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

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 Gravitation initial conditions beyond single-field slow roll #12;dark matter dark energy inflation NSF Site

Hu, Wayne

2

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

Keith A. Olive

2010-01-27T23:59:59.000Z

3

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

Joseph Silk

2010-01-08T23:59:59.000Z

4

LBNL- 61876 Dark Energy in the Dark Ages Eric V. LinderUniversity of California. Dark Energy in the Dark Ages Eric2008) Non-negligible dark energy density at high redshifts

Linder, Eric V.

2009-01-01T23:59:59.000Z

5

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

6

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

7

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

8

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsruc DocumentationP-Series to UserProduct: CrudeOffice ofINL is a U.S.11-26-20131Daren Dark Fiber

9

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

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

10

Matter Field, Dark Matter and Dark Energy

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

Masayasu Tsuge

2009-03-24T23:59:59.000Z

11

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

12

Exploring Dark Energy with SNAP

weak lensing survey. The planned dark energy program forthe Joint Dark Energy Mission (JDEM) will produce a treasureLBNL- 58276 Exploring Dark Energy with SNAP G. Aldering

Aldering, G.

2009-01-01T23:59:59.000Z

13

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

The Dark Side: from Dark Energy & Dark Matter to Washington and Science Policy Presenter: Michael: The Map Room (www.maproom.com )1949 N. Hoyne #12;The Dark Side: from Dark Energy and Dark Matter? What is the nature of the dark energy that is causing the expansion of the Universe to speed up

Collar, Juan I.

14

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

15

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

16

Dark Matter: Early Considerations

A review of the study of dark matter is given, starting with earliest studies and finishing with the establishment of the standard Cold Dark Matter paradigm in mid 1980-s. Particular attention is given to the collision of the classical and new paradigms concerning the matter content of the Universe. Also the amount of baryonic matter, dark matter and dark energy is discussed using modern estimates.

J. Einasto

2004-01-16T23:59:59.000Z

17

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

18

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

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

2009-05-08T23:59:59.000Z

19

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

20

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

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

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

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

2010-05-01T23:59:59.000Z

22

From Dark Energy and Dark Matter to Dark Metric

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

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

2008-08-04T23:59:59.000Z

23

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

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

2007-10-24T23:59:59.000Z

24

Thermodynamic properties of dark energy are discussed assuming that dark energy is described in terms of a selfinteracting complex scalar. We first show that, under certain assumptions, selfinteracting complex scalar field theories are equivalent to purely kinetic k-essence models. Then we analyze the themal properties of k-essence and in particular we show that dark-energy in the phantom regime does not necessarily yield negative entropy.

Neven Bilic

2010-09-27T23:59:59.000Z

25

On the Nature of Dark Matter and Dark Energy

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

Yu. A. Baurov; I. F. Malov

2007-10-16T23:59:59.000Z

26

Field Flows of Dark Energy Robert N. Cahn, Roland de Putter,July 8, 2008) Scalar ?eld dark energy evolving from a longthe key aspects of the dark energy evolution during much of

Cahn, Robert N.

2010-01-01T23:59:59.000Z

27

Dark Energy: Taking SidesDark Energy: Taking SidesDark Energy: Taking Sides Rocky Kolb Barocky The University of Chicago #12;#12; Cold Dark Matter: (CDM) 25% Dark Energy (): 70% Stars: 0.5% H & He: gas 4 For Dark EnergyEvidence For Dark EnergyEvidence For Dark Energy 3) Baryon acoustic oscillations 4) Weak

Yamamoto, Hirosuke

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

In these notes I will briefly summarize our knowledge about the dark matter problem, and emphasize the corresponding dynamical aspects. This covers a wide area of research, so I have been selective, and have concentrated on the subject of dark matter in nearby galaxies, in particular spirals.

A. Bosma

1998-12-01T23:59:59.000Z

30

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

31

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

32

Separating Dark Physics from Physical Darkness: Minimalist Modified Gravity vs. Dark Energy

Modified Gravity vs. Dark Energy Dragan Huterer 1 and EricModi?ed Gravity vs. Dark Energy Dragan Huterer 1 and Eric V.arising from a physical dark energy or a modi?ed Fried- mann

Huterer, Dragan

2009-01-01T23:59:59.000Z

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

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

35

Based on the analogy with superconductor physics we consider a scalar-vector-tensor gravitational model, in which the dark energy action is described by a gauge invariant electromagnetic type functional. By assuming that the ground state of the dark energy is in a form of a condensate with the U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark energy can be described in terms of the combination of a vector and of a scalar field (corresponding to the Goldstone boson), respectively. The gravitational field equations are obtained by also assuming the possibility of a non-minimal coupling between the cosmological mass current and the superconducting dark energy. The cosmological implications of the dark energy model are investigated for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two particular choices of the electromagnetic type potential, corresponding to a pure electric type field, and to a pure magnetic field, respectively. The time evolution of the scale fact...

Liang, Shi-Dong

2015-01-01T23:59:59.000Z

36

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

2005-09-14T23:59:59.000Z

37

Dark Matter and Dark Energy huncheng@math.mit.edu

Dark Matter and Dark Energy Hung Cheng huncheng@math.mit.edu January 17, 2008 Abstract We suggest. Besides producing particle masses, the mass generation mechanism also produces the observed dark energy that a candidate for dark matter is a meson with spin one the existence of which is dictated by local scale

Cheng, Hung

38

Based on the analogy with superconductor physics we consider a scalar-vector-tensor gravitational model, in which the dark energy action is described by a gauge invariant electromagnetic type functional. By assuming that the ground state of the dark energy is in a form of a condensate with the U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark energy can be described in terms of the combination of a vector and of a scalar field (corresponding to the Goldstone boson), respectively. The gravitational field equations are obtained by also assuming the possibility of a non-minimal coupling between the cosmological mass current and the superconducting dark energy. The cosmological implications of the dark energy model are investigated for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two particular choices of the electromagnetic type potential, corresponding to a pure electric type field, and to a pure magnetic field, respectively. The time evolution of the scale factor, matter energy density and deceleration parameter are obtained for both cases, and it is shown that in the presence of the superconducting dark energy the Universe ends its evolution in an exponentially accelerating vacuum de Sitter state. By using the formalism of the irreversible thermodynamic processes for open systems we interpret the generalized conservation equations in the superconducting dark energy model as describing matter creation. The particle production rates, the creation pressure and the entropy evolution are explicitly obtained.

Shi-Dong Liang; Tiberiu Harko

2015-04-10T23:59:59.000Z

39

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

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

2015-01-10T23:59:59.000Z

40

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

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

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

Petta, Jason

42

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

43

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

Freese, Katherine; Spolyar, Douglas; Valluri, Monica

2015-01-01T23:59:59.000Z

44

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

45

Wormhole solutions supported by interacting dark matter and dark energy

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

Vladimir Folomeev; Vladimir Dzhunushaliev

2014-03-10T23:59:59.000Z

46

New interactions in the dark sector mediated by dark energy

Cosmological observations have revealed the existence of a dark matter sector, which is commonly assumed to be made up of one particle species only. However, this sector might be more complicated than we currently believe: there might be more than one dark matter species (for example two components of cold dark matter or a mixture of hot and cold dark matter) and there may be new interactions between these particles. In this paper we study the possibility of multiple dark matter species and interactions mediated by a dark energy field. We study both the background and the perturbation evolution in these scenarios. We find that the background evolution of a system of multiple dark matter particles (with constant couplings) mimics a single fluid with a time-varying coupling parameter. However, this is no longer true on the perturbative level. We study the case of attractive and repulsive forces as well as a mixture of cold and hot dark matter particles.

A. W. Brookfield; C. van de Bruck; L. M. H. Hall

2008-04-10T23:59:59.000Z

47

Dark Energy vs. Dark Matter: Towards a Unifying Scalar Field?

The standard model of cosmology suggests the existence of two components, "dark matter" and "dark energy", which determine the fate of the Universe. Their nature is still under investigation, and no direct proof of their existences has emerged yet. There exist alternative models which reinterpret the cosmological observations, for example by replacing the dark energy/dark matter hypothesis by the existence of a unique dark component, the dark fluid, which is able to mimic the behaviour of both components. After a quick review of the cosmological constraints on this unifying dark fluid, we will present a model of dark fluid based on a complex scalar field and discuss the problem of the choice of the potential.

A. Arbey

2008-12-18T23:59:59.000Z

48

Dark Energy and Dark Matter as Inertial Effects

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

Serkan Zorba

2012-10-20T23:59:59.000Z

49

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

Lincoln, Don

2014-08-07T23:59:59.000Z

50

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

2014-04-15T23:59:59.000Z

51

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

52

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

Orrell, John

2014-07-24T23:59:59.000Z

53

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

54

first appear water soaked and dark, but eventually dry, and turn dark brown. Brown to black sclerotia and competes well with other saprophytic microorganisms (or- ganisms that live on decayed organic matter). R into the Figure 1. Brown, water-soaked areas temperatures reach the necessary level. will appear on infected turf

55

Dark energy and quantum entanglement

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

Mark Ya. Azbel'

2005-02-04T23:59:59.000Z

56

Embedding Dark Energy in Supergravity

We give a brief overview of some of the constraints on the embedding of dark energy in supergravity.

Philippe Brax

2007-11-15T23:59:59.000Z

57

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

58

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

59

This report discusses why axions have been postulated to exist, what cosmology implies about their presence as cold dark matter in the galactic halo, how axions might be detected in cavities wherein strong magnetic fields stimulate their conversion into photons, and relations between axions` energy spectra and galactic halos` properties.

Sikivie, P.

1996-12-31T23:59:59.000Z

60

Stealth Dark Matter: Dark scalar baryons through the Higgs portal

We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an $SU(N_D)$ strongly-coupled theory with even $N_D \\geq 4$. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vector-like representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to $SU(4)$, and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass $m_B \\gtrsim 300$ GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. We briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including: collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.

Thomas Appelquist; Richard C. Brower; Michael I. Buchoff; George T. Fleming; Xiao-Yong Jin; Joe Kiskis; Graham D. Kribs; Ethan T. Neil; James C. Osborn; Claudio Rebbi; Enrico Rinaldi; David Schaich; Chris Schroeder; Sergey Syritsyn; Pavlos Vranas; Evan Weinberg; Oliver Witzel

2015-03-13T23:59:59.000Z

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

Constraining Decaying Dark Matter

We revisited the decaying dark matter (DDM) model, in which one collisionless particle decays early into two collisionless particles, that are potentially dark matter particles today. The effect of DDM will be manifested in the cosmic microwave background (CMB) and structure formation. With a systematic modification of CMB calculation tool \\texttt{camb}, we can numerically calculated this effect, and compare it to observations. Further Markov Chain Monte Carlo \\texttt{cosmomc} runnings update the constraints in that model: the free streaming length $\\lambda_{FS}\\lesssim0.5$Mpc for nonrelativistic decay, and $((M_{DDM}/keV) Y)^2 (T_d/yr)\\lesssim5\\times10^{-5}$ for relativistic decay.

Ran Huo

2011-07-13T23:59:59.000Z

62

Dark matter, dark energy and gravitational proprieties of antimatter

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

Dragan Slavkov Hajdukovic

2009-10-21T23:59:59.000Z

63

Dark energy parameterizations and their effect on dark halos

There is a plethora of dark energy parameterizations that can fit current supernovae Ia data. However, this data is only sensitive to redshifts up to order one. In fact, many of these parameterizations break down at higher redshifts. In this paper we study the effect of dark energy models on the formation of dark halos. We select a couple of dark energy parameterizations which are sensible at high redshifts and compute their effect on the evolution of density perturbations in the linear and non-linear regimes. Using the Press-Schechter formalism we show that they produce distinguishable signatures in the number counts of dark halos. Therefore, future observations of galaxy clusters can provide complementary constraints on the behavior of dark energy.

Lamartine Liberato; Rogerio Rosenfeld

2006-04-19T23:59:59.000Z

64

Stealth Dark Matter: Dark scalar baryons through the Higgs portal

We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an $SU(N_D)$ strongly-coupled theory with even $N_D \\geq 4$. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vector-like representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to $SU(4)$, and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominant...

Appelquist, Thomas; Buchoff, Michael I; Fleming, George T; Jin, Xiao-Yong; Kiskis, Joe; Kribs, Graham D; Neil, Ethan T; Osborn, James C; Rebbi, Claudio; Rinaldi, Enrico; Schaich, David; Schroeder, Chris; Syritsyn, Sergey; Vranas, Pavlos; Weinberg, Evan; Witzel, Oliver

2015-01-01T23:59:59.000Z

65

Asymmetric condensed dark matter

We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate can be very light, $10^{-22}\\,{\\rm eV} \\lesssim m \\lesssim 10^2\\,{\\rm eV}$; the lower limit arises from constraints on small-scale structure formation, while the upper bound ensures that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of deco...

Aguirre, Anthony

2015-01-01T23:59:59.000Z

66

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

67

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

68

Dark energy and dark matter as curvature effects

Astrophysical observations are pointing out huge amounts of dark matter and dark energy needed to explain the observed large scale structures and cosmic accelerating expansion. Up to now, no experimental evidence has been found, at fundamental level, to explain such mysterious components. The problem could be completely reversed considering dark matter and dark energy as shortcomings of General Relativity and claiming for the correct theory of gravity as that derived by matching the largest number of observational data. As a result, accelerating behavior of cosmic fluid and rotation curves of spiral galaxies are reproduced by means of curvature effects.

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

2006-03-20T23:59:59.000Z

69

Dark EnergyDark Energy from variation of thefrom variation of the

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

Heermann, Dieter W.

