While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

1

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

2

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

3

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

4

The Dark Energy Survey Camera (DECam)

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

5

Transverse electric fields' effects in the Dark Energy Camera CCDs

Spurious electric fields transverse to the surface of thick, fully-depleted, high-resistivity CCDs displace the photo-generated charges in the bulk of the detector, effectively modifying the pixel area and producing noticeable signals in astrometric and photometric measurements. We use data from the science verification period of the Dark Energy Survey (DES) to characterize these effects in the Dark Energy Camera (DECam) CCDs. The transverse fields mainly manifest as concentric rings (tree rings) and bright stripes near the boundaries of the detectors (edge distortions) with relative amplitudes of about 1 % and 10 % in the flat-field images, respectively. Their nature as pixel size variations is confirmed by comparing their photometric and astrometric signatures. Using flat-field images from DECam, we derive templates in the five DES photometric bands (grizY) for the tree rings and the edge distortions as a function of their position in each DECam detector. The templates are directly incorporated into the der...

Plazas, Andres; Sheldon, Erin

2014-01-01T23:59:59.000Z

6

CCD Testing for \\{DECam\\} (Dark Energy Survey Camera)

Science Journals Connector (OSTI)

The Dark Energy Survey Camera (DECam] will be comprised of a mosaic of 74 charge-coupled devices (CCDs]. The DES science goals set stringent technical requirements for the CCDs. The \\{CCDs\\} are provided by LBNL with valuable cold probe data at 233 K, providing an indication of which \\{CCDs\\} are more likely to pass. After comprehensive testing of 270 \\{CCDs\\} at 273 K, 124 qualify as science grade. Testing this large number of \\{CCDs\\} to determine which best meet the DES requirements is a very time-consuming task. We developed a multistage testing program to automatically collect and analyze CCD test data.

Donna Kubik

2012-01-01T23:59:59.000Z

7

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...

8

The impact of camera optical alignments on weak lensing measures for the Dark Energy Survey

Science Journals Connector (OSTI)

......weak lensing measures for the Dark Energy Survey Michelle L. Antonik 1 David...with specific reference to the Dark Energy Survey (DES). We compute optics...Suprime-Cam (HSC) survey 1 and the Dark Energy Survey: DES 2 ), telescopes under......

Michelle L. Antonik; David J. Bacon; Sarah Bridle; Peter Doel; David Brooks; Sue Worswick; Gary Bernstein; Rebecca Bernstein; Darren DePoy; Brenna Flaugher; Joshua A. Frieman; Michael Gladders; Gaston Gutierrez; Bhuvnesh Jain; Michael Jarvis; Stephen M. Kent; Ofer Lahav; S.-J. Parker; Aaron Roodman; Alistair R. Walker

2013-01-01T23:59:59.000Z

9

Focal Plane Detectors for Dark Energy Camera (DECam) J. Estrada1

6 , H. Spinka7 , W. Stuermer1 , D. Tucker1 , A. Walker2 , W. Wester1 for the Dark Energy Survey for the Dark Energy Survey. This instrument will use fully depleted 250 m thick CCD detectors selected Survey. 1. DECAM CCDS AND THE DES TECHNICAL REQUIREMENTS The Dark Energy Survey (DES) is a project

10

High-Powered Dark Energy Camera Can See Billions of Light Years...

Office of Environmental Management (EM)

| Photo courtesy of Reidar Hahn at Fermilab. Allison Lantero Allison Lantero Digital Content Specialist, Office of Public Affairs What does this project do? The Dark Energy...

11

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

12

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

13

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

14

Dark Energy Probes of Dark Energy

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

15

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

16

dark matter dark energy inflation

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 Â November 28 - 29, 2005The National Science Foundation The Kavli Foundation The Theoretical Web UHE cosmic rays B

Hu, Wayne

17

Dark energy without dark energy

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

18

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

19

Dark Energy and Dark Matter Models

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

20

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

21

The Dark Energy Survey (DES) is a next genera6on op6cal survey aimed of the project will be described. ! Dark Energy Survey Camera! http is building the Dark Energy Camera (DECam), a 3 square degree, 520 Megapixel

Wechsler, Risa H.

22

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

23

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

24

Photo Credit: Peter GinterSLAC National Accelerator Laboratory Dark Energy

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.

25

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

26

Can Dark Matter Decay in Dark Energy?

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

27

Constraining Dark Matter and Dark Energy Models using Astrophysical Surveys

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.

28

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

29

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

30

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

31

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

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

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

34

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

35

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

36

UNIFIED THEORY OF DARK ENERGY AND DARK SHOUHONG WANG 2

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

37

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

38

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

39

Extended holographic dark energy

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

40

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! Â Carnot (1824), Gibbs (1876): thermodynamics and energy Â Rayleigh (1894): sound

California at Berkeley, University of

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

41

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

42

1 Dark Energy Ay 21, 2010 Measuring the Acceleration of the Expanding Universe Â· 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" Â· We don't know. We are told

Steidel, Chuck

43

Weak Lensing: Dark Matter, Dark Energy

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

44

Dark energy and dark matter from cosmological observations

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

45

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

46

Probing Dark Energy with Theory and Observations

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

47

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

48

Probing Dark Energy with Theory and Observations

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

49

High Energy Physics and Nuclear Physics Network Requirements

collaborations (e.g. , Dark Energy Survey [DES], Dark EnergyDark Energy Camera Dark Energy Survey Dark Energy ScienceDark Energy Spectroscopic Instrument 181 Large Synoptic Survey

Dart, Eli

2014-01-01T23:59:59.000Z

50

Thermodynamical properties of dark energy

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

51

Dark Energy - Dark Matter Unification: Generalized Chaplygin Gas Model

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

52

Optimizing New Dark Energy Experiments

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

53

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...

54

Cosmological constraints on dark energy

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

55

Quantum Haplodynamics, Dark Matter and Dark Energy

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

56

Emergent gravity and Dark Energy

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

57

Measuring the speed of dark: Detecting dark energy perturbations

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

58

Anisotropic charged dark energy star

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

59

Dark energy induced by neutrino mixing

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

60

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

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

61

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

62

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

63

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

64

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

65

Agegraphic Chaplygin gas model of dark energy

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

66

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

67

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

68

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

69

The Dark Force: Astrophysical Repulsion from Dark Energy

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

70

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

71

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

72

REPORT OF THE DARK ENERGY TASK FORCE

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

73

Dark Energy Data Management System : Overview and

, 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

74

Josephson junctions and dark energy

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

75

One of the most pressing, modern cosmological mysteries is the cause of the accelerated expansion of the universe. The energy density required to cause this large scale opposition to gravity is known to be both far in ...

Jackson, Brendan Marc

2011-11-23T23:59:59.000Z

76

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

77

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

78

Cosmological Acceleration: Dark Energy or Modified Gravity?

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

79

Unifying dark energy and dark matter with a scalar field

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

80

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

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

81

Dark Energy, Gravitation and Electromagnetism

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

82

Clustering properties of dynamical dark energy models

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

83

Dark energy and Josephson junctions

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

84

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

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

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

85

On the Chemical Potential of Dark Energy

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

86

Thermodynamics of dark energy interacting with dark matter and radiation

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

87

Schwarzschild black hole in dark energy background

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

88

The Fully Quantized Axion and Dark Energy

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

89

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

90

Thermodynamics of interacting holographic dark energy

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

91

Property:Cameras | Open Energy Information

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

92

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

93

Singularity-free dark energy star

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

94

Dark energy, cosmological constant and neutrino mixing

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

95

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

96

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

97

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

98

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

99

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

100

Probing the curvature and dark energy

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

101

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

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

102

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

103

The Dark Energy Survey Data Management System

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

104

#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.

105

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

106

Dark energy and dark matter from Bose-Einstein condensate

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

107

Dark energy and dark matter from Bose-Einstein condensate

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

108

Dark Energy: Observational Evidence and Theoretical Models

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

109

Is this the end of dark energy?

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

110

Falsifying Field-based Dark Energy Models

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

111

Probing dark energy with future surveys

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

112

Probing the time dependence of dark energy

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

113

Is Hubble's Expansion due to Dark Energy

{\\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

114

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

115

Brane-Bulk energy exchange and agegraphic dark energy

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

116

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

117

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

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

118

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

119

Dark Energy and the Accelerating Universe

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

120

Dark Energy and the Accelerating Universe

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

121

Neutrino mixing, flavor states and dark energy

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

122

Particle mixing, flavor condensate and dark energy

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

123

The Dark Energy Survey Data Management System

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

124

Dark matter interacts with variable vacuum energy

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

125

Cosmic Acceleration, Dark Energy and Fundamental Physics

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

126

Falsification of dark energy by fluid mechanics

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

127

Conformal Higgs model: predicted dark energy density

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

128

Energy Efficient Intrusion Detection in Camera Sensor Networks

Energy Efficient Intrusion Detection in Camera Sensor Networks Primoz Skraba1 and Leonidas Guibas2 1 Department of Electrical Engineering Stanford University, Stanford, CA 94305 primoz@stanford.edu 2 such paths is intractable, since there is generally an infinite number of potential paths. Using a geometric

Guibas, Leonidas J.

129

A Note on Agegraphic Dark Energy

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

130

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

131

Cosmological Evolution of Pilgrim Dark Energy

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

132

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

133

Testable dark energy predictions from current data

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

134

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

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

135

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

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

136

Wiggly cosmic strings accrete dark energy

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

137

Dark goo: bulk viscosity as an alternative to dark energy

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

138

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

139

Non-linear dark energy clustering

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

140

Dark Energy and Life's Ultimate Future

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

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141

Galaxy surveys, inhomogeneous reionization, and dark energy

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

142

Studying Dark Energy with Galaxy Cluster Surveys

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

143

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

144

Dark Energy: A Crisis for Fundamental Physics

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

145

Likelihood Methods for Cluster Dark Energy Surveys

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

146

Advanced Dark Energy Physics Telescope (ADEPT)

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

147

"Dark energy" as conformal dynamics of space

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

148

On the similarity of Information Energy to Dark Energy

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

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

2006-03-03T23:59:59.000Z

149

Viscous dark energy and generalized second law of thermodynamics

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

150

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

151

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

152

Can Holographic dark energy increase the mass of the wormhole?

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

153

Can Holographic dark energy increase the mass of the wormhole?

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

154

A thermodynamic motivation for dark energy

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

155

A Brief History of Dark Energy

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

156

On the determination of dark energy

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

157

Cluster Survey Studies of the Dark Energy

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

158

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

159

Property:Description of Camera Types | Open Energy Information

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

160

Chaotic scalar fields as models for dark energy Christian Beck*

. 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

While these samples are representative of the content of NLE

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We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

161

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

162

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

163

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

164

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

165

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

166

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

167

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

168

CAPUT DARK ENERGY TOPICS, 2013 1. The Cosmological Constant

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

169

Automation of Calibration System for Dark Energy Survey

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

170

Entanglement in holographic dark energy models

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

171

Dark matter interacts with variable vacuum energy

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

172

The Dark Energy Star and Stability analysis

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

173

Dark Energy from Quantum Uncertainty of Simultaneity

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

174

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

175

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

176

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:...

177

Cosmology with Coupled Gravity and Dark Energy

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

178

Cosmology with Coupled Gravity and Dark Energy

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

179

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

180

Reconstructing Dark Energy : A Comparison of Cosmological Parameters

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

181

Dark Energy and Search for the Generalized Second Law

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

182

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

183

Dark energy, gravitation and supernovae

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

Pilar Ruiz-Lapuente

2007-04-09T23:59:59.000Z

184

Redshift drift exploration for interacting dark energy

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

185

An inhomogeneous alternative to dark energy?

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

186

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

187

A Laboratory Search for Dark Energy

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

188

Dynamical system analysis for DBI dark energy interacting with dark matter

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

189

Interacting vacuum energy in the dark sector

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

190

Reissner-Nordstrom black hole in dark energy background

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

191

Cosmic dynamics with entropy corrected holographic dark energy

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

192

On Dark Energy and Accelerated Reference Frames

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

193

Probing Dark Energy with Neutrino Number

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

194

Probing Dark Energy with Neutrino Number

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

195

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

196

Optimizing New Dark Energy Experiments - Final Scientific Report

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

197

Constraining dark energy using real and mock galaxy surveys.

??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

198

The Hubble constant and dark energy from cosmological distance measures

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

199

Will multiple probes of dark energy find modified gravity?

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

200

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

201

Dark Energy: The Cosmological Challenge of the T. Padmanabhan

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.

202

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

203

Probing Dark Energy with Constellation-X

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

204

Probing Dark Energy with Constellation-X

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

205

Holographic Dark Energy with Cosmological Constant

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

206

Stable gravastars of anisotropic dark energy

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

207

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

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

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

208

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

209

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

210

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

211

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

212

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

213

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

214

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

215

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

216

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

217

Validity of Thermodynamical Laws in Dark Energy Filled Universe

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

218

The CHASE laboratory search for chameleon dark energy

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

219

Linear and nonlinear instabilities in unified dark energy models

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

220

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

221

On cosmic acceleration without dark energy

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

222

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

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

223

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...

224

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...

225

Darke County, Ohio: Energy Resources | Open Energy Information

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

226

Dark River, Minnesota: Energy Resources | Open Energy Information

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

227

Property:Number of Color Cameras | Open Energy Information

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

228

Measuring dark energy spatial inhomogeneity with supernova data

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

229

Measuring dark energy spatial inhomogeneity with supernova data

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

230

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

231

Dark matter and dark energy: summary and future directions

Science Journals Connector (OSTI)

...to tell us whether ultra-high-energy y http://www.auger.org...sensitivities to ultra- high-energy cosmic rays. 3. Calculate it...have a good idea of the matter and energy content of the Universe, and some prospects...

2003-01-01T23:59:59.000Z

232

Entropic-force dark energy reconsidered

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

233

Dark energy perturbations and cosmic coincidence

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

234

Anisotropic Dark Energy and the Generalized Second Law of Thermodynamics

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

235

Vacuum quantum fluctuation energy in expanding universe and dark energy

This article is based on the Planckon densely piled vacuum model and the principle of cosmology. With the Planck era as initial conditions and including the early inflation, we have solved the Einstein-Friedmann equations to describe the evolution of the universe. The results are: 1) the ratio of the dark energy density to the vacuum quantum fluctuation energy density is $\\frac{{{\\rho }_{de}}}{{{\\rho }_{vac}}}\\sim{{(\\frac{{{t}_{P}}}{{{T}_{0}}})}^{2}}\\sim{{10}^{-122}} $; 2) at the inflation time ${{t}_{\\inf }}={{10}^{-35}}s$, the calculated universe radiation energy density is $\\rho ({{t}_{\\inf }})\\sim{{10}^{-16}}{{\\rho }_{vac}}$ and the corresponding temperature is ${{E}_{c}}\\sim{{10}^{15}}GeV$ consistent with the GUT phase transition temperature; 3) the expanding universe with vacuum as its environment is a non-equilibrium open system constantly exchanging energy with vacuum; during its expansion, the Planckons in the universe lose quantum fluctuation energy and create the cosmic expansion quanta-cosmons, the energy of cosmons is the lost part of the vacuum quantum fluctuation energy and contributes to the universe energy with the calculated value ${{E}_{\\cos mos}}={{10}^{22}}{{M}_{\\otimes }}{{c}^{2}}$ (where ${{M}_{\\otimes }}$ is solar mass); 4) the total energy of the universe, namely the negative gravity energy plus the positive universe energy is zero; 5) the negative gravity potential and the gravity acceleration related to the creation of cosmons are derived with the nature of outward repulsive force, indicating that the cosmon may be the candidate of the dark energy quantum; 6) both the initial Planck era solution and the infinite asymptotic solution of the Einstein-Friedman equations are unstable: the former tends to expand and the latter tends to shrink, so that the Einstein-Friedman universe will undergo a cyclic evolution of successive expansion and shrinking.

Shun-Jin Wang

2014-10-27T23:59:59.000Z

236

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

237

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

238

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

239

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

240

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

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

241

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

242

Dynamical dark energy or variable cosmological parameters?

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

243

About the Geometric Solution to the Problems of Dark Energy

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

Miguel Angel García-Aspeitia

2011-02-06T23:59:59.000Z

244

Stable dark energy stars: An alternative to black holes?

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

245

Model selection as a science driver for dark energy surveys

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

246

Particle mixing as possible explanation of the dark energy conundrum

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

247

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

248

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

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

249

Measuring dark energy with the shear triplet statistics

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

250

Interacting Ghost Dark Energy in Non-Flat Universe

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

251

Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies

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

252

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

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

253

Large Synoptic Survey Telescope: Dark Energy Science Collaboration

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

254

Can a galaxy redshift survey measure dark energy clustering?

