tests in the solar system and elsewhere, and consequences for cosmology.

Professor Sean Carroll

2010-01-08T23:59:59.000Z

47

Weak Lensing: Dark Matter, Dark Energy  

SciTech Connect (OSTI)

The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted. Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.

Jain, Bhuvnesh (University of Pennsylvania) [University of Pennsylvania

2006-02-27T23:59:59.000Z

48

The Dark Energy Universe  

E-Print Network [OSTI]

Some seventy five years ago, the concept of dark matter was introduced by Zwicky to explain the anomaly of galactic rotation curves, though there is no clue to its identity or existence to date. In 1997, the author had introduced a model of the universe which went diametrically opposite to the existing paradigm which was a dark matter assisted decelarating universe. The new model introduces a dark energy driven accelarating universe though with a small cosmological constant. The very next year this new picture was confirmed by the Supernova observations of Perlmutter, Riess and Schmidt. These astronomers got the 2011 Nobel Prize for this dramatic observation. All this is discussed briefly, including the fact that dark energy may obviate the need for dark matter.

Burra G. Sidharth

2015-01-12T23:59:59.000Z

49

The Dark Energy Survey  

E-Print Network [OSTI]

We describe the Dark Energy Survey (DES), a proposed optical-near infrared survey of 5000 sq. deg of the South Galactic Cap to ~24th magnitude in SDSS griz, that would use a new 3 sq. deg CCD camera to be mounted on the Blanco 4-m telescope at Cerro Telolo Inter-American Observatory (CTIO). The survey data will allow us to measure the dark energy and dark matter densities and the dark energy equation of state through four independent methods: galaxy clusters, weak gravitational lensing tomography, galaxy angular clustering, and supernova distances. These methods are doubly complementary: they constrain different combinations of cosmological model parameters and are subject to different systematic errors. By deriving the four sets of measurements from the same data set with a common analysis framework, we will obtain important cross checks of the systematic errors and thereby make a substantial and robust advance in the precision of dark energy measurements.

The Dark Energy Survey Collaboration

2005-10-12T23:59:59.000Z

50

Dark energy and dark matter from cosmological observations  

E-Print Network [OSTI]

The present status of our knowledge about the dark matter and dark energy is reviewed. Bounds on the content of cold and hot dark matter from cosmological observations are discussed in some detail. I also review current bounds on the physical properties of dark energy, mainly its equation of state and effective speed of sound.

Steen Hannestad

2005-09-13T23:59:59.000Z

51

Dark Stars: A Review  

E-Print Network [OSTI]

Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $power the star for millions to billions of years. Depending on their DM environment, early DSs can become very massive ($>10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses DSs existing today but focuses on the early generation of dark stars.

Katherine Freese; Tanja Rindler-Daller; Douglas Spolyar; Monica Valluri

2015-01-10T23:59:59.000Z

52

Dark matter at colliders  

SciTech Connect (OSTI)

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

53

Explosives going dark  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

54

Hot and dark matter  

E-Print Network [OSTI]

In this thesis, we build new Effective Field Theory tools to describe the propagation of energetic partons in hot and dense media, and we propose two new reactions for dark matter in the early universe. In the first part, ...

D'Eramo, Francesco

2012-01-01T23:59:59.000Z

55

Nassau Street Dark shading  

E-Print Network [OSTI]

Nassau Street Dark shading indicates shelving for oversize books E Emergency exit Men Women M C-18L C-19L C-19 M-2 C-19 M-1 JAN Library Web Computers Library Seminar Room Resource Sharing

Petta, Jason

56

Dark Energy Survey  

ScienceCinema (OSTI)

Members of the Dark Energy Survey collaboration explain what they hope to learn by studying the southern sky with the world's most advanced digital camera, mounted on a telescope in Chile.

Roodman, Aaron; Nord, Brian; Elliot, Ann

2014-08-12T23:59:59.000Z

57

Dark Energy Survey  

SciTech Connect (OSTI)

Members of the Dark Energy Survey collaboration explain what they hope to learn by studying the southern sky with the world's most advanced digital camera, mounted on a telescope in Chile.

Roodman, Aaron; Nord, Brian; Elliot, Ann

2012-12-06T23:59:59.000Z

58

Dynamics of dark energy  

E-Print Network [OSTI]

In this paper we review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating Universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

Edmund J. Copeland; M. Sami; Shinji Tsujikawa

2006-06-16T23:59:59.000Z

59

Dark Stars: A Review  

E-Print Network [OSTI]

Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The curre...

Freese, Katherine; Spolyar, Douglas; Valluri, Monica

2015-01-01T23:59:59.000Z

60

Dark Energy - Dark Matter Unification: Generalized Chaplygin Gas Model  

E-Print Network [OSTI]

We review the main features of the generalized Chaplygin gas (GCG) proposal for unification of dark energy and dark matter and discuss how it admits an unique decomposition into dark energy and dark matter components once phantom-like dark energy is excluded. In the context of this approach we consider structure formation and show that unphysical oscillations or blow-up in the matter power spectrum are not present. Moreover, we demonstrate that the dominance of dark energy occurs about the time when energy density fluctuations start evolving away from the linear regime.

Orfeu Bertolami

2005-04-14T23:59:59.000Z

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

Big Questions: Dark Matter  

ScienceCinema (OSTI)

Carl Sagan's oft-quoted statement that there are "billions and billions" of stars in the cosmos gives an idea of just how much "stuff" is in the universe. However scientists now think that in addition to the type of matter with which we are familiar, there is another kind of matter out there. This new kind of matter is called "dark matter" and there seems to be five times as much as ordinary matter. Dark matter interacts only with gravity, thus light simply zips right by it. Scientists are searching through their data, trying to prove that the dark matter idea is real. Fermilab's Dr. Don Lincoln tells us why we think this seemingly-crazy idea might not be so crazy after all.

Lincoln, Don

2014-08-07T23:59:59.000Z

62

Dark Fantasies Issue 2  

E-Print Network [OSTI]

" by Kitty Fisher 1-39 Blake's Seven "Scars" by Ross A/lister andNevin Patryck 40-103 "Blood and Shadows" by Salom6 704-747 "The Beginning of the Bargain" by Lynne Franklin 148-158 Man From UNCLE "The Darkness Affair" by Mary Millard 159-185 "The Price... of Love Affair" by Susan Devereaux 186-206 Starsky and Hutch, Professionals, Forever Knight "Metamorphosis" by tasha 207-261 Art Front Cover "Liaisons Dangereux" Suzan Lovett Back Cover Karen Eaton Dark Fantasies II is an amateur publication...

Multiple Contributors

1994-01-01T23:59:59.000Z

63

Big Mysteries: Dark Energy  

ScienceCinema (OSTI)

Scientists were shocked in 1998 when the expansion of the universe wasn't slowing down as expected by our best understanding of gravity at the time; the expansion was speeding up! That observation is just mind blowing, and yet it is true. In order to explain the data, physicists had to resurrect an abandoned idea of Einstein's now called dark energy. In this video, Fermilab's Dr. Don Lincoln tells us a little about the observations that led to the hypothesis of dark energy and what is the status of current research on the subject.

Lincoln, Don

2014-08-07T23:59:59.000Z

64

The Search for Dark Matter  

ScienceCinema (OSTI)

More than 25 years ago, PNNL scientists began the first underground measurements searching for dark matter using specialized radiation detector technology. Dark matter is yet to be discovered says Physicist John L. Orrell.

Orrell, John

2014-07-24T23:59:59.000Z

65

The Search for Dark Matter  

SciTech Connect (OSTI)

More than 25 years ago, PNNL scientists began the first underground measurements searching for dark matter using specialized radiation detector technology. Dark matter is yet to be discovered says Physicist John L. Orrell.

Orrell, John

2013-11-20T23:59:59.000Z

66

Quantum Haplodynamics, Dark Matter and Dark Energy  

E-Print Network [OSTI]

In quantum haplodynamics (QHD) the weak bosons, quarks and leptons are bound states of fundamental constituents, denoted as haplons. The confinement scale of the associated gauge group SU(2)_h is of the order of $\\Lambda_h\\simeq 0.3$ TeV. One scalar state has zero haplon number and is the resonance observed at the LHC. In addition, there exist new bound states of haplons with no counterpart in the SM, having a mass of the order of 0.5 TeV up to a few TeV. In particular, a neutral scalar state with haplon number 4 is stable and can provide the dark matter in the universe. The QHD, QCD and QED couplings can unify at the Planck scale. If this scale changes slowly with cosmic time, all of the fundamental couplings, the masses of the nucleons and of the DM particles, including the cosmological term (or vacuum energy density), will evolve with time. This could explain the dark energy of the universe.

Harald Fritzsch; Joan Sola

2014-08-04T23:59:59.000Z

67

Dark Energy ---What it is---  

E-Print Network [OSTI]

Dark Energy ---What it is--- ----What it means--- Mike Lampton UC Berkeley Space Sciences Lab #12;M this by assuming Dark Matter. - Distant supernovae are less redshifted than expected: assume Dark Energy be universal physics! ­ Carnot (1824), Gibbs (1876): thermodynamics and energy ­ Rayleigh (1894): sound

California at Berkeley, University of

68

Antihelium from Dark Matter  

E-Print Network [OSTI]

Cosmic-ray anti-nuclei provide a promising discovery channel for the indirect detection of particle dark matter. Hadron showers produced by the pair-annihilation or decay of Galactic dark matter generate anti-nucleons which can in turn form light anti-nuclei. Previous studies have only focused on the spectrum and flux of low energy antideuterons which, although very rarely, are occasionally also produced by cosmic-ray spallation. Heavier elements ($A\\geq3$) have instead entirely negligible astrophysical background and a primary yield from dark matter which could be detectable by future experiments. Using a Monte Carlo event generator and an event-by-event phase space analysis, we compute, for the first time, the production spectrum of \\antihe and \\antiT for dark matter annihilating or decaying to $b\\bar{b}$ and ${W^+}{W^-}$ final states. We then employ a semi-analytic model of interstellar and heliospheric propagation to calculate the \\antihe flux as well as to provide tools to relate the anti-helium spectrum...

Carlson, Eric; Linden, Tim; Profumo, Stefano; Ibarra, Alejandro; Wild, Sebastian

2014-01-01T23:59:59.000Z

69

Antihelium from dark matter  

Science Journals Connector (OSTI)

Cosmic-ray antinuclei provide a promising discovery channel for the indirect detection of particle dark matter. Hadron showers produced by the pair annihilation or decay of Galactic dark matter generate antinucleons which can in turn form light antinuclei. Previous studies have only focused on the spectrum and flux of low energy antideuterons which, although very rarely, are occasionally also produced by cosmic-ray spallation. Heavier elements (A?3) have instead entirely negligible astrophysical background and a primary yield from dark matter which could be detectable by future experiments. Using a Monte Carlo event generator and an event-by-event phase space analysis, we compute, for the first time, the production spectrum of He¯3 and H¯3 for dark matter annihilating or decaying to bb¯ and W+W? final states. We then employ a semianalytic model of interstellar and heliospheric propagation to calculate the He¯3 flux as well as to provide tools to relate the antihelium spectrum corresponding to an arbitrary antideuteron spectrum. Finally, we discuss prospects for current and future experiments, including GAPS and AMS-02.

Eric Carlson; Adam Coogan; Tim Linden; Stefano Profumo; Alejandro Ibarra; Sebastian Wild

2014-04-08T23:59:59.000Z

70

Dark Energy and Electrons  

E-Print Network [OSTI]

In the light of recent developments in Dark Energy, we consider the electron in a such a background field and show that at the Compton wavelength the electron is stable, in that the Cassini inward pressure exactly counterbalances the outward Coulomb repulsive pressure thus answering a problem of the earlier electron theory.

Burra G. Sidharth

2008-08-05T23:59:59.000Z

71

Extended holographic dark energy  

SciTech Connect (OSTI)

The idea of relating the infrared and ultraviolet cutoffs is applied to the Brans-Dicke theory of gravitation. We find that the Hubble scale or the particle horizon as the infrared cutoff will not give accelerating expansion. The dynamical cosmological constant with the event horizon as the infrared cutoff is a viable dark energy model.

Gong Yungui [Institute of Applied Physics and College of Electronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)

2004-09-15T23:59:59.000Z

72

Dark matter, not magnetism  

Science Journals Connector (OSTI)

......Astronomical Society. Provided by the NASA Astrophysics Data System 1 March 1993 research-article Letters Dark matter, not magnetism Massimo Persic 1 2 Paolo Salucci 1 1 Notice that most optical rotation curves, coming from the gas-emitted H alpha line......

Massimo Persic; Paolo Salucci

1993-03-01T23:59:59.000Z

73

Measuring the speed of dark: Detecting dark energy perturbations  

SciTech Connect (OSTI)

The nature of dark energy can be probed not only through its equation of state but also through its microphysics, characterized by the sound speed of perturbations to the dark energy density and pressure. As the sound speed drops below the speed of light, dark energy inhomogeneities increase, affecting both cosmic microwave background and matter power spectra. We show that current data can put no significant constraints on the value of the sound speed when dark energy is purely a recent phenomenon, but can begin to show more interesting results for early dark energy models. For example, the best fit model for current data has a slight preference for dynamics [w(a){ne}-1], degrees of freedom distinct from quintessence (c{sub s{ne}}1), and early presence of dark energy [{Omega}{sub de}(a<<1){ne}0]. Future data may open a new window on dark energy by measuring its spatial as well as time variation.

Putter, Roland de [Berkeley Lab and University of California, Berkeley, California 94720 (United States); Huterer, Dragan [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan, 48109 (United States); Linder, Eric V. [Berkeley Lab and University of California, Berkeley, California 94720 (United States); Institute for the Early Universe, Ewha Womans University, Seoul (Korea, Republic of)

2010-05-15T23:59:59.000Z

74

Dark Matter Gravitational Interactions  

E-Print Network [OSTI]

We argue that the conjectured dark mater in the Universe may be endowed with a new kind of gravitational charge that couples to a short range gravitational interaction mediated by a massive vector field. A model is constructed that assimilates this concept into ideas of current inflationary cosmology. The model is also consistent with the observed behaviour of galactic rotation curves according to Newtonian dynamics. The essential idea is that stars composed of ordinary (as opposed to dark matter) experience Newtonian forces due to the presence of an all pervading background of massive gravitationally charged cold dark matter. The novel gravitational interactions are predicted to have a significant influence on pre-inflationary cosmology. The precise details depend on the nature of a gravitational Proca interaction and the description of matter. A gravitational Proca field configuration that gives rise to attractive forces between dark matter charges of like polarity exhibits homogeneous isotropic eternal cosmologies that are free of cosmological curvature singularities thus eliminating the horizon problem associated with the standard big-bang scenario. Such solutions do however admit dense hot pre-inflationary epochs each with a characteristic scale factor that may be correlated with the dark matter density in the current era of expansion. The model is based on a theory in which a modification of Einsteinian gravity at very short distances can be expressed in terms of the gradient of the Einstein metric and the torsion of a non-Riemannian connection on the bundle of linear frames over spacetime. Indeed we demonstrate that the genesis of the model resides in a remarkable simplification that occurs when one analyses the variational equations associated with a broad class of non-Riemannian actions.

R. W. Tucker; C. Wang

1996-12-09T23:59:59.000Z

75

The Universe Adventure - Dark Energy  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

76

Tunguska Dark Matter Ball  

E-Print Network [OSTI]

It is suggested that the Tunguska event in June 1908 cm-large was due to a cm-large ball of a condensate of bound states of 6 top and 6 anti-top quarks containing highly compressed ordinary matter. Such balls are supposed to make up the dark matter as we earlier proposed. The expected rate of impact of this kind of dark matter ball with the earth seems to crudely match a time scale of 200 years between the impacts. The main explosion of the Tunguska event is explained in our picture as material coming out from deep within the earth, where it has been heated and compressed by the ball penetrating to a depth of several thousand km. Thus the effect has some similarity with volcanic activity as suggested by Kundt. We discuss the possible identification of kimberlite pipes with earlier Tunguska-like events. A discussion of how the dark matter balls may have formed in the early universe is also given.

C. D. Froggatt; H. B. Nielsen

2014-03-27T23:59:59.000Z

77

Tunguska Dark Matter Ball  

E-Print Network [OSTI]

It is suggested that the Tunguska event in June 1908 cm-large was due to a cm-large ball of a condensate of bound states of 6 top and 6 anti-top quarks containing highly compressed ordinary matter. Such balls are supposed to make up the dark matter as we earlier proposed. The expected rate of impact of this kind of dark matter ball with the earth seems to crudely match a time scale of 200 years between the impacts. The main explosion of the Tunguska event is explained in our picture as material coming out from deep within the earth, where it has been heated and compressed by the ball penetrating to a depth of several thousand km. Thus the effect has some similarity with volcanic activity as suggested by Kundt. We discuss the possible identification of kimberlite pipes with earlier Tunguska-like events. A discussion of how the dark matter balls may have formed in the early universe is also given.

Froggatt, C D

2014-01-01T23:59:59.000Z

78

Unifying dark energy and dark matter with a scalar field  

E-Print Network [OSTI]

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.

A. Arbey

2005-09-20T23:59:59.000Z

79

The Dark Force: Astrophysical Repulsion from Dark Energy  

E-Print Network [OSTI]

Dark energy (i.e., a cosmological constant) leads, in the Newtonian approximation, to a repulsive force which grows linearly with distance. We discuss possible astrophysical effects of this "dark" force. For example, the dark force overcomes the gravitational attraction from an object (e.g., dwarf galaxy) of mass $10^7 M_\\odot$ at a distance of $~ 23$ kpc. It seems possible that observable velocities of bound satellites (rotation curves) could be significantly affected, and therefore used to measure the dark energy density.

Ho, Chiu Man

2015-01-01T23:59:59.000Z

80

Gamma-ray bursts and dark energy–dark matter interaction  

Science Journals Connector (OSTI)

......on a putative coupling between dark energy and dark matter. Type Ia supernovae constraints from the Sloan Digital Sky Survey II (SDSS-II) first-year results...general|cosmological parameters|dark energy|dark matter| 1 INTRODUCTION......

T. Barreiro; O. Bertolami; P. Torres

2010-12-01T23:59:59.000Z

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.


81

Direct search for dark matter  

SciTech Connect (OSTI)

Dark matter is hypothetical matter which does not interact with electromagnetic radiation. The existence of dark matter is only inferred from gravitational effects of astrophysical observations to explain the missing mass component of the Universe. Weakly Interacting Massive Particles are currently the most popular candidate to explain the missing mass component. I review the current status of experimental searches of dark matter through direct detection using terrestrial detectors.

Yoo, Jonghee; /Fermilab

2009-12-01T23:59:59.000Z

82

Direct Detection Constraints on Dark Photon Dark Matter  

E-Print Network [OSTI]

Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01-100 keV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to $O(10^{-15})$, assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity to dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. We also revisit indirect constraints from $V\\to 3\\gamma$ decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse gamma-ray flux.

Haipeng An; Maxim Pospelov; Josef Pradler; Adam Ritz

2014-12-29T23:59:59.000Z

83

Dark Energy Stars  

E-Print Network [OSTI]

Event horizons and closed time-like curves cannot exist in the real world for the simple reason that they are inconsistent with quantum mechanics. Following ideas originated by Robert Laughlin, Pawel Mazur, Emil Mottola, David Santiago, and the speaker it is now possible to describe in some detail what happens physically when one approaches and crosses a region of space-time where classical general relativity predicts there should be an infinite red shift surface. This quantum critical physics provides a new perspective on a variety of enigmatic astrophysical phenomena, including supernovae explosions, gamma ray bursts, positron emission, and dark matter.

G. Chapline

2005-04-13T23:59:59.000Z

84

Angel in the Dark  

E-Print Network [OSTI]

/HE SHRILL OF the telephone splintered through Doyle's dream like a bullet through glass. He sat straight up, grabbing the gun on the bedside table, but the room was dark and empty of any presence save his own. The phone rang again. Doyle groaned.... Not Bodie. Not again. He let out his breath in a sigh and put the gun aside to grope for the receiver. "Doyle." "Hello, sunshine." "Not so loud, will you?" Doyle said, lifting the handset away from his ear. "Trouble?" "No. All quiet on the Western...

Thomas

2013-11-27T23:59:59.000Z

85

A quintessential introduction to dark energy  

Science Journals Connector (OSTI)

...quintessence; k-essence; dark energy; cyclic models; microwave...supernovae 1. Introduction The discovery of dark energy is one of the most surprising...Planck scale. Prior to the discovery of dark energy, it had been presumed that...

2003-01-01T23:59:59.000Z

86

Probing Dark Energy with Theory and Observations  

E-Print Network [OSTI]

dark energy) before, what really changed everything was the discoveryDiscoveries of Type Ia Super- novae at z > 1: Narrowing Constraints on the Early Behavior of Dark Energy.of Dark Energy . . . 1.2 Discovery . . . . . . . . . . . .

de Putter, Roland

2010-01-01T23:59:59.000Z

87

Complementarity of future dark energy probes  

Science Journals Connector (OSTI)

......few representative future surveys, namely Dark Energy Survey (DES), Panoramic Survey Telescope and...which are currently not deployed. The Dark Energy Survey (DES) (The Dark Energy Survey Collaboration 2005) is an optical-near-infrared......

Jiayu Tang; Filipe B. Abdalla; Jochen Weller

2011-09-21T23:59:59.000Z

88

Probing Dark Energy with Theory and Observations  

E-Print Network [OSTI]

Wyder. The WiggleZ Dark Energy Survey: Direct constraints onsensitivities of dark energy surveys. Phys.Rev.D, 73(8):A Galaxy Redshift Survey Measure Dark Energy Clus- tering?

de Putter, Roland

2010-01-01T23:59:59.000Z

89

Dark Energy Ay 21, 2010  

E-Print Network [OSTI]

1 Dark Energy Ay 21, 2010 Measuring the Acceleration of the Expanding Universe · for a few decades the equation of state relating pressure and energy density: P=w, where is energy density and w has ~1.2, m~0.6 Carnegie SN Project (2010) #12;9 What is "Dark Energy" · We don't know. We are told

Steidel, Chuck

90

Optimizing New Dark Energy Experiments  

SciTech Connect (OSTI)

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

91

Berkeley Algorithms Help Researchers Understand Dark Energy  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Berkeley Algorithms Help Researchers Understand Dark Energy Berkeley Algorithms Help Researchers Understand Dark Energy November 24, 2014 | Tags: Astrophysics Contact: Linda Vu, +1...

92

Thermodynamical properties of dark energy  

SciTech Connect (OSTI)

We have investigated the thermodynamical properties of dark energy. Assuming that the dark energy temperature T{approx}a{sup -n} and considering that the volume of the Universe enveloped by the apparent horizon relates to the temperature, we have derived the dark energy entropy. For dark energy with constant equation of state w>-1 and the generalized Chaplygin gas, the derived entropy can be positive and satisfy the entropy bound. The total entropy, including those of dark energy, the thermal radiation, and the apparent horizon, satisfies the generalized second law of thermodynamics. However, for the phantom with constant equation of state, the positivity of entropy, the entropy bound, and the generalized second law cannot be satisfied simultaneously.

Gong Yungui; Wang Bin; Wang Anzhong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China) and CASPER, Department of Physics, Baylor University, Waco, Texas 76798 (United States); Department of Physics, Fudan University, Shanghai 200433 (China); CASPER, Department of Physics, Baylor University, Waco, Texas 76798 (United States)

2007-06-15T23:59:59.000Z

93

Weak lensing and dark energy: The impact of dark energy on nonlinear dark matter clustering  

SciTech Connect (OSTI)

We examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future weak lensing probes. We explicitly show that a poor approximation (off by > or approx.10%) to the nonlinear corrections causes a > or approx. 1{sigma} bias on the determination of the dark energy equation of state. Future weak lensing surveys must therefore incorporate dark energy modifications to the nonlinear matter power spectrum accurate to the percent-level, to avoid introducing significant bias in their measurements. For the WMAP5 cosmology, the more accurate power spectrum is more sensitive to dark energy properties, resulting in a factor of 2 improvement in dark energy equation of state constraints. We explore the complementary constraints on dark energy from future weak lensing and supernova surveys. A space-based, Joint Dark Energy Mission-like survey measures the equation of state in five independent redshift bins to {approx}10%, while this improves to {approx}5% for a wide-field ground-based survey like the Large Synoptic Survey Telescope. These constraints are contingent upon our ability to control weak lensing systematic uncertainties to the sub-percent level.

Joudaki, Shahab; Cooray, Asantha; Holz, Daniel E. [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2009-07-15T23:59:59.000Z

94

Weak lensing and dark energy: The impact of dark energy on nonlinear dark matter clustering  

Science Journals Connector (OSTI)

We examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future weak lensing probes. We explicitly show that a poor approximation (off by ?10%) to the nonlinear corrections causes a ?1? bias on the determination of the dark energy equation of state. Future weak lensing surveys must therefore incorporate dark energy modifications to the nonlinear matter power spectrum accurate to the percent-level, to avoid introducing significant bias in their measurements. For the WMAP5 cosmology, the more accurate power spectrum is more sensitive to dark energy properties, resulting in a factor of 2 improvement in dark energy equation of state constraints. We explore the complementary constraints on dark energy from future weak lensing and supernova surveys. A space-based, Joint Dark Energy Mission-like survey measures the equation of state in five independent redshift bins to ?10%, while this improves to ?5% for a wide-field ground-based survey like the Large Synoptic Survey Telescope. These constraints are contingent upon our ability to control weak lensing systematic uncertainties to the sub-percent level.

Shahab Joudaki; Asantha Cooray; Daniel E. Holz

2009-07-08T23:59:59.000Z

95

Tracing the “At-Risk” Oral Mucosa Field with Autofluorescence: Steps Toward Clinical Impact  

Science Journals Connector (OSTI)

...imaging uses higher-energy light to excite specific...they re-emit lower-energy light that makes up the...autofluorescence and appears as a dark brown to black region...An intriguing early discovery was that this technology...particularly in the darker areas, where small changes...

Catherine F. Poh; Calum E. MacAulay; Lewei Zhang; and Miriam P. Rosin

2009-05-01T23:59:59.000Z

96

Secluded WIMP Dark Matter  

E-Print Network [OSTI]

We consider a generic mechanism via which thermal relic WIMP dark matter may be decoupled from the Standard Model, namely through a combination of WIMP annihilation to metastable mediators with subsequent delayed decay to Standard Model states. We illustrate this with explicit examples of WIMPs connected to the Standard Model by metastable bosons or fermions. In all models, provided the WIMP mass is greater than that of the mediator, it can be secluded from the Standard Model with an extremely small elastic scattering cross-section on nuclei and rate for direct collider production. In contrast, indirect signatures from WIMP annihilation are consistent with a weak scale cross-section and provide potentially observable \\gamma-ray signals. We also point out that \\gamma-ray constraints and flavor physics impose severe restrictions on MeV-scale variants of secluded models, and identify limited classes that pass all the observational constraints.

Maxim Pospelov; Adam Ritz; Mikhail B. Voloshin

2007-11-30T23:59:59.000Z

97

Dark Matter Searches with GLAST  

E-Print Network [OSTI]

Indirect detection of particle dark matter relies upon pair annihilation of Weakly Interaction Massive Particles (WIMPs), which is complementary to the well known techniques of direct detection (WIMP-nucleus scattering) and collider production (WIMP pair production). Pair annihilation of WIMPs results in the production of gamma-rays, neutrinos, and anti-matter. Of the various experiments sensitive to indirect detection of dark matter, the Gamma-ray Large Area Space Telescope (GLAST) may play the most crucial role in the next few years. After launch in late 2007, The GLAST Large Area Telescope (LAT) will survey the gamma-ray sky in the energy range of 20MeV-300GeV. By eliminating charged particle background above 100 MeV, GLAST may be sensitive to as yet to be observed Milky Way dark matter subhalos, as well as WIMP pair annihilation spectral lines from the Milky Way halo. Discovery of gamma-ray signals from dark matter in the Milky Way would not only demonstrate the particle nature of dark matter; it would also open a new observational window on galactic dark matter substructure. Location of new dark matter sources by GLAST would dramatically alter the experimental landscape; ground based gamma ray telescopes could follow up on the new GLAST sources with precision measurements of the WIMP pair annihilation spectrum.

Lawrence Wai; GLAST LAT Collaboration

2007-01-31T23:59:59.000Z

98

Double-Disk Dark Matter  

Science Journals Connector (OSTI)

Abstract Based on observational tests of large scale structure and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component’s interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy (depending on precise alignment) can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.

JiJi Fan; Andrey Katz; Lisa Randall; Matthew Reece

2013-01-01T23:59:59.000Z

99

Thermodynamics of dark energy interacting with dark matter and radiation  

SciTech Connect (OSTI)

We investigate the validity of the generalized second law of thermodynamics, in the cosmological scenario where dark energy interacts with both dark matter and radiation. Calculating separately the entropy variation for each fluid component and for the apparent horizon itself, we show that the generalized second law is always and generally valid, independently of the specific interaction form, of the fluids equation-of-state parameters and of the background geometry.

Jamil, Mubasher [Center for Advanced Mathematics and Physics, National University of Sciences and Technology, Rawalpindi, 46000 (Pakistan); Saridakis, Emmanuel N. [Department of Physics, University of Athens, GR-15771 Athens (Greece); Setare, M. R. [Department of Science, Payame Noor University, Bijar (Iran, Islamic Republic of)

2010-01-15T23:59:59.000Z

100

NASA?s Dark Matter & Dark Energy Programs  

Science Journals Connector (OSTI)

Abstract We present an overview of selected high value scientific results and prospects for future advances from NASA?s “Dark” missions, i.e., those covering dark matter (DM) and dark energy (DE). This includes current missions HST, Chandra, Swift, GALEX, Suzaku, Fermi, and future missions JWST and WFIRST. These missions and earlier ones, such as WMAP, have brought about a revolution in our understanding of the fundamental properties of the universe – its age, rate of expansion, deceleration history, and composition (i.e., relative mix of luminous matter, dark matter, and dark energy). The next chapters in this story will be written by JWST and WFIRST. JWST was the highest priority of the 2000 Decadal Survey. It will observe in the near and medium infrared, and revolutionize our understanding of the high redshift universe. WFIRST is the highest ranked large space mission of the 2010 Decadal Survey. It is a NASA observatory designed to perform wide-field imaging and slitless spectroscopic surveys of the NIR sky (0.7 – 2.5?). WFIRST will: (i) measure the expansion history of the universe, and thereby constrain dark energy, (ii) find Earth-like planets around other stars using microlensing, and (iii) perform surveys that are ?100 times more sensitive than current NIR surveys.

N. Gehrels; J.K. Cannizzo

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark brown-to-black cement-like" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


101

A parallel world in the dark  

SciTech Connect (OSTI)

The baryon-dark matter coincidence is a long-standing issue. Interestingly, the recent observations suggest the presence of dark radiation, which, if confirmed, would pose another coincidence problem of why the density of dark radiation is comparable to that of photons. These striking coincidences may be traced back to the dark sector with particle contents and interactions that are quite similar, if not identical, to the standard model: a dark parallel world. It naturally solves the coincidence problems of dark matter and dark radiation, and predicts a sterile neutrino(s) with mass of O(0.1?1) eV, as well as self-interacting dark matter made of the counterpart of ordinary baryons. We find a robust prediction for the relation between the abundance of dark radiation and the sterile neutrino, which can serve as the smoking-gun evidence of the dark parallel world.

Higaki, Tetsutaro [Mathematical Physics Lab., RIKEN Nishina Center, Saitama 351-0198 (Japan); Jeong, Kwang Sik; Takahashi, Fuminobu, E-mail: tetsutaro.higaki@riken.jp, E-mail: ksjeong@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)

2013-08-01T23:59:59.000Z

102

Cosmological constraints on dark energy  

E-Print Network [OSTI]

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

Davis, Tamara M

2014-01-01T23:59:59.000Z

103

Cold dark matter heats up  

E-Print Network [OSTI]

One of the principal discoveries in modern cosmology is that standard model particles (including baryons, leptons and photons) together comprise only 5% of the mass-energy budget of the Universe. The remaining 95% consists of dark energy and dark matter (DM). Consequently our picture of the universe is known as {\\Lambda}CDM, with {\\Lambda} denoting dark energy and CDM cold dark matter. {\\Lambda}CDM is being challenged by its apparent inability to explain the low density of DM measured at the centre of cosmological systems, ranging from faint dwarf galaxies to massive clusters containing tens of galaxies the size of the Milky Way. But before making conclusions one should carefully include the effect of gas and stars, which were historically seen as merely a passive component during the assembly of galaxies. We now understand that these can in fact significantly alter the DM component, through a coupling based on rapid gravitational potential fluctuations.

Pontzen, Andrew

2014-01-01T23:59:59.000Z

104

Emergent gravity and Dark Energy  

E-Print Network [OSTI]

This is an invited contribution to be included in a multi-authored book on "Dark Energy", to be edited by Pilar Ruiz-Lapuente and published by Cambridge University Press.

T. Padmanabhan

2008-02-13T23:59:59.000Z

105

Thermonuclear Ignition of Dark Galaxies  

E-Print Network [OSTI]

Dark matter is thought to be at least an order of magnitude more abundant than luminous matter in the Universe, but there has yet to be an unambiguous identification of a wholly dark, galactic-scale structure. There is, however, increasing evidence that VIRGOHI 21 may be a dark galaxy. If VIRGOHI 21 turns out to be composed of dark stars, having approximately the same mass of stars found in luminous galaxies, it will pose an enigma within the framework of current astrophysical models, but will provide strong support for my concept, published in 1994 in the Proceedings of the Royal Society of London, of the thermonuclear ignition of stars by nuclear fission, and the corollary, non-ignition of stars. The possibility of galactic thermonuclear ignition is discussed from that framework and leads to my suggestion that the distribution of luminous stars in a galaxy may simply be a reflection of the galactic distribution of the heavy elements.

J. Marvin Herndon

2006-04-13T23:59:59.000Z

106

Lorentz-violating dark matter  

E-Print Network [OSTI]

LORENTZ-VIOLATING DARK MATTER A Dissertation by ANTONIO R. MONDRAGON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2007 Major Subject...: Physics LORENTZ-VIOLATING DARK MATTER A Dissertation by ANTONIO R. MONDRAGON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair...

Mondragon, Antonio Richard

2009-05-15T23:59:59.000Z

107

Anisotropic charged dark energy star  

E-Print Network [OSTI]

As the stars carry electrical charges, we present in this paper a model for charged dark energy star which is singularity free. We take Krori-Barua space time. 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 and the difference between tangential and radial pressure is proportional to the square of the electric field intensity. The solution satisfies the physical conditions inside the star

Kanika Das; Nawsad Ali

2014-02-02T23:59:59.000Z

108

The darkness that shaped the void: dark energy and cosmic voids  

Science Journals Connector (OSTI)

......a different nature of dark energy. To address the question...whether galaxy redshift surveys yield sufficiently accurate...morphologies, voids in the dark matter distribution are...et al. 2010), The Dark Energy Survey and large weak-lensing......

E. G. Patrick Bos; Rien van de Weygaert; Klaus Dolag; Valeria Pettorino

2012-10-11T23:59:59.000Z

109

Cryogenic Dark Matter Search (CDMS): The Hunt for Dark Matter  

SciTech Connect (OSTI)

Deciphering the nature of dark matter has great scientific importance. A leading hypothesis is that dark matter is made of Weakly Interactive Massive Particles (WIMPs), which may result from supersymmetry or additional spatial dimensions. The underground search for elastic scattering of WIMPs on suitable targets (the so-called 'direct detection') is currently led by the Cryogenic Dark Matter Search II (CDMS II) experiment. Its sensitivity is ten times better than any other experiment and we hope to obtain another factor ten in the coming two years. After a brief recall of our recent results, I will describe the complementarity between direct detection experiments, the LHC and the ILC and I will outline the role that SLAC could play in this SuperCDMS program.