70

Unified Field Equations Coupling Four Forces and Theory of Dark Matter and Dark Energy

Unified Field Equations Coupling Four Forces and Theory of Dark Matter and Dark Energy Tian Ma. Electroweak Theory VI. Unified Theory of Dark Energy and Dark Matter VII. Concluding Remarks 2 #12;References: 1. Tian Ma & Shouhong Wang, Gravitational Field Equations and Theory of Dark Matter and Dark Energy

Wang, Shouhong

71

Direct Detection Constraints on Dark Photon Dark Matter

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

Haipeng An; Maxim Pospelov; Josef Pradler; Adam Ritz

2014-12-29T23:59:59.000Z

72

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

73

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

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

2009-08-06T23:59:59.000Z

74

Pueblo, Colorado 81008 JkzknvfoUbgpxxvetds anh J^perfal tEUianks t0 tip staff 0f ^afrcrttk Press for ifttttr aIi00B anh 00301x0 tip rail ni 0uttr f?K?K? Judy Linda Mike Rex David Carol Caro Mary Gale And a very special thanks to the four..." by Kitty Fisher 1-39 Blake's Seven "Scars" by Ross A/lister andNevin Patryck 40-103 "Blood and Shadows" by Salom6 704-747 "The Beginning of the Bargain" by Lynne Franklin 148-158 Man From UNCLE "The Darkness Affair" by Mary Millard 159-185 "The Price...

Multiple Contributors

1994-01-01T23:59:59.000Z

75

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

Thomas

2013-11-27T23:59:59.000Z

76

We propose a new motivation for the stability of dark matter (DM). We suggest that the same non-Abelian discrete flavor symmetry which accounts for the observed pattern of neutrino oscillations, spontaneously breaks to a Z{sub 2} subgroup which renders DM stable. The simplest scheme leads to a scalar doublet DM potentially detectable in nuclear recoil experiments, inverse neutrino mass hierarchy, hence a neutrinoless double beta decay rate accessible to upcoming searches, while {theta}{sub 13}=0 gives no CP violation in neutrino oscillations.

Hirsch, M.; Morisi, S.; Peinado, E.; Valle, J. W. F. [AHEP Group, Institut de Fisica Corpuscular--C.S.I.C./Universitat de Valencia, Edificio Institutos de Paterna, Apartado 22085, E-46071 Valencia (Spain)

2010-12-01T23:59:59.000Z

77

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administrationcontroller systemsBi (2) Sr (2)ScienceScientists InSearchsuperconduct* FindDark Sector

78

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation Proposed Newcatalyst phases onOrganizationElectronic2005-2007DanMesoporousDark Energy: ADark

79

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsruc DocumentationP-Series to UserProduct: CrudeOffice ofINL is a U.S.11-26-20131Daren Dark Fiber

80

Evolving Dark Energy with w =/ -1

LBNL- 57425 Evolving Dark Energy with w =/ ?1 Lawrence J.of California. Evolving Dark Energy with w = ?1 Lawrence J.prediction of non-evolving dark energy. The small mass scale

Hall, Lawrence J.

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.

81

Dark Energy Coupled with Dark Matter in Viscous Fluid Cosmology

We investigate cosmological models with two interacting fluids: dark energy and dark matter in flat Friedmann-Robertson-Walker universe. The interaction between dark energy and dark matter is described in terms of the parameters present in the inhomogeneous equation of state when allowance is made for bulk viscosity, for the Little Rip, the Pseudo Rip, and the bounce universes. We obtain analytic representation for characteristic properties in these cosmological models, in particular the bulk viscosity $\\zeta=\\zeta(H,t)$ as function of Hubble parameter and time. We discuss the corrections of thermodynamical parameters in the equations of state due coupling between the viscous fluid and dark matter. Some common properties of these corrections are elucidated.

I. Brevik; V. V. Obukhov; A. V. Timoshkin

2014-10-10T23:59:59.000Z

82

The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construct...

Flaugher, B; Honscheid, K; Abbott, T M C; Alvarez, O; Angstadt, R; Annis, J T; Antonik, M; Ballester, O; Beaufore, L; Bernstein, G M; Bernstein, R A; Bigelow, B; Bonati, M; Boprie, D; Brooks, D; Buckley-Geer, E J; Campa, J; Cardiel-Sas, L; Castander, F J; Castilla, J; Cease, H; Cela-Ruiz, J M; Chappa, S; Chi, E; Cooper, C; da Costa, L N; Dede, E; Derylo, G; DePoy, D L; de Vicente, J; Doel, P; Drlica-Wagner, A; Eiting, J; Elliott, A E; Emes, J; Estrada, J; Neto, A Fausti; Finley, D A; Flores, R; Frieman, J; Gerdes, D; Gladders, M D; Gregory, B; Gutierrez, G R; Hao, J; Holland, S E; Holm, S; Huffman, D; Jackson, C; James, D J; Jonas, M; Karcher, A; Karliner, I; Kent, S; Kessler, R; Kozlovsky, M; Kron, R G; Kubik, D; Kuehn, K; Kuhlmann, S; Kuk, K; Lahav, O; Lathrop, A; Lee, J; Levi, M E; Lewis, P; Li, T S; Mandrichenko, I; Marshall, J L; Martinez, G; Merritt, K W; Miquel, R; Munoz, F; Neilsen, E H; Nichol, R C; Nord, B; Ogando, R; Olsen, J; Palio, N; Patton, K; Peoples, J; Plazas, A A; Rauch, J; Reil, K; Rheault, J -P; Roe, N A; Rogers, H; Roodman, A; Sanchez, E; Scarpine, V; Schindler, R H; Schmidt, R; Schmitt, R; Schubnell, M; Schultz, K; Schurter, P; Scott, L; Serrano, S; Shaw, T M; Smith, R C; Soares-Santos, M; Stefanik, A; Stuermer, W; Suchyta, E; Sypniewski, A; Tarle, G; Thaler, J; Tighe, R; Tran, C; Tucker, D; Walker, A R; Wang, G; Watson, M; Weaverdyck, C; Wester, W; Woods, R; Yanny, B

2015-01-01T23:59:59.000Z

83

Astronomical Evidence for Dark Matter

weapon in "Quake 4" is the Dark Matter Gun. In Futurama they use dark matter fuel, where "one pound is 10 of dynamics: #12;Galaxy Clusters Also with Sunyaev-Zel'dovich Effect. Inverse Compton scattering Sensitive to baryons Spectral distortion: Line of sight integral of pressure #12;Galaxy Clusters SZ Effect Compute

Golwala, Sunil

84

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

85

Dark energy and particle mixing

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

A. Capolupo; S. Capozziello; G. Vitiello

2008-08-30T23:59:59.000Z

86

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

87

We propose a new equation of state for the Dark Energy component of the Universe. It is modeled on the equation of state $p=w(\\rho-\\rho_{*})$ which can describe a liquid, for example water. We show that its energy density naturally decomposes into a component that behaves as a cosmological constant and one whose energy density scales as $a^{-3(1+w)}$, and fit the parameters specifying the equation of state to the new SNIa data, as well as WMAP and 2dF data. We find that reasonable values of the parameters can be found that give our model the same $\\chi^2$ as that of $\\Lambda$CDM. A remarkable feature of the model is that we can do all this with $w>0$.

Holman, R; Holman, Richard; Naidu, Siddartha

2004-01-01T23:59:59.000Z

88

Strangeness, Cosmological Cold Dark Matter and Dark Energy

It is now believed that the universe is composed of a small amount of the normal luminous matter, a substantial amount of matter (Cold Dark Matter: CDM) which is non-luminous and a large amount of smooth energy (Dark Energy: DE). Both CDM and DE seem to require ideas beyond the standard model of particle interactions. In this work, we argue that CDM and DE can arise entirely from the standard principles of strong interaction physics out of the same mechanism.

Sibaji Raha; Shibaji Banerjee; Abhijit Bhattacharyya; Sanjay K. Ghosh; Ernst-Michael Ilgenfritz; Bikash Sinha; Eiichi Takasugi; Hiroshi Toki

2005-01-18T23:59:59.000Z

89

Thermonuclear Ignition of Dark Galaxies

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

J. Marvin Herndon

2006-01-01T23:59:59.000Z

90

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

91

Thermonuclear Ignition of Dark Galaxies

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

J. Marvin Herndon

2006-04-13T23:59:59.000Z

92

Dark Energy From Fifth Dimension

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

H. Alavirad; N. Riazi

2008-01-21T23:59:59.000Z

93

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

Mondragon, Antonio Richard

2009-05-15T23:59:59.000Z

94

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

Aaron Trout

2012-08-15T23:59:59.000Z

95

Importance of Supernovae at zDark Energy

in Resource Book on Dark Energy, ed. E.V. Linder [astro-at z Dark Energy Eric V. Linder Berkeleyat z Dark Energy Eric V. Linder Berkeley

Linder, E.V.

2009-01-01T23:59:59.000Z

96

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

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

Carl H. Gibson

2012-11-02T23:59:59.000Z

97

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

Ellis, Richard S.

2012-09-30T23:59:59.000Z

98

Searching for an invisible dark photon with DarkLight

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

Kahn, Yonatan [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2013-11-07T23:59:59.000Z

99

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

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

Sadoulet, Bernard (UC Berkeley) [UC Berkeley

2006-03-06T23:59:59.000Z

100

Correspondence between Ricci and other dark energies

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

Surajit Chattopadhyay; Ujjal Debnath

2010-09-26T23:59:59.000Z

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

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

102

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.

P. P. Avelino

2015-03-10T23:59:59.000Z

103

Macroscopic theory of dark sector

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

Boris E. Meierovich

2014-10-06T23:59:59.000Z

104

Recent studies by a number of independent collaborations, have correlated the CMB temperatures measured by the WMAP satellite with different galaxy surveys that trace the matter distribution with light from the whole range of the electromagnetic spectrum: radio, far-infrared, optical and X-ray surveys. The new data systematically finds positive correlations, indicating a rapid slow down in the growth of structure in the universe. Individual cross-correlation measurements are of low significance, but we show that combining data at different redshifts introduces important new constraints. Contrary to what happens at low redshifts, for a fixed $\\Omm$, the higher the dark energy contend, $\\Ol$, the lower the ISW cross-correlation amplitude. At 68% confidence level, the data finds new independent evidence of dark energy: $\\Ol =0.42-1.22$ . It also confirms, to higher significance, the presence of a large dark matter component: $\\Omm =0.18-0.34$, exceeding the density of baryonic matter, but far from the critical value. Combining these new constraints with the prior of a flat universe, or the prior of an accelerating universe provides strong new evidence for a dark cosmos. Combination with supernova data yields $\\Ol = 0.71 \\pm 0.13$, $\\Omm = 0.29 \\pm 0.04$. If we also assume a flat universe, we find $\\Ol = 0.70 \\pm 0.05$ and $w = -1.02 \\pm 0.17$ for a constant dark energy equation of state.

E. Gaztanaga; M. Manera; T. Multamaki

2005-09-22T23:59:59.000Z

105

Dark Energy and Dark Matter in Stars Physic

We present the basic equations and relations for the relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which is {\\em locally} equivalent to the f(R) theories of gravity and gives an alternative description of the effects of dark matter and dark energy. The results for the simplest form of the relativistic equation of state (EOS) of neutron matter are represented. Our approach overcomes the well-known difficulties of the physics of SSSS in the f(R) theories of gravity introducing two novel EOS for cosmological energy-pressure densities and dilaton energy-pressure densities, as well as proper boundary conditions.

Plamen Fiziev

2014-11-02T23:59:59.000Z

106

From the Dark Matter Universe to the Dark Energy Universe

Till the late nineties the accepted cosmological model was that of a Universe that had originated in the Big Bang and was now decelerating under the influence of as yet undetected dark matter, so that it would come to a halt and eventually collapse. In 1997 however, the author had put forward a contra model wherein the Universe was driven by dark energy, essentially the quantum zero point field, and was accelerating with a small cosmological constant. There were other deductions too, all in total agreement with observation. All this got confirmation in 1998 and subsequent observations have reconfirmed the findings.

Burra G. Sidharth

2008-03-30T23:59:59.000Z

107

Dark energy from quantum wave function collapse of dark matter

Dynamical wave function collapse models entail the continuous liberation of a specified rate of energy arising from the interaction of a fluctuating scalar field with the matter wave function. We consider the wave function collapse process for the constituents of dark matter in our universe. Beginning from a particular early era of the universe chosen from physical considerations, the rate of the associated energy liberation is integrated to yield the requisite magnitude of dark energy around the era of galaxy formation. Further, the equation of state for the liberated energy approaches $w \\to -1$ asymptotically, providing a mechanism to generate the present acceleration of the universe.

A. S. Majumdar; D. Home; S. Sinha

2009-09-03T23:59:59.000Z

108

Gamma-Ray Bursts and Dark Energy - Dark Matter interaction

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

T. Barreiro; O. Bertolami; P. Torres

2010-12-14T23:59:59.000Z

109

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

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May Jun Jul(Summary)morphinanInformation Desert Southwest Region service area. TheEPSCI Home ItDarkDiscoveries WorldwideDark matter

110

Radial systems of dark globules

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

Gyul'budagyn, A.L.

1986-03-01T23:59:59.000Z

111

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

We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 ? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t ? b W + Z's. This is the same as the dominant top quark decay (t ? b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.

Kong, Kyoungchui [Kansas; Lee, Hye-Sung [W&M, JLAB; Park, Myeonhun [Tokyo

2014-04-01T23:59:59.000Z

112

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

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

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

2011-08-19T23:59:59.000Z

113

anaerobic dark culture: Topics by E-print Network

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

in children are Itzhak Brook; M. Sc 1983-01-01 12 Dark Group: Dark Energy and Dark Matter Astrophysics (arXiv) Summary: We study the possibility that a dark group, a gauge...

114

avian dark cells: Topics by E-print Network

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

particles, e.g. dark baryons, of the dark gauge group that give the corresponding dark matter. The mass of the dark particles is of the order of the condensation scale Lambdac...

115

Sterile dark matter and reionization

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

Alexander Kusenko

2006-09-13T23:59:59.000Z

116

Baryonic Dark Matter in Galaxies

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

B. J. Carr

2000-08-01T23:59:59.000Z

117

Do Dark Pools Harm Price Discovery?

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

Zhu, Haoxiang

118

Dark Energy: Is It of Torsion Origin?