(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

255

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

256

Missing Energy Signatures of Dark Matter at the LHC

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

257

SUPERNOVA SIMULATIONS AND STRATEGIES FOR THE DARK ENERGY SURVEY

We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 deg{sup 2} search area in the griz filter set. We forecast (1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05

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

2012-07-10T23:59:59.000Z

258

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

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

B. A. Trubnikov

2008-12-09T23:59:59.000Z

259

DarkStar VI | Open Energy Information

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 36.720014Â°, -79.91284Â° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":36.720014,"lon":-79.91284,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

260

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

261

Dark Energy, Expansion History of the Universe, and SNAP

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

Eric V. Linder

2003-02-03T23:59:59.000Z

262

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

263

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

264

Fundamentalist physics: why Dark Energy is bad for Astronomy

Astronomers carry out observations to explore the diverse processes and objects which populate our Universe. High-energy physicists carry out experiments to approach the Fundamental Theory underlying space, time and matter. Dark Energy is a unique link between them, reflecting deep aspects of the Fundamental Theory, yet apparently accessible only through astronomical observation. Large sections of the two communities have therefore converged in support of astronomical projects to constrain Dark Energy. In this essay I argue that this convergence can be damaging for astronomy. The two communities have different methodologies and different scientific cultures. By uncritically adopting the values of an alien system, astronomers risk undermining the foundations of their own current success and endangering the future vitality of their field. Dark Energy is undeniably an interesting problem to attack through astronomical observation, but it is one of many and not necessarily the one where significant progress is most likely to follow a major investment of resources.

Simon D. M. White

2007-04-18T23:59:59.000Z

265

Nonparametric reconstruction of the dark energy equation of state

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

266

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

267

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

268

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

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

269

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

270

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

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

Mubasher Jamil

2009-12-22T23:59:59.000Z

271

Science Journals Connector (OSTI)

......Constraining dynamical dark energy models through the abundance...its contribution to the energy density would become rapidly...provided by the NASA Joint Dark Energy Mission (JDEM) -Wide-Field Infrared Survey Telescope (WFIRST) space......

A. Lamastra; N. Menci; F. Fiore; C. Di Porto; L. Amendola

2012-03-01T23:59:59.000Z

272

Determining Camera Gain in Room Temperature Cameras

James R. Janesick provides a method for determining the amplification of a CCD or CMOS camera when only access to the raw images is provided. However, the equation that is provided ignores the contribution of dark current. For CCD or CMOS cameras that are cooled well below room temperature, this is not a problem, however, the technique needs adjustment for use with room temperature cameras. This article describes the adjustment made to the equation, and a test of this method.

Joshua Cogliati

2010-12-01T23:59:59.000Z

273

Dark Energy, Paradigm Shifts, and the Role of Evidence

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

274

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

275

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

276

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

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

277

What We Know About Dark Energy From Supernovae

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

Alex Filippenko

2010-01-08T23:59:59.000Z

278

Measuring dark energy clustering with CMB-galaxy correlations

Science Journals Connector (OSTI)

The integrated Sachs-Wolfe effect in the cosmic microwave background as measured through its correlation with galaxies provides a unique opportunity to study the dynamics of the dark energy through its large scale clustering properties. Ultimately, a deep all-sky galaxy survey out to z?2 can make a ?10? or ?10% measurement of the correlation and limit ?3% changes in the gravitational potential or total density fluctuation due to dark energy clustering on the Gpc scale. A canonical single scalar field or quintessence model predicts that these clustering effects will appear on the horizon scale with a strength that reflects the evolution of the dark energy density. In terms of a constant equation of state, this would allow tests of the quintessence prediction for models where |1+w|?0.05.

Wayne Hu and Ryan Scranton

2004-12-06T23:59:59.000Z

279

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 $\\alphadark 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): $\\alpha=0.359^{+0.024}_{-0.025}$ and $\\Omega_{\\rm m0}=0.318^{+0.026}_{-0.024}$. 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

2009-01-15T23:59:59.000Z

280

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

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

While these samples are representative of the content of NLE

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We encourage you to perform a real-time search of NLE

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281

Constraining dark energy with Sunyaev-Zel'dovich cluster surveys

We discuss the prospects of constraining the properties of a dark energy component, with particular reference to a time varying equation of state, using future cluster surveys selected by their Sunyaev-Zel'dovich effect. We compute the number of clusters expected for a given set of cosmological parameters and propogate the errors expected from a variety of surveys. In the short term they will constrain dark energy in conjunction with future observations of type Ia supernovae, but may in time do so in their own right.

Jochen Weller; Richard Battye; Ruediger Kneissl

2001-10-16T23:59:59.000Z

282

Reducing Zero-point Systematics in Dark Energy Supernova Experiments

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

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

2011-04-01T23:59:59.000Z

283

Dark Energy from Quantum Uncertainty of Remote Clocks

The observed cosmic acceleration was attributed to a mysterious dark energy in the framework of classical general relativity. The dark energy behaves very similar with vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a complete wrong result and leads to a severe fine-tuning. To solve the problem, the exact meaning of time in quantum mechanics is reexamined. 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 physical clock. We find that synchronization of two spatially separated clocks can not be precisely realized at quantum level. There is an intrinsic quantum uncertainty of remote simultaneity, which implies an apparent vacuum energy fluctuation and gives an observed dark energy density $\\rho_{de}=\\frac{6}{\\pi}L_{P}^{-2}L_{H}^{-2}$ at leading order, where $L_{P}$ and $L_{H}$ are the Planck and Hubble scale cutoffs. The fraction of the dark energy is given by $\\Omega_{de}=\\frac{2}{\\pi}$ at leading order approximation, which does not evolve with time, so it is "always" comparable to the critical density. This theory is consistent with current cosmic observations.

M. J. Luo

2014-03-03T23:59:59.000Z

284

Illuminating Dark Photons with High-Energy Colliders

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

285

Observational constraints on dark energy and cosmic curvature

Science Journals Connector (OSTI)

Current observational bounds on dark energy depend on our assumptions about the curvature of the universe. We present a simple and efficient method for incorporating constraints from cosmic microwave background (CMB) anisotropy data and use it to derive constraints on cosmic curvature and dark energy density as a free function of cosmic time using current CMB, Type Ia supernova (SN Ia), and baryon acoustic oscillation data. We show that there are two CMB shift parameters, R??mH02r(zCMB) (the scaled distance to recombination) and la??r(zCMB)/rs(zCMB) (the angular scale of the sound horizon at recombination), with measured values that are nearly uncorrelated with each other. Allowing nonzero cosmic curvature, the three-year WMAP (Wilkinson Microwave Anisotropy Probe) data give R=1.71±0.03, la=302.5±1.2, and ?bh2=0.02173±0.00082, independent of the dark energy model. The corresponding bounds for a flat universe are R=1.70±0.03, la=302.2±1.2, and ?bh2=0.022±0.00082. We give the covariance matrix of (R,la,?bh2) from the three-year WMAP data. We find that (R,la,?bh2) provide an efficient and intuitive summary of CMB data as far as dark energy constraints are concerned. Assuming the Hubble Space Telescope (HST) prior of H0=72±8??(km/s)?Mpc-1, using 182 SNe Ia (from the HST/GOODS program, the first year Supernova Legacy Survey, and nearby SN Ia surveys), (R,la,?bh2) from WMAP three-year data, and SDSS (Sloan Digital Sky Survey) measurement of the baryon acoustic oscillation scale, we find that dark energy density is consistent with a constant in cosmic time, with marginal deviations from a cosmological constant that may reflect current systematic uncertainties or true evolution in dark energy. A flat universe is allowed by current data: ?k=-0.006-0.012-0.025+0.013+0.025 for assuming that the dark energy equation of state wX(z) is constant, and ?k=-0.002-0.018-0.032+0.018+0.041 for wX(z)=w0+wa(1-a) (68% and 95% confidence levels). The bounds on cosmic curvature are less stringent if dark energy density is allowed to be a free function of cosmic time, and are also dependent on the assumption about the early time property of dark energy. We demonstrate this by studying two examples. Significant improvement in dark energy and cosmic curvature constraints is expected as a result of future dark energy and CMB experiments.

Yun Wang and Pia Mukherjee

2007-11-30T23:59:59.000Z

286

Detecting dark energy with wavelets on the sphere Jason D. McEwen

know very little about its nature and origin. Although strong evidence in support of dark energyDetecting dark energy with wavelets on the sphere Jason D. McEwen Astrophysics Group, Cavendish Laboratory, Cambridge CB3 0HE, UK ABSTRACT Dark energy dominates the energy density of our Universe, yet we

McEwen, Jason

287

The South Pole Telescope: A white paper for the Dark Energy Task Force

redshifts, the statistical power of the survey yields are sufficient to measure the dark energy equation energy constraints are derived from the SPT SZE survey results. To test theories of dark energyThe South Pole Telescope: A white paper for the Dark Energy Task Force J. E. Carlstrom, C. Chang, T

Collar, Juan I.

288

Thermodynamics of viscous dark energy in an RSII braneworld

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

M. R. Setare; A. Sheykhi

2011-03-05T23:59:59.000Z

289

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

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

290

Testing dark energy with the Advanced Liquid-mirror Probe of Asteroids, Cosmology and Astrophysics

Science Journals Connector (OSTI)

......Papers Testing dark energy with the Advanced...Columbia University, New York, NY 10027, USA 2...Columbia University, New York, NY 10027, USA 3...Columbia University, New York, NY 10027, USA 4...for studying dark energy. The bulk of the......

Pier Stefano Corasaniti; Marilena LoVerde; Arlin Crotts; Chris Blake

2006-06-21T23:59:59.000Z

291

Figures of merit for testing standard models: application to dark energy experiments in cosmology

Science Journals Connector (OSTI)

......Kilo-Degree Survey (KIDS), Panoramic Survey Telescope Rapid Response System (Pan-STARRS),1 Dark Energy Survey (DES),2 Large Synoptic Survey Telescope (LSST),3 Joint Dark Energy Mission (JDEM)4 and Euclid.5......

A. Amara; T. D. Kitching

2011-05-21T23:59:59.000Z

292

A one-parameter formula for testing slow-roll dark energy: observational prospects

Science Journals Connector (OSTI)

......Oscillation Spectroscopic Survey (BOSS), BigBOSS, Large Synoptic Survey Telescope, Euclid and Planck, will constrain dark energy (DE)'s equation of...website 11 ); Day 2010). Dark Energy Survey (DES), begun in late......

Zachary Slepian; J. Richard Gott; III; Joel Zinn

2014-01-01T23:59:59.000Z

293

Testing dark energy with the Advanced Liquid-mirror Probe of Asteroids, Cosmology and Astrophysics

Science Journals Connector (OSTI)

......the constraints on dark energy from the estimated...duration of the survey, and from the expected...coverage of the survey, these measurements...competitive constraints on dark energy parameters (Pogosian...al. 2005). The survey will also provide......

Pier Stefano Corasaniti; Marilena LoVerde; Arlin Crotts; Chris Blake

2006-06-21T23:59:59.000Z

294

Science Journals Connector (OSTI)

......Oscillation Spectroscopic Survey (BOSS),1 Hobby-Eberly Telescope Dark Energy Experiment (HETDEX...design for using LAMOST survey to constrain dark energy parameters is to have a MAIN1 survey, an LRG survey supplemented......

Xin Wang; Xuelei Chen; Zheng Zheng; Fengquan Wu; Pengjie Zhang; Yongheng Zhao

2009-04-21T23:59:59.000Z

295

Constraints on dark energy with the LOSS SN Ia sample

Science Journals Connector (OSTI)

......deceleration, constrain the evolution of dark energy (DE), and search for possible...et-al. 2013). Imminent or future surveys to gather large data sets at high redshift include the Dark Energy Survey (DES) and the Large Synoptic......

Mohan Ganeshalingam; Weidong Li; Alexei V. Filippenko

2013-01-01T23:59:59.000Z

296

Bound on the Equation of State of Dark Energy from the Generalized Second Law of Thermodynamics

Science Journals Connector (OSTI)

Assuming that the equation of state of dark energy is a constant, we obtain the allowed interval of the equation of state of dark energy: w D??1, bounded from the generalized second law of thermodynamics

Rong-Jia Yang; Jing-Zhao Qi; Lihua Feng

2012-06-01T23:59:59.000Z

297

Differentiating dark energy and modified gravity with galaxy redshift surveys

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 rate for cosmic large scale structure, f_g(z)=d\\ln \\delta/d\\ln a (\\delta=(\\rho_m-\\bar{\\rho_m})/\\bar{\\rho_m}), a is the cosmic scale factor). If gravity is not modified, the measured H(z) leads to a unique prediction for f_g(z), f_g^H(z). Comparing f_g^H(z) with the measured f_g(z) provides a transparent and straightforward test of gravity. We show that a simple \\chi^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 f_g(z). We study a magnitude-limited NIR galaxy redshift survey covering >10,000 (deg)^2 and the redshift range of 0.5dark energy model that predict the same expansion history, 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

2007-10-21T23:59:59.000Z

298

Evolution of spherical overdensities in holographic dark energy models

In this work we investigate the spherical collapse model in flat FRW dark energy universes. We consider the Holographic Dark Energy (HDE) model as a dynamical dark energy scenario with a slowly time-varying equation-of-state (EoS) parameter $w_{\\rm de}$ in order to evaluate the effects of the dark energy component on structure formation in the universe. We first calculate the evolution of density perturbations in the linear regime for both phantom and quintessence behavior of the HDE model and compare the results with standard Einstein-de Sitter (EdS) and $\\Lambda$CDM models. We then calculate the evolution of two characterizing parameters in the spherical collapse model, i.e., the linear density threshold $\\delta_{\\rm c}$ and the virial overdensity parameter $\\Delta_{\\rm vir}$. We show that in HDE cosmologies the growth factor $g(a)$ and the linear overdensity parameter $\\delta_{\\rm c}$ fall behind the values for a $\\Lambda$CDM universe while the virial overdensity $\\Delta_{\\rm vir}$ is larger in HDE models ...

Naderi, Tayebe; Pace, Francesco

2014-01-01T23:59:59.000Z

299

Distance measurements from supernovae and dark energy constraints

Science Journals Connector (OSTI)

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

Yun Wang

2009-12-21T23:59:59.000Z

300

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

While these samples are representative of the content of NLE

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We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

301

SNAPSNAPSuperNova/Acceleration Probe Dark Energy and the Accelerating Universe

Nova/Acceleration Probe Dark Energy and the Accelerating Universe SNAP #12;he recent discovery that the expansionSNAPSNAPSuperNova/Acceleration Probe Dark Energy and the Accelerating Universe Super attraction alone, its rate of expansion would be slowing. Acceleration requires a strange "dark energy

Perlmutter, Saul

302

Future dark energy constraints from measurements of quasar parallax: Gaia, SIM and beyond

Science Journals Connector (OSTI)

......configuration) a Key Project using 2.4 per cent...principle measure the dark energy parameters w 0 and wa...expected to constrain dark energy parameters in Section...QUASAR PARALLAX IN DARK ENERGY MODELS The Solar system is moving with......

Fiona Ding; Rupert A. C. Croft

2009-08-21T23:59:59.000Z

303

An old quasar in a young dark energy-dominated universe?

Science Journals Connector (OSTI)

......ratio to reach the solar value and (iii...existing dark energy scenarios cannot...Telescope (HST) key project, this new age...redshift for dark energy and brane world...Fe/O = 2.5 solar. On the left-hand...see that no dark energy or brane world...by the HST key project. Note also that......

A. C. S. Friaça; J. S. Alcaniz; J. A. S. Lima

2005-10-01T23:59:59.000Z

304

Probing dark energy with the next generation X-ray surveys of galaxy clusters

Science Journals Connector (OSTI)

......Papers Probing dark energy with the next generation X-ray surveys of galaxy clusters...optical [e.g. Dark Energy Survey (DES),3 EUCLID...X-ray cluster surveys for the class of...called early dark energy (EDE; Wetterich......

B. Sartoris; S. Borgani; P. Rosati; J. Weller

2012-07-01T23:59:59.000Z

305

Disentangling dark energy and cosmic tests of gravity from weak lensing systematics

Science Journals Connector (OSTI)

......structure surveys such as the Dark Energy Survey (DES), the Subaru Measurement...Hyper Suprime-Cam,3 the Dark Energy Survey (DES)4 and the Large Synoptic...for optimizing cosmic shear surveys to measure dark energy in a related paper (Kirk......