Sadoulet, Bernard (UC Berkeley) [UC Berkeley

2006-03-06T23:59:59.000Z

110

Searching for an invisible dark photon with DarkLight  

Science Journals Connector (OSTI)

The DarkLight experiment at Jefferson Lab is designed to search for a new U(1) vector boson A' in the mass range 10-100 MeV through its decay A??e + e ?. We will show that DarkLight is also sensitive to an A' decaying to invisible final states but because of QED backgrounds such a search is only feasible with photon detection. Surprisingly pileup can be mitigated with a cut on the sign of the missing invariant mass-squared. We give the DarkLight reach for the invisible search assuming a nominal two-month running time and compare to constraints from anomalous magnetic moments and rare kaon decays.

Yonatan Kahn

2013-01-01T23:59:59.000Z

111

Macroscopic theory of dark sector  

E-Print Network [OSTI]

A simple Lagrangian with squared covariant divergence of a vector field as a kinetic term turned out an adequate tool for macroscopic description of the dark sector. The zero-mass field acts as the dark energy. Its energy-momentum tensor is a simple additive to the cosmological constant. Massive fields {\\phi}_{I} with {\\phi}^{K}{\\phi}_{K}0 describe two different forms of dark matter. The space-like ({\\phi}^{K}{\\phi}_{K}0) massive field displays repulsive elasticity. In balance with dark energy and ordinary matter it provides a four parametric diversity of regular solutions of the Einstein equations describing different possible cosmological and oscillating non-singular scenarios of evolution of the universe. In particular, the singular big bang turns into a regular inflation-like transition from contraction to expansion with the accelerate expansion at late times. The fine-tuned Friedman-Robertson-Walker singular solution is a particular limiting case at the boundary of existence of regular oscillating solutions in the absence of vector fields. The simplicity of the general covariant expression for the energy-momentum tensor allows to display the main properties of the dark sector analytically and avoid unnecessary model assumptions.

Boris E. Meierovich

2014-10-06T23:59:59.000Z

112

Interacting dark energy: the role of microscopic feedback in the dark sector  

E-Print Network [OSTI]

We investigate the impact on the classical dynamics of dark matter particles and dark energy of a non-minimal coupling in the dark sector, assuming that the mass of the dark matter particles is coupled to a dark energy scalar field. We show that standard results can only be recovered if the space-time variation of the dark energy scalar field is sufficiently smooth on the characteristic length scale of the dark matter particles, and we determine the associated constraint dependent on both the mass and radius of the dark matter particles and the coupling to the dark energy scalar field. We further show, using field theory numerical simulations, that a violation of such constraint results in a microscopic feedback effect strongly affecting the dynamics of dark matter particles, with a potential impact on structure formation and on the space-time evolution of the dark energy equation of state.

Avelino, P P

2015-01-01T23:59:59.000Z

113

Dark energy and dark matter from Bose-Einstein condensate  

E-Print Network [OSTI]

We propose that gravitons with a very small mass (but consistent with experiments) may form a Bose-Einstein condensate, with its macroscopic wave function spanning the universe and producing a quantum potential. The latter's contribution to the cosmological constant accounts for the observed dark energy content and the accelerated expansion of our universe. Further, the density of the Bose-Einstein condensed gravitons in the lowest zero momentum state accounts for its cold dark matter content. In the far future this condensate is all that remains of our universe.

Das, Saurya

2014-01-01T23:59:59.000Z

114

Dark energy and dark matter from Bose-Einstein condensate  

E-Print Network [OSTI]

We propose that gravitons with a very small mass (but consistent with experiments) may form a Bose-Einstein condensate, with its macroscopic wave function spanning the universe and producing a quantum potential. The latter's contribution to the cosmological constant accounts for the observed dark energy content and the accelerated expansion of our universe. Further, the density of the Bose-Einstein condensed gravitons in the lowest zero momentum state accounts for its cold dark matter content. In the far future this condensate is all that remains of our universe.

Saurya Das; Rajat K. Bhaduri

2014-11-04T23:59:59.000Z

115

Radial systems of dark globules  

SciTech Connect (OSTI)

The author gives examples of radial systems consisting of dark globules and ''elephant trunks''. Besides already known systems, which contain hot stars at their center, data are given on three radial systems of a new kind, at the center of which there are stars of spectral types later than B. Data are given on 32 globules of radial systems of the association Cep OB2. On the basis of the observational data, it is concluded that at least some of the isolated Bok globules derive from elephant trunks and dark globules forming radial systems around hot stars. It is also suggested that the two molecular clouds situated near the Rosette nebula and possessing velocities differing by ca 20 km/sec from the velocity of the nebula could have been ejected in opposite directions from the center of the nebula. One of these clouds consists of dark globules forming the radial system of the Rosette nebula.

Gyul'budagyn, A.L.

1986-03-01T23:59:59.000Z

116

Dark Forces At The Tevatron  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

A simple explanation of the W + dijet excess recently reported by the CDF collaboration involves the introduction of a new gauge boson with sizable couplings to quarks, but with no or highly suppressed couplings to leptons. Anomaly-free theories which include such a leptophobic gauge boson must also include additional particle content, which may include a stable and otherwise viable candidate for dark matter. Based on the couplings and mass of the Z` required to generate the CDF excess, we predict such a dark matter candidate to possess an elastic scattering cross section with nucleons on the order of ? ~ 10-40 cm2, providing a natural explanation for the signals reported by the CoGeNT and DAMA/LIBRA collaborations. In this light, CDF may be observing the gauge boson responsible for the force which mediates the interactions between the dark and visible matter of our universe.

Buckley, Matt [Fermilab; Fileviez Perez, Pavel [Wisconsin U., Madison; Hooper, Dan [Fermilab; Chicago U., Astron. Astrophys. Ctr.; Neil, Ethan [Fermilab

2011-08-19T23:59:59.000Z

117

Dissipative hidden sector dark matter  

E-Print Network [OSTI]

A simple way of explaining dark matter without modifying known Standard Model physics is to require the existence of a hidden sector, which interacts with the visible one predominantly via gravity. We consider a hidden sector containing two stable particles charged under an unbroken $U(1)^{'}$ gauge symmetry, hence featuring dissipative interactions. The massless gauge field associated with this symmetry can interact via kinetic mixing with the ordinary photon. In fact, such an interaction of strength $\\epsilon \\sim 10^{-9}$ appears to be necessary in order to explain galactic structure. We calculate the effect of this new physics on Big Bang Nucleosynthesis and its contribution to the relativistic energy density at Hydrogen recombination. Subsequently we examine the process of dark recombination, during which neutral dark states are formed, which is important for large-scale structure formation. We then analyze the phenomenology of our model in the context of galactic structure, and find that it can reproduc...

Foot, R

2014-01-01T23:59:59.000Z

118

Sterile dark matter and reionization  

E-Print Network [OSTI]

Sterile neutrinos with masses in the keV range can be the dark matter, and their emission from a supernova can explain the observed velocities of pulsars. The sterile neutrino decays could produce the x-ray radiation in the early universe, which could have an important effect on the formation of the first stars. X-rays could ionize gas and could catalyze the production of molecular hydrogen during the ``dark ages''. The increased fraction of molecular hydrogen could facilitate the cooling and collapse of the primordial gas clouds in which the first stars were formed.

Alexander Kusenko

2006-09-13T23:59:59.000Z

119

Dark Energy and an Accelerating Universe  

Science Journals Connector (OSTI)

Dark energy is an enigma. It could be one of the greatest discoveries of modern cosmology, or it might not ... collectively they can offer no explanation for what dark energy, if it is real, could be ... to data ...

Martin Beech

2010-01-01T23:59:59.000Z

120

Strong gravitational lensing and dynamical dark energy  

Science Journals Connector (OSTI)

......investigate the nature of dark energy. The forthcoming observational surveys (i.e. CFHT Legacy Survey, SDSS and others...example, the RCS-2 Survey (Gladders et al...discussions on dynamical dark energy models. We also thank......

Andrea V. Macciò

2005-08-21T23:59:59.000Z

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.


121

Do Dark Pools Harm Price Discovery?  

E-Print Network [OSTI]

Dark pools are equity trading systems that do not publicly display orders. Dark pools offer potential price improvements but do not guarantee execution. Informed traders tend to trade in the same direction, crowd on the ...

Zhu, Haoxiang

122

Big Bang Synthesis of Nuclear Dark Matter  

E-Print Network [OSTI]

We investigate the physics of dark matter models featuring composite bound states carrying a large conserved dark "nucleon" number. The properties of sufficiently large dark nuclei may obey simple scaling laws, and we find that this scaling can determine the number distribution of nuclei resulting from Big Bang Dark Nucleosynthesis. For plausible models of asymmetric dark matter, dark nuclei of large nucleon number, e.g. > 10^8, may be synthesised, with the number distribution taking one of two characteristic forms. If small-nucleon-number fusions are sufficiently fast, the distribution of dark nuclei takes on a logarithmically-peaked, universal form, independent of many details of the initial conditions and small-number interactions. In the case of a substantial bottleneck to nucleosynthesis for small dark nuclei, we find the surprising result that even larger nuclei, with size >> 10^8, are often finally synthesised, again with a simple number distribution. We briefly discuss the constraints arising from the...

Hardy, Edward; March-Russell, John; West, Stephen M

2014-01-01T23:59:59.000Z

123

"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

124

Gravitational lensing: a unique probe of dark matter and dark energy  

Science Journals Connector (OSTI)

...gravitating matter (dark and visible...in subsequent surveys (e.g. Astier...presence of an energy density with...The moniker dark energy was invented...Digital Sky Survey commissioning...the hunt for dark matter and dark energy in the UniverseNew...

2010-01-01T23:59:59.000Z

125

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

126

Nonthermal dark matter in mirage mediation  

SciTech Connect (OSTI)

In mirage-mediation models there exists a modulus field whose mass is O(1000) TeV and its late decay may significantly change the standard thermal relic scenario of the dark matter. We study nonthermal production of the dark matter directly from the modulus decay, and find that for some parameter regions nonthermally produced neutralinos can become the dark matter.

Nagai, Minoru; Nakayama, Kazunori [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan)

2007-12-15T23:59:59.000Z

127

BLINC: Multilevel Traffic Classification in the Dark  

E-Print Network [OSTI]

the dark" ­ No port numbers ­ No payload web streaming P2P #12;3 The problem of workload characterizationBLINC: Multilevel Traffic Classification in the Dark Thomas Karagiannis, UC Riverside Konstantina ­ Why in the dark? · Traffic profiling based on TCP/UDP ports ­ Misleading · Payload

Rajamani, Sriram K.

128

Nonlinear Dark-Field Microscopy Hayk Harutyunyan,  

E-Print Network [OSTI]

/20/2010 Published on Web: 11/16/2010 FIGURE 1. Illustration of the nonlinear dark-field imaging method. Two incidentNonlinear Dark-Field Microscopy Hayk Harutyunyan, Stefano Palomba, Jan Renger, Romain Quidant Dark-field microscopy is a background-free imaging method that provides high sensitivity and a large

Novotny, Lukas

129

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

130

Fisher matrix decomposition for dark energy prediction  

Science Journals Connector (OSTI)

......experiments, in particular dark energy surveys, on which a large amount...attempting to constrain dark energy equation-of-state...performance of a future survey. Because of these ambiguities...not know the nature of dark energy in general any choice......

T. D. Kitching; A. Amara

2009-10-01T23:59:59.000Z

131

The WiggleZ Dark Energy Survey  

Science Journals Connector (OSTI)

......research-article Features The WiggleZ Dark Energy Survey Chris Blake and the WiggleZ...redshift surveys The WiggleZ Dark Energy Survey at the Anglo-Australian Telescope...5). The aim of the WiggleZ Dark Energy Survey is to extend this delineation......

Chris Blake; Sarah Brough; Warrick Couch; Karl Glazebrook; Greg Poole; Tamara Davis; Michael Drinkwater; Russell Jurek; Kevin Pimbblet; Matthew Colless; Rob Sharp; Scott Croom; Michael Pracy; David Woods; Barry Madore; Chris Martin; Ted Wyder

2008-10-01T23:59:59.000Z

132

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

133

Dark Energy Data Management System : Overview and  

E-Print Network [OSTI]

, Astronomy Computational Astrostatistics Workshop #12;2 Dark Energy Survey DES is 50002 degree grizY Imaging survey of Southern hemisphere to map out dark energy equation of state. CTIO Blanco 4m telescope. Replace-Starrs) Acknowledgements : Joe Mohr (LMU/UIUC), Bob Armstrong (UIUC), Emmanuel Bertin (IAP) Dark Energy Survey

134

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

135

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

136

The Pitfalls of Dark Crossings  

E-Print Network [OSTI]

We explore the connection between pair production of dark matter particles at collider experiments and annihilation of dark matter in the early and late universe, with a focus on the correlation between the two time-reversed processes. We consider both a model-independent effective theory framework, where the initial and final states are assumed to not change under time-reversal, and concrete UV-complete models within the framework of supersymmetric extensions to the Standard Model. Even within the effective theory framework (where crossing symmetry is in some sense assumed), we find that the predictions of that symmetry can vary by orders of magnitude depending on the details of the selected effective interaction. Within the supersymmetric models we consider, we find that there is an even wilder variation in the expectations one can derive for collider observables based on cross-symmetric processes such as having a thermal relic or given indirect dark matter detection rates. We also explore additional "pitfalls" where na\\"ive crossing symmetry badly fails, including models with very light mediators leading to Sommerfeld enhancements and/or dark matter bound states.

Stefano Profumo; William Shepherd; Tim Tait

2013-07-24T23:59:59.000Z

137

Grow in the dark algae  

Science Journals Connector (OSTI)

... By introducing a single human gene, researchers have equipped an alga to live off sugar and grow in the dark. The finding could facilitate the ... Kirk Apt, of Martek Biosciences in Columbia, Maryland, and colleagues genetically modified the marine alga Phaeodactylum tricornutum to contain a human glucose-transporter gene. In people, this gene encodes ...

John Whitfield

2001-06-15T23:59:59.000Z

138

Weak lensing and dark energy  

Science Journals Connector (OSTI)

We study the power of upcoming weak lensing surveys to probe dark energy. Dark energy modifies the distance-redshift relation as well as the matter power spectrum, both of which affect the weak lensing convergence power spectrum. Some dark-energy models predict additional clustering on very large scales, but this probably cannot be detected by weak lensing alone due to cosmic variance. With reasonable prior information on other cosmological parameters, we find that a survey covering 1000 sq deg down to a limiting magnitude of R=27 can impose constraints comparable to those expected from upcoming type Ia supernova and number-count surveys. This result, however, is contingent on the control of both observational and theoretical systematics. Concentrating on the latter, we find that the nonlinear power spectrum of matter perturbations and the redshift distribution of source galaxies both need to be determined accurately in order for weak lensing to achieve its full potential. Finally, we discuss the sensitivity of the three-point statistics to dark energy.

Dragan Huterer

2002-02-12T23:59:59.000Z

139

Dark Stars: the First Stars in the Universe may be powered by Dark Matter Heating  

E-Print Network [OSTI]

A new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion. Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel.

Katherine Freese; Peter Bodenheimer; Paolo Gondolo; Douglas Spolyar

2008-12-28T23:59:59.000Z

140

Clustering properties of dynamical dark energy models  

SciTech Connect (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 nonminimally coupled to dark matter.

Avelino, P. P.; Beca, L. M. G. [Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Martins, C. J. A. P. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas s/n, 4150-762 Porto (Portugal); DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2008-05-15T23:59:59.000Z

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,
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

The Cosmology of Composite Inelastic Dark Matter  

SciTech Connect (OSTI)

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

142

Cluster probes of dark energy clustering  

Science Journals Connector (OSTI)

Cluster abundances are oddly insensitive to canonical early dark energy. Early dark energy with sound speed equal to the speed of light cannot be distinguished from a quintessence model with the equivalent expansion history for zdark energy density, despite the different early growth rate. However, cold early dark energy, with a sound speed much smaller than the speed of light, can give a detectable signature. Combining cluster abundances with cosmic microwave background (CMB) power spectra can determine the early dark energy fraction to 0.3% and distinguish a true sound speed of 0.1 from 1 at 99% confidence. We project constraints on early dark energy from the Euclid cluster survey, as well as the Dark Energy Survey, using both current and projected Planck CMB data, and assess the impact of cluster mass systematics. We also quantify the importance of dark energy perturbations, and the role of sound speed during a crossing of w=-1.

Stephen A. Appleby; Eric V. Linder; Jochen Weller

2013-08-29T23:59:59.000Z

143

Vacuum energy as dark matter  

Science Journals Connector (OSTI)

We consider the vacuum energy of massive quantum fields in an expanding universe. We define a conserved renormalized energy-momentum tensor by means of a comoving cutoff regularization. Using exact solutions for de Sitter space-time, we show that in a certain range of mass and renormalization scales there is a contribution to the vacuum energy density that scales as nonrelativistic matter and that such a contribution becomes dominant at late times. By means of the WKB approximation, we find that these results can be extended to arbitrary Robertson-Walker geometries. We study the range of parameters in which the vacuum energy density would be compatible with current limits on dark matter abundance. Finally, by calculating the vacuum energy in a perturbed Robertson-Walker background, we obtain the speed of sound of density perturbations and show that the vacuum energy density contrast can grow on sub-Hubble scales as in standard cold dark matter scenarios.

F.?D. Albareti; J.?A.?R. Cembranos; A.?L. Maroto

2014-12-05T23:59:59.000Z

144

Josephson junctions and dark energy  

E-Print Network [OSTI]

In a recent paper Beck and Mackey [astro-ph/0603397] argue that the argument we gave in our paper [Phys. Lett. B 606, 77 (2005)] to disprove their claim that dark energy can be discovered in the Lab through noise measurements of Josephson junctions is incorrect. In particular, they emphasize that the measured noise spectrum in Josephson junctions is a consequence of the fluctuation dissipation theorem, while our argument was based on equilibrium statistical mechanics. In this note we show that the fluctuation dissipation relation does not depend upon any shift of vacuum (zero-point) energies, and therefore, as already concluded in our previous paper, dark energy has nothing to do with the proposed measurements.

Philippe Jetzer; Norbert Straumann

2006-04-25T23:59:59.000Z

145

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

146

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

E-Print Network [OSTI]

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

Jian-Hua He; Bin Wang

2008-01-28T23:59:59.000Z

147

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

SciTech Connect (OSTI)

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

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

2008-06-15T23:59:59.000Z

148

Dark Energy, Gravitation and Electromagnetism  

E-Print Network [OSTI]

In the context of the fact that the existence of dark energy causing the accelerated expansion of the universe has been confirmed by the WMAP and the Sloan Digital Sky Survey, we re-examine gravitation itself, starting with the formulation of Sakharov and show that it is possible to obtain gravitation in terms of the electromagnetic charge of elementary particles, once the ZPF and its effects at the Compton scale are taken into account.

B. G. Sidharth

2004-01-08T23:59:59.000Z

149

Dark energy and Josephson junctions  

SciTech Connect (OSTI)

It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum S{sub I}(?) of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, S{sub I}(?) should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function S{sub I}(?). According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of S{sub I}(?) will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms.

Branchina, Vincenzo [Department of Physics, University of Catania, Via Santa Sofia 64, I-95123, Catania (Italy); Liberto, Marco Di; Lodato, Ivano, E-mail: vincenzo.branchina@ct.infn.it, E-mail: madiliberto@ssc.unict.it, E-mail: ivlodato@ssc.unict.it [Scuola Superiore di Catania, Via S. Nullo 5/i, Catania (Italy)

2009-08-01T23:59:59.000Z

150

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

151

Nonthermal dark matter in mirage mediation  

E-Print Network [OSTI]

In mirage-mediation models there exists a modulus field whose mass is O(1000) TeV and its late-decay may significantly change the standard thermal relic scenario of the dark matter. We study nonthermal production of the dark matter directly from the modulus decay, and find that for some parameter regions non-thermally produced neutralinos can become the dark matter.

Minoru Nagai; Kazunori Nakayama

2007-09-25T23:59:59.000Z

152

Thermodynamics of interacting holographic dark energy  

E-Print Network [OSTI]

The thermodynamics of a scheme of dark matter-dark energy interaction is studied considering a holographic model for the dark energy in a flat Friedmann-Lemaitre-Robertson-Walker background. We obtain a total entropy rate for a general horizon and study the Generalized Second Law of Thermodynamics. In addition, we study two horizons related to the Ricci and Ricci-like model and its effect on an interacting system.

Arevalo, Fabiola; Pena, Francisco

2014-01-01T23:59:59.000Z

153

Anapole dark matter at the LHC  

Science Journals Connector (OSTI)

The anapole moment is the only allowed electromagnetic moment for Majorana fermions. Fermionic dark matter acquiring an anapole can have a standard thermal history and be consistent with current direct detection experiments. In this paper, we calculate the collider monojet signatures of anapole dark matter and show that the current LHC results exclude anapole dark matter with mass less than 100 GeV, for an anapole coupling that leads to the correct thermal relic abundance.

Yu Gao; Chiu Man Ho; Robert J. Scherrer

2014-02-12T23:59:59.000Z

154

MiniCLEAN Dark Matter Experiment  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

MiniCLEAN MiniCLEAN Dark Matter Experiment Investigating the field of high energy physics through experiments that strengthen our fundamental understanding of matter, energy,...

155

What are the neutrino masses. Dark matter  

E-Print Network [OSTI]

The arguments connecting detections of a reason of difficulties of a solution of a problem of a cold dark matter are adduced.

V. P. Efrosinin

2010-07-13T23:59:59.000Z

156

Gravitational lensing: a unique probe of dark matter and dark energy  

Science Journals Connector (OSTI)

...fine-scale distribution of dark matter will require exquisite...puzzle of resolving the dark matter question were...astronomers, consider the discovery from two studies of distant...gravitating matter (dark and visible), but actually...implies the presence of an energy density with a negative...

2010-01-01T23:59:59.000Z

157

Dark matter and dark energy accretion on to intermediate-mass black holes  

Science Journals Connector (OSTI)

......Dark matter and dark energy accretion on to intermediate-mass...1428 Buenos Aires, Argentina 2 Consejo Nacional de...AAJ, Buenos Aires, Argentina 3 Instituto Argentino...de Buenos Aires, Argentina In this work we investigate...the so-called dark energy on to an intermediate-mass......

C. Pepe; L. J. Pellizza; G. E. Romero

2012-03-11T23:59:59.000Z

158

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

Science Journals Connector (OSTI)

......future galaxy cluster surveys would constrain cosmological...parameters like the amount of dark energy today or the equation...the recently proposed Dark Energy Survey (DES) (Annis et al...clearly not our case. 2 Dark Energy Survey: http://cosmology......

M. Manera; D. F. Mota

2006-09-21T23:59:59.000Z

159

Dark goo: bulk viscosity as an alternative to dark energy  

SciTech Connect (OSTI)

We present a simple (microscopic) model in which bulk viscosity plays a role in explaining the present acceleration of the universe. The effect of bulk viscosity on the Friedmann equations is to turn the pressure into an 'effective' pressure containing the bulk viscosity. For a sufficiently large bulk viscosity, the effective pressure becomes negative and could mimic a dark energy equation of state. Our microscopic model includes self-interacting spin-zero particles (for which the bulk viscosity is known) that are added to the usual energy content of the universe. We study both background equations and linear perturbations in this model. We show that a dark energy behavior is obtained for reasonable values of the two parameters of the model (i.e. the mass and coupling of the spin-zero particles) and that linear perturbations are well-behaved. There is no apparent fine tuning involved. We also discuss the conditions under which hydrodynamics holds, in particular that the spin-zero particles must be in local equilibrium today for viscous effects to be important.

Gagnon, Jean-Sebastien [Technische Universität Darmstadt, Schlossgartenstrasse 2, 64289, Darmstadt (Germany); Lesgourgues, Julien, E-mail: jean-sebastien.gagnon@physik.tu-darmstadt.de, E-mail: julien.lesgourgues@cern.ch [École Polytechnique Fédérale de Lausanne, CH-1015, Lausanne (Switzerland)

2011-09-01T23:59:59.000Z

160

Dark algae, life on Mars?  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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.

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.


161

Unusual light in dark space revealed by Los Alamos, NASA  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Unusual light in dark space revealed by Los Alamos, NASA Unusual light in dark space revealed by Los Alamos, NASA By looking at the dark spaces between visible galaxies and stars...

162

Cryogenic Particle Detectors in Search for Dark Matter  

E-Print Network [OSTI]

Cryogenic Particle Detectors in Search for Dark Matter Panofsky Prize presentation American;Panofsky Prize Talk - Cryogenic Dark Matter Detectors Page Blas Cabrera - Stanford University Original Motivation for broad international program on cryogenic particle detectors was neutrino physics and dark

California at Berkeley, University of

163

Baryon oscillations and dark-energy constraints from imaging surveys  

Science Journals Connector (OSTI)

......oscillations and dark-energy constraints from imaging surveys Derek Dolney 1...the dependence of dark-energy constraints on survey depth and area...the dependence of dark-energy constraints on survey area. While the......

Derek Dolney; Bhuvnesh Jain; Masahiro Takada

2006-03-01T23:59:59.000Z

164

Measuring dark energy properties with 3D cosmic shear  

Science Journals Connector (OSTI)

......weak-lensing surveys are extremely promising for measuring dark energy properties. gravitational...lensing with other dark energy probes and discuss future surveys and finally we...Gemini) or the Dark Energy Survey (Wester 2005......

A. F. Heavens; T. D. Kitching; A. N. Taylor

2006-11-21T23:59:59.000Z

165

Imprints of dynamical dark energy on weak-lensing measurements  

Science Journals Connector (OSTI)

......Large Synoptic Survey Telescope...g. Joint Dark Energy Mission (JDEM...galaxy redshift surveys and the abundance...spectrum of dark energy P (k), as...to dynamical dark energy is potentially...weak-lensing surveys. The error......

Sirichai Chongchitnan; Lindsay King

2010-09-21T23:59:59.000Z

166

Weak lensing forecasts for dark energy, neutrinos and initial conditions  

Science Journals Connector (OSTI)

......understand the nature of dark energy. Future cosmic shear surveys show exceptional potential for constraining the dark energy equation of state w(z...quantify the potential for a survey to constrain dark energy parameters, we use the......

I. Debono; A. Rassat; A. Réfrégier; A. Amara; T. D. Kitching

2010-05-01T23:59:59.000Z

167

The dark side of galaxy formation  

Science Journals Connector (OSTI)

...formation. | I discuss the discovery of a population of extremely...rsta.2002.1088 The dark side of galaxy formation...October 2002 I discuss the discovery of a population of extremely...Galaxy which creates the dark lanes in our view of...schematic of the spectral energy distribution of a luminous...

2002-01-01T23:59:59.000Z

168

Astrophysical constraints on millicharged atomic dark matter  

E-Print Network [OSTI]

Some models of inelastic dark matter posit the existence of bound states under some new $U(1)'$ gauge symmetry. If this new dark photon kinetically mixes with the standard model photon, then the constituent particles in these bound states can acquire a fractional electric charge. This electric charge renders a dark-matter medium dispersive. We compute this frequency-dependent index of refraction for such a medium and use the frequency-dependent arrival time of light from astrophysical sources to constrain the properties of dark atoms in the medium. Using optical-wavelength observations from the Crab Pulsar, we find the electric millicharge of dark (electrons) protons to be smaller than the electric charge $e$ for dark atom masses below 100 keV, assuming a dark fine structure constant $\\boldsymbol{\\alpha}=1$. We estimate that future broadband observations of gamma-ray bursts can produce constraints on the millicharge of dark atoms with masses in the keV range that are competitive with existing collider constra...

Kvam, Audrey K

2014-01-01T23:59:59.000Z

169

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

2011-08-25T23:59:59.000Z

170

Schwarzschild black hole in dark energy background  

E-Print Network [OSTI]

In this paper we present an exact solution of Einstein's field equations describing the Schwarzschild black hole in dark energy background. It is also regarded as an embedded solution that the Schwarzschild black hole is embedded into the dark energy space producing Schwarzschild-dark energy black hole. It is found that the space-time geometry of Schwarzschild-dark energy solution is non-vacuum Petrov type $D$ in the classification of space-times. We study the energy conditions (like weak, strong and dominant conditions) for the energy-momentum tensor of the Schwarzschild-dark energy solution. We also find that the energy-momentum tensor of the Schwarzschild-dark energy solution violates the strong energy condition due to the negative pressure leading to a repulsive gravitational force of the matter field in the space-time. It is shown that the time-like vector field for an observer in the Schwarzschild-dark energy space is expanding, accelerating, shearing and non-rotating. We investigate the surface gravity and the area of the horizons for the Schwarzschild-dark energy black hole.

Ngangbam Ishwarchandra; Ng. Ibohal; K. Yugindro Singh

2014-09-27T23:59:59.000Z

171

Astrophysical constraints on millicharged atomic dark matter  

E-Print Network [OSTI]

Some models of inelastic dark matter posit the existence of bound states under some new $U(1)'$ gauge symmetry. If this new dark photon kinetically mixes with the standard model photon, then the constituent particles in these bound states can acquire a fractional electric charge. This electric charge renders a dark-matter medium dispersive. We compute this frequency-dependent index of refraction for such a medium and use the frequency-dependent arrival time of light from astrophysical sources to constrain the properties of dark atoms in the medium. Using optical-wavelength observations from the Crab Pulsar, we find the electric millicharge of dark (electrons) protons to be smaller than the electric charge $e$ for dark atom masses below 100 keV, assuming a dark fine structure constant $\\boldsymbol{\\alpha}=1$. We estimate that future broadband observations of gamma-ray bursts can produce constraints on the millicharge of dark atoms with masses in the keV range that are competitive with existing collider constraints.

Audrey K. Kvam; David C. Latimer

2014-12-01T23:59:59.000Z

172

The dark side of galaxy formation  

Science Journals Connector (OSTI)

...far-infrared survey by the infrared...which creates the dark lanes in our view...course of its survey detected it tens...of the spectral energy distribution of...most of their energy in the optical...A (2002) The dark side of galaxy...the SCUBA Lens Survey (Smail et al...

2002-01-01T23:59:59.000Z

173

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

174

Dark energy, cosmological constant and neutrino mixing  

E-Print Network [OSTI]

The today estimated value of dark energy can be achieved by the vacuum condensate induced by neutrino mixing phenomenon. Such a tiny value is recovered for a cut-off of the order of Planck scale and it is linked to the sub eV neutrino mass scale. Contributions to dark energy from auxiliary fields or mechanisms are not necessary in this approach.

A. Capolupo; S. Capozziello; G. Vitiello

2007-05-02T23:59:59.000Z

175

Possible dark energy imprints in gravitational wave spectrum of mixed neutron-dark-energy stars  

E-Print Network [OSTI]

In the present paper we study the oscillation spectrum of neutron stars containing both ordinary matter and dark energy in different proportions. Within the model we consider, the equilibrium configurations are numerically constructed and the results show that the properties of the mixed neuron-dark-energy star can differ significantly when the amount of dark energy in the stars is varied. The oscillations of the mixed neuron-dark-energy stars are studied in the Cowling approximation. As a result we find that the frequencies of the fundamental mode and the higher overtones are strongly affected by the dark energy content. This can be used in the future to detect the presence of dark energy in the neutron stars and to constrain the dark-energy models.

Stoytcho S. Yazadjiev; Daniela D. Doneva

2011-12-19T23:59:59.000Z

176

#LabChat Recap: What is Dark Energy  

Broader source: Energy.gov [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.

177

Dark matter studies entrain nuclear physics  

Science Journals Connector (OSTI)

Abstract 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 M. Fuller

2013-01-01T23:59:59.000Z

178

New Directions in Direct Dark Matter Searches  

E-Print Network [OSTI]

I present the status of direct dark matter detection with specific attention to the experimental results and their phenomenological interpretation in terms of dark matter interactions. In particular I review a new and more general approach to study signals in this field based on non-relativistic operators which parametrize more efficiently the dark matter-nucleus interactions in terms of a very limited number of relevant degrees of freedom. Then I list the major experimental results, pointing out the main uncertainties that affect the theoretical interpretation of the data. Finally, since the underlying theory that describes both the dark matter and the standard model fields is unknown, I address the uncertainties coming from the nature of the interaction. In particular, the phenomenology of a class of models in which the interaction between dark matter particles and target nuclei is of a long-range type is discussed.

Paolo Panci

2014-02-06T23:59:59.000Z

179

Probing the curvature and dark energy  

Science Journals Connector (OSTI)

Two new one-parameter tracking behavior dark energy representations ?=?0/(1+z) and ?=?0ez/(1+z)/(1+z) are used to probe the geometry of the Universe and the property of dark energy. The combined type Ia supernova, Sloan Digital Sky Survey, and Wilkinson Microwave Anisotropy Probe data indicate that the Universe is almost spatially flat and that dark energy contributes about 72% of the matter content of the present universe. The observational data also tell us that ?(0)?-1. It is argued that the current observational data can hardly distinguish different dark energy models to the zeroth order. The transition redshift when the expansion of the Universe changed from deceleration phase to acceleration phase is around zT?0.6 by using our one-parameter dark energy models.

Yungui Gong and Yuan-Zhong Zhang

2005-08-22T23:59:59.000Z

180

Probing the curvature and dark energy  

E-Print Network [OSTI]

Two new one-parameter tracking behavior dark energy representations $\\omega=\\omega_0/(1+z)$ and $\\omega=\\omega_0 e^{z/(1+z)}/(1+z)$ are used to probe the geometry of the Universe and the property of dark energy. The combined type Ia supernova (SN Ia), Sloan Digital Sky Survey (SDSS), and Wilkinson Microwave Anisotropy Probe (WMAP) data indicate that the Universe is almost spatially flat and that dark energy contributes about 72% of the matter content of the present universe. The observational data also tell us that $\\omega(0)\\sim -1$. It is argued that the current observational data can hardly distinguish different dark energy models to the zeroth order. The transition redshift when the expansion of the Universe changed from deceleration phase to acceleration phase is around $z_{\\rm T}\\sim 0.6$ by using our one-parameter dark energy models.

Yungui Gong; Yuan-Zhong Zhang

2005-02-14T23:59:59.000Z

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

Dark Energy: A Short Review  

E-Print Network [OSTI]

The accelerating expansion of the universe is the most surprising cosmological discovery in many decades. In this short review, we briefly summarize theories for the origin of cosmic acceleration and the observational methods being used to test these theories. We then discuss the current observational state of the field, with constraints from the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), Type Ia supernovae (SN), direct measurements of the Hubble constant ($H_0$), and measurements of galaxy and matter clustering. Assuming a flat universe and dark energy with a constant equation-of-state parameter $w = P/\\rho$, the combination of Planck CMB temperature anisotropies, WMAP CMB polarization, the Union2.1 SN compilation, and a compilation of BAO measurements yields $w = -1.10^{+0.08}_{-0.07}$, consistent with a cosmological constant ($w=-1$). However, with these constraints the cosmological constant model predicts a value of $H_0$ that is lower than several of the leading recent estimat...

Mortonson, Michael J; White, Martin

2014-01-01T23:59:59.000Z

182

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

183

Constraints on dissipative unified dark matter  

SciTech Connect (OSTI)

Modern cosmology suggests that the Universe contains two dark components — dark matter and dark energy — both unkown in laboratory physics and both lacking direct evidence. Alternatively, a unified dark sector, described by a single fluid, has been proposed. Dissipation is a common phenomenon in nature and it thus seems natural to consider models dominated by a viscous dark fluid. We focus on the study of bulk viscosity, as isotropy and homogeneity at large scales implies the suppression of shear viscosity, heat flow and diffusion. The generic ansatz ???{sup ?} for the coefficient of bulk viscosity (? denotes the mass/energy density), which for ? = ?1/2 mimics the ?CDM background evolution, offers excellent fits to supernova and H(z) data. We show that viscous dark fluids suffer from large contributions to the integrated Sachs-Wolfe effect (generalising a previous study by Li and Barrow) and a suppression of structure growth at small-scales (as seen from a generalized Meszaros equation). Based on recent observations, we conclude that viscous dark fluid models (with ???{sup ?} and neglecting baryons) are strongly challenged.