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

M. I. Wanas

2010-06-10T23:59:59.000Z

119

Instability of agegraphic dark energy models

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

Kyoung Yee Kim; Hyung Won Lee; Yun Soo Myung

2007-09-18T23:59:59.000Z

120

Dark matter axions and caustic rings

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

Sikivie, P.

1997-11-01T23:59:59.000Z

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

Dark Energy-Dark Matter Interaction from the Abell Cluster A586

We find that deviation from the virial equilibrium of the Abell Cluster A586 yields evidence of the interaction between dark matter and dark energy. We argue that this interaction might imply a violation of the Equivalence Principle. Our analysis show that evidence is found in the context of two different models of dark energy-dark matter interaction.

Orfeu Bertolami; Francisco Gil Pedro; Morgan Le Delliou

2007-12-31T23:59:59.000Z

122

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

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

Michelsen, Claus

123

Interacting agegraphic tachyon model of dark energy

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

A. Sheykhi

2009-11-16T23:59:59.000Z

124

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

2006-12-11T23:59:59.000Z

125

Why we need to see the dark matter to understand the dark energy

The cosmological concordance model contains two separate constituents which interact only gravitationally with themselves and everything else, the dark matter and the dark energy. In the standard dark energy models, the dark matter makes up some 20% of the total energy budget today, while the dark energy is responsible for about 75%. Here we show that these numbers are only robust for specific dark energy models and that in general we cannot measure the abundance of the dark constituents separately without making strong assumptions.

Martin Kunz

2007-10-30T23:59:59.000Z

126

Why we need to see the dark matter to understand the dark energy

The cosmological concordance model contains two separate constituents which interact only gravitationally with themselves and everything else, the dark matter and the dark energy. In the standard dark energy models, the dark matter makes up some 20% of the total energy budget today, while the dark energy is responsible for about 75%. Here we show that these numbers are only robust for specific dark energy models and that in general we cannot measure the abundance of the dark constituents separately without making strong assumptions.

Kunz, Martin

2007-01-01T23:59:59.000Z

127

Dark energy and 3-manifold topology

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

Torsten Asselmeyer-Maluga; Helge Rose

2007-11-21T23:59:59.000Z

128

Big Bang Synthesis of Nuclear Dark Matter

We investigate the physics of dark matter models featuring composite bound states carrying a large conserved dark "nucleon" number. The properties of sufficiently large dark nuclei may obey simple scaling laws, and we find that this scaling can determine the number distribution of nuclei resulting from Big Bang Dark Nucleosynthesis. For plausible models of asymmetric dark matter, dark nuclei of large nucleon number, e.g. > 10^8, may be synthesised, with the number distribution taking one of two characteristic forms. If small-nucleon-number fusions are sufficiently fast, the distribution of dark nuclei takes on a logarithmically-peaked, universal form, independent of many details of the initial conditions and small-number interactions. In the case of a substantial bottleneck to nucleosynthesis for small dark nuclei, we find the surprising result that even larger nuclei, with size >> 10^8, are often finally synthesised, again with a simple number distribution. We briefly discuss the constraints arising from the novel dark sector energetics, and the extended set of (often parametrically light) dark sector states that can occur in complete models of nuclear dark matter. The physics of the coherent enhancement of direct detection signals, the nature of the accompanying dark-sector form factors, and the possible modifications to astrophysical processes are discussed in detail in a companion paper.

Edward Hardy; Robert Lasenby; John March-Russell; Stephen M. West

2015-01-24T23:59:59.000Z

129

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

2006-06-12T23:59:59.000Z

130

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

131

Astrophysikalisches Institut Potsdam Probes of Dark Energy

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

132

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

133

On the Ricci dark energy model

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

Kyoung Yee Kim; Hyung Won Lee; Yun Soo Myung

2008-12-22T23:59:59.000Z

134

BLINC: Multilevel Traffic Classification in the Dark

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

Rajamani, Sriram K.

135

Nonlinear Dark-Field Microscopy Hayk Harutyunyan,

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

Novotny, Lukas

136

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

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

Katherine Freese; Peter Bodenheimer; Paolo Gondolo; Douglas Spolyar

2008-12-28T23:59:59.000Z

137

It is argued that dark energy -or something dynamically equivalent at the background level- is necessary if the expanding universe is to behave as an ordinary macroscopic system; that is, if it is to tend to some thermodynamic equilibrium state in the long run.

Diego Pavón; Ninfa Radicella

2012-12-31T23:59:59.000Z

138

Reconstructing Quintom from Ricci Dark Energy

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

Chao-Jun Feng

2009-02-11T23:59:59.000Z

139

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 coupled to dark matter.

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

2008-02-01T23:59:59.000Z

140

Cosmic Constraint on Ricci Dark Energy Model

In this paper, a holographic dark energy model, dubbed Ricci dark energy, is confronted with cosmological observational data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB). By using maximum likelihood method, it is found out that Ricci dark energy model is a viable candidate of dark energy model with the best fit parameters: $\\Omega_{m0}=0.34\\pm 0.04$, $\\alpha=0.38\\pm 0.03$ with $1\\sigma$ error. Here, $\\alpha$ is a dimensionless parameter related with Ricci dark energy $\\rho_{R}$ and Ricci scalar $R$, i.e., $\\rho_{R}\\propto \\alpha R$.

Lixin Xu; Wenbo Li; Jianbo Lu; Baorong Chang

2009-06-10T23:59:59.000Z

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.

141

Dissipative dark matter explains rotation curves

Dissipative dark matter, where dark matter particles interact with a massless (or very light) boson, is studied. Such dark matter can arise in simple hidden sector gauge models, including those featuring an unbroken $U(1)'$ gauge symmetry, leading to a dark photon. Previous work has shown that such models can not only explain the LSS and CMB, but potentially also dark matter phenomena on small scales, such as the inferred cored structure of dark matter halos. In this picture, dark matter halos of disk galaxies not only cool via dissipative interactions but are also heated via ordinary supernovae (facilitated by an assumed photon - dark photon kinetic mixing interaction). This interaction between the dark matter halo and ordinary baryons, a very special feature of these types of models, plays a critical role in governing the physical properties of the dark matter halo. Here, we further study the implications of this type of dissipative dark matter for disk galaxies. Building on earlier work, we develop a simpl...

Foot, R

2015-01-01T23:59:59.000Z

142

The Phase Transition of Dark Energy

Considering that the universe is filled with the nonrelativistic matter and dark energy and each component is respectively satisfied with its conservation condition in the absence of their interaction, we give the change rate of the fractional density and the density of dark energy from the conservation condition. It is clear that the fractional density of dark energy will monotonously increase and gradually become the dominating contribution to the universe as the redshift becomes low. Combining the evolutional trend of the state equation of dark energy and the change rate of the density of dark energy we find that the density of dark energy will decrease up to a minimum and whereafter it will increase again as the redshift becomes low. This can be regarded as the phase transition of dark energy from the quintessence phase to the phantom phase.

Wei Wang; Yuanxing Gui; Ying Shao

2006-12-05T23:59:59.000Z

143

Origin of holographic dark energy models

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

Yun Soo Myung; Min-Gyun Seo

2009-01-06T23:59:59.000Z

144

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

145

Dark energy from entanglement entropy

We show that quantum decoherence, in the context of observational cosmology, can be connected to the cosmic dark energy. The decoherence signature could be characterized by the existence of quantum entanglement between cosmological eras. As a consequence, the Von Neumann entropy related to the entanglement process, can be compared to the thermodynamical entropy in a homogeneous and isotropic universe. The corresponding cosmological models are compatible with the current observational bounds being able to reproduce viable equations of state without introducing {\\it a priori} any cosmological constant. In doing so, we investigate two cases, corresponding to two suitable cosmic volumes, $V\\propto a^3$ and $V\\propto H^{-3}$, and find two models which fairly well approximate the current cosmic speed up. The existence of dark energy can be therefore reinterpreted as a quantum signature of entanglement, showing that the cosmological constant represents a limiting case of a more complicated model derived from the quantum decoherence.

Salvatore Capozziello; Orlando Luongo

2013-03-06T23:59:59.000Z

146

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

147

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

148

Dark matter monopoles, vectors and photons

In a secluded dark sector which is coupled to the Standard Model via a Higgs portal interaction we arrange for the existence of 't Hooft-Polyakov magnetic monopoles and study their implications for cosmology. We point out that a dark sector which can accommodate stable monopoles will also contain massless dark photons gamma' as well as charged massive vector bosons W'. The dark matter in this scenario will be a combination of magnetically and electrically charged species under the unbroken U(1) subgroup of the dark sector. We estimate the cosmological production rate of monopoles and the rate of monopole-anti-monopole annihilation and conclude that monopoles with masses of few hundred TeV or greater, can produce sizeable contributions to the observed dark matter relic density. We scan over the parameter space and compute the relic density for monopoles and vector bosons. Turning to the dark photon radiation, we compute their contribution to the measured density of relativistic particles Neff and also apply observational constraints from the Bullet cluster and other large scale galaxies on long-range interactions for the self-interacting dark matter components made out of monopoles and out of dark vector bosons. At scales relevant for dwarf galaxies we identify regions on the parameter space where self-interacting monopole and vector dark mater components can aid solving the core-cusp and the too-big-to-fail problems.

Valentin V. Khoze; Gunnar Ro

2014-06-10T23:59:59.000Z

149

EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS

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

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

2013-07-10T23:59:59.000Z

150

Photo Credit: Peter GinterSLAC National Accelerator Laboratory Dark Energy

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

Osheroff, Douglas D.

151

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

152

Dark energy - dark matter - and black holes: The music of the universe

Here we review the recent evidence for dark energy, dark matter and black holes as components of an expanding universe, for the vantage point of a non-expert; we speculate on a specific DM particle.

Peter L. Biermann

2005-10-02T23:59:59.000Z

153

Noble Travails: Noble Liquid Dark Matter Detectors

, or water, 0.1x flux per 10 cm Cosmic Ray Muons generate high energy neutrons 50 MeV - 3 GeV which are toughGaitskell Noble Travails: Noble Liquid Dark Matter Detectors Rick Gaitskell Particle Astrophysics://particleastro.brown.edu/ http://gaitskell.brown.edu v1 #12;LUX Dark Matter Collaboration 2007 v01_7mm Dark Matter Theory

Golwala, Sunil

154

Dark Energy in Global Brane Universe

We discuss the exact solutions of brane universes and the results indicate the Friedmann equations on the branes are modified with a new density term. Then, we assume the new term as the density of dark energy. Using Wetterich's parametrization equation of state (EOS) of dark energy, we obtain the new term varies with the red-shift z. Finally, the evolutions of the mass density parameter $\\Omega_2$, dark energy density parameter $\\Omega_x$ and deceleration parameter q_2 are studied.

Yongli Ping; Lixin Xu; Chengwu Zhang; Hongya Liu

2007-12-20T23:59:59.000Z

155

Statefinder Parameters for Tachyon Dark Energy Model

In this paper we study the statefinder parameters for the tachyon dark energy model. There are two kinds of stable attractor solutions in this model. The statefinder diagrams characterize the properties of the tachyon dark energy model. Our results show that the evolving trajectories of the attractor solutions lie in the total region and pass through the LCDM fixed point, which is different from other dark energy model.

Ying Shao; Yuanxing Gui

2007-03-22T23:59:59.000Z

156

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

157

Axion Dark Matter Detection using Atomic Transitions

Dark matter axions may cause transitions between atomic states that differ in energy by an amount equal to the axion mass. Such energy differences are conveniently tuned using the Zeeman effect. It is proposed to search for dark matter axions by cooling a kilogram-sized sample to milliKelvin temperatures and count axion induced transitions using laser techniques. This appears an appropriate approach to axion dark matter detection in the $10^{-4}$ eV mass range.

P. Sikivie

2014-09-09T23:59:59.000Z

158

Unbound particles in dark matter halos

We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.

Behroozi, Peter S.; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University and SLAC National Accelerator Laboratory 2575 Sand Hill Road, Menlo Park, CA (United States); Loeb, Abraham, E-mail: behroozi@stanford.edu, E-mail: aloeb@cfa.harvard.edu, E-mail: rwechsler@stanford.edu [Department of Astronomy, Harvard University 60 Garden St, Cambridge, MA (United States)

2013-06-01T23:59:59.000Z

159

Statefinder Diagnostic for Dilaton Dark Energy

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

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

2008-05-07T23:59:59.000Z

160

Holographic Dark Energy Model: State Finder Parameters

In this work, we have studied interacting holographic dark energy model in the background of FRW model of the universe. The interaction is chosen either in linear combination or in product form of the matter densities for dark matter and dark energy. The IR cut off for holographic dark energy is chosen as Ricci's length scale or radius of the future event horizon. The analysis is done using the state finder parameter and coincidence problem has been graphically presented. Finally, universal thermodynamics has been studied using state finder parameters.

Nairwita Mazumder; Ritabrata Biswas; Subenoy Chakraborty

2011-10-30T23:59:59.000Z

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.

161

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

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

Steidel, Chuck

162

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

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1 Submitted March 12th of high matter density expected in the early Universe I show that primordial inflation and dark energy (i , 2004 ABSTRACT I present a theory of quantum gravity based on the principle of gravitational energy

Giles, C. Lee

163

Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios

We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of the Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate, that Newton's inverse square law of Gravity is understood at micron distances on an energy scale of~$10^{-14}$~eV. At this level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant~$\\beta > 5.8\\times10^8$ at~95% confidence level~(C.L.), and an attractive (repulsive) dark matter axion-like spin-mass coupling is excluded for the coupling strength $g_sg_p > 3.7\\times10^{-16}$~($5.3\\times10^{-16}$)~at a Yukawa length of~$\\lambda = 20$~{\\textmu}m~(95% (C.L.).