Istvan Laszlo; Rachel Bean; Donnacha Kirk; Sarah Bridle

2012-06-21T23:59:59.000Z

306

Robust constraints on dark energy and gravity from galaxy clustering data

Science Journals Connector (OSTI)

......about the Stage IV survey, which is at z 0.7. Figure 3 Dark energy FoM for Stage...results on probing dark energy and testing gravity from such a survey. 4SUMMARY AND...galaxy redshift survey can probe dark energy and constrain......

Yun Wang

2012-07-11T23:59:59.000Z

307

Neutrino masses, dark energy and the gravitational lensing of pre-galactic H I

Science Journals Connector (OSTI)

......Large Synoptic Survey Telescope,2 PanSTARRS,3 Dark Energy Survey4; Hannestad...ability of these surveys to measure properties of the dark energy (Hannestad...the lensing surveys by themselves...Fig. 3, the dark energy equation of......

R. Benton Metcalf

2010-01-21T23:59:59.000Z

308

Designing a space-based galaxy redshift survey to probe dark energy

Science Journals Connector (OSTI)

......space-based galaxy redshift survey to probe dark energy Yun Wang 1 * Will Percival...conventional FoM for comparing dark energy surveys proposed by the DETF (Albrecht...dramatic over ground-based surveys when dark energy density is allowed to be......

Yun Wang; Will Percival; Andrea Cimatti; Pia Mukherjee; Luigi Guzzo; Carlton M. Baugh; Carmelita Carbone; Paolo Franzetti; Bianca Garilli; James E. Geach; Cedric G. Lacey; Elisabetta Majerotto; Alvaro Orsi; Piero Rosati; Lado Samushia; Giovanni Zamorani

2010-12-01T23:59:59.000Z

309

The WiggleZ Dark Energy Survey: the transition to large-scale cosmic homogeneity

Science Journals Connector (OSTI)

......research-article Articles The WiggleZ Dark Energy Survey: the transition to large-scale...this work, we use the WiggleZ Dark Energy Survey (Drinkwater et al. ) to make...THE WiggleZ SURVEY The WiggleZ Dark Energy Survey (Drinkwater et al. ) is a......

Morag I. Scrimgeour; Tamara Davis; Chris Blake; J. Berian James; Gregory B. Poole; Lister Staveley-Smith; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2012-09-01T23:59:59.000Z

310

Detecting massive galaxies at high redshift using the Dark Energy Survey

Science Journals Connector (OSTI)

......galaxies at high redshift using the Dark Energy Survey L. J. M. Davies 1 2 C. Maraston...Porto Alegre, Brazil The Dark Energy Survey (DES) will be unprecedented...galaxy surveys (e.g. the Dark Energy survey, DES), in conjunction with......

L. J. M. Davies; C. Maraston; D. Thomas; D. Capozzi; R. H. Wechsler; M. T. Busha; M. Banerji; F. Ostrovski; C. Papovich; B. X. Santiago; R. Nichol; M. A. G. Maia; L. N. da Costa

2013-01-01T23:59:59.000Z

311

The WiggleZ Dark Energy Survey: survey design and first data release

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: survey design and first data...M5S 3H4, Canada The WiggleZ Dark Energy Survey is a survey of 240 000 emission-line...et al. 2009a). The WiggleZ Dark Energy Survey is a major large-scale structure......

Michael J. Drinkwater; Russell J. Jurek; Chris Blake; David Woods; Kevin A. Pimbblet; Karl Glazebrook; Rob Sharp; Michael B. Pracy; Sarah Brough; Matthew Colless; Warrick J. Couch; Scott M. Croom; Tamara M. Davis; Duncan Forbes; Karl Forster; David G. Gilbank; Michael Gladders; Ben Jelliffe; Nick Jones; I-hui Li; Barry Madore; D. Christopher Martin; Gregory B. Poole; Todd Small; Emily Wisnioski; Ted Wyder; H. K. C. Yee

2010-01-21T23:59:59.000Z

312

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

cosmological parameters and dark energy through weak lensing measurements in the COSMOS survey (Massey et al March 18, 2010 James Webb Space Telescope Studies of Dark Energy Jonathan P. Gardner (NASA. Introduction The Hubble Space Telescope (HST) has contributed significantly to studies of dark energy

Sirianni, Marco

313

Can dark energy viscosity be detected with the Euclid survey?

Science Journals Connector (OSTI)

Recent work has demonstrated that it is important to constrain the dynamics of cosmological perturbations, in addition to the evolution of the background, if we want to distinguish among different models of the dark sector. Especially the anisotropic stress of the (possibly effective) dark energy fluid has been shown to be an important discriminator between modified gravity and dark energy models. In this paper we use approximate analytical solutions of the perturbation equations in the presence of viscosity to study how the anisotropic stress affects the weak lensing and galaxy power spectrum. We then forecast how sensitive the photometric and spectroscopic Euclid surveys will be to both the speed of sound and the viscosity of our effective dark energy fluid when using weak lensing tomography and the galaxy power spectrum. We find that Euclid alone can only constrain models with a very small speed of sound and viscosity, while it will need the help of other observables in order to give interesting constraints on models with a sound speed close to one. This conclusion is also supported by the expected Bayes factor between models.

Domenico Sapone; Elisabetta Majerotto; Martin Kunz; Bianca Garilli

2013-08-05T23:59:59.000Z

314

Can dark energy viscosity be detected with the Euclid survey?

Recent work has demonstrated that it is important to constrain the dynamics of cosmological perturbations, in addition to the evolution of the background, if we want to distinguish among different models of the dark sector. Especially the anisotropic stress of the (possibly effective) dark energy fluid has been shown to be an important discriminator between modified gravity and dark energy models. In this paper we use approximate analytical solutions of the perturbation equations in the presence of viscosity to study how the anisotropic stress affects the weak lensing and galaxy power spectrum. We then forecast how sensitive the photometric and spectroscopic Euclid surveys will be to both the speed of sound and the viscosity of our effective dark energy fluid when using weak lensing tomography and the galaxy power spectrum. We find that Euclid alone can only constrain models with very small speed of sound and viscosity, while it will need the help of other observables in order to give interesting constraints on models with a sound speed close to one. This conclusion is also supported by the expected Bayes factor between models.

Domenico Sapone; Elisabetta Majerotto; Martin Kunz; Bianca Garilli

2013-05-08T23:59:59.000Z

315

Probing Dark Energy with Theory and Observations.

??The discovery of cosmic acceleration twelve years ago impliesthat our universe is dominated bydark energy, which is either a tiny cosmological constantor a mysterious fluid… (more)

de Putter, Roland

2010-01-01T23:59:59.000Z

316

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

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

317

Quintessence in a quandary: Prior dependence in dark energy models

Science Journals Connector (OSTI)

The archetypal theory of dark energy is quintessence: a minimally coupled scalar field with a canonical kinetic energy and potential. By studying random potentials, we show that quintessence imposes a restricted set of priors on the equation of state of dark energy. Focusing on the commonly used parametrization, w(a)?w0+wa(1?a), we show that there is a natural scale and direction in the (w0,wa) plane that distinguishes quintessence as a general framework. We calculate the expected information gain for a given survey and show that, because of the nontrivial prior information, it is a function of more than just the figure of merit. This allows us to make a quantitative case for novel survey strategies. We show that the scale of the prior sets target observational requirements for gaining significant information. This corresponds to a figure of merit FOM?200, a requirement that future galaxy redshift surveys will meet.

David J.?E. Marsh; Philip Bull; Pedro G. Ferreira; Andrew Pontzen

2014-11-18T23:59:59.000Z

318

Testing the cosmological constant as a candidate for dark energy

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

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

2003-12-03T23:59:59.000Z

319

Neutrino dark energy-revisiting the stability issue

A coupling between a light scalar field and neutrinos has been widely discussed as a mechanism for linking (time varying) neutrino masses and the present energy density and equation of state of dark energy. However, it has been pointed out that the viability of this scenario in the non-relativistic neutrino regime is threatened by the strong growth of hydrodynamic perturbations associated with a negative adiabatic sound speed squared. In this paper we revisit the stability issue in the framework of linear perturbation theory in a model independent way. The criterion for the stability of a model is translated into a constraint on the scalar-neutrino coupling, which depends on the ratio of the energy densities in neutrinos and cold dark matter. We illustrate our results by providing meaningful examples for both stable and unstable models.

Bjaelde, Ole Eggers; Hannestad, Steen [Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark); Brookfield, Anthony W; Van de Bruck, Carsten [Department of Applied Mathematics, Astro-Particle Theory and Cosmology Group, Hounsfield Road, Hicks Building, University of Sheffield, Sheffield S3 7RH (United Kingdom); Mota, David F [Institute for Theoretical Physics, University of Heidelberg, D-69120 Heidelberg (Germany); Schrempp, Lily [Deutsches Elektron-Synchroton DESY, Hamburg, Notkestrasse 85, 22607 Hamburg (Germany); Tocchini-Valentini, Domenico, E-mail: oeb@phys.au.dk, E-mail: php04awb@sheffield.ac.uk, E-mail: C.vandebruck@sheffield.ac.uk, E-mail: sth@phys.au.dk, E-mail: d.mota@thphys.uni-heidelberg.de, E-mail: lily.schrempp@desy.de, E-mail: dtv@skysrv.pha.jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

2008-01-15T23:59:59.000Z

320

Quantum Yang-Mills Condensate Dark Energy Models

We review the quantum Yang-Mills condensate (YMC) dark energy models. As the effective Yang-Mills Lagrangian is completely determined by the quantum field theory, there is no adjustable parameter in the model except the energy scale. In this model, the equation-of-state (EOS) of the YMC dark energy, $w_y > -1$ and $w_y 0$ into $w_y < -1$, which is slightly suggested by the observations. At the same time, the total EOS in the attractor solution is $w_{tot} = -1$, the universe being the de Sitter expansion in the late stage, and the cosmic big rip is naturally avoided. These features are all independent of the interacting forms.

Zhao, W; Tong, M L

2009-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

321

Probing dark energy at galactic and cluster scales

We investigate dark matter halo properties as a function of a time-varying dark energy equation of state. The dynamics of the collapse of the halo is governed by the form of the quintessence potential, the time evolution of its equation of state, the initial conditions of the field and its homogeneous nature in the highly non-linear regime. These have a direct impact on the turnaround, virialization and collapse times, altering in consequence the non-linear density contrast and virial radius. We compute halo concentrations using the Eke, Navarro and Steinmetz algorithm, examining two extreme scenarios: first, we assume that the quintessence field does not exhibit fluctuations on cluster scales and below-homogeneous fluid; second, we assume that the field inside the overdensity collapses along with the dark matter-inhomogeneous fluid. The Eke, Navarro and Steinmetz prescription reveals, in general, higher halo concentrations in inhomogeneous dark energy models than in their homogeneous equivalents. Halo concentrations appear to be controlled by both changes in formation epochs of the halo cores and differing virialization overdensities. We derive physical halo properties in all models and discuss their observational implications. We examine two possible methods for comparing observations with theoretical predictions. The first method works on galaxy cluster scales and consists of fitting the observed x-ray cluster gas density distributions to those predicted for an Navarro-Frenk-White profile. The second method works on galaxy scales and involves the observational measurement of the so-called central density parameter.

Mota, David F, E-mail: D.Mota@thphys.uni-heidelberg.de [Institute for Theoretical Physics, University of Heidelberg, 69120 Heidelberg (Germany)

2008-09-15T23:59:59.000Z

322

A divergence-free parametrization for dynamical dark energy

We introduce a new parameterization for the dark energy which is led by the same idea to the linear expansion of the equation of state both in scale factor $a$ and in redshift $z$, diverges neither in the past nor future and yields the same number of free parameters with the former ones. We present constraints of the cosmological parameters using a combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN), and found a slightly improvement to the data compared to previous models. This new parametrization allowed us to carry out successive observational analyses by decreasing its degrees of freedom systematically until ending up with a dynamical dark energy model having no additional parameters, compared to $\\Lambda$CDM, which fits slightly better to data.

Akarsu, Ozgur; Vazquez, J Alberto

2015-01-01T23:59:59.000Z

323

CONSTRAINING PERTURBATIVE EARLY DARK ENERGY WITH CURRENT OBSERVATIONS

In this work, we study a class of early dark energy (EDE) models, in which, unlike in standard dark energy models, a substantial amount of dark energy exists in the matter-dominated era. We self-consistently include dark energy perturbations, and constrain these models using current observations. We consider EDE models in which the dark energy equation of state is at least w{sub m} {approx_gt} -0.1 at early times, which could lead to an EDE density of up to {Omega}{sub DE}(z{sub CMB})= 0.03{Omega}{sub m}(z{sub CMB}). Our analysis shows that marginalizing over the non-DE parameters such as {Omega}{sub m}, H{sub 0}, andn{sub s} , current CMB observations alone can constrain the scale factor of transition from EDE to late-time dark energy to a{sub t} {approx_gt} 0.44 and width of transition to {Delta}{sub t} {approx_lt} 0.37. The equation of state at present is somewhat weakly constrained to w{sub 0} {approx_lt} -0.6, if we allow H{sub 0} < 60 km s{sup -1} Mpc{sup -1}. Taken together with other observations, such as SNe, Hubble Space Telescope, and Sloan Digital Sky Survey luminous red galaxies, w{sub 0} is constrained much more tightly to w{sub 0} {approx_lt} -0.9, while redshift of transition and width of transition are also tightly constrained to a{sub t} {approx_lt} 0.19 and{Delta}{sub t} {approx_lt} 0.21. The evolution of the equation of state for EDE models is thus tightly constrained to {Lambda}CDM-like behavior at low redshifts. Incorrectly assuming dark energy perturbations to be negligible leads to different constraints on the equation of state parameters-w{sub 0} {approx_lt} -0.8, a{sub t} {approx_lt} 0.33, and{Delta}{sub t} {approx_lt} 0.31, thus highlighting the necessity of self-consistently including dark energy perturbations in the analysis. If we allow the spatial curvature to be a free parameter, then the constraints are relaxed to w{sub 0} {approx_lt} -0.77, a{sub t} {approx_lt} 0.35, and{Delta}{sub t} {approx_lt} 0.35 with -0.014 < {Omega}{sub {kappa}} < 0.031 for CMB + other observations. For perturbed EDE models, the 2{sigma} lower limit on {sigma}{sub 8} ({sigma}{sub 8} {>=} 0.59) is much lower than that in {Lambda}CDM ({sigma}{sub 8} {>=} 0.72), thus raising the interesting possibility of discriminating EDE from {Lambda}CDM using future observations such as halo mass functions or the Sunyaev-Zeldovich power spectrum.

Alam, Ujjaini [ISR-1, ISR Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2010-05-10T23:59:59.000Z

324

Could Dark Energy be Measured from Redshift Surveys ?

We review the ability of redshift surveys to provide constraints on the Dark Energy content of the Universe. The matter power spectrum and dynamics at the present epoch are nearly `blind' to Dark Energy, but combined with the CMB they can provide a constraint on the Equation of State parameter w. A representative result from the 2dF galaxy redshift survey combined with the CMB is w = -1), consistent with Einstein's Cosmological Constant model (w=-1). More complicated forms of Quintessence (e.g. epoch-dependent w or w<-1) are not yet ruled out. At higher redshifts, the abundance of galaxies and clusters of galaxies, variants of the Alcock-Paczynski curvature test and cross correlation of the CMB with radio sources look potentially promising, but they suffer from degeneracy with other parameters such as the matter density and galaxy biasing.

Ofer Lahav

2002-12-16T23:59:59.000Z

325

Dark energy model selection with current and future data

The main goal of the next generation of weak lensing probes is to constrain cosmological parameters by measuring the mass distribution and geometry of the low redshift Universe and thus to test the concordance model of cosmology. A future all-sky tomographic cosmic shear survey with design properties similar to Euclid has the potential to provide the statistical accuracy required to distinguish between different dark energy models. In order to assess the model selection capability of such a probe, we consider the dark energy equation-of-state parameter $w_0$. We forecast the Bayes factor of future observations, in the light of current information from Planck} by computing the predictive posterior odds distribution. We find that Euclid is unlikely to overturn current model selection results, and that the future data are likely to be compatible with a cosmological constant model. This result holds for a wide range of priors.