Velten, Hermano [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); Schwarz, Dominik J., E-mail: velten@physik.uni-bielefeld.de, E-mail: dschwarz@physik.uni-bielefeld.de [Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld (Germany)

2011-09-01T23:59:59.000Z

184

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

185

Falsifying Field-based Dark Energy Models  

E-Print Network [OSTI]

We survey the application of specific tools to distinguish amongst the wide variety of dark energy models that are nowadays under investigation. The first class of tools is more mathematical in character: the application of the theory of dynamical systems to select the better behaved models, with appropriate attractors in the past and future. The second class of tools is rather physical: the use of astrophysical observations to crack the degeneracy of classes of dark energy models. In this last case the observations related with structure formation are emphasized both in the linear and non-linear regimes. We exemplify several studies based on our research, such as quintom and quinstant dark energy ones. Quintom dark energy paradigm is a hybrid construction of quintessence and phantom fields, which does not suffer from fine-tuning problems associated to phantom field and additionally it preserves the scaling behavior of quintessence. Quintom dark energy is motivated on theoretical grounds as an explanation for the crossing of the phantom divide, i.e. the smooth crossing of the dark energy state equation parameter below the value -1. On the other hand, quinstant dark energy is considered to be formed by quintessence and a negative cosmological constant, the inclusion of this later component allows for a viable mechanism to halt acceleration. We comment that the quinstant dark energy scenario gives good predictions for structure formation in the linear regime, but fails to do that in the non-linear one, for redshifts larger than one. We comment that there might still be some degree of arbitrariness in the selection of the best dark energy models.

Genly Leon; Yoelsy Leyva; Emmanuel N. Saridakis; Osmel Martin; Rolando Cardenas

2009-12-02T23:59:59.000Z

186

Cosmic steps in modeling dark energy  

Science Journals Connector (OSTI)

Past and recent data analyses gave some hints of steps in dark energy. Considering dark energy as a dynamical scalar field, we investigate several models with various steps: a step in the scalar potential, a step in the kinetic term, a step in the energy density, and a step in the equation-of-state parameter w. These toy models provide a workable mechanism to generate steps and features of dark energy. Remarkably, a single real scalar can cross w=-1 dynamically with a step in the kinetic term.

Tower Wang

2009-11-17T23:59:59.000Z

187

The first cryogenic dark matter experiment  

SciTech Connect (OSTI)

An experimental search for dark matter particle candidates using cryogenic detectors requires a low radioactive background environment. The authors discuss the status of a cryogenic dark matter experiment to be performed in the Stanford Underground Facility. The detectors will be cooled in a specially designed cryostat connected to a modified side access Oxford 400 dilution refrigerator. Details of the cryostat design and its operating performance are presented. The effectiveness of the multi-level shield surrounding the cryostat, as well as the background levels expected to be achieved in the pilot experiment are discussed. Finally, the limits which can be set on dark matter candidates with such an experiment are discussed.

Barnes, P.D.; Aubourg, E.; Akerib, D.S.; Cummings, A.; Lange, A.E.; Margulies, S.; Sadoulet, B.; Shutt, T.; Stockwell, W.; White, S.; Young, B.A. (Univ. of California, Berkeley, CA (United States)); Da Silva, A. (Univ. of British Columbia, BC (Canada)); Bauer, D.; Borden, D.; Caldwell, D.O.; Gray, M.; Hale, D.; Lu, A.; Witherell, M.; Yellin, S. (Univ. of California, Santa Barbara, CA (United States)); Cabrera, B.; Chugg, B.; Dougherty, B.L.; Irwin, K.D.; Penn, M.J. (Stanford Univ., Stanford, CA (United States)); Emes, J.; Smith, A.; Smith, G.; Taylor, J.; Wolgast, C.; Haller, E.E. (Lawrence Berkeley Lab., CA (United States)); Pritychenko, B.V.; Pomansky, A.A. (Institute for Nuclear Research, Moscow (Russian Federation)); Ross, R.R. (Univ. of California, Berkeley, CA (United States) Lawrence Berkeley Lab., CA (United States))

1993-11-01T23:59:59.000Z

188

Can dark matter be mostly massless particles?  

E-Print Network [OSTI]

We discuss an overlooked factor in dark matter studies. Namely, if massless particles are captured into a local structure and stop free streaming in the universe, they no longer lose energy by cosmological red-shift, and no longer smear out density fluctuations beyond their ``confinement'' scale. If this occurred at the stage when radiation dominated over baryonic matter in energy density, then these captured massless particles would comprise the major part of dark matter in today's universe, leaving no room for other dark matter scenarios. The most probable such particles are gravitons with non-linear self-interaction.

Xiang-Song Chen

2005-10-31T23:59:59.000Z

189

Probing dark energy with future surveys  

E-Print Network [OSTI]

I review the observational prospects to constrain the equation of state parameter of dark energy and I discuss the potential of future imaging and redshift surveys. Bayesian model selection is used to address the question of the level of accuracy on the equation of state parameter that is required before explanations alternative to a cosmological constant become very implausible. I discuss results in the prediction space of dark energy models. If no significant departure from w=-1 is detected, a precision on w of order 1% will translate into strong evidence against fluid-like dark energy, while decisive evidence will require a precision of order 10^-3.

Roberto Trotta

2006-07-21T23:59:59.000Z

190

Probing the time dependence of dark energy  

SciTech Connect (OSTI)

A new method to investigate a possible time-dependence of the dark energy equation of state w is proposed. We apply this methodology to a combination of data involving one of the most recent type Ia supernova sample (SNLS3) along with the current baryon acoustic oscillation and H(z) measurements. We show that current observations cannot rule out a non-evolving dark energy component (dw/dz = 0). The approach developed here reduces considerably the so-called smearing effect on w determinations and may be useful to probe a possible evolving dark energy component when applied to upcoming observational data.

Barboza Edésio Jr, M. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, Rua Professor Antônio Campos s/n, Mossoró (Brazil); Alcaniz, J.S., E-mail: edesiobarboza@uern.br, E-mail: alcaniz@on.br [Departamento de Astronomia, Observatório Nacional, Rua General José Cristino 77, Rio de Janeiro (Brazil)

2012-02-01T23:59:59.000Z

191

Dynamical system analysis for DBI dark energy interacting with dark matter  

E-Print Network [OSTI]

A dynamical system analysis related to Dirac Born Infeld (DBI) cosmological model has been investigated in this present work. For spatially flat FRW space time, the Einstein field equation for DBI scenario has been used to study the dynamics of DBI dark energy interacting with dark matter. The DBI dark energy model is considered as a scalar field with a nonstandard kinetic energy term. An interaction between the DBI dark energy and dark matter is considered through a phenomenological interaction between DBI scalar field and the dark matter fluid. The field equations are reduced to an autonomous dynamical system by a suitable redefinition of the basic variables. The potential of the DBI scalar field is assumed to be exponential. Finally, critical points are determined, their nature have been analyzed and corresponding cosmological scenario has been discussed.

Mahata, Nilanjana

2015-01-01T23:59:59.000Z

192

A thermodynamic motivation for dark energy  

Science Journals Connector (OSTI)

It is argued that the discovery of cosmic acceleration could have been anticipated ... large scale factor. Therefore, the existence of dark energy—or equivalently, some modified gravity theory—should...

Ninfa Radicella; Diego Pavón

2012-03-01T23:59:59.000Z

193

Dark Energy and the Accelerating Universe  

E-Print Network [OSTI]

The discovery ten years ago that the expansion of the Universe is accelerating put in place the last major building block of the present cosmological model, in which the Universe is composed of 4% baryons, 20% dark matter, and 76% dark energy. At the same time, it posed one of the most profound mysteries in all of science, with deep connections to both astrophysics and particle physics. Cosmic acceleration could arise from the repulsive gravity of dark energy -- for example, the quantum energy of the vacuum -- or it may signal that General Relativity breaks down on cosmological scales and must be replaced. We review the present observational evidence for cosmic acceleration and what it has revealed about dark energy, discuss the various theoretical ideas that have been proposed to explain acceleration, and describe the key observational probes that will shed light on this enigma in the coming years.

Joshua Frieman; Michael Turner; Dragan Huterer

2008-03-07T23:59:59.000Z

194

Disentangling Dark Matter Dynamics with Directional Detection  

SciTech Connect (OSTI)

Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a non-minimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.

Lisanti, Mariangela; Wacker, Jay G.; /SLAC

2009-12-16T23:59:59.000Z

195

Dark Matter Searches with Representing the  

E-Print Network [OSTI]

· Supernova Remnants · Unidentified Gamma-ray Sources · Gamma-Ray Bursts · Solar Physics · Dark Matter #12)United States · California State University at Sonoma (SSU) · University of California at Santa Cruz - Santa

California at Santa Cruz, University of

196

Dark Energy: Observational Evidence and Theoretical Models  

E-Print Network [OSTI]

The book elucidates the current state of the dark energy problem and presents the results of the authors, who work in this area. It describes the observational evidence for the existence of dark energy, the methods and results of constraining of its parameters, modeling of dark energy by scalar fields, the space-times with extra spatial dimensions, especially Kaluza---Klein models, the braneworld models with a single extra dimension as well as the problems of positive definition of gravitational energy in General Relativity, energy conditions and consequences of their violation in the presence of dark energy. This monograph is intended for science professionals, educators and graduate students, specializing in general relativity, cosmology, field theory and particle physics.

Novosyadlyj, B; Shtanov, Yu; Zhuk, A

2015-01-01T23:59:59.000Z

197

Dark Field Microscopy for Analytical Laboratory Courses  

Science Journals Connector (OSTI)

An innovative and inexpensive optical microscopy experiment for a quantitative analysis or an instrumental analysis chemistry course is described. The students have hands-on experience with a dark field microscope and investigate the wavelength dependence ...

Ashley E. Augspurger; Anthony S. Stender; Kyle Marchuk; Thomas J. Greenbowe; Ning Fang

2014-05-01T23:59:59.000Z

198

Is this the end of dark energy?  

E-Print Network [OSTI]

In this paper we investigate the limits imposed by thermodynamics to a dark energy fluid. We obtain the heat capacities and the compressibilities for a dark energy fluid. These thermodynamical variables are easily accessible experimentally for any terrestrial fluid. The thermal and mechanical stabilities require these quantities to be positive. We show that such requirements forbid the existence of a cosmic fluid with negative constant EoS parameter which excludes vacuum energy as a candidate to explain the cosmic acceleration. We also show that the current observational data from SN Ia, BAO and $H(z)$ are in conflict with the physical constraints that a general dark energy fluid with a time-dependent EoS parameter must obey which can be interpreted as an evidence against the dark energy hypothesis. Although our result excludes the vacuum energy, a geometrical cosmological term as originally introduced by Einstein in the field equations remains untouched.

Barboza, Edésio M; Abreu, Éverton M C; Neto, Jorge Ananias

2015-01-01T23:59:59.000Z

199

Dark Energy and the Accelerating Universe  

E-Print Network [OSTI]

The discovery ten years ago that the expansion of the Universe is accelerating put in place the last major building block of the present cosmological model, in which the Universe is composed of 4% baryons, 20% dark matter, and 76% dark energy. At the same time, it posed one of the most profound mysteries in all of science, with deep connections to both astrophysics and particle physics. Cosmic acceleration could arise from the repulsive gravity of dark energy -- for example, the quantum energy of the vacuum -- or it may signal that General Relativity breaks down on cosmological scales and must be replaced. We review the present observational evidence for cosmic acceleration and what it has revealed about dark energy, discuss the various theoretical ideas that have been proposed to explain acceleration, and describe the key observational probes that will shed light on this enigma in the coming years.

Frieman, Joshua; Huterer, Dragan

2008-01-01T23:59:59.000Z

200

What is the Evidence for Dark Matter?  

E-Print Network [OSTI]

Newtonian mechanics indicates that galaxies and galaxy clusters are much more massive than we would have guessed from their luminosities, with the discrepancy being generally attributed to dark matter halos. An alternative hypothesis is that accelerations in very weak gravitational fields are larger than predicted by Newton's laws, and there is no need for dark matter. Even though we do not currently have a satisfactory theory associated with this rival hypothesis, we can ask whether any observational tests could rule it out or prefer it over the dark matter hypothesis. Current evidence suggests that neither hypothesis enjoys a decisive advantage over the other. If dark matter turns out to be the correct interpretation however, then theories of galaxy formation face some quite severe fine-tuning problems.

J A Sellwood

2004-01-20T23:59:59.000Z

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

Muon Fluxes From Dark Matter Annihilation  

E-Print Network [OSTI]

We calculate the muon flux from annihilation of the dark matter in the core of the Sun, in the core of the Earth and from cosmic diffuse neutrinos produced in dark matter annihilation in the halos. We consider model-independent direct neutrino production and secondary neutrino production from the decay of taus produced in the annihilation of dark matter. We illustrate how muon energy distribution from dark matter annihilation has a very different shape than muon flux from atmospheric neutrinos. We consider both the upward muon flux, when muons are created in the rock below the detector, and the contained flux when muons are created in the (ice) detector. We contrast our results to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss. We comment on neutrino flavor dependence and their detection.

Arif Emre Erkoca; Mary Hall Reno; Ina Sarcevic

2009-06-23T23:59:59.000Z

202

Dark atoms: asymmetry and direct detection  

SciTech Connect (OSTI)

We present a simple UV completion of Atomic Dark Matter (aDM) in which heavy right-handed neutrinos decay to induce both dark and lepton number densities. This model addresses several outstanding cosmological problems: the matter/anti-matter asymmetry, the dark matter abundance, the number of light degrees of freedom in the early universe, and the smoothing of small-scale structure. Additionally, this realization of aDM may reconcile the CoGeNT excess with recently published null results and predicts a signal in the CRESST Oxygen band. We also find that, due to unscreened long-range interactions, the residual unrecombined dark ions settle into a diffuse isothermal halo.

Kaplan, David E.; Krnjaic, Gordan Z. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD (United States); Rehermann, Keith R. [Center for Theoretical Physics, MIT, 77 Mass Ave., Cambridge, MA (United States); Wells, Christopher M., E-mail: dkaplan@pha.jhu.edu, E-mail: gordan@pha.jhu.edu, E-mail: krmann@mit.edu, E-mail: christopher.wells@houghton.edu [Department of Physics, Houghton College, 1 Willard Avenue, Houghton, NY (United States)

2011-10-01T23:59:59.000Z

203

Conformal Higgs model: predicted dark energy density  

E-Print Network [OSTI]

Postulated universal Weyl conformal scaling symmetry provides an alternative to the $\\Lambda$CDM paradigm for cosmology. Recent applications to galactic rotation velocities, Hubble expansion, and a model of dark galactic halos explain qualitative phenomena and fit observed data without invoking dark matter. Significant revision of theory relevant to galactic collisions and clusters is implied, but not yet tested. Dark energy is found to be a consequence of conformal symmetry for the Higgs scalar field of electroweak physics. The present paper tests this implication. The conformal Higgs model acquires a gravitational effect described by a modified Friedmann cosmic evolution equation, shown to fit cosmological data going back to the cosmic microwave background epoch. The tachyonic mass parameter of the Higgs model becomes dark energy in the Friedmann equation. A dynamical model of this parameter, analogous to the Higgs mechanism for gauge boson mass, is derived and tested here. An approximate calculation yields a result consistent with the empirical magnitude inferred from Hubble expansion.

R. K. Nesbet

2014-11-03T23:59:59.000Z

204

Dark matter interacts with variable vacuum energy  

E-Print Network [OSTI]

We investigate a spatially flat Friedmann-Robertson-Walker (FRW) scenario with two interacting components, dark matter and variable vacuum energy (VVE) densities, plus two decoupled components, one is a baryon term while the other behaves as a radiation component. We consider a linear interaction in the derivative dark component density. We apply the $\\chi^2$ method to the observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era for the model. It turns out that our model fulfills the severe bound of $\\Omega_{x}(z\\simeq 1100)survey, the future constraints achievable by Euclid and CMBPol experiments, reported for the behavior of the dark energy at early times, and fulfills the stringent bound $\\Omega_{x}(z\\simeq 10^{10})<0.04$ at $2\\sigma$ level in the big-bang nucleosynthesis epoch. We a...

G, Iván E Sánchez

2014-01-01T23:59:59.000Z

205

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

206

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

207

Superheavy sterile neutrinos as dark matter  

E-Print Network [OSTI]

(Chair of Committee) Ronald A. Bryan (Member) S ephen A. Fulling (Member) Thomas Adair, III (Head of Department) May 2000 Major Subject: Physics ABSTRACT Superheavy Sterile Neutrinos as Dark Matter. (May 2000) Yongjun Tang, B. S. , Jilin... this research. Thanks also go to Dr. Ronald A. Bryan and Dr. Stephen A. Fulling for being my committee members. vu TABLE OF CONTENTS CHAPTER Page I INTRODUCTION . II DARK MATTER MODELS III NEUTRINO OSCILLATION . A. Neutrino Oscillation in Vacuum B...

Tang, Yongjun

2012-06-07T23:59:59.000Z

208

Dark Matter Density in Disk Galaxies  

E-Print Network [OSTI]

I show that the predicted densities of the inner dark matter halos in LCDM models of structure formation appear to be higher than estimates from real galaxies and constraints from dynamical friction on bars. This inconsistency would not be a problem for the LCDM model if physical processes that are omitted in the collisionless collapse simulations were able to reduce the dark matter density in the inner halos. I review the mechanisms proposed to achieve the needed density reduction.

J. A. Sellwood

2008-07-12T23:59:59.000Z

209

Dark world and the standard model  

E-Print Network [OSTI]

???????????..?????????..?.?.1 II COSMOLOGY, DARK ENERGY AND REHEATING??.???.?.??..5 Reheating??????????????????????????. 9 Particle Production Due to Elementary Theory????....??.?11 Particle Production Due to Parametric Resonance???...???.12 Dark Matter.... Both of them can be described by scalar field. One objective of my thesis is to try to unify these two different fields into one field but at different stages of universe. In reheating theory, the simplest form of potential...

Zhao, Gang

2009-06-02T23:59:59.000Z

210

Working Group Report: Dark Matter Complementarity (Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond)  

SciTech Connect (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.

Arrenberg, Sebastian; et al.,

2013-10-31T23:59:59.000Z

211

Identifying dark matter interactions in monojet searches  

E-Print Network [OSTI]

We study the discrimination of quark-initiated jets from gluon-initiated jets in monojet searches for dark matter using the technique of averaged jet energy profiles. We demonstrate our results in the context of effective field theories of dark matter interactions with quarks and gluons, but our methods apply more generally to a wide class of models. Different effective theories of dark matter and the standard model backgrounds each have a characteristic quark/gluon fraction for the leading jet. When used in conjunction with the traditional cut-and-count monojet search, the jet energy profile can be used to set stronger bounds on contact interactions of dark matter. In the event of a discovery of a monojet excess at the 14 TeV LHC, contact interactions between dark matter with quarks or with gluons can be differentiated at the 95% confidence level. For a given rate at the LHC, signal predictions at direct detection experiments for different dark matter interactions can span five orders of magnitude. The ability to identify these interactions allows us to make a tighter connection between LHC searches and direct detection experiments.

Prateek Agrawal; Vikram Rentala

2013-12-18T23:59:59.000Z

212

Falsification of dark energy by fluid mechanics  

E-Print Network [OSTI]

The 2011 Nobel Prize in Physics was awarded for the discovery of accelerating supernovae dimness, suggesting a remarkable change in the expansion rate of the Universe from a decrease since the big bang to an increase, driven by anti-gravity forces of a mysterious dark energy material comprising 70% of the Universe mass-energy. Fluid mechanical considerations falsify both the accelerating expansion and dark energy concepts. Kinematic viscosity is neglected in current standard models of self-gravitational structure formation, which rely on cold dark matter CDM condensations and clusterings that are also falsified by fluid mechanics. Weakly collisional CDM particles do not condense but diffuse away. Photon viscosity predicts superclustervoid fragmentation early in the plasma epoch and protogalaxies at the end. At the plasma-gas transition, the plasma fragments into Earth-mass gas planets in trillion planet clumps (proto-globular-star-cluster PGCs). The hydrogen planets freeze to form the dark matter of galaxies and merge to form their stars. Dark energy is a systematic dimming error for Supernovae Ia caused by dark matter planets near hot white dwarf stars at the Chandrasekhar carbon limit. Evaporated planet atmospheres may or may not scatter light from the events depending on the line of sight.

Carl H. Gibson

2012-03-23T23:59:59.000Z

213

Cosmological supersymmetric model of dark energy  

Science Journals Connector (OSTI)

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

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

2012-04-18T23:59:59.000Z

214

Dark Photon Search at BABAR  

SciTech Connect (OSTI)

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

215

DarkLight radiation backgrounds  

SciTech Connect (OSTI)

We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-on, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW CW beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, field emission inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation.

Kalantarians, N. [Department of Physics, Hampton University, Hampton VA 23668 (United States); Collaboration: DarkLight Collaboration

2013-11-07T23:59:59.000Z

216

DarkLight radiation backgrounds  

SciTech Connect (OSTI)

We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-on, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW CW beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, field emission inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation.

Kalantarians, Narbe [University of Texas

2013-11-01T23:59:59.000Z

217

Dark matter and the LHC  

E-Print Network [OSTI]

An abundance of astrophysical evidence indicates that the bulk of matter in the universe is made up of massive, electrically neutral particles that form the dark matter (DM). While the density of DM has been precisely measured, the identity of the DM particle (or particles) is a complete mystery. In fact, within the laws of physics as we know them (the Standard Model, or SM), none of the particles have the right properties to make up DM. Remarkably, many new physics extensions of the SM -- designed to address theoretical issues with the electroweak symmetry breaking sector -- require the introduction of new particles, some of which are excellent DM candidates. As the LHC era begins, there are high hopes that DM particles, along with their associated new matter states, will be produced in pp collisions. We discuss how LHC experiments, along with other DM searches, may serve to determine the identity of DM particles and elucidate the associated physics. Most of our discussion centers around theories with weak-scale supersymmetry, and allows for several different DM candidate particles.

Howard Baer; Xerxes Tata

2008-05-13T23:59:59.000Z

218

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

219

Modified holographic Ricci dark energy coupled to interacting relativistic and non-relativistic dark matter in the nonflat universe  

E-Print Network [OSTI]

The modified holographic Ricci dark energy coupled to interacting relativistic and non-relativistic dark matter is considered in the nonflat Friedmann-Robertson-Walker universe. Through examining the deceleration parameter, one can find that the transition time of the Universe from decelerating to accelerating phase in the interacting holographic Ricci dark energy model is close to that in the $\\Lambda$ cold dark matter model. The evolution of modified holographic Ricci dark energy's state parameter and the evolution of dark matter and dark energy's densities shows that the dark energy holds the dominant position from the near past to the future. By studying the statefinder diagnostic and the evolution of the total pressure, one can find that this model could explain the Universe's transition from the radiation to accelerating expansion stage through the dust stage. According to the $Om$ diagnostic, it is easy to find that when the interaction is weak and the proportion of relativistic dark matter in total da...

Li, En-Kun; Geng, Jin-Ling

2014-01-01T23:59:59.000Z

220

Testable dark energy predictions from current data  

Science Journals Connector (OSTI)

Given a class of dark energy models, constraints from one set of cosmic acceleration observables make predictions for other observables. Here we present the allowed ranges for the expansion rate H(z), distances D(z), and the linear growth function G(z) (as well as other, derived growth observables) from the current combination of cosmological measurements of supernovae, the cosmic microwave background, baryon acoustic oscillations, and the Hubble constant. With a cosmological constant as the dark energy and assuming near-minimal neutrino masses, the growth function is already predicted to better than 2% precision at any redshift, with or without spatial curvature. Direct measurements of growth that match this precision offer the opportunity to stringently test and potentially rule out a cosmological constant. While predictions in the broader class of quintessence models are weaker, it is remarkable that they are typically only a factor of 2–3 less precise than forecasted predictions for future space-based supernovae and Planck CMB measurements. In particular, measurements of growth at any redshift, or the Hubble constant H0, that exceed ?CDM predictions by substantially more than 2% would rule out not only a cosmological constant but also the whole quintessence class, with or without curvature and early dark energy. Barring additional systematic errors hiding in the data, such a discovery would require more exotic explanations of cosmic acceleration such as phantom dark energy, dark energy clustering, or modifications of gravity.

Michael J. Mortonson; Wayne Hu; Dragan Huterer

2010-03-22T23:59:59.000Z

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221

Testable dark energy predictions from current data  

SciTech Connect (OSTI)

Given a class of dark energy models, constraints from one set of cosmic acceleration observables make predictions for other observables. Here we present the allowed ranges for the expansion rate H(z), distances D(z), and the linear growth function G(z) (as well as other, derived growth observables) from the current combination of cosmological measurements of supernovae, the cosmic microwave background, baryon acoustic oscillations, and the Hubble constant. With a cosmological constant as the dark energy and assuming near-minimal neutrino masses, the growth function is already predicted to better than 2% precision at any redshift, with or without spatial curvature. Direct measurements of growth that match this precision offer the opportunity to stringently test and potentially rule out a cosmological constant. While predictions in the broader class of quintessence models are weaker, it is remarkable that they are typically only a factor of 2-3 less precise than forecasted predictions for future space-based supernovae and Planck CMB measurements. In particular, measurements of growth at any redshift, or the Hubble constant H{sub 0}, that exceed {Lambda}CDM predictions by substantially more than 2% would rule out not only a cosmological constant but also the whole quintessence class, with or without curvature and early dark energy. Barring additional systematic errors hiding in the data, such a discovery would require more exotic explanations of cosmic acceleration such as phantom dark energy, dark energy clustering, or modifications of gravity.

Mortonson, Michael J. [Center for Cosmology and AstroParticle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States); Kavli Institute for Cosmological Physics and Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Hu, Wayne [Kavli Institute for Cosmological Physics and Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637 (United States); Huterer, Dragan [Department of Physics, University of Michigan, 450 Church St, Ann Arbor, Michigan 48109-1040 (United States)

2010-03-15T23:59:59.000Z

222

Cosmic Acceleration, Dark Energy and Fundamental Physics  

E-Print Network [OSTI]

A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of general relativity the cause of cosmic acceleration is a highly elastic (p\\sim -rho), very smooth form of energy called ``dark energy'' accounting for about 75% of the Universe. The ``simplest'' explanation for dark energy is the zero-point energy density associated with the quantum vacuum; however, all estimates for its value are many orders-of-magnitude too large. Other ideas for dark energy include a very light scalar field or a tangled network of topological defects. An alternate explanation invokes gravitational physics beyond general relativity. Observations and experiments underway and more precise cosmological measurements and laboratory experiments planned for the next decade will test whether or not dark energy is the quantum energy of the vacuum or something more exotic, and whether or not general relativity can self consistently explain cosmic acceleration. Dark energy is the most conspicuous example of physics beyond the standard model and perhaps the most profound mystery in all of science.

Michael S. Turner; Dragan Huterer

2007-06-26T23:59:59.000Z

223

A Note on Agegraphic Dark Energy  

E-Print Network [OSTI]

Recently a seemingly new model of dynamical dark energy was proposed by Cai et al. by relating the energy density of quantum fluctuations in a Minkowski space-time, namely $\\rho_q \\equiv 3 n^2 m_P^2/t^2$, where $n\\sim {\\cal O}(1)$ and t is the cosmic time, to the present day dark energy density. It is true and significant that such a relation arises naturally when one considers the ultimate limits to solutions in scalar field cosmologies, with q being a canonical scalar field. The model may be adjusted to the present values of dark energy density parameter $\\Omega\\Z{q}$ ($\\simeq 0.73$) and the equation of state $w\\Z{q}$ ($\\simeq -1$) only if the numerical coefficient n takes a reasonably large value, $n> 2.1$, and the present value of a gravitational coupling of q-field to matter can also be large. Here we discuss various problems of this proposal as a viable dark energy model; especially, the bound imposed on the dark energy density parameter $\\Omega\\Z{q} <0.1$ during BBN requires $n< 1$. We conclude t...

Neupane, Ishwaree P

2007-01-01T23:59:59.000Z

224

Non-linear dark energy clustering  

SciTech Connect (OSTI)

We consider a dark energy fluid with arbitrary sound speed and equation of state and discuss the effect of its clustering on the cold dark matter distribution at the non-linear level. We write the continuity, Euler and Poisson equations for the system in the Newtonian approximation. Then, using the time renormalization group method to resum perturbative corrections at all orders, we compute the total clustering power spectrum and matter power spectrum. At the linear level, a sound speed of dark energy different from that of light modifies the power spectrum on observationally interesting scales, such as those relevant for baryonic acoustic oscillations. We show that the effect of varying the sound speed of dark energy on the non-linear corrections to the matter power spectrum is below the per cent level, and therefore these corrections can be well modelled by their counterpart in cosmological scenarios with smooth dark energy. We also show that the non-linear effects on the matter growth index can be as large as 10–15 per cent for small scales.

Anselmi, Stefano; Ballesteros, Guillermo [Dipartimento di Fisica ''G. Galilei'', Università degli Studi di Padova, via Marzolo 8, I-35131 Padua (Italy); Pietroni, Massimo, E-mail: anselmi@pd.infn.it, E-mail: ballesteros@pd.infn.it, E-mail: pietroni@pd.infn.it [INFN — Sezione di Padova, via Marzolo 8, I-35131 Padua (Italy)

2011-11-01T23:59:59.000Z

225

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":""}]}

226

Dark Energy and Life's Ultimate Future  

E-Print Network [OSTI]

The discovery of the present accelerated expansion of space changed everything regarding cosmology and life's ultimate prospects. Both the optimistic scenarios of an ever (but decelerated) expanding universe and of a collapsing universe seem to be no longer available. The final future looks deadly dark. However, the fate of the universe and intelligence depends crucially on the nature of the still mysterious dark energy which drives the accelerated expansion. Depending on its - perhaps time-dependent - equation of state, there is a confusing number of different models now, popularly called Big Rip, Big Whimper, Big Decay, Big Crunch, Big Brunch, Big Splat, etc. This paper briefly reviews possibilities and problems. It also argues that even if our universe is finally doomed, perhaps that doesn't matter ultimately because there might be some kind of eternal recurrence. - Key words: Cosmology, Universe, Dark Energy, Cosmological Constant, Quintessence, Phantom Energy, Inflation, Quantum Gravity, Far Future, Life, Intelligence

Ruediger Vaas

2007-03-19T23:59:59.000Z

227

VDM: a model for vector dark matter  

SciTech Connect (OSTI)

We construct a model based on a new U(1){sub X} gauge symmetry and a discrete Z{sub 2} symmetry under which the new gauge boson is odd. The model contains new complex scalars which carry U(1){sub X} charge but are singlets of the Standard Model. The U(1){sub X} symmetry is spontaneously broken but the Z{sub 2} symmetry is maintained, making the new gauge boson a dark matter candidate. In the minimal version there is only one complex scalar field but by extending the number of scalars to two, the model will enjoy rich phenomenology which comes in various phases. In one phase, CP is spontaneously broken. In the other phase, an accidental Z{sub 2} symmetry appears which makes one of the scalars stable and therefore a dark matter candidate along with the vector boson. We discuss the discovery potential of the model by colliders as well as the direct dark matter searches.

Farzan, Yasaman; RezaeiAkbarieh, Amin, E-mail: yasaman@theory.ipm.ac.ir, E-mail: am_rezaei@physics.sharif.ir [School of physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2012-10-01T23:59:59.000Z

228

Stable Higgs Bosons as Cold Dark Matter  

E-Print Network [OSTI]

In a class of the gauge-Higgs unification models the 4D neutral Higgs boson, which is a part of the extra-dimensional component of the gauge fields, becomes absolutely stable as a consequence of the gauge invariance and dynamically generated new parity, serving as a promising candidate for cold dark matter (CDM). We show that the observed relic abundance of cold dark matter is obtained in the SO(5) x U(1) model in the warped space with the Higgs mass around 70 GeV. The Higgs-nucleon scattering cross section is found to be close to the current CDMS II and XENON10 bounds in the direct detection of dark matter.

Yutaka Hosotani; Pyungwon Ko; Minoru Tanaka

2009-08-03T23:59:59.000Z

229

Electroweak fragmentation functions for dark matter annihilation  

E-Print Network [OSTI]

Electroweak corrections can play a crucial role in dark matter annihilation. The emission of gauge bosons, in particular, leads to a secondary flux consisting of all Standard Model particles, and may be described by electroweak fragmentation functions. To assess the quality of the fragmentation function approximation to electroweak radiation in dark matter annihilation, we have calculated the flux of secondary particles from gauge-boson emission in models with Majorana fermion and vector dark matter, respectively. For both models, we have compared cross sections and energy spectra of positrons and antiprotons after propagation through the galactic halo in the fragmentation function approximation and in the full calculation. Fragmentation functions fail to describe the particle fluxes in the case of Majorana fermion annihilation into light fermions: the helicity suppression of the lowest-order cross section in such models cannot be lifted by the leading logarithmic contributions included in the fragmentation f...

Cavasonza, Leila Ali; Pellen, Mathieu

2014-01-01T23:59:59.000Z

230

Galaxy surveys, inhomogeneous reionization, and dark energy  

E-Print Network [OSTI]

We examine the effect of inhomogeneous reionization on the galaxy power spectrum and the consequences for probing dark energy. To model feedback during reionization, we apply an ansatz setting the galaxy overdensity proportional to the underlying ionization field. Thus, inhomogeneous reionization may leave an imprint in the galaxy power spectrum. We evolve this imprint to low redshift and use the Fisher-matrix formalism to assess the effect on parameter estimation. We show that a combination of low- (z=0.3) and high- (z=3) redshift galaxy surveys can constrain the size of cosmological HII regions during reionization. This imprint can also cause confusion when using baryon oscillations or other features of the galaxy power spectrum to probe the dark energy. We show that when bubbles are large, and hence detectable, our ability to constrain w can be degraded by up to 50%. When bubbles are small, the imprint has little or no effect on measuring dark-energy parameters.

Jonathan R. Pritchard; Steven R. Furlanetto; Marc Kamionkowski

2006-04-18T23:59:59.000Z

231

Studying Dark Energy with Galaxy Cluster Surveys  

E-Print Network [OSTI]

Galaxy cluster surveys provide a powerful means of studying the density and nature of the dark energy. The redshift distribution of detected clusters in a deep, large solid angle SZE or X-ray survey is highly sensitive to the dark energy equation of state. Accurate constraints at the 5% level on the dark energy equation of state require that systematic biases in the mass estimators must be controlled at better than the ~10% level. Observed regularity in the cluster population and the availability of multiple, independent mass estimators suggests these precise measurements are possible. Using hydrodynamical simulations that include preheating, we show that the level of preheating required to explain local galaxy cluster structure has a dramatic effect on X-ray cluster surveys, but only a mild effect on SZE surveys. This suggests that SZE surveys may be optimal for cosmology while X-ray surveys are well suited for studies of the thermal history of the intracluster medium.