T. Jenke; G. Cronenberg; J. Burgdörfer; L. A. Chizhova; P. Geltenbort; A. N. Ivanov; T. Lauer; T. Lins; S. Rotter; H. Saul; U. Schmidt; H. Abele

2014-04-15T23:59:59.000Z

164

Spacetime Foam and Dark Energy

Due to quantum fluctuations, spacetime is foamy on small scales. The degree of foaminess is found to be consistent with the holographic principle. One way to detect spacetime foam is to look for halos in the images of distant quasars. Applying the holographic foam model to cosmology we "predict" that the cosmic energy density takes on the critical value; and basing only on existing archived data on active galactic nuclei from the Hubble Space Telescope, we also "predict" the existence of dark energy which, we argue, is composed of an enormous number of inert "particles" of extremely long wavelength. We speculate that these "particles" obey infinite statistics.

Y. Jack Ng

2008-08-08T23:59:59.000Z

165

From confinement to dark energy

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

B. Holdom

2011-02-24T23:59:59.000Z

166

We have recently examined a large number of points in the parameter space of the phenomenological MSSM, the 19-dimensional parameter space of the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of these points satisfied existing experimental and theoretical constraints. This analysis provides insight into general features of the MSSM without reference to a particular SUSY breaking scenario or any other assumptions at the GUT scale. This study opens up new possibilities for SUSY phenomenology both in colliders and in astrophysical experiments. Here we shall discuss the implications of this analysis relevant to the study of dark matter.

Cotta, R.C.; Gainer, J.S.; Hewett, J.L.; Rizzo, T.G.; /SLAC

2009-04-07T23:59:59.000Z

167

Unusual light in dark space revealed by Los Alamos, NASA

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

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

168

acceleration dark energy: Topics by E-print Network

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

imply the physical existence of dark energy'. Dropping the assumption that cold dark matter (CDM) is a perfect fluid opens the possibility to fit the data without dark energy....

169

A Newtonian approach to the cosmological dark fluids

We review the hydrodynamics of the dark sector components in Cosmology. For this purpose we use the approach of Newtonian gravitational instability, and thereafter we add corrections to arrive to a full relativistic description. In Cosmology and Astrophysics, it is usual to decompose the dark sector into two species, dark matter and dark energy. We will use instead a unified approach by describing a single unified dark fluid with very simple assumptions, namely the dark fluid is barotropic and its sound speed vanishes.

Aviles, Alejandro; Klapp, Jaime; Luongo, Orlando; Quevedo, Hernando

2015-01-01T23:59:59.000Z

170

I present an analysis of the density shapes of dark matter halos in LCDM and LWDM cosmologies. The main results are derived from a statistical sample of galaxy-mass halos drawn from a high resolution LCDM N-body simulation. Halo shapes show significant trends with mass and redshift: low-mass halos are rounder than high mass halos, and, for a fixed mass, halos are rounder at low z. Contrary to previous expectations, which were based on cluster-mass halos and non-COBE normalized simulations, LCDM galaxy-mass halos at z=0 are not strongly flattened, with short to long axis ratios of s = 0.70 +/- 0.17. I go on to study how the shapes of individual halos change when going from a LCDM simulation to a simulation with a warm dark matter power spectrum (LWDM). Four halos were compared, and, on average, the WDM halos are more spherical than their CDM counterparts (s =0.77 compared to s = 0.71). A larger sample of objects will be needed to test whether the trend is significant.

James S. Bullock

2001-06-21T23:59:59.000Z

171

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

172

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

173

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

174

Astrophysical constraints on millicharged atomic dark matter

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

Audrey K. Kvam; David C. Latimer

2014-12-01T23:59:59.000Z

175

Investigating Dark Energy with Black Hole Binaries

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

Laura Mersini-Houghton; Adam Kelleher

2009-06-08T23:59:59.000Z

176

The Quintom Model of Dark Energy

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

Bo Feng

2006-02-07T23:59:59.000Z

177

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

178

Collapsing Inhomogeneous Dust Fluid in the Background of Dark Energy

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

Tanwi Bandyopadhyay; Subenoy Chakraborty

2006-05-11T23:59:59.000Z

179

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

180

Collapse Dynamics of a Star of Dark Matter and Dark Energy

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

Subenoy Chakraborty; Tanwi Bandyopadhyay

2006-09-12T23:59:59.000Z

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

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

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

Hu, Wayne

182

New Directions in Direct Dark Matter Searches

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

Paolo Panci

2014-02-06T23:59:59.000Z

183

Dark Matter And The Habitability of Planets

In many models, dark matter particles can elastically scatter with nuclei in planets, causing those particles to become gravitationally bound. While the energy expected to be released through the subsequent annihilations of dark matter particles in the interior of the Earth is negligibly small (a few megawatts in the most optimistic models), larger planets that reside in regions with higher densities of slow moving dark matter could plausibly capture and annihilate dark matter at a rate high enough to maintain liquid water on their surfaces, even in the absence of additional energy from starlight or other sources. On these rare planets, it may be dark matter rather than light from a host star that makes it possible for life to emerge, evolve, and survive.

Hooper, Dan

2011-01-01T23:59:59.000Z

184

Dark Matter And The Habitability of Planets

In many models, dark matter particles can elastically scatter with nuclei in planets, causing those particles to become gravitationally bound. While the energy expected to be released through the subsequent annihilations of dark matter particles in the interior of the Earth is negligibly small (a few megawatts in the most optimistic models), larger planets that reside in regions with higher densities of slow moving dark matter could plausibly capture and annihilate dark matter at a rate high enough to maintain liquid water on their surfaces, even in the absence of additional energy from starlight or other sources. On these rare planets, it may be dark matter rather than light from a host star that makes it possible for life to emerge, evolve, and survive.

Dan Hooper; Jason H. Steffen

2012-03-06T23:59:59.000Z

185

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

186

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

187

Interacting Dark Energy: Decay into Fermions

A dark energy component is responsible for the present stage of acceleration of our universe. If no fine tuning is assumed on the dark energy potential then it will end up dominating the universe at late times and the universe will not stop this stage of acceleration. On the other hand, the equation of state of dark energy seems to be smaller than -1 as suggested by the cosmological data. We take this as an indication that dark energy does indeed interact with another fluid (we consider fermion fields) and we determine the interaction through the cosmological data and extrapolate it into the future. We study the conditions under which a dark energy can dilute faster or decay into the fermion fields. We show that it is possible to live now in an accelerating epoch dominated by the dark energy and without introducing any fine tuning parameters the dark energy can either dilute faster or decaying into fermions in the future. The acceleration of the universe will then cease.

A. de la Macorra

2007-02-08T23:59:59.000Z

188

Comparing holographic dark energy models with statefinder

We apply the statefinder diagnostic to the holographic dark energy models, including the original holographic dark energy (HDE) model, the new holographic dark energy model, the new agegraphic dark energy (NADE) model, and the Ricci dark energy model. In the low-redshift region the holographic dark energy models are degenerate with each other and with the $\\Lambda$CDM model in the $H(z)$ and $q(z)$ evolutions. In particular, the HDE model is highly degenerate with the $\\Lambda$CDM model, and in the HDE model the cases with different parameter values are also in strong degeneracy. Since the observational data are mainly within the low-redshift region, it is very important to break this low-redshift degeneracy in the $H(z)$ and $q(z)$ diagnostics by using some quantities with higher order derivatives of the scale factor. It is shown that the statefinder diagnostic $r(z)$ is very useful in breaking the low-redshift degeneracies. By employing the statefinder diagnostic the holographic dark energy models can be differentiated efficiently in the low-redshift region. The degeneracy between the holographic dark energy models and the $\\Lambda$CDM model can also be broken by this method. Especially for the HDE model, all the previous strong degeneracies appearing in the $H(z)$ and $q(z)$ diagnostics are broken effectively. But for the NADE model, the degeneracy between the cases with different parameter values cannot be broken, even though the statefinder diagnostic is used. A direct comparison of the holographic dark energy models in the $r$--$s$ plane is also made, in which the separations between the models (including the $\\Lambda$CDM model) can be directly measured in the light of the current values $\\{r_0,s_0\\}$ of the models.

Jing-Lei Cui; Jing-Fei Zhang

2014-04-20T23:59:59.000Z

189

The Bright Side of Dark Matter

We show that it is not possible in the absence of dark matter to construct a four-dimensional metric that explains galactic observations. In particular, by working with an effective potential it is shown that a metric which is constructed to fit flat rotation curves in spiral galaxies leads to the wrong sign for the bending of light i.e. repulsion instead of attraction. Hence, without dark matter the motion of particles on galactic scales cannot be explained in terms of geodesic motion on a four- dimensional metric. This reveals a new bright side to dark matter: it is indispensable if we wish to retain the cherished equivalence principle.

A. Edery

1999-05-27T23:59:59.000Z

190

Effective Theory of Interacting Dark Energy

We present a unifying treatment of dark energy and modified gravity that allows distinct conformal-disformal couplings of matter species to the gravitational sector. In this very general approach, we derive the conditions to avoid ghost and gradient instabilities. We compute the equations of motion for background quantities and linear perturbations. We illustrate our formalism with two simple scenarios, where either cold dark matter or a relativistic fluid is nonminimally coupled. This extends previous studies of coupled dark energy to a much broader spectrum of gravitational theories.

Gleyzes, Jérôme; Mancarella, Michele; Vernizzi, Filippo

2015-01-01T23:59:59.000Z

191

Is dark energy an effect of averaging?

The present standard model of cosmology states that the known particles carry only a tiny fraction of total mass and energy of the Universe. Rather, unknown dark matter and dark energy are the dominant contributions to the cosmic energy budget. We review the logic that leads to the postulated dark energy and present an alternative point of view, in which the puzzle may be solved by properly taking into account the influence of cosmic structures on global observables. We illustrate the effect of averaging on the measurement of the Hubble constant.

Nan Li; Marina Seikel; Dominik J. Schwarz

2008-01-22T23:59:59.000Z

192

Statefinder parameters in two dark energy models

The statefinder parameters ($r,s$) in two dark energy models are studied. In the first, we discuss in four-dimensional General Relativity a two fluid model, in which dark energy and dark matter are allowed to interact with each other. In the second model, we consider the DGP brane model generalized by taking a possible energy exchange between the brane and the bulk into account. We determine the values of the statefinder parameters that correspond to the unique attractor of the system at hand. Furthermore, we produce plots in which we show $s,r$ as functions of red-shift, and the ($s-r$) plane for each model.

Grigoris Panotopoulos

2007-12-07T23:59:59.000Z

193

Gravity and Anti-gravity of Fermions: the Unification of Dark Matter and Dark Energy

Massive gravity with second and fourth derivatives is shown to give both attractive and repulsive gravity between fermions. In contrast to the attractive gravity correlated with energy-momentum tensor, the repulsive gravity is proportional to the graviton mass. Therefore, weakly interacting fermions with energy smaller than the graviton mass 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.

Chen, X S

2005-01-01T23:59:59.000Z

194

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.

Nilanjana Mahata; Subenoy Chakraborty

2015-01-19T23:59:59.000Z

195

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

196

Interacting agegraphic dark energy models in non-flat universe

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

Ahmad Sheykhi

2009-09-12T23:59:59.000Z

197

Black hole and holographic dark energy

We discuss the connection between black hole and holographic dark energy. We examine the issue of the equation of state (EOS) for holographic energy density as a candidate for the dark energy carefully. This is closely related to the EOS for black hole, because the holographic dark energy comes from the black hole energy density. In order to derive the EOS of a black hole, we may use its dual (quantum) systems. Finally, a regular black hole without the singularity is introduced to describe an accelerating universe inside the cosmological horizon. Inspired by this, we show that the holographic energy density with the cosmological horizon as the IR cutoff leads to the dark energy-dominated universe with $\\omega_{\\rm \\Lambda}=-1$.

Yun Soo Myung

2007-04-11T23:59:59.000Z

198

Coherent neutrino scattering in dark matter detectors

Coherent elastic neutrino-nucleus and weakly interacting massive particle-nucleus interaction signatures are expected to be quite similar. This paper discusses how a next-generation ton-scale dark matter detector could ...

Anderson, Alexander John

199

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.

Edésio M. Barboza Jr.; Rafael C. Nunes; Éverton M. C. Abreu; Jorge Ananias Neto

2015-01-13T23:59:59.000Z

200

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 ...

Gibson, Carl H

2012-01-01T23:59:59.000Z

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.

201

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

202

Dark Energy, Inflation and Extra Dimensions

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

Paul J. Steinhardt; Daniel Wesley

2008-12-07T23:59:59.000Z

203

Holographic tachyon model of dark energy

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

M R Setare

2007-09-11T23:59:59.000Z

204

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

205

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

206

Dark atoms: asymmetry and direct detection

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

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

2011-10-01T23:59:59.000Z

207

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

208

G-corrected holographic dark energy model

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

M. Malekjani; M. Honari-Jafarpour

2013-05-01T23:59:59.000Z

209

Dark Matter Searches with Representing the

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

California at Santa Cruz, University of

210

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

211

Constraining Dark Sectors with Monojets and Dijets

We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simpli...

Chala, Mikael; McCullough, Matthew; Nardini, Germano; Schmidt-Hoberg, Kai

2015-01-01T23:59:59.000Z

212

Superheavy sterile neutrinos as dark matter

Chung, Kolb, and Riotto have proposed nonthermal mechanisms for the production of superheavy dark matter, consisting of particles with masses which may range up to the GUT scale. Shi and Fuller, on the other hand, have proposed much lighter sterile...