Debono, Ivan

2014-01-01T23:59:59.000Z

326

8/24/09 11:48 AMSPACE.com -- 'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 10http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html#comments What is Dark Energy? Universe Might Be Bigger and Older Than In New? Register: Join Now! 'Big Wave' Theory Offers Alternative to Dark Energy By Clara Moskowitz Staff

Temple, Blake

327

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

Temple, Blake

328

Solar System Constraints on Gauss-Bonnet Dark Energy

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

Stephen C. Davis

2007-08-15T23:59:59.000Z

329

On the onset of the dark energy era

The occurrence of the scaling accelerated phase after matter dominance has been shown to be rather problematic for all existing dark energy and modified gravity models. In this paper we consider a cosmic scenario where both the matter particles and scalar field are associated with sub-quantum potentials which make the effective mass associated with the matter particles to vanish at the coincidence time, so that a cosmic system where matter dominance phase followed by accelerating expansion is allowed.

Gonzalez-Diaz, Pedro F

2008-01-01T23:59:59.000Z

330

Is dark energy an artifact of decoherence?

Within the quantum Darwinist framework introduced by W. H. Zurek ({\\em Nat. Phys.}, 5:181-188, 2009), observers obtain pointer-state information about quantum systems by interacting with the surrounding environment, e.g. the ambient photon field. This framework is applied to the observation of stellar center-of-mass positions, which are assumed to be encoded in a way that is uniformly accessible to all observers regardless of their location. Assuming Landauer's Principle, constructing such environmental encodings requires $\\sim$ kT per bit. For 10$^{25}$ stars and a binary encoding of center-of-mass positions into 10 km$^{3}$ voxels, the free energy required at T = 2.7 K is $\\sim$ 5 $\\cdot$ 10$^{-27}$ kg $\\cdot$ m$^{-3}$, in striking agreement with the observed value of $\\Omega_{\\Lambda} \\rho_{c}$. Decreasing the voxel size to $l_{P}^{3}$ results in a free energy requirement 10$^{117}$ times larger.

Fields, Chris

2015-01-01T23:59:59.000Z

331

Non-existence of extended holographic dark energy with the Hubble horizon

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. We show that the infrared cutoff of the extended holographic dark energy model cannot be the Hubble horizon provided that the Brans-Dicke parameter {omega} satisfies the experimental constraint {omega}>10{sup 4}, and this is proved as a no-go theorem. The no-go theorem also applies to the case in which the dark matter interacts with the dark energy.

Gong, Yungui; Liu, Jie, E-mail: gongyg@cqupt.edu.cn, E-mail: sxtyliujie@126.com [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)] [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)

2008-09-15T23:59:59.000Z

332

Dark Energy Constraints from the CTIO Lensing Survey

Science Journals Connector (OSTI)

We perform a cosmological parameter analysis of the 75 deg2 CTIO lensing survey in conjunction with cosmic microwave background (CMB) and Type Ia supernovae data. For ?CDM cosmologies, we find that the amplitude of the power spectrum at low redshift is given by ?8 = 0.81 (95% confidence level), where the error bound includes both statistical and systematic errors. The total of all systematic errors is smaller than the statistical errors, but they do make up a significant fraction of the error budget. We find that weak lensing improves the constraints on dark energy as well. The (constant) dark energy equation of state parameter, w, is measured to be -0.89 (95% c.l.). Marginalizing over a constant w slightly changes the estimate of ?8 to 0.79 (95% c.l.). We also investigate variable w cosmologies but find that the constraints weaken considerably; next-generation surveys are needed to obtain meaningful constraints on the possible time evolution of dark energy.

Mike Jarvis; Bhuvnesh Jain; Gary Bernstein; Derek Dolney

2006-01-01T23:59:59.000Z

333

Probing dark energy dynamics from current and future cosmological observations

Science Journals Connector (OSTI)

We report the constraints on the dark energy equation-of-state w(z) using the latest “Constitution” SNe sample combined with the WMAP5 and Sloan Digital Sky Survey data. Assuming a flat Universe, and utilizing the localized principal component analysis and the model selection criteria, we find that the ?CDM model is generally consistent with the current data, yet there exists a weak hint of the possible dynamics of dark energy. In particular, a model predicting w(z)-1 at z?[0.5,0.75), which means that w(z) crosses -1 in the range of z?[0.25,0.75), is mildly favored at 95% confidence level. Given the best fit model for current data as a fiducial model, we make future forecast from the joint data sets of Joint Dark Energy Mission, Planck, and Large Synoptic Survey Telescope, and we find that the future surveys can reduce the error bars on the w bins by roughly a factor of 10 for a 5-w-bin model.

Gong-Bo Zhao and Xinmin Zhang

2010-02-10T23:59:59.000Z

334

Dark Energy Constraints from the CTIO Lensing Survey

We perform a cosmological parameter analysis of the 75 square degree CTIO lensing survey in conjunction with CMB and Type Ia supernovae data. For Lambda CDM cosmologies, we find that the amplitude of the power spectrum at low redshift is given by sigma_8 = 0.81 (+0.15,-0.10, 95% c.l.), where the error bar includes both statistical and systematic errors. The total of all systematic errors is smaller than the statistical errors, but they do make up a significant fraction of the error budget. We find that weak lensing improves the constraints on dark energy as well. The (constant) dark energy equation of state parameter, w, is measured to be -0.89 (+0.16,-0.21, 95% c.l.). Marginalizing over a constant $w$ slightly changes the estimate of sigma_8 to 0.79 (+0.17, -0.14, 95% c.l.). We also investigate variable w cosmologies, but find that the constraints weaken considerably; the next generation surveys are needed to obtain meaningful constraints on the possible time evolution of dark energy.

Mike Jarvis; Bhuvnesh Jain; Gary Bernstein; Derek Dolney

2005-02-14T23:59:59.000Z

335

Baryon Oscillations and Dark-Energy Constraints from Imaging Surveys

Baryonic oscillations in the galaxy power spectrum have been studied as a way of probing dark-energy models. While most studies have focused on spectroscopic surveys at high redshift, large multi-color imaging surveys have already been planned for the near future. In view of this, we study the prospects for measuring baryonic oscillations from angular statistics of galaxies binned using photometric redshifts. We use the galaxy bispectrum in addition to the power spectrum; this allows us to measure and marginalize over possibly complex galaxy bias mechanisms to get robust cosmological constraints. In our parameter estimation we allow for a weakly nonlinear biasing scheme that may evolve with redshift by two bias parameters in each of ten redshift bins. We find that a multi-color imaging survey that probes redshifts beyond one can give interesting constraints on dark-energy parameters. In addition, the shape of the primordial power spectrum can be measured to better accuracy than with the CMB alone. We explore the impact of survey depth, area, and calibration errors in the photometric redshifts on dark-energy constraints.

Derek Dolney; Bhuvnesh Jain; Masahiro Takada

2004-09-20T23:59:59.000Z

336

Probing dark energy dynamics from current and future cosmological observations

We report the constraints on the dark energy equation-of-state w(z) using the latest 'Constitution' SNe sample combined with the WMAP5 and Sloan Digital Sky Survey data. Assuming a flat Universe, and utilizing the localized principal component analysis and the model selection criteria, we find that the {Lambda}CDM model is generally consistent with the current data, yet there exists a weak hint of the possible dynamics of dark energy. In particular, a model predicting w(z)<-1 at z is an element of [0.25,0.5) and w(z)>-1 at z is an element of [0.5,0.75), which means that w(z) crosses -1 in the range of z is an element of [0.25,0.75), is mildly favored at 95% confidence level. Given the best fit model for current data as a fiducial model, we make future forecast from the joint data sets of Joint Dark Energy Mission, Planck, and Large Synoptic Survey Telescope, and we find that the future surveys can reduce the error bars on the w bins by roughly a factor of 10 for a 5-w-bin model.

Zhao Gongbo [Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom); Department of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada); Zhang Xinmin [Theoretical Physics Division, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918-4, Beijing 100049 (China); Theoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Sciences (China)

2010-02-15T23:59:59.000Z

337

A quantum gravitational origin of dark energy

We propose a new explanation of the origin of the small vacuum energy of the present universe within a nonperturbative quantum theory of gravity with torsional instantons. These pseudoparticles, which were recently found to exist in a first order formulation of Giddings-Strominger axionic gravity, carry nontrivial Nieh-Yan topological charge. The nonperturbative vacuum as generated due to tunneling effects and parametrised by the Barbero-Immirzi topological angle is shown to be stable under quantum fluctuations. In this theory, absence of any observable parity violating effect fixes the Barbero-Immirzi parameter to a small value, which is determined by the current estimate of the Hubble constant.

Sengupta, Sandipan

2015-01-01T23:59:59.000Z

338

Singularity and entropy of the viscosity dark energy model

In this paper bulk viscosity is introduced to describe the effects of cosmic non-perfect fluid on the cosmos evolution and to build the unified dark energy (DE) with (dark) matter models. Also we derive a general relation between the bulk viscosity form and Hubble parameter that can provide a procedure for the viscosity DE model building. Especially, a redshift dependent viscosity parameter $\\zeta\\propto\\lambda_{0}+\\lambda_{1}(1+z)^{n}$ proposed in the previous work by X.H.Meng and X.Dou in 2009\\cite{md} is investigated extensively in this present work. Further more we use the recently released supernova dataset (the Constitution dataset) to constrain the model parameters. In order to differentiate the proposed concrete dark energy models from the well known $\\Lambda$CDM model, statefinder diagnostic method is applied to this bulk viscosity model, as a complementary to the $Om$ parameter diagnostic and the deceleration parameter analysis performed by us before. The DE model evolution behavior and tendency are...

Meng, X H

2009-01-01T23:59:59.000Z

339

Tracking and coupled dark energy as seen by the Wilkinson Microwave Anisotropy Probe

Science Journals Connector (OSTI)

The satellite experiment, the Wilkinson Microwave Anisotropy Probe (WMAP), has produced for the first time a high-coverage, high-resolution survey of the microwave sky, releasing publicly available data that are likely to remain unrivaled for years to come. Here we compare the WMAP temperature power spectrum, along with an exhaustive compilation of previous experiments, to models of dark energy that allow for a tracking epoch at the present, deriving updated bounds on the dark energy equation of state and the other cosmological parameters. Moreover, we complement the analysis by including a coupling of the dark energy to dark matter. The main results are (a) the WMAP data alone constrain the equation of state of tracking dark energy to be w?-1), which implies for an inverse power-law potential an exponent ?dark matter is |?|dark energy equation of state.

Luca Amendola and Claudia Quercellini

2003-07-23T23:59:59.000Z

340

On the observability of coupled dark energy with cosmic voids

Taking N-body simulations with volumes and particle densities tuned to match the SDSS DR7 spectroscopic main sample, we asses the ability of current void catalogs (e.g., Sutter et al. 2012b) to distinguish a model of coupled dark matter-dark energy from {\\Lambda}CDM cosmology using properties of cosmic voids. Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al. (2013). In addition, we use the universal density profile of Hamaus et al. (2014) to quantify the relationship between coupling and density profile shape, finding that the coupling leads to deeper underdensities for medium-scale voids and broader, shallower, undercompensated profiles for large voids. We find that these differences are potentially measurable with existing void catalogs once effects from survey geometries and peculiar velocities are taken into accou...

Sutter, P M; Wandelt, Benjamin D; Knebe, Alexander

2014-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

341

Interacting entropy-corrected agegraphic Chaplygin gas model of dark energy

In this work, we consider the interacting agegraphic dark energy models with entropy correction terms due to loop quantum gravity. We study the correspondence between the Chaplygin gas energy density with the interacting entropy-corrected agegraphic dark energy models in non-flat FRW universe. We reconstruct the potentials and the dynamics of the interacting entropy-corrected agegraphic scalar field models. This model is also extended to the interacting entropy-corrected agegraphic generalized Chaplygin gas dark energy.

M. Malekjani; A. Khodam-Mohammadi

2010-04-07T23:59:59.000Z

342

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.

343

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

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

344

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

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

345

Dark Energy in Light of the Cosmic Horizon

Based on dramatic observations of the CMB with WMAP and of Type Ia supernovae with the Hubble Space Telescope and ground-based facilities, it is now generally believed that the Universe's expansion is accelerating. Within the context of standard cosmology, the Universe must therefore contain a third `dark' component of energy, beyond matter and radiation. However, the current data are still deemed insufficient to distinguish between an evolving dark energy component and the simplest model of a time-independent cosmological constant. In this paper, we examine the role played by our cosmic horizon R0 in our interrogation of the data, and reach the rather firm conclusion that the existence of a cosmological constant is untenable. The observations are telling us that R0=c t0, where t0 is the perceived current age of the Universe, yet a cosmological constant would drive R0 towards ct (where t is the cosmic time) only once, and that would have to occur right now. In contrast, scaling solutions simultaneously eliminate several conundrums in the standard model, including the `coincidence' and `flatness' problems, and account very well for the fact that R0=c t0. We show here that for such dynamical dark energy models, either R0=ct for all time (thus eliminating the apparent coincidence altogether), or that what we believe to be the current age of the universe is actually the horizon time th=R0/c, which is always shorter than t0. Our best fit to the Type Ia supernova data indicates that t0 would then have to be ~16.9 billion years. Though surprising at first, an older universe such as this would actually eliminate several other long-standing problems in cosmology, including the (too) early appearance of supermassive black holes (at a redshift > 6) and the glaring deficit of dwarf halos in the local group.

Fulvio Melia

2007-11-29T23:59:59.000Z

346

Confronting dark energy models using galaxy cluster number counts

The mass function of cluster-size halos and their redshift distribution are computed for 12 distinct accelerating cosmological scenarios and confronted to the predictions of the conventional flat {Lambda}CDM model. The comparison with {Lambda}CDM is performed by a two-step process. First, we determine the free parameters of all models through a joint analysis involving the latest cosmological data, using supernovae type Ia, the cosmic microwave background shift parameter, and baryon acoustic oscillations. Apart from a braneworld inspired cosmology, it is found that the derived Hubble relation of the remaining models reproduces the {Lambda}CDM results approximately with the same degree of statistical confidence. Second, in order to attempt to distinguish the different dark energy models from the expectations of {Lambda}CDM, we analyze the predicted cluster-size halo redshift distribution on the basis of two future cluster surveys: (i) an X-ray survey based on the eROSITA satellite, and (ii) a Sunayev-Zeldovich survey based on the South Pole Telescope. As a result, we find that the predictions of 8 out of 12 dark energy models can be clearly distinguished from the {Lambda}CDM cosmology, while the predictions of 4 models are statistically equivalent to those of the {Lambda}CDM model, as far as the expected cluster mass function and redshift distribution are concerned. The present analysis suggests that such a technique appears to be very competitive to independent tests probing the late time evolution of the Universe and the associated dark energy effects.

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

2010-10-15T23:59:59.000Z

347

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

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

Micheal S. Berger; Hamed Shojaei

2006-08-16T23:59:59.000Z

348

Constraints on dark energy models from radial baryon acoustic scale measurements

We use the radial baryon acoustic oscillation (BAO) measurements of Gaztanaga et al. (2008) to constrain parameters of dark energy models. These constraints are comparable with constraints from other "non-radial" BAO data. The radial BAO data are consistent with the time-independent cosmological constant model but do not rule out time-varying dark energy. When we combine radial BAO and the Kowalski et al. (2008) Union type Ia supernova data we get very tight constraints on dark energy.

Lado Samushia; Bharat Ratra

2008-10-12T23:59:59.000Z

349

The Dark Energy Survey: Prospects for Resolved Stellar Populations

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

Wide angle and deep surveys, regardless of their primary purpose, always sample a large number of stars in the Galaxy and in its satellite system. We here make a forecast of the expected stellar sample resulting from the Dark Energy Survey and the perspectives that it will open for studies of Galactic structure and resolved stellar populations in general. An estimated 1.2 x 10{sup 8} stars will be sampled in DES grizY filters in the southern equatorial hemisphere. This roughly corresponds to 20% of all DES sources. Most of these stars belong to the stellar thick disk and halo of the Galaxy.

Rossetto, Bruno M [Rio de Janeiro Observ.; Santiago, Basilio X [Rio Grande do Sul U.; Rio de Janeiro Observ.; Girardi, Leo [Padua Observ.; Rio de Janeiro Observ.; Camargo, Julio I.B. [Rio de Janeiro Observ.; Balbinot, Eduardo [Rio Grande do Sul U.; Rio de Janeiro Observ.; da Costa, Luiz N [Rio de Janeiro Observ.; Yanny, Brian [Fermilab; Maia, Marcio A.G. [Rio de Janeiro Observ.; Makler, Martin [Rio de Janeiro, CBPF; Rio de Janeiro Observ.; Ogando, Ricardo L.C. [Rio de Janeiro Observ.; Pellegrini, Paulo S [Rio de Janeiro Observ.; Rio de Janeiro Observ.