Joseph J. Mohr; Brian OShea; August E. Evrard; John Bialek; Zoltan Haiman

2002-08-05T23:59:59.000Z

232

MODELING OBSERVATIONAL CONSTRAINTS FOR DARK MATTER HALOS  

SciTech Connect (OSTI)

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

233

Search for the dark photon and the dark Higgs boson at Belle  

E-Print Network [OSTI]

The dark photon, $A^\\prime$, and the dark Higgs boson, $h^\\prime$, are hypothetical constituents featured in a number of recently proposed Dark Sector Models. Assuming prompt decays of both dark particles, we search for their production in the so-called Higgs-strahlung channel, $e^+e^- \\rightarrow A^\\prime h'$, with $h^\\prime \\rightarrow A^\\prime A^\\prime$. We investigate ten exclusive final-states with $A^\\prime \\rightarrow e^+e^-$, $\\mu^+\\mu^-$, or $\\pi^+\\pi^-$, in the mass ranges $0.1$~GeV/$c^2$~$section, $\\cal B \\times \\sigma_{\\mathrm{Born}}$, on the Born cross section, $\\sigma_{\\mathrm{Born}}$, and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the Standard Model photon and the dark photon, $\\alpha_D \\times \\epsilon^2$. These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final-states $3(\\pi^+\\pi^-)$ and $2(e^+e^-)X$ are the first placed by any experiment. For $\\alpha_D$ equal to 1/137, $m_{h'}<$ 8 GeV/$c^2$, and $m_{A^\\prime}<$ 1 GeV/$c^2$, we exclude values of the mixing parameter, $\\epsilon$, above $\\sim 8 \\times 10^{-4}$.

The Belle Collaboration

2015-01-31T23:59:59.000Z

234

Photometric redshifts for the Dark Energy Survey and VISTA and implications for large-scale structure  

Science Journals Connector (OSTI)

......Photometric redshifts for the Dark Energy Survey and VISTA and implications for...requirements for the proposed Dark Energy Survey (DES) using two sets of mock...of dark energy. The proposed Dark Energy Survey (DES) is one such experiment......

Manda Banerji; Filipe B. Abdalla; Ofer Lahav; Huan Lin

2008-05-21T23:59:59.000Z

235

Dark Energy Constraints from Baryon Acoustic Oscillations  

Science Journals Connector (OSTI)

Baryon acoustic oscillations (BAOs) in the galaxy power spectrum allow us to extract the scale of the comoving sound horizon at recombination, a cosmological standard ruler accurately determined by the cosmic microwave background anisotropy data. We examine various issues important in the use of BAOs to probe dark energy. We find that if we assume a flat universe and priors on ?m, ?mh2, and ?bh2 as expected from the Planck mission, the constraints on dark energy parameters (w0, w') scale much less steeply with survey area than (area)-1/2 for a given redshift range. The constraints on the dark energy density ?X(z), however, do scale roughly with (area)-1/2 due to the strong correlation between H(z) and ?m (which reduces the effect of priors on ?m). Dark energy constraints from BAOs are very sensitive to the assumed linear scale of matter clustering and the redshift accuracy of the survey. For a BAO survey with 0.5 ? z ? 2, ? (R) = 0.4 [corresponding to kmax (z = 0) = 0.086 h Mpc-1], and ?z/ (1 + z) = 0.001, we find = (0.115,0.183) and (0.069, 0.104) for survey areas of 1000 and 10,000 deg2, respectively. We find that it is critical to minimize the bias in the scale estimates in order to derive reliable dark energy constraints. For a 1000 (10,000) deg2 BAO survey, a 1 ? bias in ln H (z) leads to a 2 ? (3 ?) bias in w'. The bias in w' due to the same scale bias from ln DA (z) is slightly smaller and opposite in sign. The results from this paper will be useful in assessing different proposed BAO surveys and guiding the design of optimal dark energy detection strategies.

Yun Wang

2006-01-01T23:59:59.000Z

236

Dark Energy: A Crisis for Fundamental Physics  

SciTech Connect (OSTI)

Astrophysical observations provide robust evidence that our current picture of fundamental physics is incomplete. The discovery in 1998 that the expansion of the Universe is accelerating (apparently due to gravitational repulsion between regions of empty space!) presents us with a profound challenge, at the interface between gravity and quantum mechanics. This "Dark Energy" problem is arguably the most pressing open question in modern fundamental physics. The first talk will describe why the Dark Energy problem constitutes a crisis, with wide-reaching ramifications. One consequence is that we should probe our understanding of gravity at all accessible scales, and the second talk will present experiments and observations that are exploring this issue.

Stubbs, Christopher (Harvard) [Harvard

2010-04-12T23:59:59.000Z

237

Cosmological Evolution of Pilgrim Dark Energy  

E-Print Network [OSTI]

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

Sharif, M

2015-01-01T23:59:59.000Z

238

Asymmetric dark matter and the Sun  

E-Print Network [OSTI]

Cold dark matter particles with an intrinsic matter-antimatter asymmetry do not annihilate after gravitational capture by the Sun and can affect its interior structure. The rate of capture is exponentially enhanced when such particles have self-interactions of the right order to explain structure formation on galactic scales. A `dark baryon' of mass 5 GeV is a natural candidate and has the required relic abundance if its asymmetry is similar to that of ordinary baryons. We show that such particles can solve the `solar composition problem'. The predicted small decrease in the low energy neutrino fluxes may be measurable by the Borexino and SNO+ experiments.

Mads T. Frandsen; Subir Sarkar

2010-06-01T23:59:59.000Z

239

Scalar dark matter in spiral galaxies  

E-Print Network [OSTI]

An exact, axially symmetric solution to the Einstein-Klein-Gordon field equations is employed to model the dark matter in spiral galaxies. The extended rotation curves from a previous analysis are used to fit the model and a very good agreement is found. It is argued that, although our model possesses three parameters to be fitted, it is better than the non-relativistic alternatives in the sense that it is not of a phenomenological nature, since the dark matter would consist entirely of a scalar field.

F. S. Guzman; T. Matos; H. Villegas-Brena

1998-11-09T23:59:59.000Z

240

Likelihood Methods for Cluster Dark Energy Surveys  

E-Print Network [OSTI]

Galaxy cluster counts at high redshift, binned into spatial pixels and binned into ranges in an observable proxy for mass, contain a wealth of information on both the dark energy equation of state and the mass selection function required to extract it. The likelihood of the number counts follows a Poisson distribution whose mean fluctuates with the large-scale structure of the universe. We develop a joint likelihood method that accounts for these distributions. Maximization of the likelihood over a theoretical model that includes both the cosmology and the observable-mass relations allows for a joint extraction of dark energy and cluster structural parameters.

Wayne Hu; J. D. Cohn

2006-02-07T23:59:59.000Z

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 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

242

Evolution of the Dark Matter Distribution at the Galactic Center  

Science Journals Connector (OSTI)

Annihilation radiation from neutralino dark matter at the Galactic center (GC) would be greatly enhanced if the dark matter were strongly clustered around the supermassive black hole (SBH). The existence of a dark matter “spike” is made plausible by the observed, steeply rising stellar density near the GC SBH. Here the time-dependent equations describing gravitational interaction of the dark matter with the stars are solved. Scattering of dark matter particles by stars would substantially lower the dark matter density near the GC SBH over 10 Gyr, due both to kinetic heating and to capture of dark matter particles by the SBH. This evolution implies a decrease by several orders of magnitude in the observable flux of annihilation products compared with models that associate a steep, dark matter spike with the SBH.

David Merritt

2004-05-20T23:59:59.000Z

243

Robustness to systematics for future dark energy probes  

Science Journals Connector (OSTI)

......acoustic oscillation (BAO) surveys. For the simplified systematic...somewhat more robust probe of dark energy parameters than the BAO. We...upcoming large-scale cosmological surveys, such as Dark Energy Survey (DES),1 Baryon Oscillation......

Marisa C. March; Roberto Trotta; Luca Amendola; Dragan Huterer

2011-07-21T23:59:59.000Z

244

Can Holographic dark energy increase the mass of the wormhole?  

E-Print Network [OSTI]

In this work, we have studied accretion of dark energy (DE) onto Morris- Thorne wormhole with three different forms, namely, holographic dark energy, holographic Ricci dark energy and modified holographic Ricci dark energy . Considering the scale factor in power-law form we have observed that as the holographic dark energy accretes onto wormhole, the mass of the wormhole is decreasing. In the next phase we considered three parameterization schemes that are able to get hold of quintessence as well as phantom phases. Without any choice of scale factor we reconstructed Hubble parameter from conservation equation and dark energy densities and subsequently got the mass of the wormhole separately for accretion of the three dark energy candidates. It was observed that if these dark energies accrete onto the wormhole, then for quintessence stage, wormhole mass decreases up to a certain finite value and then again increases to aggressively during phantom phase of the universe.

Surajit Chattopadhyay; Davood Momeni; Aziza Altaibayeva; Ratbay Myrzakulov

2014-11-26T23:59:59.000Z

245

Dark energy model selection with current and future data  

Science Journals Connector (OSTI)

......Y., eds. (2009) New York: Am. Inst. Phys. 179. Bridle S. , King L. New J. Phys. (2007) 9...of Dark Matter and Dark Energy in the Universe: Proceedings...D. B., ed. (2009) New York: Am. Inst. Phys. 53......

Ivan Debono

2014-01-01T23:59:59.000Z

246

Can Holographic dark energy increase the mass of the wormhole?  

E-Print Network [OSTI]

Motivated by the quantum essence of wormholes, in this work, we have studied accretion of dark energy (DE) onto Morris-Thorne wormhole with three different forms, namely, holographic dark energy, holographic Ricci dark energy and modified holographic Ricci dark energy . Considering the scale factor in power-law form we have observed that as the holographic dark energy accrets onto wormhole, the mass of the wormhole is decreasing. In the next phase we considered three parameterization schemes that are able to get hold of quintessence as well as phantom phases. Without any choice of scale factor we reconstructed Hubble parameter from conservation equation and dark energy densities and subsequently got the mass of the wormhole separately for accretion of the three dark energy candidates. It was observed that if these dark energies accrete onto the wormhole, then for quintessence stage, wormhole mass decreases up to a certain finite value and then again increases to aggressively during phantom phase of the universe.

Surajit Chattopadhyay; Davood Momeni; Aziza Altaibayeva; Ratbay Myrzakulov

2014-06-27T23:59:59.000Z

247

On the capture of dark matter by neutron stars  

E-Print Network [OSTI]

We calculate the number of dark matter particles that a neutron star accumulates over its lifetime as it rotates around the center of a galaxy, when the dark matter particle is a self-interacting boson but does not self-annihilate. We take into account dark matter interactions with baryonic matter and the time evolution of the dark matter sphere as it collapses within the neutron star. We show that dark matter self-interactions play an important role in the rapid accumulation of dark matter in the core of the neutron star. We consider the possibility of determining an exclusion region of the parameter space for dark matter mass and dark matter interaction cross sections based on the observation of old neutron stars with strong dark matter self-interactions. We show that for a dark matter density of $~10^3$ GeV/cm$^3$ and dark matter mass $m_\\chi$ less than approximately 10 GeV, there is a potential exclusion region for dark matter interactions with nucleons that is three orders of magnitude more stringent than without self-interactions. The potential exclusion region for dark matter self-interaction cross sections is many orders of magnitude stronger than the current Bullet Cluster limit. For example, for high dark matter density regions, we find that for $m_\\chi\\sim 10$ GeV when the dark matter interaction cross section with the nucleons ranges from $\\sigma_{\\chi n}\\sim 10^{-52}$ cm$^2$ to $10^{-57}$ cm$^2$, the dark matter self-interaction cross section limit is $\\sigma_{\\chi\\chi}ten orders of magnitude stronger than the Bullet Cluster limit.

Tolga Guver; Arif Emre Erkoca; Mary Hall Reno; Ina Sarcevic

2014-04-09T23:59:59.000Z

248

Advanced Dark Energy Physics Telescope (ADEPT)  

SciTech Connect (OSTI)

In 2006, we proposed to NASA a detailed concept study of ADEPT (the Advanced Dark Energy Physics Telescope), a potential space mission to reliably measure the time-evolution of dark energy by conducting the largest effective volume survey of the universe ever done. A peer-review panel of scientific, management, and technical experts reported back the highest possible 'excellent' rating for ADEPT. We have since made substantial advances in the scientific and technical maturity of the mission design. With this Department of Energy (DOE) award we were granted supplemental funding to support specific extended research items that were not included in the NASA proposal, many of which were intended to broadly advance future dark energy research, as laid out by the Dark Energy Task Force (DETF). The proposed work had three targets: (1) the adaptation of large-format infrared arrays to a 2 micron cut-off; (2) analytical research to improve the understanding of the dark energy figure-of- merit; and (3) extended studies of baryon acoustic oscillation systematic uncertainties. Since the actual award was only for {approx}10% of the proposed amount item (1) was dropped and item (2) work was severely restricted, consistent with the referee reviews of the proposal, although there was considerable contradictions between reviewer comments and several comments that displayed a lack of familiarity with the research. None the less, item (3) was the focus of the work. To characterize the nature of the dark energy, ADEPT is designed to observe baryon acoustic oscillations (BAO) in a large galaxy redshift survey and to obtain substantial numbers of high-redshift Type Ia supernovae (SNe Ia). The 2003 Wilkinson Microwave Anisotropy Probe (WMAP) made a precise determination of the BAO 'standard ruler' scale, as it was imprinted on the cosmic microwave background (CMB) at z {approx} 1090. The standard ruler was also imprinted on the pattern of galaxies, and was first detected in 2005 in Sloan Digital Sky Survey (SDSS) data. A measurement of the BAO standard ruler as a function of time (or redshift) would provide powerful and reliable observational data to shed light on dark energy. In particular, the BAO data provide the angular diameter distance to each redshift, and directly give the expansion rate, H(z), at each redshift. The SNe measurements provide luminosity distances. A space mission is required to obtain the three-dimensional position of enormous numbers of galaxies at high redshift. As recognized by the Dark Energy Task Force, BAO systematic errors are naturally low. The following are the key findings: (1) The BAO method is robust. (2) Separation of the spectral and imaging detection focal planes vastly improves spectral identifications. (3) Prisms instead of grisms provide higher throughput and cleaner spectra. Prisms are clearly superior. (4) Lower prism dispersions improve signal-to-noise but high prism dispersions improve systematic. To ensure that the experiment is not systematic limited, a high dispersion should be used. (5) Counter-dispersion of the spectra reduces systematic errors on the redshift determination and assists in the reduction of confusion. (6) Small rolls are very effective for the reduction of confusion. (7) Interlopers can be recognized by a variety of methods, which combine to produce a sufficiently 'clean' survey data set so as not to limit the dark energy results. (8) A space mission can measure the BAO signature to the cosmic variance limit, limited only by statistics and not by systematic. (9) Density field reconstruction allows for significant BAO accuracy improvements, well beyond that assumed by the Dark Energy Task Force. (10) The BAO method is statistically powerful. It is more powerful than previously estimated, and far more powerful than high redshift Type 1a supernovae, for which the ultimate distance accuracy is limited by flux calibration accuracy. (11) The BAO technique is far simpler than the weak lensing technique and likely to produce more robust dark energy solutions.

Charles L. Bennett

2009-03-26T23:59:59.000Z

249

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://janus.astro.umd.edu/SolarSystems/ Planetary Motion Credit: The Astronomy Workshop A collection of interactive web-based programs and Advanced Camera for Surveys #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70% Dark

Osheroff, Douglas D.

250

DARK MATTER Tracing the "Cosmic Web" with Diffuse Gas  

E-Print Network [OSTI]

1 DARK MATTER STARS GAS NEUTRAL HYDROGEN Tracing the "Cosmic Web" with Diffuse Gas Quasar Quasar Absorption Lines Keck/HIRES Quasar Spectrum Observer baryons dark matter potential isotropic UV only on and the radiation field intensity... H I #12;5 GOAL: the primordial dark matter power spectrum

Steidel, Chuck

251

Chaotic scalar fields as models for dark energy Christian Beck*  

E-Print Network [OSTI]

. The nature and origin of the dominating dark energy component are not understood, and many different modelsChaotic scalar fields as models for dark energy Christian Beck* Kavli Institute for Theoretical stochastically quantized self-interacting scalar fields as suitable models to generate dark energy

Beck, Christian

252

Dark Rate of a Photomultiplier at Cryogenic Temperatures  

E-Print Network [OSTI]

When cooled below room temperature, the pulse response of a photomultiplier in the absence of light (dark rate) initially decreases, but then turns around near 250 K and continues to rise all the way down to 4 K. When the photomultiplier is cold, its dark response is burst-like. We have measured the characteristics of the dark response of a photomultiplier.

H. O. Meyer

2008-05-06T23:59:59.000Z

253

Measuring dark energy with the shear triplet statistics  

Science Journals Connector (OSTI)

......measurement of the dark energy properties with future weak lensing survey. 2 BASICS The...KIDS, the planned Dark Energy Survey on the CTIO Blanco...statistics as a dark energy probe in view of future galaxy survey. The main source......

M. Sereno

2007-05-01T23:59:59.000Z

254

Dark energy model selection with current and future data  

Science Journals Connector (OSTI)

......distribution for the dark energy equation-of-state...for a cosmic shear survey with the Euclid probe...primary probes of dark energy, which are weak...using the goal survey parameters, we obtain a dark energy Figure of Merit......

Ivan Debono

2014-01-01T23:59:59.000Z

255

Bayesian model selection for dark energy using weak lensing forecasts  

Science Journals Connector (OSTI)

......cosmic shear surveys show exceptional...constraining the dark energy equation of state...potential for a survey to constrain dark energy parameters for...The fiducial survey will be able...between dynamical dark energy models and lambdaCDM......

Ivan Debono

2014-01-01T23:59:59.000Z

256

Structure formation in cosmologies with oscillating dark energy  

Science Journals Connector (OSTI)

......function performed with the WiggleZ Dark Energy Survey (Drinkwater et al. 2010...error bars are from the WiggleZ Dark Energy Survey. 3.2Redshift drift An important...2011a) using the WiggleZ Dark Energy Survey data. Measurements were done......

F. Pace; C. Fedeli; L. Moscardini; M. Bartelmann

2012-05-11T23:59:59.000Z

257

Probing dark energy with the shear-ratio geometric test  

Science Journals Connector (OSTI)

......CMB) we design an optimal survey for probing dark energy. This shows that a targeted...Belfiore et al. 2005), the Dark Energy Survey on the CTIO (Wester 2005...case for, for example, the Dark Energy Survey on the CTIO Blanco telescope......

A. N. Taylor; T. D. Kitching; D. J. Bacon; A. F. Heavens

2007-02-01T23:59:59.000Z

258

Testing dark energy using pairs of galaxies in redshift space  

Science Journals Connector (OSTI)

......galaxy redshift survey to constrain...signals for dark energy and modified...theory|dark energy|large-scale...future galaxy surveys is to determine...covered by future surveys, it is likely...accepted that the dark energy challenge should......

E. Jennings; C. M. Baugh; S. Pascoli

2012-02-21T23:59:59.000Z

259

On model selection forecasting, dark energy and modified gravity  

Science Journals Connector (OSTI)

......be achieved with the dark energy survey (DES) (Wester et...considered. DES is the Dark Energy Survey, PS1 is the Pan-STARRS...imaging (weak lensing) surveys should be able decisively distinguish a dark energy GR model from a DGP......

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

2007-09-21T23:59:59.000Z

260

Bayesian model selection for dark energy using weak lensing forecasts  

Science Journals Connector (OSTI)

......this, but if dark energy really is lambda then...eds. (2009) New York: Am. Inst. Phys...Elgaroy o. , Lahav O. New J. Phys. (2005...Dark Matter and Dark Energy in the Universe-Cline...ed. (2009) New York: Am. Inst. Phys......

Ivan Debono

2014-01-01T23:59:59.000Z

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.


261

CAPUT DARK ENERGY TOPICS, 2013 1. The Cosmological Constant  

E-Print Network [OSTI]

waves rule Physics Today, april 2008, 44 - Colless M. The WiggleZ Dark Energy Survey KIAS workshop 2008 Redshift Surveys ApJ 633, 575 - Seo H-J, Eisenstein D.J., 2005 Probing Dark Energy with Baryonic AcousticCAPUT DARK ENERGY TOPICS, 2013 1 #12;1. The Cosmological Constant - The acceleration

Weijgaert, Rien van de

262

Automation of Calibration System for Dark Energy Survey  

E-Print Network [OSTI]

Automation of Calibration System for Dark Energy Survey Jason Wise1, J. P. Rheault1, D. L. DePoy1 1 from gravitational interactions. The Dark Energy Survey (DES) is a sky survey designed to find. Abstract DECalS is a fully automated remote control program for the Dark Energy Survey spectrophotometric

263

Physiology of dark fermentative growth of Rhodopseudomonas capsulata.  

Science Journals Connector (OSTI)

...requirements for anaerobic dark growth. With fructose...source of carbon and energy for anaerobic dark growth, either...experiments. A survey of potentially fermentable...1. Anaerobic dark growth of R. capsulata...and as the sole energy and electron source...

M T Madigan; J C Cox; H Gest

1980-06-01T23:59:59.000Z

264

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

265

A thermodynamic motivation for dark energy  

E-Print Network [OSTI]

It is argued that the discovery of cosmic acceleration could have been anticipated on thermodynamic grounds, namely, the generalized second law and the approach to equilibrium at large scale factor. Therefore, the existence of dark energy -or equivalently, some modified gravity theory- should have been expected. In general, cosmological models that satisfy the above criteria show compatibility with observational data.

Ninfa Radicella; Diego Pavón

2010-12-02T23:59:59.000Z

266

The World of Dark Shadows Issue 9  

E-Print Network [OSTI]

. 16. MORE DARK SHADOWS BLOOPERS by Jean Peacock When Kathy and I met with many fellow DS fans at Equicon '76. one of the topics of conversation was classic bloope:s. Bec~us~ retaping was too expensive. DS had an abundance of sld~-splltt7ng boo...

Multiple Contributors

1977-01-01T23:59:59.000Z

267

RESEARCH HIGHLIGHTS Dark matter lost and found  

E-Print Network [OSTI]

-component condensate.They considered the limited access inherent to samples confined in a diamond anvil cell the gas disks of two spiral galaxies merge. As spirals have dark-matter haloes, their elliptical offspring­Einstein condensate within a ring- shaped magnetic trap (Phys. Rev. Lett. (in the press); preprint at http

Loss, Daniel

268

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

269

Entanglement in holographic dark energy models  

E-Print Network [OSTI]

We study a process of equilibration of holographic dark energy (HDE) with the cosmic horizon around the dark-energy dominated epoch. This process is characterized by a huge amount of information conveyed across the horizon, filling thereby a large gap in entropy between the system on the brink of experiencing a sudden collapse to a black hole and the black hole itself. At the same time, even in the absence of interaction between dark matter and dark energy, such a process marks a strong jump in the entanglement entropy, measuring the quantum-mechanical correlations between the horizon and its interior. Although the effective quantum field theory (QFT) with a peculiar relationship between the UV and IR cutoffs, a framework underlying all HDE models, may formally account for such a huge shift in the number of distinct quantum states, we show that the scope of such a framework becomes tremendously restricted, devoiding it virtually any application in other cosmological epochs or particle-physics phenomena. The p...

Horvat, R

2010-01-01T23:59:59.000Z

270

Dark matter interacts with variable vacuum energy  

E-Print Network [OSTI]

We investigate a spatially flat Friedmann-Robertson-Walker (FRW) scenario with two interacting components, dark matter and variable vacuum energy (VVE) densities, plus two decoupled components, one is a baryon term while the other behaves as a radiation component. We consider a linear interaction in the derivative dark component density. We apply the $\\chi^2$ method to the observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era for the model. It turns out that our model fulfills the severe bound of $\\Omega_{x}(z\\simeq 1100)measurements from Planck survey, the future constraints achievable by Euclid and CMBPol experiments, reported for the behavior of the dark energy at early times, and fulfills the stringent bound $\\Omega_{x}(z\\simeq 10^{10})<0.04$ at $2\\sigma$ level in the big-bang nucleosynthesis epoch. We also examine the cosmic age problem at high redshift associated with the old quasar APM 08279+5255 and estimate the age of the universe today.

Iván E. Sánchez G

2014-05-06T23:59:59.000Z

271

On the determination of dark energy  

SciTech Connect (OSTI)

I consider some of the issues we face in trying to understand dark energy. Huge fluctuations in the unknown dark energy equation of state can be hidden in distance data, so I argue that model-independent tests which signal if the cosmological constant is wrong are valuable. These can be constructed to remove degeneracies with the cosmological parameters. Gravitational effects can play an important role. Even small inhomogeneity clouds our ability to say something definite about dark energy. I discuss how the averaging problem confuses our potential understanding of dark energy by considering the backreaction from density perturbations to second-order in the concordance model: this effect leads to at least a 10% increase in the dynamical value of the deceleration parameter, and could be significantly higher. Large Hubble-scale inhomogeneity has not been investigated in detail, and could conceivably be the cause of apparent cosmic acceleration. I discuss void models which defy the Copernican principle in our Hubble patch, and describe how we can potentially rule out these models.This article is a summary of two talks given at the Invisible Universe Conference, Paris, 2009.

Clarkson, Chris [Cosmology and Gravity Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa)

2010-06-23T23:59:59.000Z

272

Constraints on Resonant Dark Matter Annihilation  

E-Print Network [OSTI]

by PAMELA and FERMI satellites. In this thesis, we analyze a class of models which allow for dark matter to annihilate through an s-channel resonance. Our analysis takes into account constraints from thermal relic abundance and the recent measurements...

Backovic, Mihailo

2011-07-04T23:59:59.000Z

273

Cluster Survey Studies of the Dark Energy  

E-Print Network [OSTI]

Galaxy cluster surveys are power tools for studying the dark energy. In principle, the equation of state parameter w of the dark energy and its time evolution can be extracted from large solid angle, high yield surveys that deliver tens of thousands of clusters. Robust constraints require accurate knowledge of the survey selection, and crude cluster redshift estimates must be available. A simple survey observable like the cluster flux is connected to the underlying cluster halo mass through a so--called mass--observable relation. The calibration of this mass--observable relation and its redshift evolution is a key challenge in extracting precise cosmological constraints. Cluster survey self--calibration is a technique for meeting this challenge, and it can be applied to large solid angle surveys. In essence, the cluster redshift distribution, the cluster power spectrum, and a limited number of mass measurements can be brought together to calibrate the survey and study the dark energy simultaneously. Additional survey information like the shape of the mass function and its evolution with redshift can then be used to test the robustness of the dark energy constraints.

Joseph J Mohr

2004-08-25T23:59:59.000Z

274

Smoothly evolving supercritical-string dark energy relaxes supersymmetric-dark-matter constraints  

Science Journals Connector (OSTI)

We show that Supercritical-String-Cosmology (SSC) off-equilibrium and time-dependent-dilaton effects lead to a smoothly evolving dark energy for the last 10 billion years in concordance with all presently available astrophysical data. Such effects dilute by a factor O ( 10 ) the supersymmetric dark matter density (neutralinos), relaxing severe WMAP 1, 3 constraints on the SUSY parameter space. Thus, LHC anticipated searches/discoveries may discriminate between conventional and supercritical-string cosmology.

A.B. Lahanas; N.E. Mavromatos; D.V. Nanopoulos

2007-01-01T23:59:59.000Z

275

Dark matter and dark energy production in quantum model of the universe  

E-Print Network [OSTI]

The quantum model of the homogeneous, isotropic, and spatially closed universe predicts an existence of two types of collective quantum states in the universe. The states of one type characterize a gravitational field, the others describe a matter (uniform scalar) field. In the first stage of the evolution of the universe a primordial scalar field evolves slowly into its vacuum-like state. In the second stage the scalar field oscillates about an equilibrium due to the quantum fluctuations. The universe is being filled with matter in the form of elementary quantum excitations of the vibrations of the scalar field. The separate quantum excitations are characterized by non-zero values of their energies (masses). Under the action of gravitational forces mainly these excitations decay into ordinary particles (baryons and leptons) and dark matter. The elementary quantum excitations of the vibrations of the scalar field which have not decayed up to now form dark energy. The numerical estimations lead to realistic values of both the matter density \\Omega_{M} = 0.29 (with the contributions from dark matter, \\Omega_{DM} = 0.25, and optically bright baryons, \\Omega_{stars} = 0.0025) and the dark energy density \\Omega_{X} = 0.71 if one takes that the mean energy ~ 10 GeV is released in decay of dark energy quantum and fixes baryonic component \\Omega_{B} = 0.04 according to observational data. The energy (mass) of dark energy quantum is equal to ~ 17 GeV and the energy > 2 x 10^{10} GeV is needed in order to detect it. Dark matter particle has the mass ~ 6 GeV. The Jeans mass for dark matter which is considered as a gas of such massive particles is equal to M_{J} ~ 10^{5} M_{\\odot}.

V. E. Kuzmichev; V. V. Kuzmichev

2004-05-24T23:59:59.000Z

276

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

277

Search for pseudoscalar cold dark matter  

SciTech Connect (OSTI)

AH dynamical evidence points to the conclusion that the predominant form of matter in the universe is in a non-luminous form. Furthermore, large scale deviations from uniform Hubble flow, and the recent COBE reports of inhomogeneities in the cosmic microwave background strongly suggest that we live in an exactly closed universe. If this is true, then ordinary baryonic matter could only be a minority component (10% at most) of the missing mass, and that what constitutes the majority of the dark matter must involve new physics. The axion is one of very few well motivated candidates which may comprise the dark matter. Additionally it is a `cold` dark-matter candidate which is preferred by the COBE data. We propose to construct and operate an experiment to search for axions which may constitute the dark matter of our own galaxy. As proposed by Sikivie, dark-matter axions may be detected by their stimulated conversion into monochromatic microwave photons in a tunable high-Q cavity inside a strong magnetic field. Our ability to mount an experiment quickly and take data within one year is due to a confluence of three factors. The first is the availability of a compact high field superconducting magnet and a local industrial partner, Wang NMR, who can make a very thermally efficient and economical cryostat for it. The second is an ongoing joint venture with the Institute for Nuclear Research of the Russian Academy of Sciences to do R&D on metalized precision-formed ceramic microwave cavities for the axion search, and INR has commited to providing all the microwave cavity arrays for this experiment, should this proposal be approved. The third is a commitment of very substantial startup capital monies from MIT for all of the state-of-the-art ultra-low noise microwave electronics, to one of our outstanding young collaborators who is joining their faculty.

van Bibber, K.; Stoeffl, W.; LLNL Collaborators

1992-05-29T23:59:59.000Z

278

Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe |  

Broader source: Energy.gov (indexed) [DOE]

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

279

The Universe Adventure - The Search for Dark Matter  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

280

Dark Energy Cam: Fermilab Expands Understanding of Expanding Universe |  

Broader source: Energy.gov (indexed) [DOE]

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

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

New Camera Sheds Light on Dark Energy | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

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

282

New Camera Sheds Light on Dark Energy | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

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

283

Reconstructing Dark Energy : A Comparison of Cosmological Parameters  

E-Print Network [OSTI]

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

Pan, Alexander V

2010-01-01T23:59:59.000Z

284

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

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

285

LHC Bounds on Interactions of Dark Matter  

E-Print Network [OSTI]

We derive limits on the interactions of dark matter with quarks from ATLAS null searches for jets + missing energy based on ~1 fb^-1 of integrated luminosity, using a model-insensitive effective theory framework. We find that the new limits from the LHC significantly extend limits previously derived from CDF data at the Tevatron. Translated into the parameter space of direct searches, these limits are particularly effective for ~GeV mass WIMPs. Our limits indicate tension with isospin violating models satisfying minimal flavor violation which attempt to reconcile the purported CoGeNT excess with Xenon-100, indicating that either a light mediator or nontrivial flavor structure for the dark sector is necessary for a viable reconciliation of CoGeNT with Xenon.

Arvind Rajaraman; William Shepherd; Tim M. P. Tait; Alexander M. Wijangco

2011-08-04T23:59:59.000Z

286

Can Cosmic Structure form without Dark Matter?  

SciTech Connect (OSTI)

One of the prime pieces of evidence for dark matter is the observation of large overdense regions in the universe. Since we know from the cosmic microwave background that the regions that contained the most baryons when the universe was {approx} 400, 000 years old were overdense by only one part in ten thousand, perturbations had to have grown since then by a factor greater than (1 + z{sub *}) {approx_equal} 1180 where z{sub *} is the epoch of recombination. This enhanced growth does not happen in general relativity, so dark matter is needed in the standard theory. We show here that enhanced growth can occur in alternatives to general relativity, in particular in Bekenstein's relativistic version of Modified Newtonian Dynamics (MOND). The vector field introduced in that theory for a completely different reason plays a key role in generating the instability that produces large cosmic structures today.

Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr.; Liguori, Michele; /Fermilab /Padua U. /INFN, Padua

2006-08-01T23:59:59.000Z

287

Can Cosmic Structure form without Dark Matter?  

E-Print Network [OSTI]

One of the prime pieces of evidence for dark matter is the observation of large overdense regions in the universe. Since we know from the cosmic microwave background that the regions that contained the most baryons when the universe was ~400,000 years old were overdense by only one part in ten thousand, perturbations had to have grown since then by a factor greater than $(1+z_*)\\simeq 1180$ where $z_*$ is the epoch of recombination. This enhanced growth does not happen in general relativity, so dark matter is needed in the standard theory. We show here that enhanced growth can occur in alternatives to general relativity, in particular in Bekenstein's relativistic version of MOdified Newtonian Dynamics (MOND). The vector field introduced in that theory for a completely different reason plays a key role in generating the instability that produces large cosmic structures today.

Scott Dodelson; Michele Liguori

2006-08-29T23:59:59.000Z

288

Wiggly cosmic strings accrete dark energy  

E-Print Network [OSTI]

This paper deals with a study of the cylindrically symmetric accretion of dark energy with equation of state $p=w\\rho$ onto wiggly straight cosmic strings. We have obtained that when $w>-1$ the linear energy density in the string core gradually increases tending to a finite maximum value as time increases for all considered dark energy models. On the regime where the dominant energy condition is violated all such models predict a steady decreasing of the linear energy density of the cosmic strings as phantom energy is being accreted. The final state of the string after such an accretion process is a wiggleless defect. It is argued however that if accreation of phantom energy would proceed by successive quantum steps then the defect would continue losing linear energy density until a minimum nonzero value which can be quite smaller than that corresponding to the unperturbed string.

Pedro F. Gonzalez-Diaz; Jose A. Jimenez Madrid

2005-06-29T23:59:59.000Z

289

Interacting vacuum energy in the dark sector  

E-Print Network [OSTI]

We analyse three cosmological scenarios with interaction in the dark sector, which are particular cases of a general expression for the energy flux from vacuum to matter. In the first case the interaction leads to a transition from an unstable de Sitter phase to a radiation dominated universe, avoiding in this way the initial singularity. In the second case the interaction gives rise to a slow-roll power-law inflation. Finally, the third scenario is a concordance model for the late-time universe, with the vacuum term decaying into cold dark matter. We identify the physics behind these forms of interaction and show that they can be described as particular types of the modified Chaplygin gas.

L. P. Chimento; S. Carneiro

2014-04-02T23:59:59.000Z

290

Directional detection of dark matter streams  

Science Journals Connector (OSTI)

Directional detection of weakly interacting massive particles, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local velocity distribution of Galactic dark matter. We investigate the extent to which future directional detectors would be capable of probing dark matter substructure in the form of streams. We analyze the signal expected from a Sagittarius-like stream and also explore the full parameter space of stream speed, direction, dispersion and density. Using a combination of nonparametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times [O(10)??kg?yr for cross sections just below the current exclusion limits] future directional detectors will be sensitive to a wide range of stream velocities and densities. We also examine and discuss the importance of the energy window of the detector.