Tang, Yongjun

2000-01-01T23:59:59.000Z

213

Thermodynamical description of the interacting new agegraphic dark energy

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

A. Sheykhi; M. R. Setare

2010-09-30T23:59:59.000Z

214

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

Arrenberg, Sebastian; et al.,

2013-10-31T23:59:59.000Z

215

Dark world and the standard model

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

Zhao, Gang

2009-06-02T23:59:59.000Z

216

Braneworlds, Conformal Fields and Dark Energy

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

Rui Neves

2006-01-06T23:59:59.000Z

217

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

218

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

Greenwood, Ross N; /MIT /SLAC

2012-09-07T23:59:59.000Z

219

DarkLight radiation backgrounds

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

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

2013-11-07T23:59:59.000Z

220

Recent work on the mass distribution in spiral galaxies, using mainly HI observations, is reviewed. The principal problem is still to determine to what extent the dark matter is important in the inner parts of a galaxy, or in other words, how dominant is the self-gravitation of the disc. Studies of the shapes of rotation curves show that in detail there is sufficient individuality in spiral galaxies to prohibit the construction of ``Universal Rotation Curves''. A detailed account is given of the method of Athanassoula et al. (1987), where swing amplifier criteria are applied to set a range in the mass-to-light ratio of the disc. To restrict this range further, other methods might be useful. For a number of bright spirals the rotation curve drops just outside the optical image, but this feature by itself cannot constrain unambiguously the mass models. The use of velocity dispersions seems a promising way, though the observational problems are hard. Within the uncertainties, discs can be close to ``maximum'', even though a range of values cannot be excluded.

A. Bosma

1998-12-01T23:59:59.000Z

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

z RESEARCH ARTICLE Dark energy and extending the geodesicof motion using the Dark Energy length scale was proposed.observations. Keywords Dark energy · Galactic density pro?le

Speliotopoulos, A. D.

2010-01-01T23:59:59.000Z

222

3 RESEARCH ARTICLE Dark energy and extending the geodesicWith the discovery of Dark Energy, DE , there is now aextension is set. Keywords Dark energy · Geodesic equations

Speliotopoulos, Achilles D.

2010-01-01T23:59:59.000Z

223

From Dark Energy to Dark Matter via Non-Minimal Coupling

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

A. Borowiec

2008-12-23T23:59:59.000Z

224

Dark Sectors and New, Light, Weakly-Coupled Particles

Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibility for new physics. Nature may contain numerous dark sectors, each with their own beautiful structure, distinct particles, and forces. This review summarizes the physics motivation for dark sectors and the exciting opportunities for experimental exploration. It is the summary of the Intensity Frontier subgroup "New, Light, Weakly-coupled Particles" of the Community Summer Study 2013 (Snowmass). We discuss axions, which solve the strong CP problem and are an excellent dark matter candidate, and their generalization to axion-like particles. We also review dark photons and other dark-sector particles, including sub-GeV dark matter, which are theoretically natural, provide for dark matter candidates or new dark matter interactions, and could resolve outstanding puzzles in particle and astro-particle physics. In many cases, the explorat...

Essig, R; Wester, W; Adrian, P Hansson; Andreas, S; Averett, T; Baker, O; Batell, B; Battaglieri, M; Beacham, J; Beranek, T; Bjorken, J D; Bossi, F; Boyce, J R; Cates, G D; Celentano, A; Chou, A S; Cowan, R; Curciarello, F; Davoudiasl, H; deNiverville, P; De Vita, R; Denig, A; Dharmapalan, R; Dongwi, B; Döbrich, B; Echenard, B; Espriu, D; Fegan, S; Fisher, P; Franklin, G B; Gasparian, A; Gershtein, Y; Graham, M; Graham, P W; Haas, A; Hatzikoutelis, A; Holtrop, M; Irastorza, I; Izaguirre, E; Jaeckel, J; Kahn, Y; Kalantarians, N; Kohl, M; Krnjaic, G; Kubarovsky, V; Lee, H-S; Lindner, A; Lobanov, A; Marciano, W J; Marsh, D J E; Maruyama, T; McKeen, D; Merkel, H; Moffeit, K; Monaghan, P; Mueller, G; Nelson, T K; Neil, G R; Oriunno, M; Pavlovic, Z; Phillips, S K; Pivovaroff, M J; Poltis, R; Pospelov, M; Rajendran, S; Redondo, J; Ringwald, A; Ritz, A; Ruz, J; Saenboonruang, K; Schuster, P; Shinn, M; Slatyer, T R; Steffen, J H; Stepanyan, S; Tanner, D B; Thaler, J; Tobar, M E; Toro, N; Upadye, A; Van de Water, R; Vlahovic, B; Vogel, J K; Walker, D; Weltman, A; Wojtsekhowski, B; Zhang, S; Zioutas, K

2013-01-01T23:59:59.000Z

225

Detecting dark matter-dark energy coupling with the halo mass function

We use high-resolution simulations of large-scale structure formation to analyze the effects of interacting dark matter and dark energy on the evolution of the halo mass function. Using a chi-square likelihood analysis, we find significant differences in the mass function between models of coupled dark matter-dark energy and standard concordance cosmology Lambda-CDM out to redshift z=1.5. We also find a preliminary indication that the Dark Energy Survey should be able to distinguish these models from Lambda-CDM within its mass and redshift contraints. While we can distinguish the effects of these models from Lambda-CDM cosmologies with different fundamental parameters, DES will require independent measurements of sigma-8 to confirm these effects.

P. M. Sutter; P. M. Ricker

2008-10-03T23:59:59.000Z

226

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

A model for a flat homogeneous and isotropic Universe composed of dark energy, dark matter, neutrinos, radiation and baryons is analyzed. The fields of dark matter and neutrinos are supposed to interact with the dark energy. The dark energy is considered to obey either the van der Waals or the Chaplygin equations of state. The ratio between the pressure and the energy density of the neutrinos varies with the red-shift simulating massive and non-relativistic neutrinos at small red-shifts and non-massive relativistic neutrinos at high red-shifts. The model can reproduce the expected red-shift behaviors of the deceleration parameter and of the density parameters of each constituent.

G. M. Kremer

2007-04-03T23:59:59.000Z

227

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

228

Supercomputing Sheds Light on the Dark Universe

At Argonne National Laboratory, scientists are using supercomputers to shed light on one of the great mysteries in science today, the Dark Universe. With Mira, a petascale supercomputer at the Argonne Leadership Computing Facility, a team led by physicists Salman Habib and Katrin Heitmann will run the largest, most complex simulation of the universe ever attempted. By contrasting the results from Mira with state-of-the-art telescope surveys, the scientists hope to gain new insights into the distribution of matter in the universe, advancing future investigations of dark energy and dark matter into a new realm. The team's research was named a finalist for the 2012 Gordon Bell Prize, an award recognizing outstanding achievement in high-performance computing.

Salman Habib

2012-11-15T23:59:59.000Z

229

MODELING OBSERVATIONAL CONSTRAINTS FOR DARK MATTER HALOS

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

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

2012-12-01T23:59:59.000Z

230

The integrated Sachs-Wolfe effect in cosmologies with coupled dark matter and dark energy

The subject of this paper is the derivation of the integrated Sachs-Wolfe (iSW) effect in cosmologies with coupled dark matter and dark energy fluids. These couplings influence the iSW-effect in three ways: The Hubble function assumes a different scaling, the structure growth rate shows a different time evolution, and in addition, the Poisson equation, which relates the density perturbations to fluctuations in the gravitational potential, is changed, due to the violation of the scaling rho ~ a^{-3} of the matter density rho with scale factor a. Exemplarily, I derive the iSW-spectra for a model in which dark matter decays into dark energy, investigate the influence of the dark matter decay rate and the dark energy equation of state on the iSW-signal, and discuss the analogies for gravitational lensing. Quite generally iSW-measurements should reach similar accuracy in determining the dark energy equation of state parameter and the coupling constant.

Bjoern Malte Schaefer

2008-03-14T23:59:59.000Z

231

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

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

The Belle Collaboration

2015-01-31T23:59:59.000Z

232

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

233

Asymmetric dark matter and the Sun

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

Mads T. Frandsen; Subir Sarkar

2010-06-01T23:59:59.000Z

234

Dark energy models through nonextensive Tsallis' statistics

The accelerated expansion of the Universe is one of the greatest challenges of modern physics. One candidate to explain this phenomenon is a new field called dark energy. In this work we have used the Tsallis nonextensive statistical formulation of the Friedmann equation to explore the Barboza-Alcaniz and Chevalier-Polarski-Linder parametric dark energy models and the Wang-Meng and Dalal vacuum decay models. After that, we have discussed the observational tests and the constraints concerning the Tsallis nonextensive parameter.

Rafael da C. Nunes; Edésio M. Barboza Jr.; Everton M. C. Abreu; Jorge Ananias Neto

2014-03-22T23:59:59.000Z

235

Cosmological bounds on oscillating dark energy models

We study some cosmological constraints on the two phenomenological models of oscillating dark energy. In these scenarios, the equation of state of dark energy varies periodically and may provide a way to unify the early acceleration (inflation) and the late time acceleration of the universe. These models give also an effective way to tackle the so-called cosmic coincidence problem. We examine observational constraints on this class of models from the latest observational data including the \\emph{gold} sample of 182 type Ia supernovae, the CMB shift parameter $R$ and the BAO measurements from the Sloan Digital Sky Survey.

Deepak Jain; Abha Dev; J. S. Alcaniz

2007-09-26T23:59:59.000Z

236

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.

M. Sharif; M. Zubair

2014-09-26T23:59:59.000Z

237

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

238

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

239

axino cold dark: Topics by E-print Network

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

models and is a natural candidate for cold or warm dark matter. Here we revisit axino dark matter produced thermally and non-thermally in light of recent developments. First we...

240

Scalar perturbations in cosmological models with dark energy - dark matter interaction

Scalar cosmological perturbations are investigated in the framework of a model with interacting dark energy and dark matter. In addition to these constituents, the inhomogeneous Universe is supposed to be filled with the standard noninteracting constituents corresponding to the conventional $\\Lambda$CDM model. The interaction term is chosen in the form of a linear combination of dark sector energy densities with evolving coefficients. The methods of discrete cosmology are applied, and strong theoretical constraints on the parameters of the model are derived. A brief comparison with observational data is performed.

Eingorn, Maxim

2015-01-01T23:59:59.000Z

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.

241

The Unified Equation of State for Dark Matter and Dark Energy

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

Wei Wang; Yuan-xing Gui; Suhong Zhang; Guanghai Guo; Ying Shao

2005-04-05T23:59:59.000Z

242

On the capture of dark matter by neutron stars

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

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

2014-04-09T23:59:59.000Z

243

Discrimination of dark matter models in future experiments

Phenomenological aspects of simple dark matter models are studied. We discuss ways to discriminate the dark matter models in future experiments. We find that the measurements of the branching fraction of the Higgs boson into two photons and the electric dipole moment of the electron as well as the direct detection experiments are quite useful in discriminating particle models of dark matter. We also discuss the prospects of finding new particles in dark sector at the LHC/ILC.

Tomohiro Abe; Ryuichiro Kitano; Ryosuke Sato

2014-11-06T23:59:59.000Z

244

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

245

CAPUT DARK ENERGY TOPICS, 2013 1. The Cosmological Constant

CAPUT DARK ENERGY TOPICS, 2013 1 #12;1. The Cosmological Constant - The acceleration as curvature term in the Einstein field equation and not a form of dark energy. Provide a critical discussion., Rovelli C., 2010 Is dark energy really a mystery ? Nature, 466, 321 (July 2010) - Padmanabhan T., 2003

Weijgaert, Rien van de

246

Kaluza-Klein Cosmology With Modified Holographic Dark Energy

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

M. Sharif; Farida Khanum

2011-06-13T23:59:59.000Z

247

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 per cent dark 1 #12;energy. The key direct evidence, however, came in late ninetees from the analysis

Udgaonkar, Jayant B.

248

Holographic Dark Energy Model with Modified Variable Chaplygin Gas

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

B. C. Paul

2010-06-17T23:59:59.000Z

249

DARK MATTER Tracing the "Cosmic Web" with Diffuse Gas

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

Steidel, Chuck

250

RESEARCH HIGHLIGHTS Dark matter lost and found

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

Loss, Daniel

251

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

252

Gravitoelectromagnetism and Dark Energy in Superconductors

A gravitomagnetic analogue of the London moment in superconductors can explain the anomalous Cooper pair mass excess reported by Janet Tate. Ultimately the gravitomagnetic London moment is attributed to the breaking of the principle of general covariance in superconductors. This naturally implies non-conservation of classical energy-momentum. Possible relation with the manifestation of dark energy in superconductors is questioned.

Clovis Jacinto de Matos

2006-07-03T23:59:59.000Z

253

Direct search for WIMP dark matter

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

J. Gascon

2005-04-11T23:59:59.000Z

254

Dark Matter and Large Scale Structure

A review of the study of dark matter and large scale structure of the Universe at Tartu Observatory is given. Tartu astronomers have participated in this development, starting from Ernst "Opik and Grigori Kuzmin, and continuing with the present generation of astronomers. Our goal was to understand better the structure, origin and evolution of the Universe.

J. Einasto

2000-12-07T23:59:59.000Z

255

Testable and Untestable Aspects of Dark Energy

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

Paul H. Frampton

2005-08-11T23:59:59.000Z

256

Using Newton's Law for Dark Energy

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

Paul Frampton

2012-09-24T23:59:59.000Z

257

Stringy Model of Cosmological Dark Energy

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

Irina Ya. Aref'eva

2007-10-16T23:59:59.000Z

258

Towards Dark Energy from String-Theory

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

Axel Krause

2008-03-12T23:59:59.000Z

259

Constraints on oscillating dark energy models

The oscillating scenario of route to Lambda was recently proposed by us arXiv:0704.1651 as an alternative to a cosmological constant in a explanation of the current accelerating universe. In this scenario phantom scalar field conformally coupled to gravity drives the accelerating phase of the universe. In our model $\\Lambda$CDM appears as a global attractor in the phase space. In this paper we investigate observational constraints on this scenario from recent measurements of distant supernovae type Ia, CMB R shift, BAO and $H(z)$ observational data. The Bayesian methods of model selection are used in comparison the model with concordance $\\Lambda$CDM one as well as with model with dynamical dark energy parametrised by linear form. We conclude that $\\Lambda$CDM is favoured over FRW model with dynamical oscillating dark energy. Our analysis also demonstrate that FRW model with oscillating dark energy is favoured over FRW model with decaying dark energy parametrised in linear way.