2011-05-06T23:59:59.000Z

350

Modified GBIG Scenario as an Alternative for Dark Energy

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

Kourosh Nozari; Narges Rashidi

2009-09-02T23:59:59.000Z

351

Probing Dark Energy with Lensing Magnification in Photometric Surveys

I present an estimator for the angular cross-correlation of two tracers of the cosmological large-scale structure that utilizes redshift information to isolate separate physical contributions. The estimator is derived by solving the Limber equation for a re-weighting of the foreground tracer that nulls either clustering or lensing contributions to the cross-correlation function. Applied to future photometric surveys, the estimator can enhance the measurement of gravitational lensing magnification effects to provide a competitive independent constraint on the dark energy equation of state.

Schneider, Michael D

2014-01-01T23:59:59.000Z

352

Supernova Simulations and Strategies for the Dark Energy Survey

Science Journals Connector (OSTI)

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

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

2012-01-01T23:59:59.000Z

353

Classical Nature of the Evolution of Dark Energy Density

By ignoring the local density fluctuations, we construct an uniform Higgs-field's (inflaton's) quantum theory with varying effective Planck constant ($\\hbar_{v}(t) \\propto R(t)^{-3}$) for the evolution of the dark energy density during the epoch after inflation. With presumable sufficient inflation in the very early period (time-scale is $t_{inf}$), so that $\\hbar_{v}\\to 0$, the state of universe decomposes into some decoherent components, which could be the essential meaning of phase transition, and each of them could be well described by classical mechanics for an inharmonic oscillator in the corresponding potential-well with a viscous force. We find that the cosmological constant at present is $\\Lambda_{now}\\approx 2.05\\times 10^{-3}$ eV, which is almost independent of the choice of potential for inflaton, and agrees excellently with the recent observations. In addition, we find that, during the cosmic epoch after inflation, the dark energy is almost conserved as well as the matter's energy, therefore the ...

Yuan, W; Liu, Yu-xin; Yuan, Wei

2006-01-01T23:59:59.000Z

354

Science Journals Connector (OSTI)

With the discovery of Dark Energy, ?DE, there is now a universal length scale, $${\\ell_{\\rm DE}=c/(\\Lambda_{\\rm DE} G)^{1/2}}$$ ...

Achilles D. Speliotopoulos

2010-06-01T23:59:59.000Z

355

Reconstruction of Hessence Dark Energy and the Latest Type Ia Supernovae Gold Dataset

Recently, many efforts have been made to build dark energy models whose equation-of-state parameter can cross the so-called phantom divide $w_{de}=-1$. One of them is the so-called hessence dark energy model in which the role of dark energy is played by a non-canonical complex scalar field. In this work, we develop a simple method based on Hubble parameter $H(z)$ to reconstruct the hessence dark energy. As examples, we use two familiar parameterizations for $H(z)$ and fit them to the latest 182 type Ia supernovae Gold dataset. In the reconstruction, measurement errors are fully considered.

Hao Wei; Ningning Tang; Shuang Nan Zhang

2007-02-28T23:59:59.000Z

356

Sandage–Loeb test for the new agegraphic and Ricci dark energy models

Science Journals Connector (OSTI)

The Sandage–Loeb (SL) test is a unique method to explore dark energy at the “redshift desert” ( 2 ? z ? 5 ), an era not covered by any other dark energy probes, by directly measuring the temporal variation of the redshift of quasar (QSO) Lyman-? absorption lines. In this Letter, we study the prospects for constraining the new agegraphic dark energy (NADE) model and the Ricci dark energy (RDE) model with the SL test. We show that, assuming only a ten-year survey, the SL test can constrain these two models with high significance.

Jingfei Zhang; Li Zhang; Xin Zhang

2010-01-01T23:59:59.000Z

357

Constraints on early dark energy from CMB lensing and weak lensing tomography

Dark energy can be studied by its influence on the expansion of the Universe as well as on the growth history of the large-scale structure. In this paper, we follow the growth of the cosmic density field in early dark energy cosmologies by combining observations of the primary CMB temperature and polarisation power spectra at high redshift, of the CMB lensing deflection field at intermediate redshift and of weak cosmic shear at low redshifts for constraining the allowed amount of early dark energy. We present these forecasts using the Fisher matrix formalism and consider the combination of Planck data with the weak lensing survey of Euclid. We find that combining these data sets gives powerful constraints on early dark energy and is able to break degeneracies in the parameter set inherent to the various observational channels. The derived statistical 1{sigma}-bound on the early dark energy density parameter is {sigma}({Omega}{sup e}{sub d}) = 0.0022 which suggests that early dark energy models can be well examined in our approach. In addition, we derive the dark energy figure of merit for the considered dark energy parameterisation and comment on the applicability of the growth index to early dark energy cosmologies.

Hollenstein, Lukas; Crittenden, Robert [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom)] [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Sapone, Domenico [Departement de Physique Theorique, Universite de Geneve, 24 Quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland)] [Departement de Physique Theorique, Universite de Geneve, 24 Quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland); Schaefer, Bjoern Malte, E-mail: lukas.hollenstein@port.ac.uk, E-mail: domenico.sapone@unige.ch, E-mail: robert.crittenden@port.ac.uk, E-mail: spirou@ita.uni-heidelberg.de [Astronomisches Recheninstitut, Zentrum fuer Astronomie, Universitaet Heidelberg, Moenchhofstrasse 12, 69120 Heidelberg (Germany)

2009-04-15T23:59:59.000Z

358

Sandage-Loeb test for the new agegraphic and Ricci dark energy models

The Sandage-Loeb (SL) test is a unique method to explore dark energy at the ``redshift desert'' ($2\\lesssim z\\lesssim 5$), an era not covered by any other dark energy probes, by directly measuring the temporal variation of the redshift of quasar (QSO) Lyman-$\\alpha$ absorption lines. In this paper, we study the prospects for constraining the new agegraphic dark energy (NADE) model and the Ricci dark energy (RDE) model with the SL test. We show that, assuming only a ten-year survey, the SL test can constrain these two models with high significance.

Jingfei Zhang; Li Zhang; Xin Zhang

2010-06-09T23:59:59.000Z

359

Dark Energy Models and Laws of Thermodynamics in Bianchi I Model

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

M. Sharif; Rabia Saleem

2013-02-20T23:59:59.000Z

360

New constraints on coupled dark energy from the Planck satellite experiment

Science Journals Connector (OSTI)

We present new constraints on coupled dark energy from the recent measurements of the cosmic microwave background anisotropies from the Planck satellite mission. We found that a coupled dark energy model is fully compatible with the Planck measurements, deriving a weak bound on the dark matter–dark energy coupling parameter ?=-0.49-0.31+0.19 at 68% C.L. Moreover if Planck data are fitted to a coupled dark energy scenario, the constraint on the Hubble constant is relaxed to H0=72.1-2.3+3.2??km/s/Mpc, solving the tension with the Hubble Space Telescope (HST) value. We show that a combined PLANCK+HST analysis provides significant evidence for coupled dark energy finding a nonzero value for the coupling parameter ?, with -0.90Survey, the Sloan Digital Sky Survey and the Baron Oscillation Spectroscopic Survey.

Valentina Salvatelli; Andrea Marchini; Laura Lopez-Honorez; Olga Mena

2013-07-24T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

361

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

By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for even polytropic index by choosing $K>Ba^{\\frac{3}{n}}$, one can obtain $\\omega^{\\rm eff}_{\\Lambda}<-1$, which corresponds to a universe dominated by phantom dark energy.

K. Karami; S. Ghaffari; J. Fehri

2009-11-25T23:59:59.000Z

362

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

Office of Science (SC) Website

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

363

Constraining dark energy from the abundance of weak gravitational lenses

We examine the prospect of using the observed abundance of weak gravitational lenses to constrain the equation-of-state parameter w of the dark energy. Here we solve the spherical-collapse model with dark energy, clarifying some ambiguities found in the literature, and provide fitting formulas for the overdensity at virialization and the linear-theory overdensity at collapse. We then compute the variation in the predicted weak-lens abundance with w. We find that the predicted redshift distribution and number count of weak lenses are highly degenerate in w and \\Omega_0. If we fix \\Omega_0 the number count for w=-2/3 is a factor of 2 smaller than for the \\LambdaCDM model. However, if we allow \\Omega_0 to vary with w such that the amplitude of the matter power spectrum as measured by COBE matches that obtained from the X-ray cluster abundance, the decrease in the predicted lens abundance is less than 25% for -1 40 degree^2 in order for the number count to differentiate a \\LambdaCDM cosmology from a w=-0.9 model...

Weinberg, N N; Weinberg, Nevin N.; Kamionkowski, Marc

2003-01-01T23:59:59.000Z

364

$\\sigma$CDM coupled to radiation. Dark energy and Universe acceleration

Recently the Chiral Cosmological Model (CCM) coupled to cold dark matter (CDM) has been investigated as $\\sigma$CDM model to study the observed accelerated expansion of the Universe. Dark sector fields (as Dark Energy content) coupled to cosmic dust were considered as the source of Einstein gravity in Friedmann-Robertson-Walker (FRW) cosmology. Such model had a beginning at the matter-dominated era. The purposes of our present investigation are two folds: to extend > of the $\\sigma$CDM for earlier times to radiation-dominated era and to take into account variation of the exponential potential via variation of the interaction parameter $\\lambda $. We use Markov Chain Monte Carlo (MCMC) procedure to investigate possible values of initial conditions constrained by the measured amount of the dark matter, dark energy and radiation component today. Our analysis includes dark energy contribution to critical density, the ratio of the kinetic and potential energies, deceleration parameter, effective equation of state ...

Abbyazov, Renat R; Müller, Volker

2014-01-01T23:59:59.000Z

365

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

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

M. Malekjani; A. Khodam-Mohammadi

2012-01-03T23:59:59.000Z

366

Importance of supernovae at z>1.5 to probe dark energy

Science Journals Connector (OSTI)

The accelerating expansion of the universe suggests that an unknown component with strongly negative pressure, called dark energy, currently dominates the dynamics of the universe. Such a component makes up ?70% of the energy density of the universe yet has not been predicted by the standard model of particle physics. The best method for exploring the nature of this dark energy is to map the recent expansion history, at which type Ia supernovae have proved adept. We examine here the depth of survey necessary to provide a precise and qualitatively complete description of dark energy. A realistic analysis of parameter degeneracies, allowance for natural time variation of the dark energy equation of state, and systematic errors in astrophysical observations all demonstrate the importance of a survey covering the full range 0dark energy.

Eric V. Linder and Dragan Huterer

2003-04-21T23:59:59.000Z

367

Puzzles of the dark energy in the universe - phantom

This paper is devoted to some simple approach based on general physics tools to describe the physical properties of a hypothetical particle which can be the source of dark energy in the Universe known as phantom. Phantom is characterized by the fact that it possesses negative momentum and kinetic energy and that it gives large negative pressure which acts as antigravity. We consider phantom harmonic oscillator in comparison to a standard harmonic oscillator. By using the first law of thermodynamics we explain why the energy density of the Universe grows when it is filled with phantom. We also show how the collision of phantom with a standard particle leads to exploration of energy from the former by the latter (i.e. from phantom to the standard) if their masses are different. The most striking of our conclusions is that the collision of phantom and standard particles of the same masses is impossible unless both of them are at rest and suddenly start moving with the opposite velocities and kinetic energies. This effect is a classic analogue of a quantum mechanical particle pair creation in a strong electric field or in physical vacuum.

Mariusz P. Dabrowski

2014-11-08T23:59:59.000Z

368

Dark Energy Rules the Universe (and why the dinosaurs do not!) (LBNL Science at the Theater)

The revolutionary discovery that the expansion of the universe is speeding up, not slowing down from gravity, means that 75 percent of our universe consists of mysterious dark energy. Berkeley Lab theoretical physicist Eric Linder delves into the mystery of dark energy as part of the Science in the Theatre lecture series on Nov. 24, 2008.

Linder, Eric

2008-11-28T23:59:59.000Z

369

Dark Energy Rules the Universe (and why the dinosaurs do not!) (LBNL Science at the Theater)

The revolutionary discovery that the expansion of the universe is speeding up, not slowing down from gravity, means that 75 percent of our universe consists of mysterious dark energy. Berkeley Lab theoretical physicist Eric Linder delves into the mystery of dark energy as part of the Science in the Theatre lecture series on Nov. 24, 2008.

Linder, Eric

2011-04-28T23:59:59.000Z

370

Constraining the dark energy equation of state with double-source plane strong lenses

Science Journals Connector (OSTI)

......possibility of constraining the dark energy equation of state by measuring...as Cambridge and Sloan survey of wide arcs in the sky...such as Sloan Lens ACS survey. We find that constraints...cosmological parameters|dark energy| 1 Introduction We appear......

T. E. Collett; M. W. Auger; V. Belokurov; P. J. Marshall; A. C. Hall

2012-08-21T23:59:59.000Z

371

Probing dark energy with baryonic oscillations and future radio surveys of neutral hydrogen

Science Journals Connector (OSTI)

......largest volume is not necessarily the best survey to probe dark energy. A survey at high redshift may have more wiggles...5 have to be reached in order to probe dark energy optimally with this survey, then a full SKA-like sensitivity is......

F. B. Abdalla; S. Rawlings

2005-06-11T23:59:59.000Z

372

Weak lensing predictions for coupled dark energy cosmologies at non-linear scales

Science Journals Connector (OSTI)

......models, for forthcoming ground-based [such as Dark Energy Survey (DES)] and space-based (Euclid) weak...lensing (WL) surveys - both a ground-based survey similar to the Dark Energy Survey (DES)1 and a space-based survey, i.e......

Emma Beynon; Marco Baldi; David J. Bacon; Kazuya Koyama; Cristiano Sabiu

2012-06-01T23:59:59.000Z

373

Science Journals Connector (OSTI)

......Wang (2008), where a new dark energy description in terms of...Ruiz-Lapuente P., ed., Dark Energy. Cambridge Univ. Press...Regression, 1st edn. Wiley, New York. Efstathiou G. , Bond...Am. Inst. Phys., New York, p.21. McDonald P......

Irene Sendra; Ruth Lazkoz

2012-05-01T23:59:59.000Z

374

A global fit study on the new agegraphic dark energy model

Science Journals Connector (OSTI)

We perform a global fit study on the new agegraphic dark energy (NADE) model in a non-flat ... , BAO data from SDSS DR7 and WiggleZ Dark Energy Survey, and the latest measurements of H 0 from HST....

Jing-Fei Zhang; Yun-He Li; Xin Zhang

2013-01-01T23:59:59.000Z

375

Reconstruction of f-essence and fermionic Chaplygin gas models of dark energy

Recently, it was proposed a new fermionic model of dark energy, the so-called f-essence. In this work, we explicitly reconstruct the different f-essence models. In particular, these models include the fermionic Chaplygin gas and the fermionic generalized Chaplygin gas models of dark energy. We also derive the equation of state parameter of the selected f-essence models.

P. Tsyba; K. Yerzhanov; K. Esmakhanova; I. Kulnazarov; G. Nugmanova; R. Myrzakulov

2011-03-30T23:59:59.000Z

376

Development of a dual MCP framing camera for high energy x-rays

Recently developed diagnostic techniques at LLNL require recording backlit images of extremely dense imploded plasmas using hard x-rays, and demand the detector to be sensitive to photons with energies higher than 50 keV [R. Tommasini et al., Phys. Phys. Plasmas 18, 056309 (2011); G. N. Hall et al., “AXIS: An instrument for imaging Compton radiographs using ARC on the NIF,” Rev. Sci. Instrum. (these proceedings)]. To increase the sensitivity in the high energy region, we propose to use a combination of two MCPs. The first MCP is operated in a low gain regime and works as a thick photocathode, and the second MCP works as a high gain electron multiplier. We tested the concept of this dual MCP configuration and succeeded in obtaining a detective quantum efficiency of 4.5% for 59 keV x-rays, 3 times larger than with a single plate of the thickness typically used in NIF framing cameras.

Izumi, N., E-mail: izumi2@llnl.gov; Hall, G. N.; Carpenter, A. C.; Allen, F. V.; Cruz, J. G.; Felker, B.; Hargrove, D.; Holder, J.; Lumbard, A.; Montesanti, R.; Palmer, N. E.; Piston, K.; Stone, G.; Thao, M.; Vern, R.; Zacharias, R.; Landen, O. L.; Tommasini, R.; Bradley, D. K.; Bell, P. M. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); and others

2014-11-15T23:59:59.000Z

377

Science Journals Connector (OSTI)

......measurement and dark energy constraints...Digital Sky Survey luminous red...Digital Sky Survey (SDSS) data...assuming a dark energy model or a...constraints on the dark energy and cosmological...largest effective survey volume to date......