Ciaran A.?J. O’Hare and Anne M. Green

2014-12-08T23:59:59.000Z

291

LHC bounds on interactions of dark matter  

Science Journals Connector (OSTI)

We derive limits on the interactions of dark matter with quarks from ATLAS null searches for jets+missing energy based on ?1??fb-1 of integrated luminosity, using a model-insensitive effective theory framework. We find that the new limits from the LHC significantly extend limits previously derived from CDF data at the Tevatron. Translated into the parameter space of direct searches, these limits are particularly effective for ???GeV mass weakly interacting massive particles. Our limits indicate tension with isospin-violating models satisfying minimal flavor violation which attempt to reconcile the purported CoGeNT excess with Xenon-100, indicating that either a light mediator or nontrivial flavor structure for the dark sector is necessary for a viable reconciliation of CoGeNT with Xenon.

Arvind Rajaraman; William Shepherd; Tim M. P. Tait; Alexander M. Wijangco

2011-11-09T23:59:59.000Z

292

Axion dark matter detection with cold molecules  

Science Journals Connector (OSTI)

Current techniques cannot detect axion dark matter over much of its parameter space, particularly in the theoretically well-motivated region where the axion decay constant fa lies near the grand unified theory (GUT) and Planck scales. We suggest a novel experimental method to search for QCD axion dark matter in this region. The axion field oscillates at a frequency equal to its mass when it is a component of dark matter. These oscillations induce time varying CP-odd nuclear moments, such as electric dipole and Schiff moments. The coupling between internal atomic fields and these nuclear moments gives rise to time varying shifts to atomic energy levels. These effects can be enhanced by using elements with large Schiff moments such as the light Actinides, and states with large spontaneous parity violation, such as molecules in a background electric field. The energy level shift in such a molecule can be ?10-24??eV or larger. While challenging, this energy shift may be observable in a molecular clock configuration with technology presently under development. The detectability of this energy shift is enhanced by the fact that it is a time varying shift whose oscillation frequency is set by fundamental physics, and is therefore independent of the details of the experiment. This signal is most easily observed in the sub-MHz range, allowing detection when fa is ?1016??GeV, and possibly as low as 1015??GeV. A discovery in such an experiment would not only reveal the nature of dark matter and confirm the axion as the solution to the strong CP problem, it would also provide a glimpse of physics at the highest energy scales, far beyond what can be directly probed in the laboratory.

Peter W. Graham and Surjeet Rajendran

2011-09-15T23:59:59.000Z

293

An Alternative to Particle Dark Matter  

E-Print Network [OSTI]

We propose an alternative to particle dark matter that borrows ingredients of MOdified Newtonian Dynamics (MOND) while adding new key components. The first new feature is a dark matter fluid, in the form of a scalar field with small equation of state and sound speed. This component is critical in reproducing the success of cold dark matter for the expansion history and the growth of linear perturbations, but does not cluster significantly on non-linear scales. Instead, the missing mass problem on non-linear scales is addressed by a modification of the gravitational force law. The force law approximates MOND at large and intermediate accelerations, and therefore reproduces the empirical success of MOND at fitting galactic rotation curves. At ultra-low accelerations, the force law reverts to an inverse-square-law, albeit with a larger Newton's constant. This latter regime is important in galaxy clusters and is consistent with their observed isothermal profiles, provided the characteristic acceleration scale of MOND is mildly varying with scale or mass, such that it is ~12 times higher in clusters than in galaxies. We present an explicit relativistic theory in terms of two scalar fields. The first scalar field is governed by a Dirac-Born-Infeld action and behaves as a dark matter fluid on large scales. The second scalar field also has single-derivative interactions and mediates a fifth force that modifies gravity on non-linear scales. Both scalars are coupled to matter via an effective metric that depends locally on the fields. The form of this effective metric implies the equality of the two scalar gravitational potentials, which ensures that lensing and dynamical mass estimates agree. Further work is needed in order to make both the acceleration scale of MOND and the fraction at which gravity reverts to an inverse-square law explicitly dynamical quantities, varying with scale or mass.

Justin Khoury

2014-12-11T23:59:59.000Z

294

"Dark energy" as conformal dynamics of space  

E-Print Network [OSTI]

The exact solution for dynamic of conform-flat space homogeneous since dynamic equation is given. Conform mode of space metric changing in Global time theory has negative energy density. Swap of energy to this mode from another ones lead to increasing of Universe homogeneity although probability of this swap from local objects is negligibly small. Conform mode is corresponding to "dark energy" in observation astronomy.

D. Burlankov

2006-10-23T23:59:59.000Z

295

The Dark Energy Star and Stability analysis  

E-Print Network [OSTI]

We have proposed a new model of dark energy star consisting of five zones namely, solid core of constant energy density, the thin shell between core and interior, an inhomogeneous interior region with anisotropic pressures, thin shell and the exterior vacuum region. We have discussed various physical properties. The model satisfies all the physical requirements. The stability condition under small linear perturbation has also been discussed.

Piyali Bhar; Farook Rahaman

2015-01-12T23:59:59.000Z

296

Search for the dark photon and the dark Higgs boson at Belle  

E-Print Network [OSTI]

The dark photon, $A^\\prime$, and the dark Higgs boson, $h^\\prime$, are hypothetical constituents featured in a number of recently proposed Dark Sector Models. Assuming prompt decays of both dark particles, we search for their production in the so-called Higgs-strahlung channel, $e^+e^- \\rightarrow A^\\prime h'$, with $h^\\prime \\rightarrow A^\\prime A^\\prime$. We investigate ten exclusive final-states with $A^\\prime \\rightarrow e^+e^-$, $\\mu^+\\mu^-$, or $\\pi^+\\pi^-$, in the mass ranges $0.1$~GeV/$c^2$~$< m_{A^\\prime} < 3.5$~GeV/$c^2$ and $0.2$~GeV/$c^2$~$< m_{h'} < 10.5$~GeV/$c^2$. We also investigate three inclusive final-states, $2(e^+e^-)X$, $2(\\mu^+\\mu^-)X$, and $(e^+e^-)(\\mu^+\\mu^-)X$, where $X$ denotes a dark photon candidate detected via missing mass, in the mass ranges $1.1$~GeV/$c^2$~$< m_{A^\\prime} < 3.5$~GeV/$c^2$ and $2.2$~GeV/$c^2$~$< m_{h'} < 10.5$~GeV/$c^2$. Using the entire $977\\,\\mathrm{fb}^{-1}$ data set collected by Belle, we observe no significant signal. We obtain ind...

,

2015-01-01T23:59:59.000Z

297

Dark energy, dark matter and fermion families in the two measures theory  

E-Print Network [OSTI]

A field theory is proposed where the regular fermionic matter and the dark fermionic matter are different states of the same "primordial" fermion fields. In regime of the fermion densities typical for normal particle physics, each of the primordial fermions splits into three generations identified with regular fermions. In a simple model, this fermion families birth effect is accompanied with the right lepton numbers conservation laws. It is possible to fit the muon to electron mass ratio without fine tuning of the Yukawa coupling constants. When fermion energy density becomes comparable with dark energy density, the theory allows new type of states - Cosmo-Low Energy Physics (CLEP) states. Neutrinos in CLEP state can be both a good candidate for dark matter and responsible for a new type of dark energy. In the latter case the total energy density of the universe is less than it would be in the universe free of fermionic matter at all. The (quintessence) scalar field is coupled to dark matter but its coupling to regular fermionic matter appears to be extremely suppressed.

E. I. Guendelman; A. B. Kaganovich

2004-08-10T23:59:59.000Z

298

Direct and indirect detection of dissipative dark matter  

E-Print Network [OSTI]

We study the constraints from direct detection and solar capture on dark matter scenarios with a subdominant dissipative component. This dissipative dark matter component in general has both a symmetric and asymmetric relic abundance. Dissipative dynamics allow this subdominant dark matter component to cool, resulting in its partial or total collapse into a smaller volume inside the halo (e.g., a dark disk) as well as a reduced thermal velocity dispersion compared to that of normal cold dark matter. We first show that these features considerably relax the limits from direct detection experiments on the couplings between standard model (SM) particles and dissipative dark matter. On the other hand, indirect detection of the annihilation of the symmetric dissipative dark matter component inside the Sun sets stringent and robust constraints on the properties of the dissipative dark matter. In particular, IceCube observations force dissipative dark matter particles with mass above 50 GeV to either have a small coupling to the SM or a low local density in the solar system, or to have a nearly asymmetric relic abundance. Possible helioseismology signals associated with purely asymmetric dissipative dark matter are discussed, with no present constraints.

JiJi Fan; Andrey Katz; Jessie Shelton

2013-12-04T23:59:59.000Z

299

Coherent neutrino scattering in dark matter detectors  

Science Journals Connector (OSTI)

Coherent elastic neutrino-nucleus and weakly interacting massive particle-nucleus interaction signatures are expected to be quite similar. This paper discusses how a next-generation ton-scale dark matter detector could discover neutrino-nucleus coherent scattering, a precisely-predicted standard model process. A high-intensity pion- and muon- decay-at-rest neutrino source recently proposed for oscillation physics at underground laboratories would provide the neutrinos for these measurements. In this paper, we calculate raw rates for various target materials commonly used in dark matter detectors and show that discovery of this interaction is possible with a 2??ton·year GEODM exposure in an optimistic energy threshold and efficiency scenario. We also study the effects of the neutrino source on weakly interacting massive particle sensitivity and discuss the modulated neutrino signal as a sensitivity/consistency check between different dark matter experiments at the Deep Underground Science and Engineering Laboratory. Furthermore, we consider the possibility of coherent neutrino physics with a GEODM module placed within tens of meters of the neutrino source.

A. J. Anderson; J. M. Conrad; E. Figueroa-Feliciano; K. Scholberg; J. Spitz

2011-07-15T23:59:59.000Z

300

Redshift drift exploration for interacting dark energy  

E-Print Network [OSTI]

By detecting redshift drift in the spectra of Lyman-$\\alpha$ forest of distant quasars, Sandage-Loeb (SL) test directly measures the expansion of the universe, covering the "redshift desert" of $2 \\lesssim z \\lesssim5$. Thus this method is definitely an important supplement to the other geometric measurements and will play a crucial role in cosmological constraints. In this paper, we quantify the ability of SL test signal by a CODEX-like spectrograph for constraining interacting dark energy. Four typical interacting dark energy models are considered: (\\romannumeral1) $Q=\\gamma H\\rho_c$, (\\romannumeral2) $Q=\\gamma H\\rho_{de}$, (\\romannumeral3) $Q=\\gamma H_0\\rho_c$, and (\\romannumeral4) $Q=\\gamma H_0\\rho_{de}$. The results show that for all the considered interacting dark energy models, relative to the current joint SN+BAO+CMB+$H_0$ observations, the constraints on $\\Omega_m$ and $H_0$ would be improved by about 60\\% and 30--40\\%, while the constraints on $w$ and $\\gamma$ would be slightly improved, with a 30-y...

Geng, Jia-Jia; Zhang, Jing-Fei; Zhang, Xin

2015-01-01T23:59:59.000Z

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.


301

Tensor Detection Severely Constrains Axion Dark Matter  

E-Print Network [OSTI]

The recent detection of tensor modes by BICEP2 has non-trivial implications for axion dark matter implied by combining the tensor detection with isocurvature constraints from Planck. In this paper the measurement is taken as fact, and its implications considered, though further experimental verification is required. In the simplest inflation models $r=0.2$ implies $H_I=1.1\\times 10^{14}\\text{ GeV}$. If the axion decay constant $f_a>H_I$ then isocurvature constraints effectively rule out the QCD axion as dark matter for $m_a \\lesssim 0.06\\mu$ eV, contributing only a fraction $\\Omega_a/\\Omega_d\\lesssim 10^{-11}(f_a/10^{16}\\text{ GeV})^{5/6}$ (where $\\Omega_i$ is the fraction of the critical density), with misalignment angle $\\theta_i\\lesssim 3.1 \\times 10^{-8}(f_a/10^{16}\\text{ GeV})^{-1/6}$ . Implications of this fine tuning are discussed. Constraints on axion-like particles, as a function of their mass and dark matter fraction are also considered. For heavy axions with $m_a\\gtrsim 10^{-22}\\text{ eV}$ we find ...

Marsh, David J E; Hlozek, Renee; Ferreira, Pedro G

2014-01-01T23:59:59.000Z

302

Dark jets in solar coronal holes  

E-Print Network [OSTI]

A new solar feature termed a dark jet is identified from observations of an extended solar coronal hole that was continuously monitored for over 44 hours by the EUV Imaging Spectrometer on board the Hinode spacecraft in 2011 February 8-10. Line-of-sight velocity maps derived from the coronal Fe XII $\\lambda$195.12 emission line, formed at 1.5 MK, revealed a number of large-scale, jet-like structures that showed significant blueshifts. The structures had either weak or no intensity signal in 193 A filter images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, suggesting that the jets are essentially invisible to imaging instruments. The dark jets are rooted in bright points and occur both within the coronal hole and at the quiet Sun-coronal hole boundary. They exhibit a wide range of shapes, from narrow columns to fan-shaped structures, and sometimes multiple jets are seen close together. A detailed study of one dark jet showed line-of-sight speeds increasing along the jet axis fr...

Young, Peter R

2015-01-01T23:59:59.000Z

303

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

304

Cosmology with Coupled Gravity and Dark Energy  

E-Print Network [OSTI]

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

Ti-Pei Li

2015-01-13T23:59:59.000Z

305

Cosmology with Coupled Gravity and Dark Energy  

E-Print Network [OSTI]

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

Ti-Pei Li

2014-09-01T23:59:59.000Z

306

Electrical dark compacton generator: Theory and simulations  

Science Journals Connector (OSTI)

A modified Colpitts oscillator (MCO) associated with a nonlinear transmission line (NLTL) with intersite nonlinearity is introduced as a self-sustained generator of a train of modulated dark signals with compact shape. Equations of state describing the dynamics of the MCO part are derived and the stationary state is obtained. Using the Routh-Hurwitz criterion, the result of a stability analysis indicates the existence of a limit cycle in certain parameter regimes and there the oscillation of the circuit delivers pulselike electrical signals. The train of generated signals is then transformed into a train of compact modulated dark voltage solitons by the NLTL. The exactness of this analytical analysis is confirmed by numerical simulations performed on the circuit equations. Finally, simulations show the capacity of this circuit to work as a generator of compactlike dark voltage solitons. The performance of the generator, namely, the pulse width and the repetition rate, is controlled by the magnitude of the characteristic parameters of the electronic components of the device.

Fabien Kenmogne; David Yemélé; Paul Woafo

2012-05-22T23:59:59.000Z

307

An inhomogeneous alternative to dark energy?  

E-Print Network [OSTI]

Recently, there have been suggestions that the apparent accelerated expansion of the universe is not caused by repulsive gravitation due to dark energy, but is rather a result of inhomogeneities in the distribution of matter. In this work, we investigate the behaviour of a dust dominated inhomogeneous Lemaitre-Tolman-Bondi universe model, and confront it with various astrophysical observations. We find that such a model can easily explain the observed luminosity distance-redshift relation of supernovae without the need for dark energy, when the inhomogeneity is in the form of an underdense bubble centered near the observer. With the additional assumption that the universe outside the bubble is approximately described by a homogeneous Einstein-de Sitter model, we find that the position of the first CMB peak can be made to match the WMAP observations. Whether or not it is possible to reproduce the entire CMB angular power spectrum in an inhomogeneous model without dark energy, is still an open question.

Havard Alnes; Morad Amarzguioui; Oyvind Gron

2006-04-18T23:59:59.000Z

308

Evolving Dark Energy with w?-1  

Science Journals Connector (OSTI)

Theories of evolving quintessence are constructed that generically lead to deviations from the w=-1 prediction of nonevolving dark energy. The small mass scale that governs evolution, m??10-33??eV, is radiatively stable, and the “Why now?” problem is solved. These results rest on seesaw cosmology: Fundamental physics and cosmology can be broadly understood from only two mass scales, the weak scale v and the Planck scale M. Requiring a scale of dark energy ?DE1/4 governed by v2/M and a radiatively stable evolution rate m? given by v4/M3 leads to a distinctive form for the equation of state w(z). Dark energy resides in the potential of a hidden axion field that is generated by a new QCD-like force that gets strong at the scale ??v2/M??DE1/4. The evolution rate is given by a second seesaw that leads to the axion mass m???2/f, with f?M.

Lawrence J. Hall; Yasunori Nomura; Steven J. Oliver

2005-09-29T23:59:59.000Z

309

Will multiple probes of dark energy find modified gravity?  

SciTech Connect (OSTI)

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

310

SU(5) Grand Unified Model and Dark Matter  

E-Print Network [OSTI]

A dark matter model which is called w-matter or mirror dark matter is concretely constructed based on (f-SU(5))X(w-SU(5)) symmetry. There is no Higgs field and all masses originate from interactions in the present model. W-matter is dark matter relatively to f-matter and vice versa. In high-energy processes or when temperature is very high, visible matter and dark matter can transform from one into another. In such process energy seems to be non-conservational, because dark matter cannot be detected. In low-energy processes or when temperature is low, there is only gravitation interaction of dark matter for visible matter.

Shi-Hao Chen

2009-12-12T23:59:59.000Z

311

Will multiple probes of dark energy find modified gravity?  

Science Journals Connector (OSTI)

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 w0-wa 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.

Charles Shapiro; Scott Dodelson; Ben Hoyle; Lado Samushia; Brenna Flaugher

2010-08-17T23:59:59.000Z

312

Clustering GCG: a viable option for unified dark matter-dark energy?  

E-Print Network [OSTI]

We study the clustering Generalized Chaplygin Gas (GCG) as a possible candidate for dark matter-dark energy unification. The vanishing speed of sound ($c_{s}^2 = 0$) for the GCG fluid can be obtained by incorporating higher derivative operator in the original K-essence Lagrangian. The evolution of the density fluctuations in the GCG+Baryon fluid is studied in the linear regime. The observational constraints on the model are obtained using latest data from SNIa, $H(z)$, BAO and also for the $f\\sigma_{8}$ measurements. The matter power spectra for the allowed parameter values are well behaved without any unphysical features.

Sumit Kumar; Anjan A. Sen

2014-10-21T23:59:59.000Z

313

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.

B. Echenard

2012-05-15T23:59:59.000Z

314

Cosmic dynamics with entropy corrected holographic dark energy  

E-Print Network [OSTI]

We investigate the model of holographic dark energy with logarithmic correction to its energy density. This modification is motivated from the loop quantum gravity corrections to the entropy-area law. We also consider an interaction between dark energy and dark matter. The behavior of the Hubble parameter (specially in the late time) is studied. Besides, conditions under which an accelerated universe can decelerate and also successive acceleration-deceleration phases can be occurred in the evolution of the universe is investigated.

Sadjadi, H Mohseni

2010-01-01T23:59:59.000Z

315

Self-interacting dark matter and the Higgs boson  

Science Journals Connector (OSTI)

Self-interacting dark matter has been suggested in order to overcome the difficulties of the cold dark matter model on galactic scales. We argue that a scalar gauge singlet coupled to the Higgs boson, which could lead to an invisibly decaying Higgs boson, is an interesting candidate for this self-interacting dark matter particle. We also present estimates on the abundance of these particles today as well as the consequences to non-Newtonian forces.

M. C. Bento; O. Bertolami; R. Rosenfeld; L. Teodoro

2000-07-25T23:59:59.000Z

316

Insects Attacking Forage Crops.  

E-Print Network [OSTI]

on alfalfa leaves within web. Also attacks young corn ant1 soqhllm plants near ground. Have three dark spots in triangular shape on sides of most segments. GARDEN WEBWORM. Paqe II. 12. Foliage devoured by very hairy or wooly caterpillars up to 2 inches long... with irregular holes with ragged edges. Dark green worm up to nearly 2 inches long; light-coloretl line down middle of back and on each side of this line is a greenish-brown to black band. General feeder on all fora: ARMYWORM. Page 7. 3. Holes eaten in leaves...

Randolph, N. M.; Garner, C. F.

1961-01-01T23:59:59.000Z

317

Recent Developments in Supersymmetric and Hidden Sector Dark Matter  

SciTech Connect (OSTI)

New results which correlate SUSY dark matter with LHC signals are presented, and a brief review of recent developments in supersymmetric and hidden sector dark matter is given. It is shown that the direct detection of dark matter is very sensitive to the hierarchical SUSY sparticle spectrum and the spectrum is very useful in distinguishing models. It is shown that the prospects of the discovery of neutralino dark matter are very bright on the 'Chargino Wall' due to a copious number of model points on the Wall, where the NLSP is the Chargino, and the spin independent neutralino-proton cross section is maintained at high values in the 10{sup -44} cm{sup 2} range for neutralino masses up to {approx}850 GeV. It is also shown that the direct detection of dark matter along with lepton plus jet signatures and missing energy provide dual, and often complementary, probes of supersymmetry. Finally, we discuss an out of the box possibility for dark matter, which includes dark matter from the hidden sector, which could either consist of extra weakly interacting dark matter (a Stino XWIMP), or milli-charged dark matter arising from the Stueckelberg extensions of the MSSM or the SM.

Feldman, Daniel; Liu Zuowei [Department of Physics, Northeastern University, Boston, MA 02115 (United States); Nath, Pran [Department of Physics, Northeastern University, Boston, MA 02115 (United States); TH Division, PH Department, CERN, CH-1211 Geneva 23 (Switzerland)

2008-11-23T23:59:59.000Z

318

Optimizing New Dark Energy Experiments - Final Scientific Report  

SciTech Connect (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

319

Recent Developments in Supersymmetric and Hidden Sector Dark Matter  

E-Print Network [OSTI]

New results which correlate SUSY dark matter with LHC signals are presented, and a brief review of recent developments in supersymmetric and hidden sector dark matter is given. It is shown that the direct detection of dark matter is very sensitive to the hierarchical SUSY sparticle spectrum and the spectrum is very useful in distinguishing models. It is shown that the prospects of the discovery of neutralino dark matter are very bright on the "Chargino Wall" due to a copious number of model points on the Wall, where the NLSP is the Chargino, and the spin independent neutralino-proton cross section is maintained at high values in the $10^{-44}$cm$^{2}$ range for neutralino masses up to $\\sim 850$ GeV . It is also shown that the direct detection of dark matter along with lepton plus jet signatures and missing energy provide dual, and often complementary, probes of supersymmetry. Finally, we discuss an out of the box possibility for dark matter, which includes dark matter from the hidden sector, which could either consist of extra weakly interacting dark matter (a Stino XWIMP), or milli-charged dark matter arising from the Stueckelberg extensions of the MSSM or the SM.

Daniel Feldman; Zuowei Liu; Pran Nath

2008-06-29T23:59:59.000Z

320

Inert scalar dark matter in an extra dimension inspired model  

E-Print Network [OSTI]

In this paper we analyze a dark matter model inspired by theories with extra dimensions. The dark matter candidate corresponds to the first Kaluza-Klein mode of a real scalar added to the Standard Model. The tower of new particles enriches the calculation of the relic abundance. For large mass splitting, the model converges to the predictions of the inert singlet dark matter model. For nearly degenerate mass spectrum, coannihilations increase the cross-sections used for direct and indirect dark matter searches. Moreover, the Kaluza-Klein zero mode can mix with the SM higgs and further constraints can be applied.

R. A. Lineros; F. A. Pereira dos Santos

2014-11-12T23:59:59.000Z

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

Direct/indirect detection signatures of nonthermally produced dark matter  

E-Print Network [OSTI]

We study direct and indirect detection possibilities of neutralino dark matter produced non-thermally by e.g. the decay of long-lived particles, as is easily implemented in the case of anomaly or mirage mediation models. In this scenario, large self-annihilation cross sections are required to account for the present dark matter abundance, and it leads to significant enhancement of the gamma-ray signature from the Galactic Center and the positron flux from the dark matter annihilation. It is found that GLAST and PAMELA will find the signal or give tight constraints on such nonthermal production scenarios of neutralino dark matter.

Minoru Nagai; Kazunori Nakayama

2008-07-10T23:59:59.000Z

322

Direct/indirect detection signatures of nonthermally produced dark matter  

SciTech Connect (OSTI)

We study direct and indirect detection possibilities of neutralino dark matter produced nonthermally by, e.g., the decay of long-lived particles, as is easily implemented in the case of anomaly or mirage-mediation models. In this scenario, large self-annihilation cross sections are required to account for the present dark matter abundance, and it leads to significant enhancement of the gamma-ray signature from the galactic center and the positron flux from the dark matter annihilation. It is found that GLAST and PAMELA will find the signal or give tight constraints on such nonthermal production scenarios of neutralino dark matter.

Nagai, Minoru [Theory Group, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan); Nakayama, Kazunori [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)

2008-09-15T23:59:59.000Z

323

Backgrounds and Projected Limits from Dark Matter Direct Detection Experiments  

E-Print Network [OSTI]

A simple formula is introduced which indicates the amount by which projections of dark matter direct detection experiments are expected to be degraded due to backgrounds.

Scott Dodelson

2008-12-08T23:59:59.000Z

324

Constraining dark energy using real and mock galaxy surveys.  

E-Print Network [OSTI]

??In this thesis, we study how dark energy may be constrained by measurements of large-scale clustering in future galaxy surveys, and through the imprint of… (more)

CAI, YANCHUAN

2009-01-01T23:59:59.000Z

325

Fermilab | Newsroom | Press Releases | September 3, 2013: Dark...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

presspasspressreleases2013DES-2013-images.html http:www.noao.edunews2013pr1310.php http:www.darkenergysurvey.org Interactive online Dark Energy Camera feature: http:...

326

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

2010-02-06T23:59:59.000Z

327

Reissner-Nordstrom black hole in dark energy background  

E-Print Network [OSTI]

In this paper we propose a stationary solution of Einstein's field equations describing Reissner-Nordstrom black hole in dark energy background. It is to be regarded as the Reissner-Nordstrom black hole is embedded into the dark energy solution producing Reissner-Nordstrom-dark energy black hole. We find that the space-time geometry of Reissner-Nordstrom-dark energy solution is Petrov type $D$ in the classification of space-times. It is also shown that the embedded space-time possesses an energy-momentum tensor of the electromagnetic field interacting with the dark energy having negative pressure. We find the energy-momentum tensor for dark energy violates the the strong energy condition due to the negative pressure, whereas that of the electromagnetic field obeys the strong energy condition. It is shown that the time-like vector field for an observer in the Reissner-Nordstrom-dark energy space is expanding, accelerating, shearing and non-rotating. We investigate the surface gravity of the horizons for the embedded dark energy black hole. The characteristic properties of relativistic dark energy based on the de Sitter solution is discussed in an appendix.

Ngangbam Ishwarchandra; Ng. Ibohal; K. Yugindro Singh

2014-11-29T23:59:59.000Z

328

The Hubble constant and dark energy from cosmological distance measures  

E-Print Network [OSTI]

We study how the determination of the Hubble constant from cosmological distance measures is affected by models of dark energy and vice versa. For this purpose, constraints on the Hubble constant and dark energy are investigated using the cosmological observations of cosmic microwave background, baryon acoustic oscillations and type Ia suprenovae. When one investigates dark energy, the Hubble constant is often a nuisance parameter, thus it is usually marginalized over. On the other hand, when one focuses on the Hubble constant, simple dark energy models such as a cosmological constant and a constant equation of state are usually assumed. Since we do not know the nature of dark energy yet, it is interesting to investigate the Hubble constant assuming some types of dark energy and see to what extent the constraint on the Hubble constant is affected by the assumption concerning dark energy. We show that the constraint on the Hubble constant is not affected much by the assumption for dark energy. We furthermore show that this holds true even if we remove the assumption that the universe is flat. We also discuss how the prior on the Hubble constant affects the constraints on dark energy and/or the curvature of the universe.

Kazuhide Ichikawa; Tomo Takahashi

2007-10-22T23:59:59.000Z

329

Neutrinoless double beta decay can constrain neutrino dark matter  

E-Print Network [OSTI]

We examine how constraints can be placed on the neutrino component of dark matter by an accurate measurement of neutrinoless double beta ($0\

V. Barger; S. L. Glashow; D. Marfatia; K. Whisnant

2002-02-26T23:59:59.000Z

330

Thermodynamics of the unified dark fluid with fast transition  

E-Print Network [OSTI]

In the so-called unified dark fluid models, the dark sector gets simplified because dark matter and dark energy are replaced by a single fluid that behaves as the former at early times and as the latter at late times. In this short paper we analyze this class of models from the thermodynamic viewpoint. While the second law of thermodynamics is satisfied, the first two derivatives of the entropies of the apparent horizon and of the energy components suffer such a sharp oscillation that doubts are raised about the soundness of this class of models.

Ninfa Radicella; Diego Pavon

2014-03-11T23:59:59.000Z

331

Fermilab | Newsroom | Press Releases | August 18, 2014: Dark...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Dark Energy Survey: photos & videos Click on links below images for medium- and high-resolution jpeg images. When using this material please credit Fermilab unless noted otherwise....

332

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

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

in physics: why the expansion of the universe is speeding up. Scientists on the Dark Energy Survey collaboration, including representatives from the U.S. Department of Energy's...

333

Linear and nonlinear instabilities in unified dark energy models  

SciTech Connect (OSTI)

We revisit the paradigm of unified dark energy discussing in detail the averaging problem in this type of scenario, highlighting the need for a full nonlinear treatment. We also address the question of if and how models with one or several dark fluids can be observationally distinguished. Simpler and physically clearer derivations of some key results, most notably on the relation between the generalized Chaplygin gas and the standard ({lambda}CDM) 'concordance' model and on a Jeans-type small-scale instability of some coupled dark energy/dark matter models are presented.

Avelino, P. P.; Beca, L. M. G. [Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Martins, C. J. A. P. [Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Centro de Astrofisica, Universidade do Porto, Rua das Estrelas s/n, 4150-762 Porto (Portugal); Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2008-03-15T23:59:59.000Z

334

Dark spaces could change the way we think about galaxies  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

methane levels three times larger than expected over Four Corners region Probing Fukushima with cosmic rays should help speed cleanup of damaged plant Dark spaces could change...

335

Dark-matter admixed white dwarfs  

Science Journals Connector (OSTI)

We study the equilibrium structures of white dwarfs with dark matter cores formed by non-self-annihilating dark matter (DM) particles with masses ranging from 1 GeV to 100 GeV, which are assumed to form an ideal degenerate Fermi gas inside the stars. For DM particles of mass 10 GeV and 100 GeV, we find that stable stellar models exist only if the mass of the DM core inside the star is less than O(10-3)M? and O(10-6)M?, respectively. The global properties of these stars, and in particular the corresponding Chandrasekhar mass limits, are essentially the same as those of traditional white dwarf models without DM. Nevertheless, in the 10 GeV case, the gravitational attraction of the DM core is strong enough to squeeze the normal matter in the core region to densities above neutron drip, far above those in traditional white dwarfs. For DM with a particle mass of 1 GeV, the DM core inside the star can be as massive as ?0.1M? and affects the global structure of the star significantly. In this case, the radius of a stellar model with DM can be about two times smaller than that of a traditional white dwarf. Furthermore, the Chandrasekhar mass limit can also be decreased by as much as 40%. Our results may have implications on the extent to which type Ia supernovae can be regarded as standard candles—a key assumption in the discovery of dark energy.

S.-C. Leung; M.-C. Chu; L.-M. Lin; K.-W. Wong

2013-06-07T23:59:59.000Z

336

Accretions of Dark Matter and Dark Energy onto ($n+2$)-dimensional Schwarzschild Black Hole and Morris-Thorne Wormhole  

E-Print Network [OSTI]

We have studied accretion of the dark matter and dark energy onto of $(n+2)$-dimensional Schwarzschild black hole and Morris-Thorne wormhole. The mass and the rate of change of mass for $(n+2)$-dimensional Schwarzschild black hole and Morris-Thorne wormhole have been found. We have assumed some candidates of dark energy like holographic dark energy, new agegraphic dark energy, quintessence, tachyon, DBI-essence, etc. The black hole mass and the wormhole mass have been calculated in term of redshift when dark matter and above types of dark energies accrete onto them separately. We have shown that the black hole mass increases and wormhole mass decreases for holographic dark energy, new agegraphic dark energy, quintessence, tachyon accretion and the slope of increasing/decreasing of mass sensitively depends on the dimension. But for DBI-essence accretion, the black hole mass first increases and then decreases and the wormhole mass first decreases and then increases and the slope of increasing/decreasing of mass not sensitively depends on the dimension.

Ujjal Debnath

2015-02-08T23:59:59.000Z

337

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

338

MSSM Inflaton: SUSY Dark Matter and LHC  

SciTech Connect (OSTI)

In this talk we will discuss how inflation can be embedded within a minimal extension of the Standard Model where the inflaton carries the Standard Model charges. There is no need of an ad-hoc scalar field to be introduced in order to explain the temperature anisotropy of the cosmic microwave background radiation, all the ingredients are present within a minimal supersymmetric Standard Model. For the first time inflaton properties can be directly linked to the particle phenomenology, dark matter, and the baryons of the Standard Model.

Mazumdar, A. [Physics Department, Lancaster University, Lancaster, LA1 4YB (United Kingdom) and Niels Bohr Institute, Copenhagen University, Blegdamsvej-17, DK-2100 (Denmark)

2009-09-08T23:59:59.000Z

339

Scalar Dark Matter and Cold Stars  

E-Print Network [OSTI]

In a medium composed of scalar particles with non-zero mass, the range of Van-der-Waals-type scalar mediated interactions among nucleons becomes infinite when the medium makes a transition to a Bose-Einstein condensed phase. We explore this phenomenon in an astrophysical context. Namely, we study the effect of a scalar dark matter background on the equilibrium of degenerate stars.In particular we focus on white dwarfs and the changes induced in their masses and in their radii.

J. A. Grifols

2005-05-30T23:59:59.000Z

340

Newtonian Collapse of Scalar Field Dark Matter  

E-Print Network [OSTI]

In this letter, we develop a Newtonian approach to the collapse of galaxy fluctuations of scalar field dark matter under initial conditions inferred from simple assumptions. The full relativistic system, the so called Einstein-Klein-Gordon, is reduced to the Schr\\"odinger-Newton one in the weak field limit. The scaling symmetries of the SN equations are exploited to track the non-linear collapse of single scalar matter fluctuations. The results can be applied to both real and complex scalar fields.

F. Siddhartha Guzman; L. Arturo Urena-Lopez

2003-03-19T23:59:59.000Z

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

Scalar Field Dark Matter and Galaxy Formation  

E-Print Network [OSTI]

We present a general description of the scalar field dark matter (SFDM) hypothesis in the cosmological context. The scenario of structure formation under such a hypothesis is based on Jeans instabilities of fluctuations of the scalar field. It is shown that it is possible to form stable long lived objects consisting of a wide range of typical galactic masses around $10^{12}M_{\\odot}$ once the parameters of the effective theory are fixed with the cosmological constraints. The energy density at the origin of such an object is smooth as it should.

Miguel Alcubierre; F. Siddhartha Guzman; Tonatiuh Matos; Dario Nunez; L. Arturo Urena-Lopez; Petra Wiederhold

2002-04-18T23:59:59.000Z

342

On Dark Energy and Accelerated Reference Frames  

E-Print Network [OSTI]

The paper is devoted to an explanation of the accelerated rate of expansion of the Universe. Usually the acceleration of the Universe, which is described by FRW metric, is due to dark energy. It is shown that this effect may be considered as a manifestation of torsion tensor for a flat Universe in the realm of Teleparallel gravity. An observer with radial field velocity obey Hubble's Law. As a consequence it is established that this is radial acceleration in a flat Universe. In Eq. (\\ref{24}) the acceleration is written in terms of the deceleration parameter, the Hubble's constant and the proper distance. This may be interpreted as an acceleration of the Universe.