Aleksandra Kurek; Orest Hrycyna; Marek Szydlowski

2007-11-23T23:59:59.000Z

260

Scalar-Tensor Dark Energy Models

We present here some recent results concerning scalar-tensor Dark Energy models. These models are very interesting in many respects: they allow for a consistent phantom phase, the growth of matter perturbations is modified. Using a systematic expansion of the theory at low redshifts, we relate the possibility to have phantom like DE to solar system constraints.

R. Gannouji; D. Polarski; A. Ranquet; A. A. Starobinsky

2007-01-23T23:59:59.000Z

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

The World of Dark Shadows Issue 9

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

Multiple Contributors

1977-01-01T23:59:59.000Z

262

Particle Dark Matter and its Detection

The status and prospects of the experimental efforts in the detection of Particle Dark Matter is reviewed. Emphasis is put in the direct searches for WIMPs (Weakly Interacting Massive Particles), outlining the various strategies and techniques currently followed and sumarizing the results. A briefing of the indirect methods of WIMP detection is also presented.

Angel Morales

1998-10-21T23:59:59.000Z

263

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

264

Dark matter and dark energy proposals: maintaining cosmology as a true science?

I consider the relation of explanations for the observed data to testability in the following contexts: observational and experimental detection of dark matter; observational and experimental detection of dark energy or a cosmological constant $\\Lambda$; observational or experimental testing of the multiverse proposal to explain a small non-zero value of $\\Lambda$; and observational testing of the possibility of large scale spatial inhomogeneity with zero $\\Lambda$.

George F. R. Ellis

2008-11-21T23:59:59.000Z

265

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

2005-06-07T23:59:59.000Z

266

Search for pseudoscalar cold dark matter

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

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

1992-05-29T23:59:59.000Z

267

Communication with SIMP dark mesons via Z'-portal

We consider a consistent extension of the SIMP models with dark mesons by including a dark U(1)_D gauge symmetry. Dark matter density is determined by a thermal freeze-out of the $3\\to2$ self-annihilation process, thanks to the Wess-Zumino-Witten term. In the presence of a gauge kinetic mixing between the dark photon and the SM hypercharge gauge boson, dark mesons can undergo a sufficient scattering off the Standard Model particles and keep in kinetic equilibrium until freeze-out in this SIMP scenario. Taking the SU(N_f)xSU(N_f)/SU(N_f) flavor symmetry under the SU(N_c) confining group, we show how much complementary the SIMP constraints on the parameters of the dark photon are to be for current experimental searches for dark photon.

Hyun Min Lee; Min-Seok Seo

2015-04-03T23:59:59.000Z

268

Present and future evidence for evolving dark energy

We compute the Bayesian evidences for one- and two-parameter models of evolving dark energy, and compare them to the evidence for a cosmological constant, using current data from Type Ia supernova, baryon acoustic oscillations, and the cosmic microwave background. We use only distance information, ignoring dark energy perturbations. We find that, under various priors on the dark energy parameters, LambdaCDM is currently favoured as compared to the dark energy models. We consider the parameter constraints that arise under Bayesian model averaging, and discuss the implication of our results for future dark energy projects seeking to detect dark energy evolution. The model selection approach complements and extends the figure-of-merit approach of the Dark Energy Task Force in assessing future experiments, and suggests a significantly-modified interpretation of that statistic.

Andrew R Liddle; Pia Mukherjee; David Parkinson; Yun Wang

2006-12-04T23:59:59.000Z

269

Detecting dark energy with wavelets on the sphere

Dark energy dominates the energy density of our Universe, yet we know very little about its nature and origin. Although strong evidence in support of dark energy is provided by the cosmic microwave background, the relic radiation of the Big Bang, in conjunction with either observations of supernovae or of the large scale structure of the Universe, the verification of dark energy by independent physical phenomena is of considerable interest. We review works that, through a wavelet analysis on the sphere, independently verify the existence of dark energy by detecting the integrated Sachs-Wolfe effect. The effectiveness of a wavelet analysis on the sphere is demonstrated by the highly statistically significant detections of dark energy that are made. Moreover, the detection is used to constrain properties of dark energy. A coherent picture of dark energy is obtained, adding further support to the now well established cosmological concordance model that describes our Universe.

J. D. McEwen

2007-08-29T23:59:59.000Z

270

Present and future evidence for evolving dark energy

We compute the Bayesian evidences for one- and two-parameter models of evolving dark energy, and compare them to the evidence for a cosmological constant, using current data from Type Ia supernova, baryon acoustic oscillations, and the cosmic microwave background. We use only distance information, ignoring dark energy perturbations. We find that, under various priors on the dark energy parameters, {lambda}CDM is currently favored as compared to the dark energy models. We consider the parameter constraints that arise under Bayesian model averaging, and discuss the implication of our results for future dark energy projects seeking to detect dark energy evolution. The model selection approach complements and extends the figure-of-merit approach of the Dark Energy Task Force in assessing future experiments, and suggests a significantly-modified interpretation of that statistic.

Liddle, Andrew R.; Mukherjee, Pia; Parkinson, David [Astronomy Centre, University of Sussex, Brighton BN1 9QH (United Kingdom); Wang Yun [Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019 (United States)

2006-12-15T23:59:59.000Z

271

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

272

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

273

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

274

Can Cosmic Structure form without Dark Matter?

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

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

2006-08-01T23:59:59.000Z

275

Can Cosmic Structure form without Dark Matter?

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

Scott Dodelson; Michele Liguori

2006-08-29T23:59:59.000Z

276

The World of Dark Shadows Issue 13

said quie tly. "You • ••d ied •• • 1 was ther e •• • 1 mean--you said you would retur n, but • •• but you were dea.d ••• " He r voice t rail ed of f a nd she shuddered convuls ive ly. "I di d di e, but ••• but I am st i ll her e. Don ' t a sk ho...01 1'!3.Af{ -/1N~ The WOl'ld -q~0 Dark ~hDdQ~ number thirteen - -- - - ~ Il~r IDllrlb QH Dark ~lla~l1w6 I- 13. oct"ober , 19'17. A Pent"Bgram Pilbllcahon. Bimontb.rY!sn zina/fan club . ' 1 .25 per issue; ~hree for }.75; six tor 57...

Multiple Contributors

1977-01-01T23:59:59.000Z

277

Atom-interferometry constraints on dark energy

If dark energy---which drives the accelerated expansion of the universe---consists of a new light scalar field, it might be detectable as a "fifth force" between normal-matter objects, in potential conflict with precision tests of gravity. There has, however, been much theoretical progress in developing theories with screening mechanisms, which can evade detection by suppressing forces in regions of high density, such as the laboratory. One prominent example is the chameleon field. We reduce the effect of this screening mechanism by probing the chameleon with individual atoms rather than bulk matter. Using a cesium matter-wave interferometer near a spherical mass in an ultra-high vacuum chamber, we constrain a wide class of dynamical dark energy theories. Our experiment excludes a range of chameleon theories that reproduce the observed cosmic acceleration.

Hamilton, Paul; Haslinger, Philipp; Simmons, Quinn; Müller, Holger; Khoury, Justin

2015-01-01T23:59:59.000Z

278

Two Component Model of Dark Energy

We consider the possibility that the dark energy is made up of two or more independent components, each having a different equation of state. We fit the model with supernova and gamma-ray burst (GRB) data from resent observations, and use the Markov Chain Monte Carlo (MCMC) technique to estimate the allowed parameter regions. We also use various model selection criteria to compare the two component model with the LCDM, one component dark energy model with static or variable w(XCDM), and with other multi-component models. We find that the two component models can give reasonably good fit to the current data. For some data sets, and depending somewhat on the model selection criteria, the two component model can give better fit to the data than XCDM with static w and XCDM with variable w parameterized by w = w_0 + w_az/(1+z).

Yan Gong; Xuelei Chen

2007-10-18T23:59:59.000Z

279

"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

280

Electromagnetic Dark Energy and Gravitoelectrodynamics of Superconductors

It is shown that Beck and Mackey electromagnetic model of dark energy in superconductors can account for the non-classical inertial properties of superconductors, which have been conjectured by the author to explain the Cooper pair's mass excess reported by Cabrera and Tate. A new Einstein-Planck regime for gravitation in condensed matter is proposed as a natural scale to host the gravitoelectrodynamic properties of superconductors.

Clovis Jacinto de Matos

2007-10-29T23:59:59.000Z

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.

281

Dark Matter Search with Moderately Superheated Liquids

We suggest the use of moderately superheated liquids in the form of superheated droplet detectors for a new type of neutralino search experiment. The advantage of this method for Dark Matter detection is, that the detector material is cheap, readily available and that it is easily possible to fabricate a large mass detector. Moreover the detector can be made "background blind", i.e. exclusively sensitive to nuclear recoils.

L. A. Hamel; L. Lessard; V. Zacek; Bhaskar Sur

1996-02-14T23:59:59.000Z

282

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

283

A Casimir approach to dark energy

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

Allan Rosencwaig

2006-06-26T23:59:59.000Z

284

Gauss Bonnet dark energy Chaplygin Gas Model

In this work we incorporate GB dark energy density and its modification, MGB, with Chaplygin gas component. We show that, presence of Chaplygin gas provides us a feature to obtain an exact solution for scalar field and potential of scalar field. Investigation on squared of sound speed provides a lower limit for constant parameters of MGB model. Also, we could find some bounds for free parameters of model.

Karimkhani, Elahe; Khodam-Mohammadi, Abdolhossein

2015-01-01T23:59:59.000Z

285

Cosmological dark energy effects from entanglement

The thorny issue of relating information theory to cosmology is here addressed by assuming a possible connection between quantum entanglement measures and observable universe. In particular, we propose a cosmological toy model, where the equation of state of the cosmological fluid, which drives the today observed cosmic acceleration, can be inferred from quantum entanglement between different cosmological epochs. In such a way the dynamical dark energy results as byproduct of quantum entanglement.

S. Capozziello; O. Luongo; S. Mancini

2013-02-24T23:59:59.000Z

286

Quark Nuggets as Baryonic Dark Matter

The cosmic first order phase transition from quarks to hadrons, occurring a few microseconds after the Big Bang, would lead to the formation of quark nuggets which would be stable on a cosmological time scale, if the associated baryon number is larger than a critical value. We examine the possibility that these surviving quark nuggets may not only be viable candidates for cold dark matter but even close the universe.

Jan-e Alam; Sibaji Raha; Bikash Sinha

1997-04-23T23:59:59.000Z

287

An Alternative to Particle Dark Matter

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

Justin Khoury

2014-12-11T23:59:59.000Z

288

Dark Field Microscopy for Analytical Laboratory Courses

An innovative and inexpensive optical microscopy experiment for a quantitative analysis or an instrumental analysis chemistry course is described. The students have hands-on experience with a dark field microscope and investigate the wavelength dependence of localized surface plasmon resonance in gold and silver nanoparticles. Students also observe and measure individual crystal growth during a replacement reaction between copper and silver nitrate. The experiment allows for quantitative, qualitative, and image data analyses for undergraduate students.

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

2014-06-10T23:59:59.000Z

289

Limits in late time conversion of cold dark matter into dark radiation

Structure formation creates high temperature and density regions in the Universe that allow the conversion of matter into more stable states, with a corresponding emission of relativistic matter and radiation. An example of such a mechanism is the supernova event, that releases relativistic neutrinos corresponding to 99% of the binding energy of remnant neutron star. We take this phenomena as a starting point for an assumption that similar processes could occur in the dark sector, where structure formation would generate a late time conversion of cold dark matter into a relativistic form of dark matter. We performed a phenomenological study about the limits of this conversion, where we assumed a transition profile that is a generalized version of the neutrino production in supernovae events. With this assumption, we obtained an interesting modification for the constraint over the cold dark matter density. We show that when comparing with the standard ?CDM cosmology, there is no preference for conversion, although the best fit is within 1? from the standard model best fit. The methodology and the results obtained qualify this conversion hypothesis, from the large scale structure point of view, as a viable and interesting model to be tested in the future with small scale data, and mitigate discrepancies between observations at this scale and the pure cold dark matter model.

Boriero, D.; Holanda, P. C. de; Motta, M., E-mail: danielb@ifi.unicamp.br, E-mail: holanda@ifi.unicamp.br, E-mail: mmota@ifi.unicamp.br [Instituto de Física Gleb Wataghin – UNICAMP, 13083-859, Campinas SP (Brazil)

2013-06-01T23:59:59.000Z

290

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

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

Prabir Rudra; Ujjal Debnath

2014-05-29T23:59:59.000Z

291

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

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

,

2015-01-01T23:59:59.000Z

292

Direct and indirect detection of dissipative dark matter

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

JiJi Fan; Andrey Katz; Jessie Shelton

2014-07-02T23:59:59.000Z

293

Dark jets in solar coronal holes

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

Young, Peter R

2015-01-01T23:59:59.000Z

294

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

295

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

296

The physics and identity of dark energy

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

Tom Gehrels

2011-01-06T23:59:59.000Z

297

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

298

Dark Matter Balls Help Supernovae to Explode

As a solution to the well-known problem that the shock wave potentially responsible for the explosion of a supernova actually tends to stall, we propose a new energy source arising from our model for dark matter. Our earlier model proposed that dark matter should consist of cm-large white dwarf-like objects kept together by a skin separating two different sorts of vacua. These dark matter balls or pearls will collect in the middle of any star throughout its lifetime. At some stage during the development of a supernova the balls will begin to take in neutrons and then other surrounding material. By passing into a ball nucleons fall through a potential of order 10 MeV, causing a severe production of heat - of order 10 foe for a solar mass of material eaten by the balls. The temperature in the iron core will thereby be raised, splitting up the iron into smaller nuclei. This provides a mechanism for reviving the shock wave when it arrives and making the supernova explosion really occur. The onset of the heating d...