Chia-Hsun Chuang; Yun Wang; Maddumage Don P. Hemantha

2012-06-21T23:59:59.000Z

378

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

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

379

Collider constraints on interactions of dark energy with the Standard Model

We study models in which a light scalar dark energy particle couples to the gauge fields of the electroweak force, the photon, Z and W bosons. Our analysis applies to a large class of interacting dark energy models, including those in which the dark energy mass can be adjusted to evade fifth-force bounds by the so-called chameleon mechanism. We conclude that--with the usual choice of Higgs sector--electroweak precision observables are screened from the indirect effects of dark energy, making such corrections effectively unobservable at present-day colliders, and limiting the dark energy discovery potential of any future International Linear Collider. We show that a similar screening effect applies to processes mediated by flavour-changing neutral currents, which can be traced to the Glashow-Iliopoulos-Maiani mechanism. However, Higgs boson production at the Large Hadron Collider via weak boson fusion may receive observable corrections.

Philippe Brax; Clare Burrage; Anne-Christine Davis; David Seery; Amanda Weltman

2009-04-20T23:59:59.000Z

380

Observations of high-redshift supernovae indicate that the universe is accelerating at the present stage, and we refer to the cause for this cosmic acceleration as ``dark energy''. In particular, the analysis of current data of type Ia supernovae (SNIa), cosmic large-scale structure (LSS), and the cosmic microwave background (CMB) anisotropy implies that, with some possibility, the equation-of-state parameter of dark energy may cross the cosmological-constant boundary ($w=-1$) during the recent evolution stage. The model of ``quintom'' has been proposed to describe this $w=-1$ crossing behavior for dark energy. As a single-real-scalar-field model of dark energy, the generalized ghost condensate model provides us with a successful mechanism for realizing the quintom-like behavior. In this paper, we reconstruct the generalized ghost condensate model in the light of three forms of parametrization for dynamical dark energy, with the best-fit results of up-to-date observational data.

Jingfei Zhang; Xin Zhang; Hongya Liu

2007-03-21T23:59:59.000Z

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381

Baryon Acoustic Oscillation Intensity Mapping as a Test of Dark Energy

The expansion of the universe appears to be accelerating, and the mysterious anti-gravity agent of this acceleration has been called ``dark energy''. To measure the dynamics of dark energy, Baryon Acoustic Oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as $10^9$ individual galaxies, by observing the 21cm line or by detecting optical emission. Here we show how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.

Tzu-Ching Chang; Ue-Li Pen; Jeffrey B. Peterson; Patrick McDonald

2008-01-27T23:59:59.000Z

382

Observing dark energy dynamics with supernova, microwave background, and galaxy clustering

Science Journals Connector (OSTI)

Observing dark energy dynamics is the most important aspect of the current dark energy research. In this paper we perform a global analysis of the constraints on the property of dark energy from the current observations. We pay particular attention to the effects of dark energy perturbations. Using the data from SNIa (157 gold sample), WMAP, and SDSS we find that the best fitting dark energy model is given by the dynamical model with the equation of state crossing -1. Nevertheless the standard ?CDM model is still a good fit to the current data and evidence for dynamics is currently not very strong. We also consider the constraints with the recent released SNIa data from Supernova Legacy Survey.

Jun-Qing Xia; Gong-Bo Zhao; Bo Feng; Hong Li; Xinmin Zhang

2006-03-20T23:59:59.000Z

383

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

Temple, Blake

384

Mega-masers, Dark Energy and the Hubble Constant

Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a kinematic model. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities: ALMA, EVLA, VLBA and GBT, for addressing key astrophysical problems

Lo, Fred K. Y.

2007-10-15T23:59:59.000Z

385

The Energy Cascade from Warm Dark Matter Decays

We use a set of Monte Carlo simulations to follow the cascade produced by a primary electron of energy E_in in the intergalactic medium. We choose E_in=3-10 keV as expected from the decay of one of the most popular Warm Dark Matter (WDM) candidates, sterile neutrinos. Our simulation takes into account processes previously neglected such as free-free interactions with ions and recombinations and uses the best available cross sections for collisional ionizations and excitations with H and He and for electron-electron collisions. We precisely derive the fraction of the primary electron energy that heats the gas, ionizes atoms and produces line and continuum photons as a function of the ionization fraction. Handy fitting formulae for all the above energy depositions are provided. By keeping track of the individual photons we can distinguish between photons in the Ly-alpha resonance and those with energy E gas. This separation is important because a Ly-alpha background can heat or cool the gas depending on the nature of the photons, and can have effects on the 21 cm radiation emitted by neutral H, which will probably become detectable at z > 6 in the near future by the next generation radio interferometers.

M. Valdés; A. Ferrara

2008-03-04T23:59:59.000Z

386

Science Journals Connector (OSTI)

......Rapid Response System (Pan-STARRS; Kaiser et al. 2002), Hobby-Eberly Telescope Dark Energy Experiment (HETDEX; Hill et al. 2008), Dark Energy Survey (DES; Abbott et al. 2005), Large Synoptic Survey Telescope (LSST; Ivezic et al......

Marco Baldi

2012-05-11T23:59:59.000Z

387

N-body simulations with a cosmic vector for dark energy

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......modifications induced in the new cosmological picture...of the dynamical dark energy or a straightforward...without introducing any new dimensional parameter. The energy density of the vector...Am. Inst. Phys., New York, p. 107. Jing Y......

Edoardo Carlesi; Alexander Knebe; Gustavo Yepes; Stefan Gottlöber; Jose Beltrán Jiménez; Antonio L. Maroto

2012-07-21T23:59:59.000Z

388

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

Temple, Blake

389

9/18/09 2:09 PM'Big Wave' Theory Offers Alternative to Dark Energy - Physical Science Page 1 of 3http://scienceblips.dailyradar.com/story/big_wave_theory_offers_alternative_to_dark_energy/ Gadget.com - 30 days ago 'Big Wave' Theory Offers Alternative to Dark Energy -- Mathematicians have proposed

Temple, Blake

390

Evolution of the interacting viscous dark energy model in Einstein cosmology

In this paper we investigate the evolution of the viscous cosmology model which the dark energy interacting with the dark matter. Using the linearizing theory of dynamical system, we find, in our model, there exists a stable late time scaling solution which corresponds to the accelerating universe. But we also find the unstable solution under some appropriated parameters. In order to alleviate the coincidence problem some authors considered the effect of quantum correction due to the conform anomaly and the interacting dark energy model. But if we take into account the bulk viscosity of the cosmic fluid, the viscosity will soften the coincidence problem as the interacting dark energy cosmology model. That's to say both the non-perfect fluid model and the interacting models of the dark energy can alleviate or soften the singularity of the universe.

Chen, Juhua

2009-01-01T23:59:59.000Z

391

Dynamics of interacting phantom scalar field dark energy in Loop Quantum Cosmology

We study the dynamics of a phantom scalar field dark energy interacting with dark matter in loop quantum cosmology (LQC). Two kinds of coupling of the form $\\alpha{\\rho_m}{\\dot\\phi}$ (case I) and $3\\beta H (\\rho_\\phi +\\rho_m)$ (case II) between the phantom energy and dark matter are examined with the potential for the phantom field taken to be exponential. For both kinds of interactions, we find that the future singularity appearing in the standard FRW cosmology can be avoided by loop quantum gravity effects. In case II, if the phantom field is initially rolling down the potential, the loop quantum effect has no influence on the cosmic late time evolution and the universe will accelerate forever with a constant energy ratio between the dark energy and dark matter.

Fu, Xiangyun; Wu, Puxun

2008-01-01T23:59:59.000Z

392

Probing Neutrino Dark Energy with Extremely High-Energy Cosmic Neutrinos

Recently, a new non-Standard Model neutrino interaction mediated by a light scalar field was proposed, which renders the big-bang relic neutrinos of the cosmic neutrino background a natural dark energy candidate, the so-called Neutrino Dark Energy. As a further consequence of this interaction, the neutrino masses become functions of the neutrino energy densities and are thus promoted to dynamical, time/redshift dependent quantities. Such a possible neutrino mass variation introduces a redshift dependence into the resonance energies associated with the annihilation of extremely high-energy cosmic neutrinos on relic anti-neutrinos and vice versa into Z-bosons. In general, this annihilation process is expected to lead to sizeable absorption dips in the spectra to be observed on earth by neutrino observatories operating in the relevant energy region above 10^13 GeV. In our analysis, we contrast the characteristic absorption features produced by constant and varying neutrino masses, including all thermal background effects caused by the relic neutrino motion. We firstly consider neutrinos from astrophysical sources and secondly neutrinos originating from the decomposition of topological defects using the appropriate fragmentation functions. On the one hand, independent of the nature of neutrino masses, our results illustrate the discovery potential for the cosmic neutrino background by means of relic neutrino absorption spectroscopy. On the other hand, they allow to estimate the prospects for testing its possible interpretation as source of Neutrino Dark Energy within the next decade by the neutrino observatories ANITA and LOFAR.

Andreas Ringwald; Lily Schrempp

2006-06-13T23:59:59.000Z

393

Phantom Energy: Dark Energy with w<-1 Causes a Cosmic Doomsday

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We explore the consequences that follow if the dark energy is phantom energy, in which the sum of the pressure and energy density is negative. The positive phantom-energy density becomes infinite in finite time, overcoming all other forms of matter, such that the gravitational repulsion rapidly brings our brief epoch of cosmic structure to a close. The phantom energy rips apart the Milky Way, solar system, Earth, and ultimately the molecules, atoms, nuclei, and nucleons of which we are composed, before the death of the Universe in a “big rip.”

Robert R. Caldwell; Marc Kamionkowski; Nevin N. Weinberg

2003-08-13T23:59:59.000Z

394

The WiggleZ Dark Energy Survey: small-scale clustering of Lyman-break galaxies at z < 1

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......research-article Papers The WiggleZ Dark Energy Survey: small-scale clustering of...Canada V6T 1Z1 The WiggleZ Dark Energy Survey is a large-scale structure...science goals. The WiggleZ Dark Energy Survey, using the AAOmega multi-object......

Chris Blake; Russell J. Jurek; Sarah Brough; Matthew Colless; Warrick Couch; Scott Croom; Tamara Davis; Michael J. Drinkwater; Duncan Forbes; Karl Glazebrook; Barry Madore; Chris Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Todd Small; David Woods

2009-05-01T23:59:59.000Z

395

Science Journals Connector (OSTI)

......research-article Article The WiggleZ Dark Energy Survey: measuring the cosmic growth...galaxy redshifts from the WiggleZ Dark Energy Survey. We divide the data into four...correlation function of the WiggleZ Dark Energy Survey (hereafter WiggleZ; Drinkwater......

Carlos Contreras; Chris Blake; Gregory B. Poole; Felipe Marin; Sarah Brough; Matthew Colless; Warrick Couch; Scott Croom; Darren Croton; Tamara M. Davis; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2013-01-01T23:59:59.000Z

396

The WiggleZ Dark Energy Survey: joint measurements of the expansion and growth history at z < 1

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......research-article Articles The WiggleZ Dark Energy Survey: joint measurements of the...galaxy clustering in the WiggleZ Dark Energy Survey, using a large ensemble of...measurements using the WiggleZ Dark Energy Survey (Drinkwater et al. ), which......

Chris Blake; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Tamara M. Davis; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2012-09-01T23:59:59.000Z

397

Science Journals Connector (OSTI)

......research-article Article The WiggleZ Dark Energy Survey: probing the epoch of radiation...using data from the WiggleZ Dark Energy Survey. We find this feature to lie...using data from the WiggleZ Dark Energy Survey (Drinkwater et-al. 2010......

Gregory B. Poole; Chris Blake; David Parkinson; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Darren J. Croton; Scott Croom; Tamara Davis; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2013-01-01T23:59:59.000Z

398

Science Journals Connector (OSTI)

......research-article Article The WiggleZ Dark Energy Survey: improved distance measurements...measurements from the WiggleZ Dark Energy Survey, achieved by applying the reconstruction...galaxies mapped by the WiggleZ Dark Energy Survey (Drinkwater et-al. 2010......

Eyal A. Kazin; Jun Koda; Chris Blake; Nikhil Padmanabhan; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren J. Croton; Tamara M. Davis; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2014-01-01T23:59:59.000Z

399

The WiggleZ Dark Energy Survey: the growth rate of cosmic structure since redshift z=0.9

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......research-article Papers The WiggleZ Dark Energy Survey: the growth rate of cosmic...power spectrum of the WiggleZ Dark Energy Survey. Our results, which have a...have constructed the WiggleZ Dark Energy Survey (Drinkwater et al. 2010......

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

2011-08-11T23:59:59.000Z

400

Science Journals Connector (OSTI)

......research-article Article The WiggleZ Dark Energy Survey: star formation in UV-luminous...data release of the WiggleZ Dark Energy Survey. Our sample consists of 39-996...observations of the WiggleZ Dark Energy Survey of UV-selected galaxies using......

Russell J. Jurek; Michael J. Drinkwater; Kevin Pimbblet; Karl Glazebrook; Chris Blake; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Tamara M. Davis; Karl Forster; David Gilbank; Mike Gladders; Ben Jelliffe; I-hui Li; Barry Madore; D. Christopher Martin; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2013-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

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401

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: direct constraints on blue...spectroscopic redshifts from the WiggleZ Dark Energy Survey. Our null detection allows...shape measurements, the WiggleZ Dark Energy Survey (Drinkwater et al. 2010......

Rachel Mandelbaum; Chris Blake; Sarah Bridle; Filipe B. Abdalla; Sarah Brough; Matthew Colless; Warrick Couch; Scott Croom; Tamara Davis; Michael J. Drinkwater; Karl Forster; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; Chris Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted Wyder

2011-01-11T23:59:59.000Z

402

The WiggleZ Dark Energy Survey: high-resolution kinematics of luminous star-forming galaxies

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: high-resolution kinematics...galaxies selected from the WiggleZ Dark Energy Survey. Selected via ultraviolet and...surveys, such as the WiggleZ Dark Energy Survey. The WiggleZ survey contains......

Emily Wisnioski; Karl Glazebrook; Chris Blake; Ted Wyder; Chris Martin; Gregory B. Poole; Rob Sharp; Warrick Couch; Glenn G. Kacprzak; Sarah Brough; Matthew Colless; Carlos Contreras; Scott Croom; Darren Croton; Tamara Davis; Michael J. Drinkwater; Karl Forster; David G. Gilbank; Michael Gladders; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; Kevin Pimbblet; Michael Pracy; David Woods; H. K. C. Yee

2011-11-11T23:59:59.000Z

403

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: testing the cosmological model...emission-line galaxies in the WiggleZ Dark Energy Survey. We quantify BAOs using three...et al. 2007). The WiggleZ Dark Energy Survey at the Australian Astronomical......

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

2011-08-11T23:59:59.000Z

404

The WiggleZ Dark Energy Survey: the selection function and z= 0.6 galaxy power spectrum

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: the selection function and...redshift z 0.6 from the WiggleZ Dark Energy Survey at the Anglo-Australian Telescope...optical wavebands. The WiggleZ Dark Energy Survey at the Anglo-Australian Telescope......

Chris Blake; Sarah Brough; Matthew Colless; Warrick Couch; Scott Croom; Tamara Davis; Michael J. Drinkwater; Karl Forster; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; Chris Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted Wyder

2010-08-01T23:59:59.000Z

405

Science Journals Connector (OSTI)

......research-article Article The WiggleZ Dark Energy Survey: constraining galaxy bias and...187-000 galaxies from the WiggleZ Dark Energy Survey (Drinkwater et-al. 2010...WiggleZ Galaxy Survey The WiggleZ Dark Energy Survey (Drinkwater et-al. 2010......

Felipe A. Marín; Chris Blake; Gregory B. Poole; Cameron K. McBride; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Darren J. Croton; Scott Croom; Tamara Davis; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2013-01-01T23:59:59.000Z

406

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: mapping the distance-redshift...final data set of the WiggleZ Dark Energy Survey. We combine our correlation...6: the SDSS, the WiggleZ Dark Energy Survey and the 6-degree Field Galaxy......