S. C. Ulhoa

2011-12-10T23:59:59.000Z

343

Probing Dark Energy with Neutrino Number  

E-Print Network [OSTI]

From measurements of the cosmic microwave background (CMB), the effective number of neutrino is found to be close to the standard model value Neff = 3.046 for the \\LambdaCDM cosmology. One can obtain the same CMB angular power spectrum as that of \\LambdaCDM for the different value of Neff by using the different dark energy model (i.e. for the different value of w). This degeneracy between Neff and w in CMB can be broken from future galaxy survey using the matter power spectrum.

Seokcheon Lee

2014-10-06T23:59:59.000Z

344

Probing Dark Energy with Neutrino Number  

E-Print Network [OSTI]

From measurements of the cosmic microwave background (CMB), the effective number of neutrino is found to be close to the standard model value Neff = 3.046 for the \\LambdaCDM cosmology. One can obtain the same CMB angular power spectrum as that of \\LambdaCDM for the different value of Neff by using the different dark energy model (i.e. for the different value of w). This degeneracy between Neff and w in CMB can be broken from future galaxy survey using the matter power spectrum.

Lee, Seokcheon

2014-01-01T23:59:59.000Z

345

Dark energy and extending the geodesic equations of motion: its construction and experimental constraints  

E-Print Network [OSTI]

Abstract With the discovery of Dark Energy, DE , there isThe recent discovery of Dark Energy (see [1,2] anddiscovery: with the discovery of Dark Energy, DE , there is

Speliotopoulos, Achilles D.

2010-01-01T23:59:59.000Z

346

Disentangling interacting dark energy cosmologies with the three-point correlation function  

Science Journals Connector (OSTI)

......Oscillation Spectroscopic Survey and Euclid. cosmology...cosmology: theory|dark energy|dark matter|large-scale...Oscillation Spectroscopic Survey (BOSS, Schlegel, White...2009), the WiggleZ Dark Energy Survey (Blake et-al. 2011b......

Michele Moresco; Federico Marulli; Marco Baldi; Lauro Moscardini; Andrea Cimatti

2014-10-01T23:59:59.000Z

347

Hydrodynamical simulations of galaxy clusters in dark energy cosmologies – I. General properties  

Science Journals Connector (OSTI)

......among different dark energy models. For each dark energy model we evaluated the volumes that a cluster survey must cover in order...0, PRIN MIUR 2009 Dark Energy and Cosmology with Large Galaxy Survey and PRIN INAF 2009......

C. De Boni; K. Dolag; S. Ettori; L. Moscardini; V. Pettorino; C. Baccigalupi

2011-08-11T23:59:59.000Z

348

Photometric redshift analysis in the Dark Energy Survey Science Verification data  

Science Journals Connector (OSTI)

......Photometric redshift analysis in the Dark Energy Survey Science Verification data C...redshift performance of the Dark Energy Survey (DES), using the early data...the photometric survey. The Dark Energy Survey (DES; Flaugher 2005) is one......

C. Sánchez; M. Carrasco Kind; H. Lin; R. Miquel; F. B. Abdalla; A. Amara; M. Banerji; C. Bonnett; R. Brunner; D. Capozzi; A. Carnero; F. J. Castander; L. A. N. da Costa; C. Cunha; A. Fausti; D. Gerdes; N. Greisel; J. Gschwend; W. Hartley; S. Jouvel; O. Lahav; M. Lima; M. A. G. Maia; P. Martí; R. L. C. Ogando; F. Ostrovski; P. Pellegrini; M. M. Rau; I. Sadeh; S. Seitz; I. Sevilla-Noarbe; A. Sypniewski; J. de Vicente; T. Abbot; S. S. Allam; D. Atlee; G. Bernstein; J. P. Bernstein; E. Buckley-Geer; D. Burke; M. J. Childress; T. Davis; D. L. DePoy; A. Dey; S. Desai; H. T. Diehl; P. Doel; J. Estrada; A. Evrard; E. Fernández; D. Finley; B. Flaugher; J. Frieman; E. Gaztanaga; K. Glazebrook; K. Honscheid; A. Kim; K. Kuehn; N. Kuropatkin; C. Lidman; M. Makler; J. L. Marshall; R. C. Nichol; A. Roodman; E. Sánchez; B. X. Santiago; M. Sako; R. Scalzo; R. C. Smith; M. E. C. Swanson; G. Tarle; D. Thomas; D. L. Tucker; S. A. Uddin; F. Valdés; A. Walker; F. Yuan; J. Zuntz

2014-01-01T23:59:59.000Z

349

Forecasting neutrino masses from galaxy clustering in the Dark Energy Survey combined with the Planck measurements  

Science Journals Connector (OSTI)

......from galaxy clustering in the Dark Energy Survey combined with the Planck measurements...photometric redshift shells of the Dark Energy Survey (DES) over a volume of 20...in the photometric redshift survey Dark Energy Survey (DES), combined with......

Ofer Lahav; Angeliki Kiakotou; Filipe B. Abdalla; Chris Blake

2010-06-11T23:59:59.000Z

350

Supernova and baryon acoustic oscillation constraints on (new) polynomial dark energy parametrizations: current results and forecasts  

Science Journals Connector (OSTI)

......knowledge of dark energy. In Percival (2010),3 a survey is proposed...forthcoming surveys to describe...features of dark energy. 5CONCLUSIONS...that future surveys will decrease...ignorance about dark energy evolution considerably......

Irene Sendra; Ruth Lazkoz

2012-05-01T23:59:59.000Z

351

Probing decisive answers to dark energy questions from cosmic complementarity and lensing tomography  

Science Journals Connector (OSTI)

......improvements to the dark energy parameter constraints...sophisticated surveys are required...Digital Sky Survey (SDSS...and the Dark Energy Camera Project...deep-space-based-like survey with 10-bin...presented for the dark energy parameters......

Mustapha Ishak

2005-10-21T23:59:59.000Z

352

Generalizing thawing dark energy models: the standard vis-à-vis model independent diagnostics  

Science Journals Connector (OSTI)

......w X for thawing dark energy models which include...Oscillation Spectroscopic Survey data. Our analysis...type of thawing dark energy is favoured up...Oscillation Spectroscopic Survey (BOSS) data...fluid, namely dark energy, in huge abundances......

Debabrata Adak; Debasish Majumdar; Supratik Pal

2014-01-01T23:59:59.000Z

353

Baryonic acoustic oscillations in 21-cm emission: a probe of dark energy out to high redshifts  

Science Journals Connector (OSTI)

......Galaxy redshift surveys are best suited to studies of the dark energy at relatively late...parameters in models of dark energy, with the ability of a survey to discriminate among different models of dark energy governed by the accuracy......

J. Stuart B. Wyithe; Abraham Loeb; Paul M. Geil

2008-01-21T23:59:59.000Z

354

The Dark UNiverse Explorer (DUNE): proposal to ESA’s cosmic vision  

Science Journals Connector (OSTI)

The Dark UNiverse Explorer (DUNE) is a wide- ... imager whose primary goal is the study of dark energy and dark matter with unprecedented precision. For this purpose...2.... DUNE will carry out an all-sky survey,...

A. Refregier

2009-03-01T23:59:59.000Z

355

Matter sourced anisotropic stress for dark energy  

Science Journals Connector (OSTI)

Usually a dark energy as a perfect fluid is characterized by the ratio of pressure to energy density (w=p/?) and the ratio of their perturbations in its rest frame (cs2=?p/??). However, a dark energy would have other characteristics beyond its equation of state and the effective speed of sound. Here the extra property is the anisotropic stress sourced by matter as a simple extension to the perfect fluid model. At the background level, this anisotropic stress is zero with respect to the cosmological principle, but not at the first-order perturbation. We tested the viability of the existence of this kind of anisotropic stress by using the currently available cosmic observations through the geometrical and dynamical measurements. Using the Markov-chain Monte Carlo method, we found that the upper bounds on the anisotropic stress which enters into the summation of the Newtonian potentials should be of the order O(10?3)?m. We did not find any strong evidence for the existence of this matter-sourced anisotropic stress, even in the 1? region.

Baorong Chang; Jianbo Lu; Lixin Xu

2014-11-24T23:59:59.000Z

356

Probing Dark Energy with Constellation-X  

E-Print Network [OSTI]

Constellation-X (Con-X) will carry out two powerful and independent sets of tests of dark energy based on X-ray observations of galaxy clusters, providing comparable accuracy to other leading dark energy probes. The first group of tests will measure the absolute distances to clusters, primarily using measurements of the X-ray gas mass fraction in the largest, dynamically relaxed clusters, but with additional constraining power provided by follow-up observations of the Sunyaev-Zel'dovich (SZ) effect. As with supernovae studies, such data determine the transformation between redshift and true distance, d(z), allowing cosmic acceleration to be measured directly. The second, independent group of tests will use the exquisite spectroscopic capabilities of Con-X to determine scaling relations between X-ray observables and mass. Together with forthcoming X-ray and SZ cluster surveys, these data will help to constrain the growth of structure, which is also a strong function of cosmological parameters.

Rapetti, D; Rapetti, David; Allen, Steven W.

2006-01-01T23:59:59.000Z

357

Probing Dark Energy with Constellation-X  

SciTech Connect (OSTI)

Constellation-X (Con-X) will carry out two powerful and independent sets of tests of dark energy based on X-ray observations of galaxy clusters, providing comparable accuracy to other leading dark energy probes. The first group of tests will measure the absolute distances to clusters, primarily using measurements of the X-ray gas mass fraction in the largest, dynamically relaxed clusters, but with additional constraining power provided by follow-up observations of the Sunyaev-Zel'dovich (SZ) effect. As with supernovae studies, such data determine the transformation between redshift and true distance, d(z), allowing cosmic acceleration to be measured directly. The second, independent group of tests will use the exquisite spectroscopic capabilities of Con-X to determine scaling relations between X-ray observables and mass. Together with forthcoming X-ray and SZ cluster surveys, these data will help to constrain the growth of structure, which is also a strong function of cosmological parameters.

Rapetti, David; Allen, Steven W.; /KIPAC, Menlo Park

2006-09-08T23:59:59.000Z

358

CMB constraints on light dark matter candidates  

E-Print Network [OSTI]

Unveiling the nature of cosmic dark matter is an urgent issue in cosmology. Here we make use of a strategy based on the search for the imprints left on the CMB temperature and polarization spectra by the energy deposition due to annihilations of the most promising dark matter candidate, a stable WIMP of mass 1-20 GeV. A major improvement with respect to previous similar studies is a detailed treatment of the annihilation cascade and its energy deposition in the cosmic gas. This is vital as this quantity is degenerate with the annihilation cross-section . The strongest constraints are obtained from Monte Carlo Markov Chains analysis of the combined WMAP7 and SPT datasets up to lmax = 3100. If annihilation occurs via the e+e- channel, a light WIMP can be excluded at 2-{\\sigma} c.l. as a viable DM candidate in the above mass range. However, if annihilation occurs via {\\mu}+{\\mu}- or {\\tau}+{\\tau}- channels instead we find that WIMPs with mass > 5 GeV might represent a viable cosmological DM candidate. We compare...

Evoli, Carmelo; Ferrara, Andrea

2012-01-01T23:59:59.000Z

359

Holographic Dark Energy with Cosmological Constant  

E-Print Network [OSTI]

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

Hu, Yazhou; Li, Nan; Zhang, Zhenhui

2015-01-01T23:59:59.000Z

360

The Dark Energy Survey Camera (DECam)  

Science Journals Connector (OSTI)

The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the expansion rate of the Universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the survey, the DES Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera that will be mounted at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. CCD production has finished, yielding roughly twice the required 62 2kx4k detectors. The construction of \\{DECam\\} is nearly finished. Integration and commissioning on a “telescope simulator” of the major hardware and software components, except for the optics, recently concluded at Fermilab. Final assembly of the optical corrector has started at University College, London. Some components have already been received at CTIO. “First-light” will be sometime in 2012. This oral presentation concentrates on the technical challenges involved in building \\{DECam\\} (and how we overcame them), and the present status of the instrument.

H. Thomas Diehl

2012-01-01T23:59:59.000Z

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.


361

The Dark Energy Survey Camera (DECam)  

SciTech Connect (OSTI)

The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the expansion rate of the Universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the survey, the DES Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera that will be mounted at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. CCD production has finished, yielding roughly twice the required 62 2k x 4k detectors. The construction of DECam is nearly finished. Integration and commissioning on a 'telescope simulator' of the major hardware and software components, except for the optics, recently concluded at Fermilab. Final assembly of the optical corrector has started at University College, London. Some components have already been received at CTIO. 'First-light' will be sometime in 2012. This oral presentation concentrates on the technical challenges involved in building DECam (and how we overcame them), and the present status of the instrument.

Diehl, H.Thomas; /Fermilab

2011-09-09T23:59:59.000Z

362

Stable gravastars of anisotropic dark energy  

SciTech Connect (OSTI)

Dynamical models of prototype gravastars made of anisotropic dark energy fluid are constructed, in which an infinitely thin spherical shell of a perfect fluid with the equation of state p = (1-{gamma}){sigma} divides the whole spacetime into two regions, the internal region is filled with an anisotropic dark energy fluid, and the external region is the Schwarzschild. It is found that in some cases the models represent the ''bounded excursion'' stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes or normal stars. In the phase space, the region for the ''bounded excursion'' gravastars is very small in comparison to that of black holes, but not empty, as found in our previous papers. Therefore, although the existence of gravastars can not be completely excluded from current analysis, the opposite is not possible either, that is, even if gravastars exist, they do not exclude the existence of black holes.

Chan, R. [Coordenacao de Astronomia e Astrofisica, Observatorio Nacional, Rua General Jose Cristino 77, Sao Cristovao 20921-400, Rio de Janeiro, RJ (Brazil)] [Coordenacao de Astronomia e Astrofisica, Observatorio Nacional, Rua General Jose Cristino 77, Sao Cristovao 20921-400, Rio de Janeiro, RJ (Brazil); Silva, M.F.A. da; Rocha, P. [Departamento de Fisica Teorica, Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier 524, Maracana 20550-900, Rio de Janeiro, RJ (Brazil)] [Departamento de Fisica Teorica, Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier 524, Maracana 20550-900, Rio de Janeiro, RJ (Brazil); Wang, Anzhong, E-mail: chan@on.br, E-mail: mfasnic@gmail.com, E-mail: pedrosennarocha@gmail.com, E-mail: anzhong_wang@baylor.edu [GCAP-CASPER, Department of Physics, Baylor University, Waco, TX 76798 (United States)] [GCAP-CASPER, Department of Physics, Baylor University, Waco, TX 76798 (United States)

2009-03-15T23:59:59.000Z

363

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

E-Print Network [OSTI]

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

R. C. Gupta; Anirudh Pradhan

2009-07-28T23:59:59.000Z

364

Hierarchy in the Phase Space and Dark Matter Astronomy  

E-Print Network [OSTI]

We develop a theoretical framework for describing the hierarchical structure of the phase space of cold dark matter haloes, due to gravitationally bound substructures. Because it includes the full hierarchy of the cold dark matter initial conditions and is hence complementary to the halo model, the stable clustering hypothesis is applied for the first time here to the small-scale phase space structure. As an application, we show that the particle dark matter annihilation signal could be up to two orders of magnitude larger than that of the smooth halo within the Galactic virial radius. The local boost is inversely proportional to the smooth halo density, and thus is O(1) within the solar radius, which could translate into interesting signatures for dark matter direct detection experiments: The temporal correlation of dark matter detection can change by a factor of 2 in the span of 10 years, while there will be significant correlations in the velocity space of dark matter particles. This can introduce O(1) uncertainty in the direction of local dark matter wind, which was believed to be a benchmark of directional dark matter searches or the annual modulation signal.

Niayesh Afshordi; Roya Mohayaee; Edmund Bertschinger

2009-11-02T23:59:59.000Z

365

Phenomenological models for unified dark matter with fast transition  

Science Journals Connector (OSTI)

......alternative to lambdaCDM itself or other forms of dark energy (DE) or modified gravity theories invoked to...against the new data that will become available from surveys such as Dark Energy Survey (DES), Planck and Euclid. It is also relevant......

Marco Bruni; Ruth Lazkoz; Alberto Rozas-Fernández

2013-01-01T23:59:59.000Z

366

The Phenomenology of Gravitino Dark Matter Scenarios in Supergravity Models  

E-Print Network [OSTI]

We review the phenomenology of gravitino dark matter within supergravity framework. Gravitino can be dark matter if it is the lightest supersymmetric particle, which is stable if R-parity is conserved. There are several distinct scenarios depending on what the next to lightest supersymmetric particle (NLSP) is. We discuss the constraints and summarize the phenomenology of neutralino, stau, stop and sneutrino NLSPs.

Yudi Santoso

2009-03-16T23:59:59.000Z

367

Oculomotor Responses to Active Head Movements in Darkness  

E-Print Network [OSTI]

information on head rotation from the vestibular system to the saccade-generating mechanism in the brain stem482 Oculomotor Responses to Active Head Movements in Darkness Formulation and Testing Sistemistica, Università di Pavia, Pavia, Italy Passive head rotation in darkness produces vestibular nystagmus

Ramat, Stefano

368

Anisotropic Dark Energy and the Generalized Second Law of Thermodynamics  

E-Print Network [OSTI]

We consider a Bianchi type $I$ model in which anisotropic dark energy is interacting with dark matter and anisotropic radiation. With this scenario, we investigate the validity of the generalized second law of thermodynamics. It is concluded that the validity of this law depends on different parameters like shear, skewness and equation of state.

M. Sharif; Farida Khanum

2011-11-12T23:59:59.000Z

369

Making the Dark Matter Connection Between Particle Physics and Cosmology  

E-Print Network [OSTI]

recently been determined very accurately by the Wilkinson Microwave Anisotropy Probe (WMAP) [1] to be 23% dark matter and 73% Dark Energy. This leaves only 4% of the content of the energy density of the universe which can be explained by the SM...

Krislock, Abram Michael

2012-10-19T23:59:59.000Z

370

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 energy came in 1990 in a galaxy survey study led by G. Efsthathiou of Cambridge. The analysis

Udgaonkar, Jayant B.

371

What do we really know about dark energy?  

Science Journals Connector (OSTI)

...omega m plane. But future surveys like the Dark Energy Survey (DES) or Euclid (a satellite...the future from large galaxy surveys such as DES or Euclid, which...spectrum. Other tests of whether dark energy is truly a new component in...

2011-01-01T23:59:59.000Z

372

E-Print Network 3.0 - acceleration dark energy Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

dark energy Search Powered by Explorit Topic List Advanced Search Sample search results for: acceleration dark energy Page: << < 1 2 3 4 5 > >> 1 The big picture Victoria...

373

E-Print Network 3.0 - alternative dark energy Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

1 92409 2:12 PMErasing Dark Energy SEEDMAGAZINE.COM Page 1 of 23http:seedmagazine.comcontentarticleerasingdarkenergy Summary: do we need dark energy to explain the...

374

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

375

E-Print Network 3.0 - axion dark matter Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

with Axions Summary: Lecture April 23, 2009 Outline: From neutrons to axions Axion phenomenology Axion dark matter Thursday... Axion phenomenology Axion dark matter Inflationary...

376

E-Print Network 3.0 - axion hot dark Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

with Axions Summary: Lecture April 23, 2009 Outline: From neutrons to axions Axion phenomenology Axion dark matter Thursday... Axion phenomenology Axion dark matter Inflationary...

377

E-Print Network 3.0 - axion cold dark Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

with Axions Summary: Lecture April 23, 2009 Outline: From neutrons to axions Axion phenomenology Axion dark matter Thursday... Axion phenomenology Axion dark matter Inflationary...

378

Dark spot formation relative to ITO surface roughness for polyfluorene  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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.

379

Light Higgses and Dark Matter at Bottom and Charm Factories  

E-Print Network [OSTI]

Neither Dark Matter nor scalar particles in the Higgs sector are ruled out at energies accessible to bottom and charm factories. In Dark Matter searches, the error on the mass of Dark Matter is $\\sim 4$ GeV in the best LHC studies. For light Dark Matter this could represent a 100% (or more) error. In Higgs searches, the presence of a light singlet Higgs can make the LHC Higgs search difficult, if not impossible. If Dark Matter or a Higgs scalar is light, it will {\\it require} a low-energy machine to precisely determine the couplings. We review the models, modes of discovery and rate expectations for these new particle searches at bottom and charm factories. We also discuss the options for new runs at bottom and charm factories relevant for these searches.

Bob McElrath

2007-12-03T23:59:59.000Z

380

Dark radiation from particle decay: cosmological constraints and opportunities  

SciTech Connect (OSTI)

We study particle decay as the origin of dark radiation. After elaborating general properties and useful parametrisations we provide model-independent and easy-to-use constraints from nucleosynthesis, the cosmic microwave background and structure formation. Bounds on branching ratios and mass hierarchies depend in a unique way on the time of decay. We demonstrate their power to exclude well-motivated scenarios taking the example of the lightest ordinary sparticle decaying into the gravitino. We point out signatures and opportunities in cosmological observations and structure formation. For example, if there are two dark decay modes, dark radiation and the observed dark matter with adjustable free-streaming can originate from the same decaying particle, solving small-scale problems of structure formation. Hot dark matter mimicking a neutrino mass scale as deduced from cosmological observations can arise and possibly be distinguished after a discovery. Our results can be used as a guideline for model building.

Hasenkamp, Jasper; Kersten, Jörn, E-mail: Jasper.Hasenkamp@desy.de, E-mail: Joern.Kersten@desy.de [II. Institute for Theoretical Physics, University of Hamburg, 22761 Hamburg (Germany)

2013-08-01T23:59:59.000Z

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

Dark radiation from particle decay: cosmological constraints and opportunities  

E-Print Network [OSTI]

We study particle decay as the origin of dark radiation. After elaborating general properties and useful parametrisations we provide model-independent and easy-to-use constraints from nucleosynthesis, the cosmic microwave background and structure formation. Bounds on branching ratios and mass hierarchies depend in a unique way on the time of decay. We demonstrate their power to exclude well-motivated scenarios taking the example of the lightest ordinary sparticle decaying into the gravitino. We point out signatures and opportunities in cosmological observations and structure formation. For example, if there are two dark decay modes, dark radiation and the observed dark matter with adjustable free-streaming can originate from the same decaying particle, solving small-scale problems of structure formation. Hot dark matter mimicking a neutrino mass scale as deduced from cosmological observations can arise and possibly be distinguished after a discovery. Our results can be used as a guideline for model building.

Jasper Hasenkamp; Jörn Kersten

2014-02-13T23:59:59.000Z

382

Validity of Thermodynamical Laws in Dark Energy Filled Universe  

E-Print Network [OSTI]

We have considered the flat FRW model of the universe which is filled with only dark energy. The general descriptions of first and second laws of thermodynamics are investigated on the apparent horizon and event horizon of the universe. We have assumed the equation of state of three different types of dark energy models. We have examined the validity of first and second laws of thermodynamics on apparent and event horizons for these dark energies. For these dark energy models, it has been found that on the apparent horizon, first and second laws are always valid. On the event horizon, the laws are break down for dark energy models 1 and 2. For model 3, first law cannot be satisfied on the event horizon, but second law may be satisfied at the late stage of the evolution of the universe and so the validity of second law on the event horizon depends on the values of the parameters only.

Samarpita Bhattacharya; Ujjal Debnath

2010-12-26T23:59:59.000Z

383

The CHASE laboratory search for chameleon dark energy  

SciTech Connect (OSTI)

A scalar field is a favorite candidate for the particle responsible for dark energy. However, few theoretical means exist that can simultaneously explain the observed acceleration of the Universe and evade tests of gravity. The chameleon mechanism, whereby the properties of a particle depend upon the local environment, is one possible avenue. We present the results of the Chameleon Afterglow Search (CHASE) experiment, a laboratory probe for chameleon dark energy. CHASE marks a significant improvement other searches for chameleons both in terms of its sensitivity to the photon/chameleon coupling as well as its sensitivity to the classes of chameleon dark energy models and standard power-law models. Since chameleon dark energy is virtually indistinguishable from a cosmological constant, CHASE tests dark energy models in a manner not accessible to astronomical surveys.

Steffen, Jason H.; /Fermilab

2010-11-01T23:59:59.000Z

384

Missing energy signatures of dark matter at the LHC  

Science Journals Connector (OSTI)

We use ATLAS and CMS searches in the monojet + missing energy and monophoton + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing monojet analyses and find that searches with high pT cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter–standard model interactions and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular, spin-independent dark matter–gluon couplings and spin-dependent dark matter–quark couplings, LHC constraints from the monojet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below ?15–70??GeV, depending on the Lorentz structure of the effective couplings. Monophoton limits are somewhat weaker than monojet bounds but still provide an important cross check in the case of a discovery in monojets. We also discuss the possibility that dark matter–standard model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. Further, we discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.

Patrick J. Fox; Roni Harnik; Joachim Kopp; Yuhsin Tsai

2012-03-30T23:59:59.000Z

385

Missing Energy Signatures of Dark Matter at the LHC  

E-Print Network [OSTI]

We use ATLAS and CMS searches in the mono-jet + missing energy and mono-photon + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing mono-jet analyses and find that searches with high p_T cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter-Standard Model interactions, and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular spin-independent dark matter-gluon couplings and spin-dependent dark matter-quark couplings, LHC constraints from the mono-jet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below ~ 15-70 GeV, depending on the Lorentz structure of the effective couplings. Mono-photon limits are somewhat weaker than mono-jet bounds, but still provide an important cross check in the case of a discovery in mono-jets. We also discuss the possibility that dark matter--Standard Model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. We also discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.

Patrick J. Fox; Roni Harnik; Joachim Kopp; Yuhsin Tsai

2011-09-20T23:59:59.000Z

386

Dark matter and dark energy production in quantum model of the universe  

E-Print Network [OSTI]

The quantum model of the homogeneous, isotropic, and spatially closed universe predicts an existence of two types of collective quantum states in the universe. The states of one type characterize a gravitational field, the others describe a matter (uniform scalar) field. In the first stage of the evolution of the universe a primordial scalar field evolves slowly into its vacuum-like state. In the second stage the scalar field oscillates about an equilibrium due to the quantum fluctuations. The universe is being filled with matter in the form of elementary quantum excitations of the vibrations of the scalar field. The separate quantum excitations are characterized by non-zero values of their energies (masses). Under the action of gravitational forces mainly these excitations decay into ordinary particles (baryons and leptons) and dark matter. The elementary quantum excitations of the vibrations of the scalar field which have not decayed up to now form dark energy. The numerical estimations lead to realistic va...

Kuzmichev, V E

2004-01-01T23:59:59.000Z

387

The Future of the Local Large Scale Structure: the roles of Dark Matter and Dark Energy  

E-Print Network [OSTI]

We study the distinct effects of Dark Matter and Dark Energy on the future evolution of nearby large scale structures using constrained N-body simulations. We contrast a model of Cold Dark Matter and a Cosmological Constant (LCDM) with an Open CDM (OCDM) model with the same matter density Omega_m =0.3 and the same Hubble constant h=0.7. Already by the time the scale factor increased by a factor of 6 (29 Gyr from now in LCDM; 78 Gyr from now in OCDM) the comoving position of the Local Group is frozen. Well before that epoch the two most massive members of the Local Group, the Milky Way and Andromeda, will merge. However, as the expansion rates of the scale factor in the two models are different, the Local Group will be receding in physical coordinates from Virgo exponentially in a LCDM model and at a roughly constant velocity in an OCDM model. More generally, in comoving coordinates the future large scale structure will look like a sharpened image of the present structure: the skeleton of the cosmic web will remain the same, but clusters will be more `isolated' and the filaments will become thinner. This implies that the long-term fate of large scale structure as seen in comoving coordinates is determined primarily by the matter density. We conclude that although the LCDM model is accelerating at present due to its Dark Energy component while the OCDM model is non accelerating, their large scale structure in the future will look very similar in comoving coordinates.

Yehuda Hoffman; Ofer Lahav; Gustavo Yepes; Yaniv Dover

2007-10-10T23:59:59.000Z

388

A Dark Year for Tidal Disruption Events  

E-Print Network [OSTI]

The disruption of a main-sequence star by a supermassive black hole results in the initial production of an extended debris stream that winds repeatedly around the black hole, producing a complex three-dimensional figure that may self-intersect. Both analytical work and simulations have shown that typical encounters generate streams that are extremely thin. In this paper we show that this implies that even small relativistic precessions attributed to black hole spin can induce deflections that prevent the stream from self-intersecting even after many windings. Additionally, hydrodynamical simulations have demonstrated that energy is deposited very slowly via hydrodynamic processes alone, resulting in the liberation of very little gravitational binding energy in the absence of stream-stream collisions. This naturally leads to a "dark period" in which the flare is not observable for some time, persisting for up to a dozen orbital periods of the most bound material, which translates to years for disruptions arou...

Guillochon, James

2015-01-01T23:59:59.000Z

389

"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

390

Neutrinos, Dark Matter and Nuclear Detection  

SciTech Connect (OSTI)

Solutions to problems in nuclear non-proliferation and counter-terrorism may be found at the forefront of modern physics. Neutrino oscillation experiments, dark matter searches, and high energy astrophysics, are based on technology advances that have may also have application to nuclear detection. The detection problems share many characteristics, including energy scales, time structures, particle-type, and, of course, the combination of high backgrounds and low signal levels. This convergence of basic and applied physics is realized in non-proliferation and homeland security projects at Lawrence Livermore National Laboratory. Examples described here include reactor anti-neutrino monitoring, dual-phase noble liquid TPC development, gamma-ray telescopes, and nuclear resonance fluorescence.

Goldstein, W H; Bernstein, A; Craig, W W; Johnson, M

2007-05-29T23:59:59.000Z

391

Antiproton Limits on Decaying Gravitino Dark Matter  

E-Print Network [OSTI]

We report on constraints on the lifetime of decaying gravitino dark matter in models with bilinear R-parity violation derived from observations of cosmic-ray antiprotons with the PAMELA experiment. Performing a scan over a viable set of cosmic-ray propagation parameters we find lower limits ranging from $8\\times 10^{28}$s to $6\\times 10^{28}$s for gravitino masses from roughly 100 GeV to 10 TeV. Comparing these limits to constraints derived from gamma-ray and neutrino observations we conclude that the presented antiproton limits are currently the strongest and most robust limits on the gravitino lifetime in the considered mass range. These constraints correspond to upper limits on the size of the bilinear R-parity breaking parameter in the range of $10^{-8}$ to $8\\times 10^{-13}$.

Grefe, Michael

2014-01-01T23:59:59.000Z

392

The World of Dark Shadows Issue 19  

E-Print Network [OSTI]

'111£ ill rId of Dl1rJ{ ShadoUls 'ThOy£f Douid - "In his mEmory." VolumE no.l9 wl,r .orlll (Of Dark t}~nllCluts ~-October, 1978 , h P-entagrarn Publ i cat i on. Bi monthly­ fanzine / fan club. Sl.50 per issue; 3 f or J4.50; ( f or i9...:00 or make your own subscription. I From Kathy Resch, PO Box 2262 l1ission Sea., Santa Cl a r a, Ce;. 950~. ' Writers this issue: Barb Fi st er-Liltz, Geoffrey Hamell, Li Gsa Hoffman, Kathleen Resch, Marcy Robin, Sandy Smith, J eff Thompson...

Multiple Contributors

1978-01-01T23:59:59.000Z

393

Stability of BEC galactic dark matter halos  

E-Print Network [OSTI]

In this paper we show that spherically symmetric BEC dark matter halos, with the $\\sin r/r$ density profile, that accurately fit galactic rotation curves and represent a potential solution to the cusp-core problem are unstable. We do this by introducing back the density profiles into the fully time-dependent Gross-Pitaevskii-Poisson system of equations. Using numerical methods to track the evolution of the system, we found that these galactic halos lose mass at an approximate rate of half of its mass in a time scale of dozens of Myr. We consider this time scale is enough as to consider these halos are unstable and unlikely to be formed. We provide some arguments to show that this behavior is general and discuss some other drawbacks of the model that restrict its viability.

F. S. Guzman; F. D. Lora-Clavijo; J. J. Gonzalez-Aviles; F. J. Rivera-Paleo

2013-08-22T23:59:59.000Z

394

On cosmic acceleration without dark energy  

SciTech Connect (OSTI)

We elaborate on the proposal that the observed acceleration of the Universe is the result of the backreaction of cosmological perturbations, rather than the effect of a negative-pressure dark energy fluid or a modification of general relativity. Through the effective Friedmann equations describing an inhomogeneous Universe after smoothing, we demonstrate that acceleration in our local Hubble patch is possible even if fluid elements do not individually undergo accelerated expansion. This invalidates the no-go theorem that there can be no acceleration in our local Hubble patch if the Universe only contains irrotational dust. We then study perturbatively the time behavior of general-relativistic cosmological perturbations, applying, where possible, the renormalization group to regularize the dynamics. We show that an instability occurs in the perturbative expansion involving sub-Hubble modes, which indicates that acceleration in our Hubble patch may originate from the backreaction of cosmological perturbations on observable scales.

Kolb, E.W.; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI; Matarrese, S.; /Padua U. /INFN, Padua; Riotto, A.; /INFN, Padua; ,

2005-06-01T23:59:59.000Z

395

The World of Dark Shadows Issue 31  

E-Print Network [OSTI]

The World 01 llltfiK ~llltDaW~ 31 ~. 1 ~ I ­ ~ I ..\\ I I •~ J \\ .. ~ ! 1(18" !! ~ \\ 1 \\ U ;: 0 ~ I ' c " o'q~~\\ '0 l ~~ ", 9 I I r I - I ~ ( -;,­ ~l~ ~ . I ( ~"'"VW" " ) J!. d,.", .'\\ _C]~I ~ ~ ~ /';".!.t ~0-. THE WORLD OF DARK.... * JONATHAN FRID Address; SHAOOIICON 5I X - JULY 3, 1982 Transcription by Mar ia Barbosa Th e co nve,\\t.i.on 6Jm-lLoom L<.IU 6.dted t o c.a.pa.c.i.ty . Th e. Ilwn 06 the 6aM eon­ veJt,~.i.n9 e

Multiple Contributors

1982-01-01T23:59:59.000Z

396

Bi-metric Gravity and "Dark Matter"  

E-Print Network [OSTI]

We present a bi-metric theory of gravity containing a length scale of galactic size. For distances less than this scale the theory satisfies the standard tests of General Relativity. For distances greater than this scale the theory yields an effective gravitational constant much larger than the locally observed value of Newton's constant. The transition from one regime to the other through the galactic scale can explain the observed rotation curves of galaxies and hence the effects normally attributed to the presence of dark matter. Phenomena on an extragalactic scale such as galactic clusters and the expansion of the universe are controlled by the enhanced gravitational coupling. This provides an explanation of the missing matter normally invoked to account for the observed value of Hubble's constant in relation to observed matter.

I. T. Drummond

2000-08-18T23:59:59.000Z

397

Neutrino constraints on the dark matter total annihilation cross section  

SciTech Connect (OSTI)

In the indirect detection of dark matter through its annihilation products, the signals depend on the square of the dark matter density, making precise knowledge of the distribution of dark matter in the Universe critical for robust predictions. Many studies have focused on regions where the dark matter density is greatest, e.g., the galactic center, as well as on the cosmic signal arising from all halos in the Universe. We focus on the signal arising from the whole Milky Way halo; this is less sensitive to uncertainties in the dark matter distribution, and especially for flatter profiles, this halo signal is larger than the cosmic signal. We illustrate this by considering a dark matter model in which the principal annihilation products are neutrinos. Since neutrinos are the least detectable standard model particles, a limit on their flux conservatively bounds the dark matter total self-annihilation cross section from above. By using the Milky Way halo signal, we show that previous constraints using the cosmic signal can be improved on by 1-2 orders of magnitude; dedicated experimental analyses should be able to improve both by an additional 1-2 orders of magnitude.