Froggatt, Colin D

2015-01-01T23:59:59.000Z

299

Halo Formation in Warm Dark Matter Models

Discrepancies have emerged between the predictions of standard cold dark matter (CDM) theory and observations of clustering on sub-galactic scales. Warm dark matter (WDM) is a simple modification of CDM in which the dark matter particles have initial velocities due either to their having decoupled as thermal relics, or having been formed via non-equilibrium decay. We investigate the nonlinear gravitational clustering of WDM with a high resolution N-body code, and identify a number of distinctive observational signatures. Relative to CDM, halo concentrations and core densities are lowered, core radii are increased, and large halos emerge with far fewer low mass satellites. The number of small halos is suppressed, and those present are formed by `top down' fragmentation of caustics, as part of a `cosmic web' connecting massive halos. Few small halos form outside this web. If we identify small halos with dwarf galaxies, their number, spatial distribution, and formation epoch appear in better agreement with the observations for WDM than they are for CDM.

Paul Bode; Jeremiah P. Ostriker; Neil Turok

2001-05-29T23:59:59.000Z

300

A Dark Energy Model interacting with Dark Matter described by an effective EoS

In this latter author would like to consider interaction between a dark energy based on Generalized Uncertainty Principle (GUP) and a Dark Matter described by effective EoS: $P = (\\gamma-1)\\rho+p_{0}+\\omega_{H}H+\\omega_{H2}H^{2}+\\omega_{dH}\\dot{H}$ [1]-[3], which could be interpreted as a modification concerning to the some interaction between fluid $P=(\\gamma-1)\\rho$ with different components of the Darkness of the Universe. Two types of interaction, called sign-changeable, $Q=q(3Hb\\rho_{m}+\\beta\\dot{\\rho}_{m})$ [4],[5] and $Q=3Hb\\rho_{m}+\\beta\\dot{\\rho}_{m}$ are considered. EoS parameter of the mixture $\\omega_{tot}$ are investigated. Statefinder diagnostics provided also.

Martiros Khurshudyan

2013-01-31T23:59:59.000Z

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.

301

Gravitational Field Equations and Theory of Dark Matter and Dark Energy

The main objective of this article is to derive a new set of gravitational field equations and to establish a new unified theory for dark energy and dark matter. The new gravitational field equations with scalar potential $\\varphi$ are derived using the Einstein-Hilbert functional, and the scalar potential $\\varphi$ is a natural outcome of the divergence-free constraint of the variational elements. Gravitation is now described by the Riemannian metric $g_{ij}$, the scalar potential $\\varphi$ and their interactions, unified by the new gravitational field equations. Associated with the scalar potential $\\varphi$ is the scalar potential energy density $\\frac{c^4}{8\\pi G} \\Phi=\\frac{c^4}{8\\pi G} g^{ij}D_iD_j \\varphi$, which represents a new type of energy caused by the non-uniform distribution of matter in the universe. The negative part of this potential energy density produces attraction, and the positive part produces repelling force. This potential energy density is conserved with mean zero: $\\int_M \\Phi dM=0$. The sum of this new potential energy density $\\frac{c^4}{8\\pi G} \\Phi$ and the coupling energy between the energy-momentum tensor $T_{ij}$ and the scalar potential field $\\varphi$ gives rise to a new unified theory for dark matter and dark energy: The negative part of this sum represents the dark matter, which produces attraction, and the positive part represents the dark energy, which drives the acceleration of expanding galaxies. In addition, the scalar curvature of space-time obeys $R=\\frac{8\\pi G}{c^4} T + \\Phi$. Furthermore, the new field equations resolve a few difficulties encountered by the classical Einstein field equations.

Tian Ma; Shouhong Wang

2012-07-11T23:59:59.000Z

302

Taming astrophysical bias in direct dark matter searches

We explore systematic biases in the identification of dark matter in future direct detection experiments and compare the reconstructed dark matter properties when assuming a self-consistent dark matter distribution function and the standard Maxwellian velocity distribution. We find that the systematic bias on the dark matter mass and cross-section determination arising from wrong assumptions for its distribution function is of order ? 1?. A much larger systematic bias can arise if wrong assumptions are made on the underlying Milky Way mass model. However, in both cases the bias is substantially mitigated by marginalizing over galactic model parameters. We additionally show that the velocity distribution can be reconstructed in an unbiased manner for typical dark matter parameters. Our results highlight both the robustness of the dark matter mass and cross-section determination using the standard Maxwellian velocity distribution and the importance of accounting for astrophysical uncertainties in a statistically consistent fashion.

Pato, Miguel [Physik-Department T30d, Technische Universität München, James-Franck-Straße, 85748 Garching (Germany); Strigari, Louis E. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Trotta, Roberto [Astrophysics Group and Imperial Centre for Inference and Cosmology, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Bertone, Gianfranco, E-mail: miguel.pato@tum.de, E-mail: strigari@stanford.edu, E-mail: r.trotta@imperial.ac.uk, E-mail: gf.bertone@gmail.com [GRAPPA Institute, University of Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands)

2013-02-01T23:59:59.000Z

303

The Structure of Dark Matter Haloes in Dwarf Galaxies

Recent observations indicate that dark matter haloes have flat central density profiles. Cosmological simulations with non-baryonic dark matter predict however self similar haloes with central density cusps. This contradiction has lead to the conclusion that dark matter must be baryonic. Here it is shown that the dark matter haloes of dwarf spiral galaxies represent a one parameter family with self similar density profiles. The observed global halo parameters are coupled with each other through simple scaling relations which can be explained by the standard cold dark matter model if one assumes that all the haloes formed from density fluctuations with the same primordial amplitude. We find that the finite central halo densities correlate with the other global parameters. This result rules out scenarios where the flat halo cores formed subsequently through violent dynamical processes in the baryonic component. These cores instead provide important information on the origin and nature of dark matter in dwarf galaxies.

A. Burkert

1995-04-12T23:59:59.000Z

304

Indirect Dark Matter search with large neutrino telescopes

Dark matter is one of the main goals of neutrino astronomy. At present, there are two big neutrino telescopes based on the Cherenkov technique in ice and water: IceCube at the South Pole and ANTARES in the northern hemisphere. Both telescopes are performing an indirect search for Dark Matter by looking for a statistical excess of neutrinos coming from astrophysical massive objects. This excess could be an evidence of the possible annihilation of dark matter particles in the centre of these objects. In one of the most popular scenarios the Dark Matter is composed of WIMP particles. The analysis and results of the ANTARES neutrino telescope for the indirect detection of Dark Matter fluxes from the Sun are here presented, as well as the latest IceCube published sensitivity results, for different Dark Matter models.

Fermani, Paolo

2013-01-01T23:59:59.000Z

305

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

306

From dark matter to neutrinoless double beta decay

Associated with two TeV-scale leptoquark scalars, a dark matter fermion which is the neutral component of an isotriplet can mediate a testable neutrinoless double beta decay at one-loop level. The dark matter fermion with determined mass and spin-independent scattering can be verified by the future dark matter direct detection experiments. We also discuss the implications on neutrino masses and baryon asymmetry.

Pei-Hong Gu

2012-09-13T23:59:59.000Z

307

Dark Matter Annihilations in the Large Magellanic Cloud

The flat rotation curve obtained for the outer star clusters of the Large Magellanic Cloud is suggestive of an LMC dark matter halo. From the composite HI and star cluster rotation curve, I estimate the parameters of an isothermal dark matter halo added to a `maximum disk.' I then examine the possibility of detecting high energy gamma-rays from non-baryonic dark matter annihilations in the central region of the Large Magellanic Cloud.

P Gondolo

1993-12-06T23:59:59.000Z

308

Ricci Dark Energy in Brans-Dicke theory

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

Chao-Jun Feng

2008-06-04T23:59:59.000Z

309

Backgrounds and Projected Limits from Dark Matter Direct Detection Experiments

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

Scott Dodelson

2008-12-08T23:59:59.000Z

310

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

311

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

312

anisotropic dark energy: Topics by E-print Network

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

universe, it was necessary to introduce a new component of matter distribution called dark energy. The standard cosmological model considers isotropy of the pressure and assumes...

313

Statefinder diagnosis and the interacting ghost model of dark energy

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

M. Malekjani; A. Khodam-Mohammadi

2012-02-19T23:59:59.000Z

314

asymmetric dark matter: Topics by E-print Network

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

the baryon asymmetry as a way to address the observed similarity between the baryonic and dark matter energy densities today. Focusing on this framework we calculate the evolution...

315

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

2008-05-03T23:59:59.000Z

316

Neutrinoless double beta decay can constrain neutrino dark matter

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

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

2002-02-26T23:59:59.000Z

317

Generalized holographic dark energy model described at the Hubble length

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

M. Malekjani

2012-09-25T23:59:59.000Z

318

Modeling dark energy with a top-down approach

We investigate a top-down approach for modeling the dark energy where we fit the luminosity distances directly rather than indirectly fitting the equation of state.

Duane A. Dicus; Wayne W. Repko

2006-06-22T23:59:59.000Z

319

Holographic Dark Energy Model with Modified Generalized Chaplygin Gas

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

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

2007-11-21T23:59:59.000Z

320

Inert scalar dark matter in an extra dimension inspired model

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

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

2014-11-12T23:59:59.000Z

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

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

322

Astrophysical search strategies for accelerator blind dark matter

A weakly interacting dark-matter particle may be difficult to discover at an accelerator because it either (1) is too massive, (2) has no standard-model gauge interactions, or (3) is almost degenerate with other states. In each of these cases, searches for annihilation products in the Galactic halo are useful probes of dark-matter properties. Using the example of supersymmetric dark matter, I discuss how astrophysical searches for dark matter may provide discovery and mass information inaccessible to collider physics programs such as the Tevatron and LHC.

James D. Wells

1998-08-06T23:59:59.000Z

323

Insects Attacking Forage Crops.

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

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

1961-01-01T23:59:59.000Z

324

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...

Debnath, Ujjal

2015-01-01T23:59:59.000Z

325

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

326

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

2015-03-06T23:59:59.000Z

327

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

Temple, Blake

328

The World of Dark Shadows Issue 26

Stroka and Humbert Allen Astredo . Hope you enjoy the material feat . them, and the characters they created, as \\'Iel1 as the t~r~ng regular features. 0 er !Text issue is the special Joan Bennett/Dennis Pt.(Cont. pg. 43) 4. . a r~ck one, 5. EPITAPHS..., who enterest i n stealth, his nose behind him, his face turned backward, who loses that for which he came. " Run out, thou who comest in darkness, w~o enterest in stealth, her nose behind her, her face turned backward, who loses that for which she...

Multiple Contributors

1980-01-01T23:59:59.000Z

329

MSSM Inflaton: SUSY Dark Matter and LHC

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

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

2009-09-08T23:59:59.000Z

330

The World of Dark Shadows Issue 31

The World 01 llltfiK ~llltDaW~ 31 ~. 1 ~ I ~ I ..\\ I I •~ J \\ .. ~ ! 1(18" !! ~ \\ 1 \\ U ;: 0 ~ I ' c " o'q~~\\ '0 l ~~ ", 9 I I r I - I ~ ( -;, ~l~ ~ . I ( ~"'"VW" " ) J!. d,.", .'\\ _C]~I ~ ~ ~ /';".!.t ~0-. THE WORLD OF DARK... ............ 60 Jayne Largent ........ 19. 36 Chri s Nokes .......... 13 Kathi Swan ........... 68 Val Verse .... .. .. .. .. 29. 37 Photos used on page 38 - upper left corner - Maria Barbosa lower 1eft corner - Ma rcy Robi n Pages 39 and 42. courtesy...

Multiple Contributors

1982-01-01T23:59:59.000Z

331

The World of Dark Shadows Issue 8

't:l l~..:)'t hare! her. 8e ba;l his hUilonit;r I)nCII ;lE;01n. he l~kod U~WD. Th" dark .1"8 ot the thi~ stor.d out ot the bell.. '" , bloouh•• teoo, an.l tbe Douth vaa .tretob&J 10 0 vido ~1·1t1. "It hODn't ' w~rtoJ - whatever lOU oxe. It h~en't w...

Multiple Contributors

1976-01-01T23:59:59.000Z

332

Probing Dark Energy with Atom Interferometry

Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too small to screen the chameleon field inside a large high-vacuum chamber, and therefore can detect the field with high sensitivity. We derive new limits on the chameleon parameters from existing experiments, and show that most of the remaining chameleon parameter space is readily accessible using atom interferometry.

Clare Burrage; Edmund J. Copeland; E. A. Hinds

2014-08-06T23:59:59.000Z

333

Viscous dark energy and phantom evolution

In order to study if the bulk viscosity may induce a big rip singularity on the flat FRW cosmologies, we investigate dissipative processes in the universe within the framework of the standard Eckart theory of relativistic irreversible thermodynamics, and in the full causal Israel–Stewart-Hiscock theory. We have found cosmological solutions which exhibit, under certain constraints, a big rip singularity. We show that the negative pressure generated by the bulk viscosity cannot avoid that the dark energy of the universe to be phantom energy.

Mauricio Cataldo; Norman Cruz; Samuel Lepe

2005-06-17T23:59:59.000Z

334

Inflation and New Agegraphic Dark Energy

In the note, we extend the discussion of the new agegraphic dark energy (NADE) model to include the inflation stage. Usually, in the inflation models, for convenience the conformal time $\\eta$ is set to be zero at the end of inflation. This is incompatible with the NADE model since $\\eta=0$ indicates the divergence of NADE. To avoid the difficulty, we can redefine the conformal time as $\\eta+\\delta$. However, we find that the positive constant $\\delta$ must be so large that NADE can not become dominated at present time.

Cheng-Yi Sun; Rui-Hong Yue

2011-04-23T23:59:59.000Z

335

Neutron Interferometry constrains dark energy chameleon fields

We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant $\\beta$ is less than 1.9 $\\times10^7$~for $n=1$ at 95\\% confidence level, where $n$ is an input parameter of the self--interaction of the chameleon field $\\varphi$ inversely proportional to $\\varphi^n$.

Lemmel, H; Ivanov, A N; Jenke, T; Pignol, G; Pitschmann, M; Potocar, T; Wellenzohn, M; Zawisky, M; Abele, H

2015-01-01T23:59:59.000Z

336

Neutron Interferometry constrains dark energy chameleon fields

We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant $\\beta$ is less than 1.9 $\\times10^7$~for $n=1$ at 95\\% confidence level, where $n$ is an input parameter of the self--interaction of the chameleon field $\\varphi$ inversely proportional to $\\varphi^n$.