Chris Blake; Eyal A. Kazin; Florian Beutler; Tamara M. Davis; David Parkinson; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2011-12-11T23:59:59.000Z

407

Science Journals Connector (OSTI)

......g. the properties of dark energy) and redshift would be absent...especially in the context of dark energy cosmologies. Is the halo mass...conclusions in Section 7. 2 DARK ENERGY AND STRUCTURE FORMATION 2...for the ellipsoidal collapse (Audit, Teyssier Alimi 1997; Sheth......

J. Courtin; Y. Rasera; J.-M. Alimi; P.-S. Corasaniti; V. Boucher; A. Füzfa

2011-01-21T23:59:59.000Z

408

arXiv:astro-ph/0602147v17Feb2006 Likelihood Methods for Cluster Dark Energy Surveys

arXiv:astro-ph/0602147v17Feb2006 Likelihood Methods for Cluster Dark Energy Surveys Wayne Hu1 and J on both the dark energy equation of state and the mass selection function required to extract it-mass relations allows for a joint extraction of dark energy and cluster structural parameters. I. INTRODUCTION

Hu, Wayne

409

Probing interaction and spatial curvature in the holographic dark energy model

In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term Q is proportional to the energy densities of dark energy (?{sub ?}), matter (?{sub m}), and matter plus dark energy (?{sub m}+?{sub ?}). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type Ia supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our results show that the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model.

Li, Miao [Kavli Institute for Theoretical Physics China, Chinese Academy of Sciences, Beijing 100190 (China); Li, Xiao-Dong [Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, Hefei 230026 (China); Wang, Shuang [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Wang, Yi [Physics Department, McGill University, Montreal, H3A2T8 (Canada); Zhang, Xin, E-mail: mli@itp.ac.cn, E-mail: renzhe@mail.ustc.edu.cn, E-mail: swang@mail.ustc.edu.cn, E-mail: wangyi@hep.physics.mcgill.ca, E-mail: zhangxin@mail.neu.edu.cn [Department of Physics, College of Sciences, Northeastern University, Shenyang 110004 (China)

2009-12-01T23:59:59.000Z

410

Probing interaction and spatial curvature in the holographic dark energy model

In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term $Q$ is proportional to the energy densities of dark energy ($\\rho_{\\Lambda}$), matter ($\\rho_{m}$), and matter plus dark energy ($\\rho_m+\\rho_{\\Lambda}$). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type Ia supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our results show that the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model.

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

2009-10-20T23:59:59.000Z

411

Linear Perturbation constraints on Multi-coupled Dark Energy

The Multi-coupled Dark Energy (McDE) scenario has been recently proposed as a specific example of a cosmological model characterized by a non-standard physics of the dark sector of the universe that nevertheless gives an expansion history which does not significantly differ from the one of the standard $\\Lambda $CDM model. In this work, we present the first constraints on the McDE scenario obtained by comparing the predicted evolution of linear density perturbations with a large compilation of recent data sets for the growth rate $f\\sigma_{8}$, including 6dFGS, LRG, BOSS, WiggleZ and VIPERS. Confirming qualitative expectations, growth rate data provide much tighter bounds on the model parameters as compared to the extremely loose bounds that can be obtained when only the background expansion history is considered. In particular, the $95\\%$ confidence level on the coupling strength $|\\beta |$ is reduced from $|\\beta |\\leq 83$ (background constraints only) to $|\\beta |\\leq 0.88$ (background and linear perturbation constraints). We also investigate how these constraints further improve when using data from future wide-field surveys such as supernova data from LSST and growth rate data from Euclid-type missions. In this case the $95\\%$ confidence level on the coupling further reduce to $|\\beta |\\leq 0.85$. Such constraints are in any case still consistent with a scalar fifth-force of gravitational strength, and we foresee that tighter bounds might be possibly obtained from the investigation of nonlinear structure formation in McDE cosmologies.[Abridged

Arpine Piloyan; Valerio Marra; Marco Baldi; Luca Amendola

2014-01-12T23:59:59.000Z

412

ESTIMATING THE ''DARK'' ENERGY CONTENT OF THE SOLAR CORONA

The discovery of ubiquitous low-frequency (3-5 mHz) Alfvenic waves in the solar chromosphere (with Hinode/Solar Optical Telescope) and corona (with CoMP and SDO) has provided some insight into the non-thermal energy content of the outer solar atmosphere. However, many questions remain about the true magnitude of the energy flux carried by these waves. Here we explore the apparent discrepancy in the resolved coronal Alfvenic wave amplitude ({approx}0.5 km s{sup -1}) measured by the Coronal Multi-channel Polarimeter (CoMP) compared to those of the Hinode and the Solar Dynamics Observatory (SDO) near the limb ({approx}20 km s{sup -1}). We use a blend of observational data and a simple forward model of Alfvenic wave propagation to resolve this discrepancy and determine the Alfvenic wave energy content of the corona. Our results indicate that enormous line-of-sight superposition within the coarse spatio-temporal sampling of CoMP hides the strong wave flux observed by Hinode and SDO and leads to the large non-thermal line broadening observed. While this scenario has been assumed in the past, our observations with CoMP of a strong correlation between the non-thermal line broadening with the low-amplitude, low-frequency Alfvenic waves observed in the corona provide the first direct evidence of a wave-related non-thermal line broadening. By reconciling the diverse measurements of Alfvenic waves, we establish large coronal non-thermal line widths as direct signatures of the hidden, or ''dark'', energy content in the corona and provide preliminary constraints on the energy content of the wave motions observed.

McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); De Pontieu, Bart, E-mail: mscott@ucar.edu [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover St., Org. A021S, Bldg. 252, Palo Alto, CA 94304 (United States)

2012-12-20T23:59:59.000Z

413

Chemical Potential and the Nature of the Dark Energy: The case of phantom

The influence of a possible non zero chemical potential $\\mu$ on the nature of dark energy is investigated by assuming that the dark energy is a relativistic perfect simple fluid obeying the equation of state (EoS), $p=\\omega \\rho$ ($\\omega 0$, the $\\omega$-parameter must be greater than -1 (vacuum is forbidden) while for $\\mu 0$ are permmited only if $-1 < \\omega < -1/2$. The thermodynamics and statistical arguments constrain the EoS parameter to be $\\omega < -1/2$, a result surprisingly close to the maximal value required to accelerate a FRW type universe dominated by matter and dark energy ($\\omega \\lesssim -10/21$).

J. A. S. Lima; S. H. Pereira

2008-01-02T23:59:59.000Z

414

Interaction between modified Chaplygin gas and ghost dark energy in presence of extra dimensions

In this paper, we consider three different models of dark energy in higher dimensional space-time and discuss about some cosmological parameters numerically. The first model is a single component universe including viscous varying modified Chaplygin gas. In the second model, we consider two-component universe including viscous varying modified Chaplygin gas and ghost dark energy. In the third model, we consider another two-component universe including viscous modified cosmic Chaplygin gas and ghost dark energy. In the cases of two-component fluids we also consider possibility of interaction between components.

M. Khurshudyan; J. Sadeghi; M. Hakobyan; H. Farahani; R. Myrzakulov

2014-02-13T23:59:59.000Z

415

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

416

Are Dark Matter and Dark Energy the Residue of the Expansion-Reaction to the Big Bang ?

We derive the phenomenological Milgrom square-law acceleration, describing the apparent behavior of dark matter, as the reaction to the Big Bang from a model based on the Lorentz-Dirac equation of motion traditionally describing radiation reaction in electromagnetism but proven applicable to expansion reaction in cosmology. The model is applied within the Robertson-Walker hypersphere, and suggests that the Hubble expansion exactly cancels the classical reaction imparted to matter following the Big Bang, leaving behind a residue proportional to the square of the acceleration. The model further suggests that the energy density associated with the reaction acceleration is precisely the critical density for flattening the universe thus providing a potential explanation of dark energy as well. A test of this model is proposed.

Harry I. Ringermacher; Lawrence R. Mead

2006-10-16T23:59:59.000Z

417

Modelling the Transfer Function for the Dark Energy Survey

We present a forward-modelling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function -- a mapping from cosmological and astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator, Berge et al. 2013) and catalogs representative of the DES data. In this work we simulate the 244 sq. deg coadd images and catalogs in 5 bands for the DES Science Verification (SV) data. The simulation output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples, star/galaxy classification and proximity effects on object detection, are then used to demonstrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modelling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies which is sufficiently realistic and highly controllable.

Chang, C.

2014-10-31T23:59:59.000Z

418

Dark energy: a quantum fossil from the inflationary Universe?

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

Joan Sola

2008-02-06T23:59:59.000Z

419

The effective Lagrangian of dark energy from observations

Using observational data on the expansion rate of the universe (H(z)) we constrain the effective Lagrangian of the current accelerated expansion. Our results show that the effective potential is consistent with being flat i.e., a cosmological constant; it is also consistent with the field moving along an almost flat potential like a pseudo-Goldstone boson. We show that the potential of dark energy does not deviate from a constant at more than 6% over the redshift range 0 < z < 1. The data can be described by just a constant term in the Lagrangian and do not require any extra parameters; therefore there is no evidence for augmenting the number of parameters of the LCDM paradigm. We also find that the data justify the effective theory approach to describe accelerated expansion and that the allowed parameters range satisfy the expected hierarchy. Future data, both from cosmic chronometers and baryonic acoustic oscillations, that can measure H(z) at the % level, could greatly improve constraints on the flatness of the potential or shed some light on possible mechanisms driving the accelerated expansion. Besides the above result, it is shown that the effective Lagrangian of accelerated expansion can be constrained from cosmological observations in a model-independent way and that direct measurements of the expansion rate H(z) are most useful to do so.

Jimenez, Raul; Verde, Licia [ICREA and ICC, Institut de Ciencies del Cosmos, Universitat de Barcelona (IEEC-UB), Marti i Franques 1, Barcelona 08028 (Spain); Talavera, P. [DFEN and ICC, Universitat Politècnica de Catalunya, Comte Urgell 187, Barcelona (Spain); Moresco, Michele; Cimatti, Andrea [Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna (Italy); Pozzetti, Lucia, E-mail: raul.jimenez@icc.ub.edu, E-mail: pere.talavera@icc.ub.edu, E-mail: liciaverde@icc.ub.edu, E-mail: michele.moresco@unibo.it, E-mail: a.cimatti@unibo.it, E-mail: lucia.pozzetti@oabo.inaf.it [INAF — Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna (Italy)

2012-03-01T23:59:59.000Z

420

'Swiss-cheese' inhomogeneous cosmology and the dark energy problem

We study an exact Swiss-cheese model of the universe, where inhomogeneous LTB patches are embedded in a flat FLRW background, in order to see how observations of distant sources are affected. We focus mainly on the redshift, both perturbatively and non-perturbatively: the net effect given by one patch is suppressed by (L/R{sub H}){sup 3} (where L is the size of one patch and R{sub H} is the Hubble radius). We disentangle this effect from the Doppler term (which is much larger and has been used recently (Biswas et al 2007 J. Cosmol. Astropart. Phys. JCAP12(2007)017 [astro-ph/0606703]) to try to fit the SN curve without dark energy) by making contact with cosmological perturbation theory. Then, the correction to the angular distance is discussed analytically and estimated to be larger, O(L/R{sub H}){sup 2}, perturbatively and non-perturbatively (although it should go to zero after angular averaging)

Biswas, Tirthabir; Notari, Alessio, E-mail: tbiswas@gravity.psu.edu, E-mail: notari@hep.physics.mcgill.ca [Physics Department, McGill University, 3600 University Road, Montreal, QC, H3A 2T8 (Canada)] [Physics Department, McGill University, 3600 University Road, Montreal, QC, H3A 2T8 (Canada)

2008-06-15T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

421

Modelling the Transfer Function for the Dark Energy Survey

We present a forward-modelling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function -- a mapping from cosmological and astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator, Berge et al. 2013) and catalogs representative of the DES data. In this work we simulate the 244 sq. deg coadd images and catalogs in 5 bands for the DES Science Verification (SV) data. The simulation output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples, star/galaxy classification and proximity effects on object detection, are then used to demonstrate how one can use the simulations to address systematics issues in data ana...

Chang, C; Wechsler, R H; Refregier, A; Amara, A; Rykoff, E; Becker, M R; Bruderer, C; Gamper, L; Leistedt, B; Peiris, H; Abbott, T; Abdalla, F B; Banerji, M; Bernstein, R A; Bertin, E; Brooks, D; Rosell, A Carnero; Desai, S; da Costa, L N; Cunha, C E; Eifler, T; Evrard, A E; Neto, A Fausti; Gerdes, D; Gruen, D; James, D; Kuehn, K; Maia, M A G; Makler, M; Ogando, R; Plazas, A; Sanchez, E; Schubnell, M; Sevilla-Noarbe, I; Smith, C; Soares-Santos, M; Suchyta, E; Swanson, M E C; Tarle, G; Zuntz, J

2014-01-01T23:59:59.000Z

422

Exploring the Properties of Dark Energy Using Type Ia Supernovae and Other Datasets

We reconstruct dark energy properties from two complementary supernova datasets -- the newly released Gold+HST sample and SNLS. The results obtained are consistent with standard $\\Lambda$CDM model within $2\\sigma$ error bars although the Gold+HST data favour evolving dark energy slightly more than SNLS. Using complementary data from baryon acoustic oscillations and the cosmic microwave background to constrain dark energy, we find that our results in this case are strongly dependent on the present value of the matter density $\\Omega_m$. Consequently, no firm conclusions regarding constancy or variability of dark energy density can be drawn from these data alone unless the value of $\\Omega_m$ is known to an accuracy of a few percent. However, possible variability is significantly restricted if this data is used in conjunction with supernova data.

Ujjaini Alam; Varun Sahni; Alexei A. Starobinsky

2006-12-14T23:59:59.000Z

423

Constraints on dark energy from baryon acoustic peak and galaxy cluster gas mass measurements

We use baryon acoustic peak measurements by Eisenstein et al. (2005) and Percival et al. (2007a) and galaxy cluster gas mass fraction measurements of Allen et al. (2008) to constrain parameters of three different dark energy models. For time-independent dark energy, the Percival et al. (2007a) constraints, which make use of the WMAP measurement of the apparent acoustic horizon angle, most effectively constrain a cosmological parameter close to spatial curvature and favor a close to spatially flat model. In a spatially-flat model the Percival et al. (2007a) data less effectively constrain time-varying dark energy. The joint baryon acoustic peak and galaxy cluster gas mass constraints are consistent with but tighter than those derived from other data. A time-independent cosmological constant in a spatially-flat model provides a good fit to the joint data, but slowly-evolving dark energy can not yet be ruled out.

Lado Samushia; Bharat Ratra

2008-06-17T23:59:59.000Z

424

Is w?-1 evidence for a dynamical dark energy equation of state?

Science Journals Connector (OSTI)

Current constraints on the dark energy equation of state parameter, w, are expected to be improved by more than 1 order of magnitude in the next decade. If |w-1|?0.01 around the present time, but the dark energy dynamics is sufficiently slow, it is possible that future constraints will rule out a cosmological constant while being consistent with a time-independent equation of state parameter. In this paper, we show that although models with such behavior can be constructed, they do require significant fine-tuning. Therefore, if the observed acceleration of the Universe is induced by a dark energy component, then finding w?-1 would, on its own, constitute very strong evidence for a dynamical dark energy equation of state.

P. P. Avelino; A. M. M. Trindade; P. T. P. Viana

2009-09-29T23:59:59.000Z

425

Comparison of dark energy models: A perspective from the latest observational data

Science Journals Connector (OSTI)

We compare some popular dark energy models under the assumption of a flat ... acoustic oscillation measurement from the Sloan Digital Sky Survey, the cosmic microwave background measurement given by...H ...

Miao Li; XiaoDong Li; Xin Zhang

2010-09-01T23:59:59.000Z

426

Introduction The Dark Energy Survey (DES) requires a photometric precision of

Introduction The Dark Energy Survey (DES) requires a photometric precision of 0.02 mag for a wide in the atmospheric throughput ultimately limit survey photometric precision to ~0.01 mag. Therefore, real time

427

Self-calibration of cluster dark energy studies: Observable-mass distribution

Science Journals Connector (OSTI)

The exponential sensitivity of cluster number counts to the properties of the dark energy implies a comparable sensitivity to not only the mean but also the actual distribution of an observable-mass proxy given the true cluster mass. For example a 25% scatter in mass can provide a ?50% change in the number counts at z?2 for the upcoming SPT survey. Uncertainty in the scatter of this amount would degrade dark energy constraints to uninteresting levels. Given the shape of the actual mass function, the properties of the distribution may be internally monitored by the shape of the observable mass function. As a proof of principle, for a simple mass-independent Gaussian distribution the scatter may be self-calibrated to allow a measurement of the dark energy equation of state of ?(w)?0.1. External constraints on the mass variance of the distribution that are more accurate than ??ln?M2dark energy constraints.