Yueksel, Hasan [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Horiuchi, Shunsaku [Department of Physics, School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Beacom, John F. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Astronomy, Ohio State University, Columbus, Ohio 43210 (United States); Ando, Shin'ichiro [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States)

2007-12-15T23:59:59.000Z

398

Cosmic Coincidence and Asymmetric Dark Matter in a Stueckelberg Extension  

E-Print Network [OSTI]

We discuss the possibility of cogenesis generating the ratio of baryon asymmetry to dark matter in a Stueckelberg U(1) extension of the standard model and of the minimal supersymmetric standard model. For the U(1) we choose $L_{\\mu}-L_{\\tau}$ which is anomaly free and can be gauged. The dark matter candidate arising from this extension is a singlet of the standard model gauge group but is charged under $L_{\\mu}-L_{\\tau}$. Solutions to the Boltzmann equations for relics in the presence of asymmetric dark matter are discussed. It is shown that the ratio of the baryon asymmetry to dark matter consistent with the current WMAP data, i.e., the cosmic coincidence, can be successfully explained in this model with the depletion of the symmetric component of dark matter from resonant annihilation via the Stueckelberg gauge boson. For the extended MSSM model it is shown that one has a two component dark matter picture with asymmetric dark matter being the dominant component and the neutralino being the subdominant compo...

Feng, Wan-Zhe; Peim, Gregory

2012-01-01T23:59:59.000Z

399

Diurnal modulation signal from dissipative hidden sector dark matter  

E-Print Network [OSTI]

We consider a simple generic dissipative dark matter model: a hidden sector featuring two dark matter particles charged under an unbroken $U(1)'$ interaction. Previous work has shown that such a model has the potential to explain dark matter phenomena on both large and small scales. In this framework, the dark matter halo in spiral galaxies features nontrivial dynamics, with the halo energy loss due to dissipative interactions balanced by a heat source. Ordinary supernovae can potentially supply this heat provided kinetic mixing interaction exists with strength $\\epsilon \\sim 10^{-9}$. This type of kinetically mixed dark matter can be probed in direct detection experiments. Importantly, this self-interacting dark matter can be captured within the Earth and shield a dark matter detector from the halo wind, giving rise to a diurnal modulation effect. We estimate the size of this effect for detectors located in the Southern hemisphere, and find that the modulation is large ($\\gtrsim 10\\%$) for a wide range of pa...

Foot, R

2014-01-01T23:59:59.000Z

400

Constraints on particle dark matter from cosmic-ray antiprotons  

E-Print Network [OSTI]

Cosmic-ray antiprotons represent an important channel for dark matter indirect-detection studies. Current measurements of the antiproton flux at the top of the atmosphere and theoretical determinations of the secondary antiproton production in the Galaxy are in good agreement, with no manifest deviation which could point to an exotic contribution in this channel. Therefore, antiprotons can be used as a powerful tool for constraining particle dark matter properties. By using the spectrum of PAMELA data from 50 MV to 180 GV in rigidity, we derive bounds on the dark matter annihilation cross section (or decay rate, for decaying dark matter) for the whole spectrum of dark matter annihilation (decay) channels and under different hypotheses of cosmic-rays transport in the Galaxy and in the heliosphere. For typical models of galactic propagation, the constraints are significantly strong, setting a lower bound on the dark matter mass of a "thermal" relic at about 50 -- 90 GeV for hadronic annihilation channels. These bounds are enhanced to about 150 GeV on the dark matter mass, when large cosmic-rays confinement volumes in the Galaxy are considered, and are reduced to 4-5 GeV for annihilation to light quarks (no bound for heavy-quark production) when the confinement volume is small. Bounds for dark matter lighter than few tens of GeV are due to the low energy part of the PAMELA spectrum, an energy region where solar modulation is relevant: to this aim, we have implemented a detailed solution of the transport equation in the heliosphere, which allowed us not only to extend bounds to light dark matter, but also to determine the uncertainty on the constraints arising from solar modulation modeling. Finally, we estimate the impact of soon-to-come AMS-02 data on the antiproton constraints.

N. Fornengo; L. Maccione; A. Vittino

2013-12-12T23:59:59.000Z

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401

Constraints on particle dark matter from cosmic-ray antiprotons  

E-Print Network [OSTI]

Cosmic-ray antiprotons represent an important channel for dark matter indirect-detection studies. Current measurements of the antiproton flux at the top of the atmosphere and theoretical determinations of the secondary antiproton production in the Galaxy are in good agreement, with no manifest deviation which could point to an exotic contribution in this channel. Therefore, antiprotons can be used as a powerful tool for constraining particle dark matter properties. By using the spectrum of PAMELA data from 50 MV to 180 GV in rigidity, we derive bounds on the dark matter annihilation cross section (or decay rate, for decaying dark matter) for the whole spectrum of dark matter annihilation (decay) channels and under different hypotheses of cosmic-rays transport in the Galaxy and in the heliosphere. For typical models of galactic propagation, the constraints are significantly strong, setting a lower bound on the dark matter mass of a "thermal" relic at about 50-90 GeV for hadronic annihilation channels. These bounds are enhanced to about 150 GeV on the dark matter mass, when large cosmic-rays confinement volumes in the Galaxy are considered, and are reduced to 4-5 GeV for annihilation to light quarks (no bound for heavy-quark production) when the confinement volume is small. Bounds for dark matter lighter than few tens of GeV are due to the low energy part of the PAMELA spectrum, an energy region where solar modulation is relevant: to this aim, we have implemented a detailed solution of the transport equation in the heliosphere, which allowed us not only to extend bounds to light dark matter, but also to determine the uncertainty on the constraints arising from solar modulation modeling. Finally, we estimate the impact of soon-to-come AMS-02 data on the antiproton constraints.

N. Fornengo; L. Maccione; A. Vittino

2015-01-30T23:59:59.000Z

402

Measuring dark energy spatial inhomogeneity with supernova data  

E-Print Network [OSTI]

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

Asantha Cooray; Daniel E. Holz; Robert Caldwell

2008-12-01T23:59:59.000Z

403

Measuring dark energy with the shear triplet statistics  

E-Print Network [OSTI]

The shear triplet statistics is a geometric method to measure cosmological parameters with observations in the weak gravitational lensing regime towards massive haloes. Here, this proposal is considered to probe the dark energy equation of state and its time derivative in view of future wide-field galaxy surveys. A survey with a median redshift of nearly 0.7 and a total area of nearly 10000 square degrees would be pretty effective in determining the dark matter cosmological density and in putting useful constraints on the dark energy properties.

Mauro Sereno

2007-02-02T23:59:59.000Z

404

Measuring dark energy spatial inhomogeneity with supernova data  

SciTech Connect (OSTI)

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

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

2010-11-01T23:59:59.000Z

405

Neutrino Mass and Dark Energy from Weak Lensing  

Science Journals Connector (OSTI)

Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the Universe. This distribution is sensitive to both the dark energy and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000??deg2 survey, we find that the expected (1-?) error on a neutrino mass is 0.1 eV, if the dark-energy parameters are allowed to vary. The constraints on dark-energy parameters are similarly restrictive, with errors on w of 0.09.

Kevork N. Abazajian and Scott Dodelson

2003-07-24T23:59:59.000Z

406

An Overview of Dark Matter Experiments at Jefferson Lab  

SciTech Connect (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

407

Holographic Ricci dark energy: Current observational constraints, quintom feature, and the reconstruction of scalar-field dark energy  

Science Journals Connector (OSTI)

In this work, we consider the cosmological constraints on the holographic Ricci dark energy proposed by Gao et al. [Phys. Rev. D 79, 043511 (2009)], by using the observational data currently available. The main characteristic of holographic Ricci dark energy is governed by a positive numerical parameter ? in the model. When ?dark energy will exhibit a quintomlike behavior; i.e., its equation of state will evolve across the cosmological-constant boundary w=-1. The parameter ? can be determined only by observations. Thus, in order to characterize the evolving feature of dark energy and to predict the fate of the Universe, it is of extraordinary importance to constrain the parameter ? by using the observational data. In this paper, we derive constraints on the holographic Ricci dark energy model from the latest observational data including the Union sample of 307 type Ia supernovae, the shift parameter of the cosmic microwave background given by the five-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey. The joint analysis gives the best-fit results (with 1? uncertainty): ?=0.359-0.025+0.024 and ?m0=0.318-0.024+0.026. That is to say, according to the observations, the holographic Ricci dark energy takes on the quintom feature. Finally, in light of the results of the cosmological constraints, we discuss the issue of the scalar-field dark energy reconstruction, based on the scenario of the holographic Ricci vacuum energy.

Xin Zhang

2009-05-08T23:59:59.000Z

408

Dynamics of a scalar field, with a double exponential potential, interacting with dark matter  

E-Print Network [OSTI]

We study the interaction between dark matter and dark energy, with dark energy described by a scalar field having a double exponential effective potential. We discover conditions under which such a scalar field driven solution is a late time attractor. We observe a realistic cosmological evolution which consists of sequential stages of dominance of radiation, matter and dark energy, respectively.

Gupta, Vartika; Mukherjee, Amitabha; Lohiya, Daksh

2015-01-01T23:59:59.000Z

409

Looking for Dark Matter through the Bottom of a Wine Glass!  

E-Print Network [OSTI]

, and detect the imprint of dark energy on the web of dark matter that winds across the cosmos. Café Email listLooking for Dark Matter through the Bottom of a Wine Glass! (IYA Strange Telescope Series://cfcpwork.uchicago.edu/mailman/listinfo/cafe! #12;Looking for Dark Matter through the Bottom of a Wine Glass! (IYA Strange Telescope Series

Collar, Juan I.

410

Spectroscopic needs for imaging dark energy experiments  

Science Journals Connector (OSTI)

Abstract Ongoing and near-future imaging-based dark energy experiments are critically dependent upon photometric redshifts (a.k.a. photo-z’s): i.e., estimates of the redshifts of objects based only on flux information obtained through broad filters. Higher-quality, lower-scatter photo-z’s will result in smaller random errors on cosmological parameters; while systematic errors in photometric redshift estimates, if not constrained, may dominate all other uncertainties from these experiments. The desired optimization and calibration is dependent upon spectroscopic measurements for secure redshift information; this is the key application of galaxy spectroscopy for imaging-based dark energy experiments. Hence, to achieve their full potential, imaging-based experiments will require large sets of objects with spectroscopically-determined redshifts, for two purposes:• Training: Objects with known redshift are needed to map out the relationship between object color and z (or, equivalently, to determine empirically-calibrated templates describing the rest-frame spectra of the full range of galaxies, which may be used to predict the color-z relation). The ultimate goal of training is to minimize each moment of the distribution of differences between photometric redshift estimates and the true redshifts of objects, making the relationship between them as tight as possible. The larger and more complete our “training set” of spectroscopic redshifts is, the smaller the RMS photo-z errors should be, increasing the constraining power of imaging experiments. Requirements: Spectroscopic redshift measurements for ?30,000 objects over >?15 widely-separated regions, each at least ?20 arcmin in diameter, and reaching the faintest objects used in a given experiment, will likely be necessary if photometric redshifts are to be trained and calibrated with conventional techniques. Larger, more complete samples (i.e., with longer exposure times) can improve photo-z algorithms and reduce scatter further, enhancing the science return from planned experiments greatly (increasing the Dark Energy Task Force figure of merit by up to ?50%). Options: This spectroscopy will most efficiently be done by covering as much of the optical and near-infrared spectrum as possible at modestly high spectral resolution (?/?? > ?3000), while maximizing the telescope collecting area, field of view on the sky, and multiplexing of simultaneous spectra. The most efficient instrument for this would likely be either the proposed GMACS/MANIFEST spectrograph for the Giant Magellan Telescope or the OPTIMOS spectrograph for the European Extremely Large Telescope, depending on actual properties when built. The PFS spectrograph at Subaru would be next best and available considerably earlier, c. 2018; the proposed ngCFHT and SSST telescopes would have similar capabilities but start later. Other key options, in order of increasing total time required, are the WFOS spectrograph at TMT, MOONS at the VLT, and DESI at the Mayall 4 m telescope (or the similar 4MOST and WEAVE projects); of these, only DESI, MOONS, and PFS are expected to be available before 2020. Table 2-3 of this white paper summarizes the observation time required at each facility for strawman training samples. To attain secure redshift measurements for a high fraction of targeted objects and cover the full redshift span of future experiments, additional near-infrared spectroscopy will also be required; this is best done from space, particularly with WFIRST-2.4 and JWST. Calibration: The first several moments of redshift distributions (the mean, RMS redshift dispersion, etc.), must be known to high accuracy for cosmological constraints not to be systematics-dominated (equivalently, the moments of the distribution of differences between photometric and true redshifts could be determined instead). The ultimate goal of calibration is to characterize these moments for every subsample used in analyses - i.e., to minimize the uncertainty in their mean redshift, RMS dispersion, et

Jeffrey A. Newman; Alexandra Abate; Filipe B. Abdalla; Sahar Allam; Steven W. Allen; Réza Ansari; Stephen Bailey; Wayne A. Barkhouse; Timothy C. Beers; Michael R. Blanton; Mark Brodwin; Joel R. Brownstein; Robert J. Brunner; Matias Carrasco Kind; Jorge L. Cervantes-Cota; Elliott Cheu; Nora Elisa Chisari; Matthew Colless; Johan Comparat; Jean Coupon; Carlos E. Cunha; Axel de la Macorra; Ian P. Dell’Antonio; Brenda L. Frye; Eric J. Gawiser; Neil Gehrels; Kevin Grady; Alex Hagen; Patrick B. Hall; Andew P. Hearin; Hendrik Hildebrandt; Christopher M. Hirata; Shirley Ho; Klaus Honscheid; Dragan Huterer; Željko Ivezi?; Jean-Paul Kneib; Jeffrey W. Kruk; Ofer Lahav; Rachel Mandelbaum; Jennifer L. Marshall; Daniel J. Matthews; Brice Ménard; Ramon Miquel; Marc Moniez; H.W. Moos; John Moustakas; Adam D. Myers; Casey Papovich; John A. Peacock; Changbom Park; Mubdi Rahman; Jason Rhodes; Jean-Stephane Ricol; Iftach Sadeh; Anže Slozar; Samuel J. Schmidt; Daniel K. Stern; J. Anthony Tyson; Anja von der Linden; Risa H. Wechsler; W.M. Wood-Vasey; Andrew R. Zentner

2015-01-01T23:59:59.000Z

411

Direct Detection of Sub-GeV Dark Matter  

SciTech Connect (OSTI)

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

412

Dynamical 3-Space: Alternative Explanation of the `Dark Matter Ring'  

E-Print Network [OSTI]

NASA has claimed the discovery of a `Ring of Dark Matter' in the galaxy cluster CL 0024+17, see Jee M.J. et al. arXiv:0705.2171, based upon gravitational lensing data. Here we show that the lensing can be given an alternative explanation that does not involve `dark matter'. This explanation comes from the new dynamics of 3-space. This dynamics involves two constant G and alpha - the fine structure constant. This dynamics has explained the bore hole anomaly, spiral galaxy flat rotation speeds, the masses of black holes in spherical galaxies, gravitational light bending and lensing, all without invoking `dark matter', and also the supernova redshift data without the need for `dark energy'.

Reginald T Cahill

2007-05-20T23:59:59.000Z

413

Dark Energy, Paradigm Shifts, and the Role of Evidence  

E-Print Network [OSTI]

We comment on cases in the history of Astronomy, which may shed some light on the current established but enigmatic concordance model of Cosmology. Should the model be understood by adding new entities such as Dark Matter and Dark Energy, or by modifying the underlying theory? For example, the prediction and discovery of planet Neptune can be regarded as analogous to finding a dark component; while explaining the anomalous perihelion precession of Mercury by General Relativity can be taken as analogous to the possibility that modified gravity is an alternative to dark components of the universe. In this paper, we revise this analogy coming from the history of astronomy with an eye to illustrating some of the similarities and differences between the two cases.

Lahav, Ofer

2014-01-01T23:59:59.000Z

414

Constraints on dark matter annihilation from AMS-02 results  

Science Journals Connector (OSTI)

We use recently released data on the positron-to-electron ratio in cosmic rays from the AMS-02 experiment to constrain dark matter annihilation in the Milky Way. Due to the yet unexplained positron excess, limits are generally weaker than those obtained using other probes, especially gamma rays. This also means that explaining the positron excess in terms of dark matter annihilation is difficult. Only if very conservative assumptions on the dark matter distribution in the Galactic center region are adopted, it may be possible to accommodate dark matter annihilating to leptons with a cross section above 10-24??cm3/sec?. We comment on several theoretical mechanisms to explain such large annihilation cross sections.

Joachim Kopp

2013-10-24T23:59:59.000Z

415

Energy weighted x-ray dark-field imaging  

Science Journals Connector (OSTI)

The dark-field image obtained in grating-based x-ray phase-contrast imaging can provide information about the objects’ microstructures on a scale smaller than the pixel size...

Pelzer, Georg; Zang, Andrea; Anton, Gisela; Bayer, Florian; Horn, Florian; Kraus, Manuel; Rieger, Jens; Ritter, Andre; Wandner, Johannes; Weber, Thomas; Fauler, Alex; Fiederle, Michael; Wong, Winnie S; Campbell, Michael; Meiser, Jan; Meyer, Pascal; Mohr, Jürgen; Michel, Thilo

2014-01-01T23:59:59.000Z

416

Neutrino masses, leptogenesis, and sterile neutrino dark matter  

E-Print Network [OSTI]

We analyze a scenario in which the lightest heavy neutrino $N_1$ is a dark matter candidate and the second- heaviest neutrino $N_2$ decays producing a lepton number. If $N_1$ were in thermal equilibrium, its energy density today would be much larger than that of the observed dark matter, so we consider energy injection by the decay of $N_2$. In this paper, we show the parameters of this scenario that give the correct abundances of dark matter and baryonic matter and also induce the observed neutrino masses. This model can explain a possible sterile neutrino dark matter signal of $M_1$=7 keV in the x-ray observation of x-ray multi-mirror mission.

Takanao Tsuyuki

2014-07-20T23:59:59.000Z

417

Dark Colored Cool Pigments for Materials Exposed to the Sun ...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

& Renewable Energy. (1,201 KB) Technology Marketing Summary For the building and automobile industries in need of dark-colored products that can stay cool in the sun, this...

418

Design and Construction of Prototype Dark Matter Detectors  

SciTech Connect (OSTI)

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

419

New Analysis of SUSY Dark Matter Scenarios at ILC  

E-Print Network [OSTI]

Applying realistic veto efficiencies for the low angle electromagnetic calorimeter located in the very forward direction of the future international linear collider, we revisited the Standard Model background contributions studied previously in stau analyses with supersymmetrical dark matter scenarios.

Zhiqing Zhang

2008-01-31T23:59:59.000Z

420

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: the real part yields dispersive effects in propagation, and the imaginary part yields such in attenuation. 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. As a first application we use the time delay determined from radio afterglow observations of gamma-ray bursts to limit the charge-to-mass ratio of dark matter to |\\epsilon/M|< 1.8 x 10^{-5}/eV at 95% CL.

Gardner, S

2009-01-01T23:59:59.000Z

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,
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421

Neutrinos from dark matter annihilations at the galactic center  

Science Journals Connector (OSTI)

We discuss the prospects for detection of high energy neutrinos from dark matter (DM) annihilation at the galactic center (GC). Despite the large uncertainties associated with our poor knowledge of the distribution of dark matter in the innermost regions of the Galaxy, we determine an upper limit on the neutrino flux by requiring that the associated gamma-ray emission does not exceed the observed flux. We conclude that a neutrino flux from the GC will not be observable by Antares if dark matter is made of neutralinos with mass smaller than 650 GeV, while for heavier neutralinos, corresponding to models that will soon be probed by HESS (high energy stereoscopic system), the upper limit on the neutrino flux is barely above the Antares sensitivity. The detection of a larger flux would either require an alternative explanation, in terms of astrophysical processes, or the adoption of other dark matter candidates, disfavouring the case for neutralinos.

Gianfranco Bertone; Emmanuel Nezri; Jean Orloff; Joseph Silk

2004-09-02T23:59:59.000Z

422

Navigation without vision: bumblebee orientation in complete darkness  

E-Print Network [OSTI]

system for dissecting possible non-visual components of navigation used in daylight. It also allows us o¡ered the opportu- nity to collect sucrose solution outside the nest in complete darkness

Chittka, Lars

423

What do we really know about dark energy?  

Science Journals Connector (OSTI)

...In the concordance model, the energy content of the Universe is dominated by...can relate the luminosity to the energy content of the Universe via the standard...is the contribution from dark energy. For a cosmological constant...

2011-01-01T23:59:59.000Z

424

Cosmic-ray electron signatures of dark matter  

SciTech Connect (OSTI)

There is evidence for an excess in cosmic-ray electrons at about 500 GeV energy, that may be related to dark-matter annihilation. I have calculated the expected electron contributions from a pulsar and from Kaluza-Klein dark matter, based on a realistic treatment of the electron propagation in the Galaxy. Pulsars younger than about 10{sup 5} years naturally cause a narrow peak at a few hundred GeV in the locally observed electron spectrum, similar to that observed. On the other hand, if electron production by dark matter is predominantly occurring in high-mass clumps (> or approx. 10{sup 3}M{sub {center_dot}}), the sharp cutoff in the contribution from Kaluza-Klein particles is sometimes more pronounced, but often smoothed out and indistinguishable from a pulsar source, and therefore the spectral shape of the electron excess is insufficient to discriminate a dark-matter origin from more conventional astrophysical explanations.

Pohl, Martin [Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

2009-02-15T23:59:59.000Z

425

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

426

Constraining warm dark matter with cosmic shear power spectra  

SciTech Connect (OSTI)

We investigate potential constraints from cosmic shear on the dark matter particle mass, assuming all dark matter is made up of light thermal relic particles. Given the theoretical uncertainties involved in making cosmological predictions in such warm dark matter scenarios we use analytical fits to linear warm dark matter power spectra and compare (i) the halo model using a mass function evaluated from these linear power spectra and (ii) an analytical fit to the non-linear evolution of the linear power spectra. We optimistically ignore the competing effect of baryons for this work. We find approach (ii) to be conservative compared to approach (i). We evaluate cosmological constraints using these methods, marginalising over four other cosmological parameters. Using the more conservative method we find that a Euclid-like weak lensing survey together with constraints from the Planck cosmic microwave background mission primary anisotropies could achieve a lower limit on the particle mass of 2.5 keV.

Markovic, Katarina; Weller, Jochen [University Observatory Munich, Ludwig-Maximilian University, Scheinerstr. 1, 81679 Munich (Germany); Bridle, Sarah [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Slosar, Anže, E-mail: markovic@usm.lmu.de, E-mail: sarah.bridle@ucl.ac.uk, E-mail: anze@bnl.gov, E-mail: jochen.weller@usm.lmu.de [Brookhaven National Laboratory, Building 510A, Upton, NY 11973-5000 (United States)

2011-01-01T23:59:59.000Z

427

Model selection as a science driver for dark energy surveys  

E-Print Network [OSTI]

A key science goal of upcoming dark energy surveys is to seek time evolution of the dark energy. This problem is one of {\\em model selection}, where the aim is to differentiate between cosmological models with different numbers of parameters. However, the power of these surveys is traditionally assessed by estimating their ability to constrain parameters, which is a different statistical problem. In this paper we use Bayesian model selection techniques, specifically forecasting of the Bayes factors, to compare the abilities of different proposed surveys in discovering dark energy evolution. We consider six experiments -- supernova luminosity measurements by the Supernova Legacy Survey, SNAP, JEDI, and ALPACA, and baryon acoustic oscillation measurements by WFMOS and JEDI -- and use Bayes factor plots to compare their statistical constraining power. The concept of Bayes factor forecasting has much broader applicability than dark energy surveys.

Pia Mukherjee; David Parkinson; Pier Stefano Corasaniti; Andrew R. Liddle; Martin Kunz

2005-12-20T23:59:59.000Z

428

Fermilab | Newsroom | Press Releases | August 18, 2014: Dark...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

2 Aug. 18, 2014 FOR IMMEDIATE RELEASE Dark Energy Survey kicks off second season cataloging the wonders of deep space With its second year under way, the DES team posts highlights...

429

Particle mixing as possible explanation of the dark energy conundrum  

E-Print Network [OSTI]

The vacuum condensate due to neutrino and quark mixing behaves as a perfect fluid and, at the present epoch, as a cosmological constant. The very small breaking of the Lorentz invariance constrains today the value of the dark energy.

Antonio Capolupo; Giuseppe Vitiello

2009-01-28T23:59:59.000Z

430

Three Flavor Neutrino Mixing and Dark Energy Above GUT Scale  

Science Journals Connector (OSTI)

Neutrino mixing lead to a non zero contribution to the dark energy of the universe. We assume that the neutrino masses and mixing arise through physics at a scale intermediate ... the electroweak scale. The mecha...

Bipin Singh Koranga; Rajesh Pandey

2011-05-01T23:59:59.000Z

431

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

432

Can we discover dual-component thermal WIMP dark matter?  

SciTech Connect (OSTI)

We address the question of whether the upcoming generation of dark matter search experiments and colliders will be able to discover if the dark matter in the Universe has two components of weakly interacting massive particles (WIMPs). We outline a model-independent approach, and we study the specific cases of (1) direct detection with low-background 1 ton noble-gas detectors and (2) a 0.5 TeV center of mass energy electron-positron linear collider. We also analyze the case of indirect detection via two gamma-ray lines, which would provide a verification of such a discovery, although multiple gamma-ray lines can in principle originate from the annihilation of a single dark matter particle. For each search ''channel'', we outline a few assumptions to relate the very small set of parameters we consider (defining the masses of the two WIMPs and their relative abundance in the overall dark matter density) with the relevant detection rates. We then draw general conclusions on which corners of a generic dual-component dark matter scenario can be explored with current and next generation experiments. We find that in all channels the ideal setup is one where the relative mass splitting between the two WIMP species is of order 1, and where the two dark matter components contribute in a ratio close to 1:1 to the overall dark matter content of the Universe. Interestingly, in the case of direct detection, future experiments might detect multiple states even if only ? 10% of the energy-density of dark matter in the Universe is in the subdominant species.

Profumo, Stefano; Ubaldi, Lorenzo [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz CA 95064 (United States); Sigurdson, Kris, E-mail: profumo@scipp.ucsc.edu, E-mail: krs@physics.ubc.ca, E-mail: ubaldi@physics.ucsc.edu [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)

2009-12-01T23:59:59.000Z

433

Direct Search for Low Mass Dark Matter Particles with CCDs  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

A direct dark matter search is performed using fully-depleted high-resistivity CCD detectors. Due to their low electronic readout noise (RMS ~7 eV) these devices operate with a very low detection threshold of 40 eV, making the search for dark matter particles with low masses (~5 GeV) possible. The results of an engineering run performed in a shallow underground site are presented, demonstrating the potential of this technology in the low mass region.

Barreto, J [Rio de Janeiro Federal U.; Cease, H.; Diehl, H.T.; Estrada, J.; Flaugher, B.; Harrison, N.; Jones, J.; Kilminster, B [Fermilab; Molina, J [Asuncion Natl. U.; Smith, J.; Sonnenschein, A [Fermilab

2012-05-15T23:59:59.000Z

434

Gif Lectures on direct detection of Dark Matter  

E-Print Network [OSTI]

These notes cover some of the topics associated with direct detection of dark matter at an introductory level. The general principles of dark matter search are summarized. The current status of some experiments is described, with an emphasis on bolometric and noble liquid techniques. Plots and illustrations associated to these notes may be found on transparencies presented during the lecture, on the web site of Gif school 2009.

Eric Armengaud

2010-03-11T23:59:59.000Z

435

Interacting Ghost Dark Energy in Non-Flat Universe  

E-Print Network [OSTI]

A new dark energy model called "ghost dark energy" was recently suggested to explain the observed accelerating expansion of the universe. This model originates from the Veneziano ghost of QCD. The dark energy density is proportional to Hubble parameter, $\\rho_D=\\alpha H$, where $\\alpha$ is a constant of order $\\Lambda_{\\rm QCD}^3$ and $\\Lambda_{\\rm QCD}\\sim 100 MeV$ is QCD mass scale. In this paper, we extend the ghost dark energy model to the universe with spatial curvature in the presence of interaction between dark matter and dark energy. We study cosmological implications of this model in detail. In the absence of interaction the equation of state parameter of ghost dark energy is always $w_D > -1 $ and mimics a cosmological constant in the late time, while it is possible to have $w_D dark energy in flat universe are recovered. To check the observational consistency, we use Supernova type Ia (SNIa) Gold sample, shift parameter of Cosmic Microwave Background radiation (CMB) and the Baryonic Acoustic Oscillation peak from Sloan Digital Sky Survey (SDSS). The best fit values of free parameter at $1\\sigma$ confidence interval are: $\\Omega_m^0= 0.35^{+0.02}_{-0.03}$, $\\Omega_D^0=0.75_{-0.04}^{+0.01}$ and $b^2=0.08^{+0.03}_{-0.03}$. Consequently the total energy density of universe at present time in this model at 68% level equates to $\\Omega_{\\rm tot}^0=1.10^{+0.02}_{-0.05}$.

A. Sheykhi; M. Sadegh Movahed

2011-04-25T23:59:59.000Z

436

Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies  

E-Print Network [OSTI]

For dynamical dark energy cosmologies we carry out a series of N-body gravitational simulations, achieving percent level accuracy in the relative mass power spectra at any redshift. Such accuracy in the power spectrum is necessary for next generation cosmological mass probes. Our matching procedure reproduces the CMB distance to last scattering and delivers subpercent level power spectra at z=0 and z~3. We discuss the physical implications for probing dark energy with surveys of large scale structure.

Matthew J. Francis; Geraint F. Lewis; Eric V. Linder

2007-04-03T23:59:59.000Z

437

The Maximum Patch Method for Directional Dark Matter Detection  

E-Print Network [OSTI]

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

Shawn Henderson; Jocelyn Monroe; Peter Fisher

2008-01-10T23:59:59.000Z

438

Maximum patch method for directional dark matter detection  

SciTech Connect (OSTI)

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

Henderson, Shawn; Monroe, Jocelyn; Fisher, Peter [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Laboratory for Nuclear Science, MIT Kavli Institute for Astrophysics and Space Research, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-07-01T23:59:59.000Z

439

New Light on Dark Energy (LBNL Science at the Theater)  

ScienceCinema (OSTI)

A panel of Lab scientists ? including Eric Linder, Shirly Ho, and Greg Aldering ? along with Andrew Fraiknoi, the Bay Area's most popular astronomy explainer, gathered at the Berkeley Repertory Theatre on Monday, April 25, 2011, for a discussion about "New Light on Dark Energy." Topics will include hunting down Type 1a supernovae, measuring the universe using baryon oscillation, and whether dark energy is the true driver of the universe.

Linder, Eric; Ho, Shirly; Aldering, Greg; Fraiknoi, Andrew

2011-06-08T23:59:59.000Z

440

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.


441

Can a galaxy redshift survey measure dark energy clustering?  

E-Print Network [OSTI]

(abridged) A wide-field galaxy redshift survey allows one to probe galaxy clustering at largest spatial scales, which carries an invaluable information on horizon-scale physics complementarily to the cosmic microwave background (CMB). Assuming the planned survey consisting of z~1 and z~3 surveys with areas of 2000 and 300 square degrees, respectively, we study the prospects for probing dark energy clustering from the measured galaxy power spectrum, assuming the dynamical properties of dark energy are specified in terms of the equation of state and the effective sound speed c_e in the context of an adiabatic cold dark matter dominated model. The dark energy clustering adds a power to the galaxy power spectrum amplitude at spatial scales greater than the sound horizon, and the enhancement is sensitive to redshift evolution of the net dark energy density, i.e. the equation of state. We find that the galaxy survey, when combined with Planck, can distinguish dark energy clustering from a smooth dark energy model such as the quintessence model (c_e=1), when c_esurvey of z~1 galaxies allows the detection when c_edark energy clustering and the non-relativistic neutrinos implied from the neutrino oscillation experiments, because the two effects both induce a scale-dependent modification in the galaxy power spectrum shape at largest spatial scales accessible from the galaxy survey. It is shown that a wider redshift coverage can efficiently separate the two effects by utilizing the different redshift dependences, where dark energy clustering is apparent only at low redshifts z<1.

Masahiro Takada

2006-06-21T23:59:59.000Z

442

Limits on electrophilic Dark Matter from LHC Monojets  

E-Print Network [OSTI]

Searches for WIMP Dark Matter particle at the LHC are considered from the point of view of the existence of a Dark Matter particle which couples primarily through the heavy gauge boson Z, as suggested by recent tentative evidence for a 130 GeV gamma line in the FermiLAT data. We compare three models in which the WIMP is a neutrino-like particle and consider the limits on such particle and interactions from LHC.

K. G. Savvidy

2014-10-22T23:59:59.000Z

443

Can dark matter be a Bose-Einstein condensate?  

E-Print Network [OSTI]

We consider the possibility that the dark matter, which is required to explain the dynamics of the neutral hydrogen clouds at large distances from the galactic center, could be in the form of a Bose-Einstein condensate. To study the condensate we use the non-relativistic Gross-Pitaevskii equation. By introducing the Madelung representation of the wave function, we formulate the dynamics of the system in terms of the continuity equation and of the hydrodynamic Euler equations. Hence dark matter can be described as a non-relativistic, Newtonian Bose-Einstein gravitational condensate gas, whose density and pressure are related by a barotropic equation of state. In the case of a condensate with quartic non-linearity, the equation of state is polytropic with index $n=1$. To test the validity of the model we fit the Newtonian tangential velocity equation of the model with a sample of rotation curves of low surface brightness and dwarf galaxies, respectively. We find a very good agreement between the theoretical rotation curves and the observational data for the low surface brightness galaxies. The deflection of photons passing through the dark matter halos is also analyzed, and the bending angle of light is computed. The bending angle obtained for the Bose-Einstein condensate is larger than that predicted by standard general relativistic and dark matter models. Therefore the study of the light deflection by galaxies and the gravitational lensing could discriminate between the Bose-Einstein condensate dark matter model and other dark matter models.

C. G. Boehmer; T. Harko

2007-06-21T23:59:59.000Z

444

Dark energy and matter evolution from lensing tomography  

Science Journals Connector (OSTI)

Reconstructed from lensing tomography, the evolution of the dark matter density field in the well-understood linear regime can provide model-independent constraints on the growth function of structure and the evolution of the dark energy density. We examine this potential in the context that high-redshift cosmology has in the future been fixed by cosmic microwave background measurements. We construct sharp tests for the existence of multiple dark matter components or a dark energy component that is not a cosmological constant. These functional constraints can be transformed into physically motivated model parameters. From the growth function, the fraction of the dark matter in a smooth component, such as a light neutrino, may be constrained to a statistical precision of ?(f)?0.0006fsky-1/2 by a survey covering a fraction of sky fsky with a redshift resolution ?z=0.1. For the dark energy, a parametrization in terms of the present energy density ?DE, equation of state w, and its redshift derivative w?, the constraints correspond to ?(w)=0.009fsky-1/2 and a degenerate combination of the other two parameters. For a fixed ?DE, ?(w?)=0.046fsky-1/2.