Marcos Lima and Wayne Hu

2005-08-23T23:59:59.000Z

428

Modified Chaplygin Gas as Scalar Field and Holographic Dark Energy Model

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

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

2008-09-20T23:59:59.000Z

429

Is w{ne}-1 evidence for a dynamical dark energy equation of state?

Current constraints on the dark energy equation of state parameter, w, are expected to be improved by more than 1 order of magnitude in the next decade. If |w-1| > or approx. 0.01 around the present time, but the dark energy dynamics is sufficiently slow, it is possible that future constraints will rule out a cosmological constant while being consistent with a time-independent equation of state parameter. In this paper, we show that although models with such behavior can be constructed, they do require significant fine-tuning. Therefore, if the observed acceleration of the Universe is induced by a dark energy component, then finding w{ne}-1 would, on its own, constitute very strong evidence for a dynamical dark energy equation of state.

Avelino, P. P. [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); Trindade, A. M. M. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Viana, P. T. P. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Departamento de Matematica Aplicada da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

2009-09-15T23:59:59.000Z

430

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

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

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

2008-05-27T23:59:59.000Z

431

While there is mounting evidence in all fronts of experimental cosmology for a non-vanishing dark energy component in the Universe, we are still far away from understanding its ultimate nature. A fundamental cosmological constant, Lambda, is the most natural candidate, but many dynamical mechanisms to generate an effective Lambda have been devised which postulate the existence of a peculiar scalar field (so-called quintessence, and generalizations thereof). These models are essentially ad hoc, but they lead to the attractive possibility of a time-evolving dark energy with a non-trivial equation of state (EOS). Most, if not all, future experimental studies on precision cosmology (e.g. the SNAP and PLANCK projects) address very carefully the determination of an EOS parametrized ``a la quintessence''. Here we show that by fitting cosmological data to an EOS of that kind can also be interpreted as a hint of a fundamental, but time-evolving, cosmological term: Lambda=Lambda(t). We exemplify this possibility by studying the effective EOS associated to a renormalization group (RG) model for Lambda. We find that the effective EOS can correspond to both normal quintessence and phantom dark energy, depending on the value of a single parameter of the RG model. We conclude that behind a non-trivial EOS of a purported quintessence or phantom scalar field there can actually be a running cosmological term of a fundamental quantum field theory.

Joan Sola; Hrvoje Stefancic

2005-08-20T23:59:59.000Z

432

Thermodynamics second law and $?=-1$ crossing(s) in interacting holographic dark energy model

By the assumption that the thermodynamics second law is valid, we study the possibility of $\\omega=-1$ crossing in interacting holographic dark energy model. Depending on the choice of the horizon and the interaction, the transition from quintessence to phantom regime and subsequently from phantom to quintessence phase may be possible. The second transition avoids the big rip singularity. We compute the dark energy density at transition time and show that by choosing appropriate parameters we can alleviate the coincidence problem.

H. Mohseni Sadjadi; M. Honardoost

2006-09-20T23:59:59.000Z

433

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: measuring the cosmic expansion...clustering within the WiggleZ Dark Energy Survey, using the Alcock-Paczynski...with a cosmological-constant dark energy. surveys|dark energy|distance scale......

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

2011-12-11T23:59:59.000Z

434

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

435

Ten scenarios from early radiation to late time acceleration with a minimally coupled dark energy

We consider General Relativity with matter, radiation and a minimally coupled dark energy defined by an equation of state w. Using dynamical system method, we find the equilibrium points of such a theory assuming an expanding Universe and a positive dark energy density. Two of these points correspond to classical radiation and matter dominated epochs for the Universe. For the other points, dark energy mimics matter, radiation or accelerates Universe expansion. We then look for possible sequences of epochs describing a Universe starting with some radiation dominated epoch(s) (mimicked or not by dark energy), then matter dominated epoch(s) (mimicked or not by dark energy) and ending with an accelerated expansion. We find ten sequences able to follow this Universe history without singular behaviour of w at some saddle points. Most of them are new in dark energy literature. To get more than these ten sequences, w has to be singular at some specific saddle equilibrium points. This is an unusual mathematical proper...

Fay, Stephane

2015-01-01T23:59:59.000Z

436

Constraining dark energy evolution with gravitational lensing by large scale structures

Science Journals Connector (OSTI)

We study the sensitivity of weak lensing by large scale structures as a probe of the evolution of dark energy. We explore a two-parameters model of dark energy evolution, inspired by tracking quintessence models. To this end, we compute the likelihood of a few fiducial models with varying and nonvarying equation of states. For the different models, we investigate the dark energy parameter degeneracies with the mass power spectrum shape ?, normalization ?8, and with the matter mean density ?M. We find that degeneracies are such that weak lensing turns out to be a good probe of dark energy evolution, even with limited knowledge on ?, ?8, and ?M. This result is a strong motivation for performing large scale structure simulations beyond the simple constant dark energy models, in order to calibrate the nonlinear regime accurately. Such calibration could then be used for any large scale structure tests of dark energy evolution. Prospective for the Canada France Hawaii Telescope Legacy Survey and Super-Novae Acceleration Probe are given. These results complement nicely the cosmic microwave background and supernovae constraints.

Karim Benabed and Ludovic Van Waerbeke

2004-12-09T23:59:59.000Z

437

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

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

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

2008-04-15T23:59:59.000Z

438

Probing the Evolution of the Dark Energy Density with Future Supernova Surveys

The time dependence of the dark energy density can be an important clue to the nature of dark energy in the universe. We show that future supernova data from dedicated telescopes (such as SNAP), when combined with data of nearby supernovae, can be used to determine how the dark energy density $\\rho_X(z)$ depends on redshift, if $\\rho_X(z)$ is not too close to a constant. For quantitative comparison, we have done an extensive study of a number of dark energy models. Based on these models we have simulated data sets in order to show that we can indeed reconstruct the correct sign of the time dependence of the dark energy density, outside of a degeneracy region centered on $1+w_0 = -w_1 z_{max}/3$ (where $z_{max}$ is the maximum redshift of the survey, e.g., $z_{max}=1.7$ for SNAP). We emphasize that, given the same data, one can obtain much more information about the dark energy density directly (and its time dependence) than about its equation of state.

Yun Wang; Veselin Kostov; Katherine Freese; Joshua A. Frieman; Paolo Gondolo

2004-02-03T23:59:59.000Z

439

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

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

Ariadna Montiel; Nora Bretón

2012-02-14T23:59:59.000Z

440

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

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

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

2013-04-16T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

441

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

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

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

2013-01-01T23:59:59.000Z

442

Curvature dark energy reconstruction through different cosmographic distance definitions

In the context of $f(\\mathcal{R})$ gravity, dark energy is a geometrical fluid with negative equation of state. Since the function $f(\\mathcal{R})$ is not known \\emph{a priori}, the need of a model independent reconstruction of its shape represents a relevant technique to determine which $f(\\mathcal{R})$ model is really favored with respect to others. To this aim, we relate cosmography to a generic $f(\\mathcal R)$ and its derivatives in order to provide a model independent investigation at redshift $z \\sim 0$. Our analysis is based on the use of three different cosmological distance definitions, in order to alleviate the duality problem, i.e. the problem of which cosmological distance to use with specific cosmic data sets. We therefore consider the luminosity, $d_L$, flux, $d_F$, and angular, $d_A$, distances and we find numerical constraints by the Union 2.1 supernovae compilation and measurement of baryonic acoustic oscillations, at $z_{BAO}=0.35$. We notice that all distances reduce to the same expression, i.e. $d_{L;F;A}\\sim\\frac{1}{\\mathcal H_0}z$, at first order. Thus, to fix the cosmographic series of observables, we impose the initial value of $H_0$ by fitting $\\mathcal H_0$ through supernovae only, in the redshift regime $ztheoretical bounds, while its variation, namely the jerk parameter, is compatible with $j_0>1$. Finally, we infer the functional form of $f(\\mathcal{R})$ by means of a truncated polynomial approximation, in terms of fourth order scale factor $a(t)$.

Salvatore Capozziello; Mariafelicia De Laurentis; Orlando Luongo

2014-06-26T23:59:59.000Z

443

Unbiased Estimate of Dark Energy Density from Type Ia Supernova Data

Science Journals Connector (OSTI)

Type Ia supernovae (SNe Ia) are currently the best probes of the dark energy in the universe. To constrain the nature of dark energy, we assume a flat universe and that the weak energy condition is satisfied, and we allow the density of dark energy, ?X(z), to be an arbitrary function of redshift. Using simulated data from a space-based SN pencil-beam survey, we find that by optimizing the number of parameters used to parameterize the dimensionless dark energy density, f(z) = ?X(z)/?X(z = 0), we can obtain an unbiased estimate of both f(z) and the fractional matter density of the universe, ?m. A plausible SN pencil-beam survey (with a square degree field of view and for an observational duration of 1 yr) can yield about 2000 SNe Ia with 0 ? z ? 2. Such a survey in space would yield SN peak luminosities with a combined intrinsic and observational dispersion of ?(mint) = 0.16 mag. We find that for such an idealized survey, ?m can be measured to 10% accuracy, and the dark energy density can be estimated to ~20% to z ~ 1.5, and ~20%-40% to z ~ 2, depending on the time dependence of the true dark energy density. Dark energy densities that vary more slowly can be more accurately measured. For the anticipated Supernova/Acceleration Probe (SNAP) mission, ?m can be measured to 14% accuracy, and the dark energy density can be estimated to ~20% to z ~ 1.2. Our results suggest that SNAP may gain much sensitivity to the time dependence of the dark energy density and ?m by devoting more observational time to the central pencil-beam fields to obtain more SNe Ia at z > 1.2. We use both a maximum likelihood analysis and a Monte Carlo analysis (when appropriate) to determine the errors of estimated parameters. We find that the Monte Carlo analysis gives a more accurate estimate of the dark energy density than the maximum likelihood analysis.

Yun Wang; Geoffrey Lovelace

2001-01-01T23:59:59.000Z

444

Probing Dark Forces and Light Hidden Sectors at Low-Energy e+e- Colliders

A dark sector - a new non-Abelian gauge group Higgsed or confined near the GeV scale - can be spectacularly probed in low-energy e{sup +}e{sup -} collisions. A low-mass dark sector can explain the annual modulation signal reported by DAMA/LIBRA and the PAMELA, ATIC, and INTEGRAL observations by generating small mass splittings and new interactions for weak-scale dark matter. Some of these observations may be the first signs of a low-mass dark sector that collider searches can definitively confirm. Production and decay of {Omicron}(GeV)-mass dark states is mediated by a Higgsed Abelian gauge boson that mixes kinetically with hypercharge. Existing data from BaBar, BELLE, CLEO-c, and KLOE may contain thousands of striking dark-sector events with a high multiplicity of leptons that reconstruct mass resonances and possibly displaced vertices. We discuss the production and decay phenomenology of Higgsed and confined dark sectors and propose e{sup +}e{sup -} collider search strategies. We also use the DAMA/LIBRA signal to estimate the production cross-sections and decay lifetimes for dark-sector states.

Essig, Rouven; Schuster, Philip; /SLAC; Toro, Natalia; /Stanford U., ITP

2009-06-19T23:59:59.000Z

445

What measurable zero point fluctuations can(not) tell us about dark energy

We show that laboratory experiments cannot measure the absolute value of dark energy. All known experiments rely on electromagnetic interactions. They are thus insensitive to particles and fields that interact only weakly with ordinary matter. In addition, Josephson junction experiments only measure differences in vacuum energy similar to Casimir force measurements. Gravity, however, couples to the absolute value. Finally we note that Casimir force measurements have tested zero point fluctuations up to energies of ~10 eV, well above the dark energy scale of ~0.01 eV. Hence, the proposed cut-off in the fluctuation spectrum is ruled out experimentally.

Michael Doran; Joerg Jaeckel

2006-05-30T23:59:59.000Z

446

A Short History of the Missing Mass and Dark Energy Paradigms

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

Sidney van den Bergh

2000-05-15T23:59:59.000Z

447

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....

448

The Dark Energy Survey: Prospects for Resolved Stellar Populations

Science Journals Connector (OSTI)

Wide angle and deep surveys, regardless of their primary purpose, always sample a large number of stars in the Galaxy and in its satellite system. Here we make a forecast of the expected stellar sample resulting from the Dark Energy Survey (DES) and the perspectives that it will open for studies of Galactic structure and resolved stellar populations in general. An estimated 1.2 ? 108 stars will be sampled in DES grizY filters in the southern equatorial hemisphere. This roughly corresponds to 20% of all DES sources. Most of these stars belong to the stellar thick disk and halo of the Galaxy. DES will probe low-mass stellar and sub-stellar objects at depths from three to eight times larger than those in the Sloan Digital Sky Survey (SDSS). The faint end of the main sequence (MS) will be densely sampled beyond 10 kpc. The slope of the low mass end of the stellar initial mass function (IMF) will be constrained to within a few hundredths of dex, even in the thick disk and halo. In the sub-stellar mass regime, the IMF slope will be potentially constrained to within dlog (m)/dlog m 0.1. About 3 ? 104 brown dwarf candidates and at least 7.6 ? 105 white dwarf candidates will be selected, the latter embedded into the thick disk and halo, for future follow-up. The stellar halo flattening will also be constrained to within a few percent. DES will probe the MS of new Milky Way satellites and halo clusters for distances out to 120 kpc, therefore yielding stellar surface density contrasts 1.6-1.7 times larger than those attainable with SDSS. It will also allow detection of these objects in the far reaches of the stellar halo, substantially increasing the number and quality of probes to the Galactic potential. Combined with northern samples, such as the SDSS, the DES stellar sample will yield constraints on the structure and stellar populations of Galactic components in unprecedented detail. In particular, the combined sample from both hemispheres will allow detailed studies of halo and thick disk asymmetries and triaxiality.

Bruno M. Rossetto; Basílio X. Santiago; Léo Girardi; Julio I. B. Camargo; Eduardo Balbinot; Luiz N. da Costa; Brian Yanny; Marcio A. G. Maia; Martin Makler; Ricardo L. C. Ogando; Paulo S. Pellegrini; Beatriz Ramos; Fernando de Simoni; R. Armstrong; E. Bertin; S. Desai; N. Kuropatkin; H. Lin; J. J. Mohr; D. L. Tucker

2011-01-01T23:59:59.000Z

449

Cosmological implications of interacting polytropic gas dark energy model in non-flat universe

The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model including the evolution of EoS parameter $w_{\\Lambda}$, energy density $\\Omega_{\\Lambda}$ and deceleration parameter $q$ are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of $q$ in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are reconstructed according to the evolution of interacting polytropic gas.

M. Malekjani; A. Khodam-Mohammadi; M. Taji

2010-12-13T23:59:59.000Z

450

Dark energy from cosmological fluids obeying a Shan-Chen non-ideal equation of state

We consider a Friedmann-Robertson-Walker universe with a fluid source obeying a non-ideal equation of state with "asymptotic freedom," namely ideal gas behavior (pressure changes directly proportional to density changes) both at low and high density regimes, following a fluid dynamical model due to Shan and Chen. It is shown that, starting from an ordinary energy density component, such fluids naturally evolve towards a universe with a substantial "dark energy" component at the present time, with no need of invoking any cosmological constant. Moreover, we introduce a quantitative indicator of darkness abundance, which provides a consistent picture of the actual matter-energy content of the universe.

Bini, Donato; Gregoris, Daniele; Succi, Sauro

2014-01-01T23:59:59.000Z

451

Dark energy from cosmological fluids obeying a Shan-Chen non-ideal equation of state

We consider a Friedmann-Robertson-Walker universe with a fluid source obeying a non-ideal equation of state with "asymptotic freedom," namely ideal gas behavior (pressure changes directly proportional to density changes) both at low and high density regimes, following a fluid dynamical model due to Shan and Chen. It is shown that, starting from an ordinary energy density component, such fluids naturally evolve towards a universe with a substantial "dark energy" component at the present time, with no need of invoking any cosmological constant. Moreover, we introduce a quantitative indicator of darkness abundance, which provides a consistent picture of the actual matter-energy content of the universe.

Donato Bini; Andrea Geralico; Daniele Gregoris; Sauro Succi

2014-08-23T23:59:59.000Z