Wayne Hu

2002-10-30T23:59:59.000Z

445

Illuminating Dark Photons with High-Energy Colliders  

E-Print Network [OSTI]

High-energy colliders offer a unique sensitivity to dark photons, the mediators of a broken dark U(1) gauge theory that kinetically mixes with the Standard Model (SM) hypercharge. Dark photons can be detected in the exotic decay of the 125 GeV Higgs boson, h -> Z Z_D -> 4l, and in Drell-Yan events, pp -> Z_D -> ll. If the dark U(1) is broken by a hidden-sector Higgs mechanism, then mixing between the dark and SM Higgs bosons also allows the exotic decay h -> Z_D Z_D -> 4l. We show that the 14 TeV LHC and a 100 TeV proton-proton collider provide powerful probes of both exotic Higgs decay channels. In the case of kinetic mixing alone, direct Drell-Yan production offers the best sensitivity to Z_D, and can probe epsilon >~ 9 x 10^(-4) (4 x 10^(-4)) at the HL-LHC (100 TeV pp collider). The exotic Higgs decay h -> Z Z_D offers slightly weaker sensitivity, but both measurements are necessary to distinguish the kinetically mixed dark photon from other scenarios. If Higgs mixing is also present, then the decay h -> Z...

Curtin, David; Gori, Stefania; Shelton, Jessie

2014-01-01T23:59:59.000Z

446

Tensor Detection Severely Constrains Axion Dark Matter  

E-Print Network [OSTI]

The recent detection of B-modes by BICEP2 has non-trivial implications for axion dark matter implied by combining the tensor interpretation with isocurvature constraints from Planck. In this paper the measurement is taken as fact, and its implications considered, though further experimental verification is required. In the simplest inflation models $r=0.2$ implies $H_I=1.1\\times 10^{14}\\text{ GeV}$. If the axion decay constant $f_a1$ accounts for theoretical uncertainty). If $f_a>H_I/2\\pi$ then vacuum fluctuations of the axion field place conflicting demands on axion DM: isocurvature constraints require a DM abundance which is too small to be reached when the back reaction of fluctuations is included. High $f_a$ QCD axions are thus ruled out. Constraints on axion-like particles, as a function of their mass and DM fraction, are also considered. For heavy axions with $m_a\\gtrsim 10^{-22}\\text{ eV}$ we find $\\Omega_a/\\Omega_d\\lesssim 10^{-3}$, with stronger constraints on heavier axions. Lighter axions, however, are allowed and (inflationary) model-independent constraints from the CMB temperature power spectrum and large scale structure are stronger than those implied by tensor modes.

David J. E. Marsh; Daniel Grin; Renee Hlozek; Pedro G. Ferreira

2014-03-17T23:59:59.000Z

447

Entropic-force dark energy reconsidered  

E-Print Network [OSTI]

We reconsider the entropic-force model in which both kind of Hubble terms ${\\dot H}$ and $H^{2}$ appear in the effective dark energy (DE) density affecting the evolution of the main cosmological functions, namely the scale factor, deceleration parameter, matter density and growth of linear matter perturbations. However, we find that the entropic-force model is not viable at the background and perturbation levels due to the fact that the entropic formulation does not add a constant term in the Friedmann equations. On the other hand, if on mere phenomenological grounds we replace the ${\\dot H}$ dependence of the effective DE density with a linear term $H$ without including a constant additive term, we find that the transition from deceleration to acceleration becomes possible but the recent structure formation data strongly disfavors this cosmological scenario. Finally, we briefly compare the entropic-force models with some related DE models (based on dynamical vacuum energy) which overcome these difficulties and are compatible with the present observations.

Spyros Basilakos; Joan Sola

2014-05-21T23:59:59.000Z

448

Dynamical dark energy or variable cosmological parameters?  

E-Print Network [OSTI]

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

Joan Sola; Hrvoje Stefancic

2005-12-21T23:59:59.000Z

449

Dark energy perturbations and cosmic coincidence  

E-Print Network [OSTI]

While there is plentiful evidence in all fronts of experimental cosmology for the existence of a non-vanishing dark energy (DE) density \\rho_D in the Universe, we are still far away from having a fundamental understanding of its ultimate nature and of its current value, not even of the puzzling fact that \\rho_D is so close to the matter energy density \\rho_M at the present time (i.e. the so-called "cosmic coincidence" problem). The resolution of some of these cosmic conundrums suggests that the DE must have some (mild) dynamical behavior at the present time. In this paper, we examine some general properties of the simultaneous set of matter and DE perturbations (\\delta\\rho_M, \\delta\\rho_D) for a multicomponent DE fluid. Next we put these properties to the test within the context of a non-trivial model of dynamical DE (the LXCDM model) which has been previously studied in the literature. By requiring that the coupled system of perturbation equations for \\delta\\rho_M and \\delta\\rho_D has a smooth solution throughout the entire cosmological evolution, that the matter power spectrum is consistent with the data on structure formation and that the "coincidence ratio" r=\\rho_D/\\rho_M stays bounded and not unnaturally high, we are able to determine a well-defined region of the parameter space where the model can solve the cosmic coincidence problem in full compatibility with all known cosmological data.

Javier Grande; Ana Pelinson; Joan Sola

2009-04-29T23:59:59.000Z

450

Dark Matter Constraints on Composite Higgs Models  

E-Print Network [OSTI]

In composite Higgs models the pseudo-Nambu-Goldstone Boson (pNGB) nature of the Higgs field is an interesting alternative for explaning the smallness of the electroweak scale with respect to the beyond the Standard Model scale. In non-minimal models additional pNGB states are present and can be a Dark Matter (DM) candidate, if there is an approximate symmetry suppressing their decay. Here we assume that the low energy effective theory (for scales much below the compositeness scale) corresponds to the Standard Model with a pNGB Higgs doublet and a pNGB DM multiplet. We derive general effective DM Lagrangians for several possible DM representations (under the SM gauge group), including the singlet, doublet and triplet cases. Within this framework we discuss how the DM observables (relic abundance, direct and indirect detection) constrain the dimension-6 operators induced by the strong sector assuming that DM behaves as a Weakly Interacting Particle (WIMP) and that the relic abundance is settled through the free...

Fonseca, Nayara; Lessa, Andre; Lopez-Honorez, Laura

2015-01-01T23:59:59.000Z

451

The Dark Energy Survey Data Management System  

SciTech Connect (OSTI)

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

452

MSSM inflation, dark matter, and the LHC  

Science Journals Connector (OSTI)

Inflation can occur near a point of inflection in the potential of flat directions of the minimal supersymmetric standard model (MSSM). In this paper we elaborate on the complementarity between the bounds from cosmic microwave background measurements, dark matter, and particle physics phenomenology in determining the underlying parameters of MSSM inflation by specializing to the minimal supergravity scenario. We show that the future measurements from the Large Hadron Collider in tandem with all these constraints will significantly restrict the allowed parameter space. We also suggest a new perspective on the fine tuning issue of MSSM inflation. With quantum corrections taken into account, the necessary condition between the soft supersymmetry breaking parameters in the inflaton potential can be satisfied at scales of interest without a fine tuning of their boundary values at a high scale. The requirement that this happens at the inflection point determines a dimensionless coupling, which is associated with a nonrenormalizable interaction term in the Lagrangian and has no bearing for phenomenology, to very high accuracy.

Rouzbeh Allahverdi; Bhaskar Dutta; Yudi Santoso

2010-08-17T23:59:59.000Z

453

Searching a Dark Photon with HADES  

E-Print Network [OSTI]

We present a search for the e+e- decay of a hypothetical dark photon, also names U vector boson, in inclusive dielectron spectra measured by HADES in the p (3.5 GeV) + p, Nb reactions, as well as the Ar (1.756 GeV/u) + KCl reaction. An upper limit on the kinetic mixing parameter squared epsilon^{2} at 90% CL has been obtained for the mass range M(U) = 0.02 - 0.55 GeV/c2 and is compared with the present world data set. For masses 0.03 - 0.1 GeV/c^2, the limit has been lowered with respect to previous results, allowing now to exclude a large part of the parameter region favoured by the muon g-2 anomaly. Furthermore, an improved upper limit on the branching ratio of 2.3 * 10^{-6} has been set on the helicity-suppressed direct decay of the eta meson, eta-> e+e-, at 90% CL.

HADES Collaboration; G. Agakishiev; A. Balanda; D. Belver; A. Belyaev; J. C. Berger-Chen; A. Blanco; M. Boehmer; J. L. Boyard; P. Cabanelas; S. Chernenko; A. Dybczak; E. Epple; L. Fabbbietti; O. Fateev; P. Finocchiaro; P. Fonte; J. Friese; I. Froehlich; T. Galatyuk; J. A. Garzon; R. Gernhaeuser; K. Goebel; M. Golubeva; D. Gonzalez-Diaz; F. Guber; M. Gumberidze; T. Heinz; T. Hennino; R. Holzmann; A. Ierusalimov; I. Iori; A. Ivashkin; M. Jurkovic; B. Kaempfer; T. Karavicheva; I. Koenig; W. Koenig; B. W. Kolb; G. Kornakov; R. Kotte; A. Krasa; F. Krizek; R. Kruecken; H. Kuc; W. Kuehn; A. Kugler; A. Kurepin; V. Ladygin; R. Lalik; S. Lang; K. Lapidus; A. Lebedev; T. Liu; L. Lopes; M. Lorenz; L. Maier; A. Mangiarotti; J. Markert; V. Metag; B. Michalska; J. Michel; C. Muentz; L. Naumann; Y. C. Pachmayer; M. Palka; Y. Parpottas; V. Pechenov; O. Pechenova; V. Petousis; J. Pietraszko; W. Przygoda; B. Ramstein; A. Reshetin; A. Rustamov; A. Sadovsky; P. Salabura; T. Scheib; H. Schuldes; A. Schmah; E. Schwab; J. Siebenson; Yu. G. Sobolev; S. Spataro; B. Spruck; H. Stroebele; J. Stroth; C. Sturm; A. Tarantola; K. Teilab; P. Tlusty; M. Traxler; R. Trebacz; H. Tsertos; T. Vasiliev; V. Wagner; M. Weber; C. Wendisch; J. Wuestenfeld; S. Yurevich; Y. Zanevsky

2013-11-01T23:59:59.000Z

454

Searching a Dark Photon with HADES  

E-Print Network [OSTI]

We present a search for the e+e- decay of a hypothetical dark photon, also names U vector boson, in inclusive dielectron spectra measured by HADES in the p (3.5 GeV) + p, Nb reactions, as well as the Ar (1.756 GeV/u) + KCl reaction. An upper limit on the kinetic mixing parameter squared epsilon^{2} at 90% CL has been obtained for the mass range M(U) = 0.02 - 0.55 GeV/c2 and is compared with the present world data set. For masses 0.03 - 0.1 GeV/c^2, the limit has been lowered with respect to previous results, allowing now to exclude a large part of the parameter region favoured by the muon g-2 anomaly. Furthermore, an improved upper limit on the branching ratio of 2.3 * 10^{-6} has been set on the helicity-suppressed direct decay of the eta meson, eta-> e+e-, at 90% CL.

Agakishiev, G; Belver, D; Belyaev, A; Berger-Chen, J C; Blanco, A; Boehmer, M; Boyard, J L; Cabanelas, P; Chernenko, S; Dybczak, A; Epple, E; Fabbbietti, L; Fateev, O; Finocchiaro, P; Fonte, P; Friese, J; Froehlich, I; Galatyuk, T; Garzon, J A; Gernhaeuser, R; Goebel, K; Golubeva, M; Gonzalez-Diaz, D; Guber, F; Gumberidze, M; Heinz, T; Hennino, T; Holzmann, R; Ierusalimov, A; Iori, I; Ivashkin, A; Jurkovic, M; Kaempfer, B; Karavicheva, T; Koenig, I; Koenig, W; Kolb, B W; Kornakov, G; Kotte, R; Krasa, A; Krizek, F; Kruecken, R; Kuc, H; Kuehn, W; Kugler, A; Kurepin, A; Ladygin, V; Lalik, R; Lang, S; Lapidus, K; Lebedev, A; Liu, T; Lopes, L; Lorenz, M; Maier, L; Mangiarotti, A; Markert, J; Metag, V; Michalska, B; Michel, J; Muentz, C; Naumann, L; Pachmayer, Y C; Palka, M; Parpottas, Y; Pechenov, V; Pechenova, O; Petousis, V; Pietraszko, J; Przygoda, W; Ramstein, B; Reshetin, A; Rustamov, A; Sadovsky, A; Salabura, P; Scheib, T; Schuldes, H; Schmah, A; Schwab, E; Siebenson, J; Sobolev, Yu G; Spataro, S; Spruck, B; Stroebele, H; Stroth, J; Sturm, C; Tarantola, A; Teilab, K; Tlusty, P; Traxler, M; Trebacz, R; Tsertos, H; Vasiliev, T; Wagner, V; Weber, M; Wendisch, C; Wuestenfeld, J; Yurevich, S; Zanevsky, Y

2013-01-01T23:59:59.000Z

455

Pantry and Fabric Pests in the Home  

E-Print Network [OSTI]

insects in windows or light fixtures. When fully grown, these larvae sometimes bore into the wood or other hard substances to pupate, leaving 1/8-inch-wide holes. Adult hide beetles are relatively large?? to 3/8 inch long. They are dark brown to black... naturally outdoors. In homes, they may be found in accumulations of pet hair or feed- ing on dead insects. The adult webbing clothes moth is gold colored with a tuft of reddish, hairlike scales on its head and a wingspan of about ? inch. The larvae...

Merchant, Michael E.; Brown, Wizzie

2008-10-22T23:59:59.000Z

456

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

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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.

457

On Einstein - Weyl unified model of dark energy and dark matter  

E-Print Network [OSTI]

Here I give a more detailed account of the part of the conference report that was devoted to reinterpreting the Einstein `unified models of gravity and electromagnetism' (1923) as the unified theory of dark energy (cosmological constant) and dark matter (neutral massive vector particle having only gravitational interactions). After summarizing Einstein's work and related earlier work of Weyl and Eddington, I present an approach to finding spherically symmetric solutions of the simplest variant of the Einstein models that was earlier mentioned in Weyl's work as an example of his generalization of general relativity. The spherically symmetric static solutions and homogeneous cosmological models are considered in some detail. As the theory is not integrable we study approximate solutions. In the static case, we show that there may exist two horizons and derive solutions near horizons. In cosmology, we propose to study the corresponding expansions of possible solutions near the origin and derive these expansions in a simplified model neglecting anisotropy. The structure of the solutions seems to hint at a possibility of an inflation mechanism that does not require adding scalar fields.

A. T. Filippov

2009-05-29T23:59:59.000Z

458

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

SciTech Connect (OSTI)

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

459

Differentiating dark energy and modified gravity with galaxy redshift surveys  

Science Journals Connector (OSTI)

The observed cosmic acceleration today could be due to an unknown energy component (dark energy), or a modification to general relativity (modified gravity). If dark energy models and modified gravity models are required to predict the same cosmic expansion history H(z), they will predict different growth rates for cosmic large scale structure, fg(z). If gravity is not modified, the measured H(z) leads to a unique prediction for fg(z), fgH(z), if dark energy and dark matter are separate. Comparing fgH(z) with the measured fg(z) provides a transparent and straightforward test of gravity. We show that a simple ?2 test provides a general figure of merit for our ability to distinguish between dark energy and modified gravity given the measured H(z) and fg(z). We find that a magnitude-limited NIR galaxy redshift survey covering >10?000 (deg)2 and a redshift range of 0.5zH(z) to 1–2% accuracy via baryon acoustic oscillation measurements, and fg(z) to the accuracy of a few per cent via the measurement of redshift-space distortions and the bias factor which describes how light traces mass. We show that if the H(z) data are fitted by both a DGP gravity model and an equivalent dark energy model that predict the same H(z), a survey area of 11?931 (deg)2 is required to rule out the DGP gravity model at the 99.99% confidence level. It is feasible for such a galaxy redshift survey to be carried out by the next generation space missions from NASA and ESA, and it will revolutionize our understanding of the universe by differentiating between dark energy and modified gravity.

Yun Wang

2008-01-01T23:59:59.000Z

460

Joint galaxy-lensing observables and the dark energy  

Science Journals Connector (OSTI)

Deep multicolor galaxy surveys with photometric redshifts will provide a large number of two-point correlation observables: galaxy-galaxy angular correlations, galaxy-shear cross correlations, and shear-shear correlations between all redshifts. These observables can potentially enable a joint determination of the dark-energy-dependent evolution of the dark matter and distances as well as the relationship between galaxies and dark matter halos. With recent cosmic microwave background determinations of the initial power spectrum, a measurement of the mass clustering at even a single redshift will constrain a well-specified combination of dark energy (DE) parameters in a flat universe; we provide convenient fitting formulas for such studies. The combination of galaxy-shear and galaxy-galaxy correlations can determine this amplitude at multiple redshifts. We illustrate this ability in a description of the galaxy clustering with 5 free functions of redshift which can be fitted from the data. The galaxy modeling is based on a mapping onto halos of the same abundance that models a flux-limited selection. In this context and under a flat geometry, a 4000 deg2 galaxy-lensing survey can achieve a statistical precision of ?(?DE)=0.005 for the dark energy density, ?(wDE)=0.02 and ?(wa)=0.17 for its equation of state and evolution, evaluated at dark energy matter equality z?0.4, as well as constraints on the 5 halo functions out to z=1. More importantly, a joint analysis can make dark energy constraints robust against systematic errors in the shear-shear correlation and halo modeling.

Wayne Hu and Bhuvnesh Jain

2004-08-26T23:59:59.000Z

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461

The Dark Energy Survey Data Management System  

SciTech Connect (OSTI)

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

462

Can a galaxy redshift survey measure dark energy clustering?  

Science Journals Connector (OSTI)

A wide-field galaxy redshift survey allows one to probe galaxy clustering at largest spatial scales, which carries invaluable information on horizon-scale physics complementarily to the cosmic microwave background (CMB). Assuming the planned survey consisting of z?1 and z?3 surveys with areas of 2000 and 300??deg2, respectively, we study the prospects for probing dark energy clustering from the measured galaxy power spectrum, assuming the dynamical properties of dark energy are specified in terms of the equation of state and the effective sound speed ce in the context of an adiabatic cold dark dominated matter model. The dark energy clustering adds a power to the galaxy power spectrum amplitude at spatial scales greater than the sound horizon, and the enhancement is sensitive to redshift evolution of the net dark energy density, i.e. the equation of state. We find that the galaxy survey, when combined with CMB expected from the Planck satellite mission, can distinguish dark energy clustering from a smooth dark energy model such as the quintessence model (ce=1), when ce?0.04 (0.02) in the case of the constant equation of state w0=-0.9 (-0.95). An ultimate full-sky survey of z?1 galaxies allows the detection when ce?0.08 (0.04) for w0=0.9 (-0.95). These forecasts show a compatible power with an all-sky CMB and galaxy cross correlation that probes the integrated Sachs-Wolfe effect. We also investigate a degeneracy between the dark energy clustering and the nonrelativistic neutrinos implied from the neutrino oscillation experiments, because the two effects both induce a scale-dependent modification in the galaxy power spectrum shape at largest spatial scales accessible from the galaxy survey. It is shown that a wider redshift coverage can efficiently separate the two effects by utilizing the different redshift dependences, where dark energy clustering is apparent only at low redshifts z?1.

Masahiro Takada

2006-08-04T23:59:59.000Z

463

Dynamical behavior of the extended holographic dark energy with the Hubble horizon  

SciTech Connect (OSTI)

The extended holographic dark energy model with the Hubble horizon as the infrared cutoff avoids the problem of the circular reasoning of the holographic dark energy model. Unfortunately, it is hit with the no-go theorem. In this paper, we consider the extended holographic dark energy model with a potential, V({phi}), for the Brans-Dicke scalar field. With the addition of a potential for the Brans-Dicke scalar field, the extended holographic dark energy model using the Hubble horizon as the infrared cutoff is a viable dark energy model, and the model has the dark energy dominated attractor solution.

Liu Jie; Gong Yungui; Chen Ximing [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)

2010-04-15T23:59:59.000Z

464

Holographic Ricci dark energy: Current observational constraints, quintom feature, and the reconstruction of scalar-field dark energy  

SciTech Connect (OSTI)

In this work, we consider the cosmological constraints on the holographic Ricci dark energy proposed by Gao et al.[Phys. Rev. D 79, 043511 (2009)], by using the observational data currently available. The main characteristic of holographic Ricci dark energy is governed by a positive numerical parameter {alpha} in the model. When {alpha}<1/2, the holographic Ricci dark energy will exhibit a quintomlike behavior; i.e., its equation of state will evolve across the cosmological-constant boundary w=-1. The parameter {alpha} can be determined only by observations. Thus, in order to characterize the evolving feature of dark energy and to predict the fate of the Universe, it is of extraordinary importance to constrain the parameter {alpha} by using the observational data. In this paper, we derive constraints on the holographic Ricci dark energy model from the latest observational data including the Union sample of 307 type Ia supernovae, the shift parameter of the cosmic microwave background given by the five-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey. The joint analysis gives the best-fit results (with 1{sigma} uncertainty): {alpha}=0.359{sub -0.025}{sup +0.024} and {omega}{sub m0}=0.318{sub -0.024}{sup +0.026}. That is to say, according to the observations, the holographic Ricci dark energy takes on the quintom feature. Finally, in light of the results of the cosmological constraints, we discuss the issue of the scalar-field dark energy reconstruction, based on the scenario of the holographic Ricci vacuum energy.

Zhang Xin [Department of Physics, College of Sciences, Northeastern University, Shenyang 110004 (China); Kavli Institute for Theoretical Physics China, Chinese Academy of Sciences, Beijing 100080 (China)

2009-05-15T23:59:59.000Z

465

On The Origin of Light Dark Matter Species  

SciTech Connect (OSTI)

TeV-mass dark matter charged under a new GeV-scale gauge force can explain electronic cosmic-ray anomalies. We propose that the CoGeNT and DAMA direct detection experiments are observing scattering of light stable states 'GeV-Matter' that are charged under this force and constitute a small fraction of the dark matter halo. Dark higgsinos in a supersymmetric dark sector are natural candidates for GeV-Matter that scatter off protons with a universal cross-section of 5 x 10{sup -38} cm{sup 2} and can naturally be split by 10-30 keV so that their dominant interaction with protons is down-scattering. As an example, down-scattering of an O(5) GeV dark higgsino can simultaneously explain the spectra observed by both CoGeNT and DAMA. The event rates in these experiments correspond to a GeV-Matter abundance of 0.2-1% of the halo mass density. This abundance can arise directly from thermal freeze-out at weak coupling, or from the late decay of an unstable TeV-scale WIMP. Our proposal can be tested by searches for exotics in the BaBar and Belle datasets.

Essig, Rouven; Kaplan, Jared; Schuster, Philip; /SLAC; Toro, Natalia; /Stanford U., Phys. Dept.

2010-06-04T23:59:59.000Z

466

Dark matter identification with gamma rays from dwarf galaxies  

SciTech Connect (OSTI)

If the positron fraction and combined electron-positron flux excesses recently observed by PAMELA, Fermi and HESS are due to dark matter annihilation into lepton-rich final states, the accompanying final state radiation (FSR) photons may be detected by ground-based atmospheric Cherenkov telescopes (ACTs). Satellite dwarf galaxies in the vicinity of the Milky Way are particularly promising targets for this search. We find that current and near-future ACTs have an excellent potential for discovering the FSR photons from dwarfs, although a discovery cannot be guaranteed due to large uncertainties in the fluxes resulting from lack of precise knowledge of dark matter distribution within the dwarfs. We also investigate the possibility of discriminating between different dark matter models based on the measured FSR photon spectrum. For typical parameters, we find that the ACTs can reliably distinguish models predicting dark matter annihilation into two-lepton final states from those favoring four-lepton final states (as in, for example, ''axion portal'' models). In addition, we find that the dark matter particle mass can also be determined from the FSR spectrum.

Perelstein, Maxim; Shakya, Bibhushan, E-mail: mp325@cornell.edu, E-mail: bs475@cornell.edu [Institute for High Energy Phenomenology, Newman Laboratory of Elementary Particle Physics, Cornell University, Ithaca, NY 14853 (United States)

2010-10-01T23:59:59.000Z

467

Nonparametric reconstruction of the dark energy equation of state  

SciTech Connect (OSTI)

The major aim of ongoing and upcoming cosmological surveys is to unravel the nature of dark energy. In the absence of a compelling theory to test, a natural approach is to first attempt to characterize the nature of dark energy in detail, the hope being that this will lead to clues about the underlying fundamental theory. A major target in this characterization is the determination of the dynamical properties of the dark energy equation of state w. The discovery of a time variation in w(z) could then lead to insights about the dynamical origin of dark energy. This approach requires a robust and bias-free method for reconstructing w(z) from data, which does not rely on restrictive expansion schemes or assumed functional forms for w(z). We present a new non parametric reconstruction method for the dark energy equation of state based on Gaussian Process models. This method reliably captures nontrivial behavior of w(z) and provides controlled error bounds. We demollstrate the power of the method on different sets of simulated supernova data. The GP model approach is very easily extended to include diverse cosmological probes.

Heitmann, Katrin [Los Alamos National Laboratory; Holsclaw, Tracy [Los Alamos National Laboratory; Alam, Ujjaini [Los Alamos National Laboratory; Habib, Salman [Los Alamos National Laboratory; Higdon, David [Los Alamos National Laboratory; Sanso, Bruno [UC SANTA CRUZ; Lee, Herbie [UC SANTA CRUZ

2009-01-01T23:59:59.000Z

468

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

2010-12-10T23:59:59.000Z

469

Non-relativistic effective theory of dark matter direct detection  

SciTech Connect (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.

Fan, JiJi; Wang, Lian-Tao [Department of Physics, Princeton University, Princeton, NJ, 08540 (United States); Reece, Matthew, E-mail: jijifan@princeton.edu, E-mail: mreece@princeton.edu, E-mail: lianwang@princeton.edu [Princeton Center for Theoretical Science, Princeton University, Princeton, NJ, 08540 (United States)

2010-11-01T23:59:59.000Z

470

Complementarity of Dark Matter Searches in the pMSSM  

E-Print Network [OSTI]

As is well known, the search for and eventual identification of dark matter in supersymmetry requires a simultaneous, multi-pronged approach with important roles played by the LHC as well as both direct and indirect dark matter detection experiments. We examine the capabilities of these approaches in the 19-parameter p(henomenological)MSSM which provides a general framework for complementarity studies of neutralino dark matter. We summarize the sensitivity of dark matter searches at the 7, 8 (and eventually 14) TeV LHC, combined with those by \\Fermi, CTA, IceCube/DeepCore, COUPP, LZ and XENON. The strengths and weaknesses of each of these techniques are examined and contrasted and their interdependent roles in covering the model parameter space are discussed in detail. We find that these approaches explore orthogonal territory and that advances in each are necessary to cover the Supersymmetric WIMP parameter space. We also find that different experiments have widely varying sensitivities to the various dark matter annihilation mechanisms, some of which would be completely excluded by null results from these experiments.

Matthew Cahill-Rowley; Randy Cotta; Alex Drlica-Wagner; Stefan Funk; JoAnne Hewett; Ahmed Ismail; Tom Rizzo; Matthew Wood

2014-05-26T23:59:59.000Z

471

Influence of Dark Matter on Light Propagation in Solar System  

E-Print Network [OSTI]

We investigated the influence of dark matter on light propagation in the solar system. We assumed the spherical symmetry of spacetime and derived the approximate solution of the Einstein equation, which consists of the gravitational attractions caused by the central celestial body, i.e. the Sun, and the dark matter surrounding it. We expressed the dark matter density in the solar system in the following simple power-law form, $\\varrho(t, r) = \\rho(t)(\\ell/r)^k$, where $t$ is the coordinate time; $r$, the radius from the central body; $\\ell$, the normalizing factor; $k$, the exponent characterizing $r$-dependence of dark matter density; and $\\rho(t)$, the arbitrary function of time $t$. On the basis of the derived approximate solution, we focused on light propagation and obtained the additional corrections of the gravitational time delay and the relative frequency shift caused by the dark matter. As an application of our results, we considered the secular increase in the astronomical unit reported by Krasinsky and Brumberg (2004) and found that it was difficult to provide an explanation for the observed $d{\\rm AU}/dt = 15 \\pm 4 ~[{\\rm m/century}]$.

Hideyoshi Arakida

2009-11-17T23:59:59.000Z

472

Invisible Quarkonium Decays as a Sensitive Probe of Dark Matter  

E-Print Network [OSTI]

We examine in a model-independent manner the measurements that can be performed at B-factories with sensitivity to dark matter. If a singlet scalar, pseudo-scalar, or vector is present and mediates the Standard Model - dark matter interaction, it can mediate invisible decays of quarkonium states such as the $\\Upsilon$, $J/\\Psi$, and $\\eta$. Such scenarios have arisen in the context of supersymmetry, extended Higgs sectors, solutions the supersymmetric $\\mu$ problem, and extra U(1) gauge groups from grand unified theories and string theory. Existing B-factories running at the $\\Upsilon(4S)$ can produce lower $\\Upsilon$ resonances by emitting an Initial State Radiation (ISR) photon. Using a combination of ISR and radiative decays, the initial state of an invisibly decaying quarkonium resonance can be tagged, giving sensitivity to the spin and CP-nature of the particle that mediates standard model-dark matter interactions. These measurements can discover or place strong constraints on dark matter scenarios where the dark matter is approximately lighter than the $b$-quark. For the decay chains $\\Upsilon(nS) \\to \\pi^+ \\pi^- \\Upsilon(1S)$ (n=2,3) we analyze the dominant backgrounds and determine that with $400 fb^{-1}$ collected at the $\\Upsilon(4S)$, the B-factories can limit $BR(\\Upsilon(1S) \\to invisible) \\lsim 0.1%$.

Bob McElrath

2005-06-15T23:59:59.000Z

473

Testing and selecting dark energy models with lens redshift data  

Science Journals Connector (OSTI)

In this paper, we compare seven popular dark energy models under the assumption of a flat universe by using the latest observational data of gravitationally-lensed image separations observed in the Cosmic Lens All-Sky Survey (CLASS), the PMN-NVSS Extragalactic Lens Survey (PANELS), the Sloan Digital Sky Survey (SDSS) and other surveys, which are (nearly) complete for the image separation range 0??.3????7??. We combine the 29 lens redshift data with the cosmic microwave background (CMB) observation from the Wilkinson Microwave Anisotropy Probe (WMAP7) results, the baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release. The model comparison statistic, the Bayesian information criterion is also applied to assess the worth of the models. This statistic favors models that give a good fit with fewer parameters. Based on this analysis, we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data. For the other dynamical dark energy models, we find that some of them, such as the Ricci dark energy model, the Affine equation-of-state dark energy, and the generalized Chaplygin gas, can provide good fits to the current data. The Dvali-Gabadadze-Porrati model is the only one-parameter model that can give a rather good fit but also nest ? while the three-parameter model, namely, the interactive dark energy, is clearly disfavored by the data, as it is unable to provide a good fit.

Shuo Cao; Zong-Hong Zhu; Ren Zhao

2011-07-07T23:59:59.000Z

474

Dark energy constraints after the new Planck data  

Science Journals Connector (OSTI)

The Planck Collaboration has recently published maps of the cosmic microwave background radiation with the highest precision. In the standard flat ? cold dark matter framework, Planck data show that the Hubble constant H0 is in tension with that measured by the several direct probes on H0. In this paper, we perform a global analysis from the current observational data in the general dark energy models and find that resolving this tension requires the dark energy model with its equation of state (EOS) w?-1. Firstly, assuming the w to be a constant, the Planck data favor wsurvey” compilation. Consequently the value derived on H0, H0=71.3±2.0??km?s-1?Mpc-1 (68% C.L.) is consistent with that from direct H0 probes. We then investigate the dark energy model with a time-evolving w, and obtain the 68% C.L. constraints w0=-0.81±0.19 and wa=-1.9±1.1 from the Planck data and the “supernova legacy survey” compilation. Current data still slightly favor the quintom dark energy scenario with EOS across the cosmological constant boundary w?-1.

Jun-Qing Xia; Hong Li; Xinmin Zhang

2013-09-03T23:59:59.000Z

475

Neutrinos at IceCube from heavy decaying dark matter  

Science Journals Connector (OSTI)

A monochromatic line in the cosmic neutrino spectrum would be a smoking gun signature of dark matter. It is intriguing that the IceCube experiment has recently reported two PeV neutrino events with energies that may be equal up to experimental uncertainties, and which have a probability of being a background fluctuation estimated to be less than a percent. Here we explore prospects for these events to be the first indication of a monochromatic line signal from dark matter. While measurable annihilation signatures would seem to be impossible at such energies, we discuss the dark matter quantum numbers, effective operators, and lifetimes which could lead to an appropriate signal from dark matter decays. We will show that the set of possible decay operators is rather constrained and will focus on the following viable candidates which could explain the IceCube events: R-parity violating gravitinos, hidden sector gauge bosons, and singlet fermions in an extra dimension. In essentially all cases we find that a PeV neutrino line signal from dark matter would be accompanied by a potentially observable continuum spectrum of neutrinos rising towards lower energies.

Brian Feldstein; Alexander Kusenko; Shigeki Matsumoto; Tsutomu T. Yanagida

2013-07-02T23:59:59.000Z

476

DARK MATTER AS AN ACTIVE GRAVITATIONAL AGENT IN CLOUD COMPLEXES  

SciTech Connect (OSTI)

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

477

Signals of a Light Dark Force in the Galactic Center  

E-Print Network [OSTI]

Recent evidence for an excess of gamma rays in the GeV energy range about the Galactic Center have refocused attention on models of dark matter in the low mass regime ($m_\\chi \\lesssim m_Z/2$). Because this is an experimentally well-trod energy range, it can be a challenge to develop simple models that explain this excess, consistent with other experimental constraints. We reconsider models where the dark matter couples to dark photon, which has a weak kinetic mixing to the Standard Model photon, or scalars with a weak mixing with the Higgs boson. We focus on the light ($\\lesssim 1.5 GeV$) dark mediator mass regime. Annihilations into the dark mediators can produce observable gamma rays through decays to $\\pi^0$, through radiative processes when decaying to charged particles ($e^+e^-, \\mu^+\\mu^-,...$), and subsequent interactions of high energy $e^+e^-$ with gas and light. However, these models have no signals of $\\bar p$ production, which is kinematically forbidden. We find that in these models, the shape of...

Liu, Jia; Xue, Wei

2014-01-01T23:59:59.000Z

478

Seeking Answers in the Darkness | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

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

479

Bright Lights From Dark Places | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

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

480

Boldly Illuminating Biology's "Dark Matter"  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

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481

Mono-Higgs Detection of Dark Matter at the LHC  

E-Print Network [OSTI]

Motivated by the recent discovery of the Higgs boson, we investigate the possibility that a missing energy plus Higgs final state is the dominant signal channel for dark matter at the LHC. We consider examples of higher-dimension operators where a Higgs and dark matter pair are produced through an off-shell Z or photon, finding potential sensitivity at the LHC to cutoff scales of around a few hundred GeV. We generalize this production mechanism to a simplified model by introducing a Z' as well as a second Higgs doublet, where the pseudoscalar couples to dark matter. Resonant production of the Z' which decays to a Higgs plus invisible particles gives rise to a potential mono-Higgs signal. This may be observable at the 14 TeV LHC at low tan beta and when the Z' mass is roughly in the range 600 GeV to 1.3 TeV.

Berlin, Asher; Wang, Lian-Tao

2014-01-01T23:59:59.000Z

482

Mono-Higgs Detection of Dark Matter at the LHC  

E-Print Network [OSTI]

Motivated by the recent discovery of the Higgs boson, we investigate the possibility that a missing energy plus Higgs final state is the dominant signal channel for dark matter at the LHC. We consider examples of higher-dimension operators where a Higgs and dark matter pair are produced through an off-shell Z or photon, finding potential sensitivity at the LHC to cutoff scales of around a few hundred GeV. We generalize this production mechanism to a simplified model by introducing a Z' as well as a second Higgs doublet, where the pseudoscalar couples to dark matter. Resonant production of the Z' which decays to a Higgs plus invisible particles g