H. Lemmel; Ph. Brax; A. N. Ivanov; T. Jenke; G. Pignol; M. Pitschmann; T. Potocar; M. Wellenzohn; M. Zawisky; H. Abele

2015-02-20T23:59:59.000Z

337

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

338

Constraints of Dark Energy at High Redshift

Constrains of dark energy (DE) at high redshift from current and mock future observational data are obtained. It is found that present data give poor constraints of DE even beyond redshift z=0.4, and mock future 2298 type Ia supernove data only give a little improvement of the constraints. We analyze in detail why constraints of DE decrease rapidly with the increasing of redshift. Then we try to improve the constraints of DE at high redshift. It is shown that the most efficient way is to improve the error of observations.

Qiping Su; Rong-Gen Cai

2014-08-24T23:59:59.000Z

339

DarkStar VI | Open Energy Information

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublic Utilities Address:011-DNA Jump to: navigation, searchIllinois: Energy Resources Jump to: navigation,DarkStar

340

Counting voids to probe dark energy

We show that the number of observed voids in galaxy redshift surveys is a sensitive function of the equation of state of dark energy. Using the Fisher matrix formalism we find the error ellipses in the $w_0-w_a$ plane when the equation of state of dark energy is assumed to be of the form $w_{CPL}(z)=w_0 +w_a z/(1+z)$. We forecast the number of voids to be observed with the ESA Euclid satellite and the NASA WFIRST mission, taking into account updated details of the surveys to reach accurate estimates of their power. The theoretical model for the forecast of the number of voids is based on matches between abundances in simulations and the analytical prediction. To take into account the uncertainties within the model, we marginalize over its free parameters when calculating the Fisher matrices. The addition of the void abundance constraints to the data from Planck, HST and supernova survey data noticeably tighten the $w_0-w_a$ parameter space. We thus quantify the improvement in the constraints due to the use of...

Pisani, Alice; Hamaus, Nico; Alizadeh, Esfandiar; Biswas, Rahul; Wandelt, Benjamin D; Hirata, Christopher M

2015-01-01T23:59:59.000Z

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

Dissipative or Conservative cosmology with dark energy ?

All evolutional paths for all admissible initial conditions of FRW cosmological models with dissipative dust fluid (described by dark matter, baryonic matter and dark energy) are analyzed using dynamical system approach. With that approach, one is able to see how generic the class of solutions leading to the desired property -- acceleration -- is. The theory of dynamical systems also offers a possibility of investigating all possible solutions and their stability with tools of Newtonian mechanics of a particle moving in a 1-dimensional potential which is parameterized by the cosmological scale factor. We demonstrate that flat cosmology with bulk viscosity can be treated as a conservative system with a potential function of the Chaplygin gas type. We also confront viscous models with SNIa observations. The best fitted models are obtained by minimizing the $\\chi^{2}$ function which is illustrated by residuals and $\\chi^{2}$ levels in the space of model independent parameters. The general conclusion is that SNIa data supports the viscous model without the cosmological constant. The obtained values of $\\chi^{2}$ statistic are comparable for both the viscous model and LCDM model. The Bayesian information criteria are used to compare the models with different power law parameterization of viscous effects. Our result of this analysis shows that SNIa data supports viscous cosmology more than the LCDM model if the coefficient in viscosity parameterization is fixed. The Bayes factor is also used to obtain the posterior probability of the model.

Marek Szydlowski; Orest Hrycyna

2007-11-24T23:59:59.000Z

342

A fluid mechanical explanation of dark matter

Matter in the universe has become ``dark'' or ``missing'' through misconceptions about the fluid mechanics of gravitational structure formation. Gravitational condensation occurs on non-acoustic density nuclei at the largest Schwarz length scale L_{ST}, L_{SV}, L_{SM}, L_{SD} permitted by turbulence, viscous, or magnetic forces, or by the fluid diffusivity. Non-baryonic fluids have diffusivities larger (by factors of trillions or more) than baryonic (ordinary) fluids, and cannot condense to nucleate baryonic galaxy formation as is usually assumed. Baryonic fluids begin to condense in the plasma epoch at about 13,000 years after the big bang to form proto-superclusters, and form proto-galaxies by 300,000 years when the cooling plasma becomes neutral gas. Condensation occurs at small planetary masses to form ``primordial fog particles'' from nearly all of the primordial gas by the new theory, Gibson (1996), supporting the Schild (1996) conclusion from quasar Q0957+651A,B microlensing observations that the mass of the lens galaxy is dominated by ``rogue planets ... likely to be the missing mass''. Non-baryonic dark matter condenses on superclusters at scale L_{SD} to form massive super-halos.

Carl H. Gibson

1999-04-22T23:59:59.000Z

343

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

344

Dark Energy as the Remnant of Inflation

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

H. M. Fried; Y. Gabellini

2013-02-24T23:59:59.000Z

345

Recently it was shown that the inclusion of higher signal harmonics in the inspiral signals of binary supermassive black holes (SMBH) leads to dramatic improvements in parameter estimation with the Laser Interferometer Space Antenna (LISA). In particular, the angular resolution becomes good enough to identify the host galaxy or galaxy cluster, in which case the redshift can be determined by electromagnetic means. The gravitational wave signal also provides the luminosity distance with high accuracy, and the relationship between this and the redshift depends sensitively on the cosmological parameters, such as the equation-of-state parameter $w=p_{\\rm DE}/\\rho_{\\rm DE}$ of dark energy. With a single binary SMBH event at $z < 1$ having appropriate masses and orientation, one would be able to constrain $w$ to within a few percent. We show that, if the measured sky location is folded into the error analysis, the uncertainty on $w$ goes down by an additional factor of 2-3, leaving weak lensing as the only limiting factor in using LISA as a dark energy probe.

K G Arun; Chandra Kant Mishra; Chris Van Den Broeck; B R Iyer; B S Sathyaprakash; Siddhartha Sinha

2009-04-20T23:59:59.000Z

346

The Dark Energy Survey instrument design

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

Flaugher, B.; /Fermilab

2006-05-01T23:59:59.000Z

347

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

348

Analytic study on backreacting holographic superconductors with dark matter sector

The variational method for Sturm-Liouville eigenvalue problem was employed to study analytically properties of the holographic superconductor with dark matter sector, in which a coupling between Maxwell field and another U(1)-gauge field was considered. The backreaction of the dark matter sector on gravitational background in question was also examined.

Lukasz Nakonieczny; Marek Rogatko

2014-11-04T23:59:59.000Z

349

Oculomotor Responses to Active Head Movements in Darkness

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

Ramat, Stefano

350

Looking for dark matter annihilations in dwarf galaxies

We calculate the flux of high energy gamma-rays from annihilation of neutralino dark matter in the centre of the Milky Way and the three nearest dwarf spheroidals (Sagittarius, Draco and Canis Major), using realistic models of the dark matter distribution.

F. Ferrer

2004-06-09T23:59:59.000Z

351

Hierarchy in the Phase Space and Dark Matter Astronomy

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

Niayesh Afshordi; Roya Mohayaee; Edmund Bertschinger

2009-11-02T23:59:59.000Z

352

Dark matter at the LHC: EFTs and gauge invariance

Effective field theory (EFT) formulations of dark matter interactions have proven to be a convenient and popular way to quantify LHC bounds on dark matter. However, some of the non-renormalizable EFT operators considered do not respect the gauge symmetries of the Standard Model. We carefully discuss under what circumstances such operators can arise, and outline potential issues in their interpretation and application.

Bell, Nicole F; Dent, James B; Leane, Rebecca K; Weiler, Thomas J

2015-01-01T23:59:59.000Z

353

The Phenomenology of Gravitino Dark Matter Scenarios in Supergravity Models

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

Yudi Santoso

2009-03-16T23:59:59.000Z

354

argon dark matter: Topics by E-print Network

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

argon dark matter First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 The Argon Dark Matter Experiment HEP...

355

EDELWEISS dark matter search: Latest results and future plans

EDELWEISS dark matter search: Latest results and future plans Johann Gironnet Institut de Physique is a direct search for WIMP dark matter using cryogenic heat-and-ionization germanium detectors. We report the 4850 meter- water-equivalent rock cover reduces the cosmic-ray background by six order of magnitude

Boyer, Edmond

356

Indirect Search for Dark Matter with the ANTARES Neutrino Telescope

significant high energy neutrino fluxes. Indirect search for Dark Matter looking at such neutrino fluxes for the Cherenkov light induced by high energy muons during their travel in the sea water throughout the detectorIndirect Search for Dark Matter with the ANTARES Neutrino Telescope V. Bertin1 on behalf

Paris-Sud XI, UniversitÃ© de

357

Spherical Collapse Model And Dark Energy(I)

In existing literatures about the top-hat spherical collapse model of galaxy clusters formation in cosmology containing dark energies, dark energies are usually assumed not to cluster on this scale. But all these literatures ignored the current describing the flowing of dark energies outside the clusters which should exist under this assumption, so the conclusions of these literatures are worth further explorations. In this paper we study this model in QCDM or Phantom-CDM cosmologies(flat) by assuming that dark energies will cluster synchronously with ordinary matters on the scale of galaxy clusters so the dark energy current flowing outside the clusters does not exist at all and find that in this case, the key parameters of the model exhibit rather non-trivial and remarkable dependence on the equation of state coefficients of dark energies. We then apply the results in Press-Scheter theory and calculate the number density of galaxy clusters and its evolutions. We find that this two quantities are both affected exponentially by the equation of state coefficients of dark energies. We leave the study of this model with the assumption that dark energies do not cluster on the scale of galaxy clusters at all as the topic of another paper where similar conclusions will be obtained also.

Ding-fang Zeng; Yi-hong Gao

2005-05-09T23:59:59.000Z

358

Number counts in homogeneous and inhomogeneous dark energy models

In the simple case of a constant equation of state, redshift distribution of collapsed structures may constrain dark energy models. Different dark energy models having the same energy density today but different equations of state give quite different number counts. Moreover, we show that introducing the possibility that dark energy collapses with dark matter (``inhomogeneous'' dark energy) significantly complicates the picture. We illustrate our results by comparing four dark energy models to the standard $\\Lambda$-model. We investigate a model with a constant equation of state equal to -0.8, a phantom energy model and two scalar potentials (built out of a combination of two exponential terms). Although their equations of state at present are almost indistinguishable from a $\\Lambda$-model, both scalar potentials undergo quite different evolutions at higher redshifts and give different number counts. We show that phantom dark energy induces opposite departures from the $\\Lambda$-model as compared with the other models considered here. Finally, we find that inhomogeneous dark energy enhances departures from the $\\Lambda$-model with maximum deviations of about 15% for both number counts and integrated number counts. Larger departures from the $\\Lambda$-model are obtained for massive structures which are rare objects making it difficult to statistically distinguish between models.

N. J. Nunes; A. C. da Silva; N. Aghanim

2006-02-01T23:59:59.000Z

359

Constraints on the interacting holographic dark energy model

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

Bin Wang; Chi-Yong Lin; Elcio Abdalla

2006-03-31T23:59:59.000Z

360

Constraints on Dark Energy Models from Weak Gravity Conjecture

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

Ximing Chen; Jie Liu; Yungui Gong

2008-06-15T23:59:59.000Z

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

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

362

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

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

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

363

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

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

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

364

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

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

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

365

The dynamics of universe for exponential decaying dark energy

In this study we consider an exponential decaying form for dark energy as EoS parameter in order to discuss the dynamics of the universe. Firstly, assuming that universe is filled with an ideal fluid which consists of exponential decaying dark energy we obtain time dependent behavior of several physical quantities such as energy density, pressure and others for dark energy, dark energy-matter coupling and non-coupling cases. Secondly, using scalar field instead of an ideal fluid we obtain these physical quantities in terms of scalar potential and kinetic term for the same cases in scalar-tensor formalism. Finally we show that ideal fluid and scalar-tensor description of dark energy give mathematically equivalent results for this EoS parameter.

Bostan, Nilay

2015-01-01T23:59:59.000Z

366

Dark radiation from particle decay: cosmological constraints and opportunities

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

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

2013-08-01T23:59:59.000Z

367

Dark radiation from particle decay: cosmological constraints and opportunities

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

Jasper Hasenkamp; Jörn Kersten

2014-02-13T23:59:59.000Z

368

Baryon Acoustic Oscillation Intensity Mapping 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 brightness 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.

Chang, Tzu-Ching; Peterson, Jeffrey B; McDonald, Patrick

2007-01-01T23:59:59.000Z

369

Analysis of Generalized Ghost Version of Pilgrim Dark Energy

The proposal of pilgrim dark energy is based on the speculation that phantom-like dark energy possesses enough resistive force to preclude the black hole formation in the later universe. We explore this phenomenon by assuming the generalized ghost version of pilgrim dark energy. We find that most of the values of the interacting ($\\xi^2$) as well as pilgrim dark energy ($u$) parameters push the equation of state parameter towards phantom region. The squared speed of sound shows that this model remains stable in most of the cases of $\\xi^2$ and $u$. We also develop $\\omega_\\Lambda-\\omega'_\\Lambda$ plane and observe that this model corresponds to thawing as well as freezing regions. Finally, it is shown that the non-interacting and interacting generalized ghost versions of pilgrim dark energy correspond to $\\Lambda$CDM limit on the statefinder plane.

M. Sharif; Abdul Jawad

2014-08-18T23:59:59.000Z

370

Dark energy rest frame and the CMB dipole

If dark energy can be described as a perfect fluid, then, apart from its equation of state relating energy density and pressure, we should also especify the corresponding rest frame. Since dark energy is typically decoupled from the rest of components of the universe, in principle such a frame could be different from that of matter and radiation. In this work we consider the potential observable effects of the motion of dark energy and the possibility to measure the dark energy velocity relative to matter. In particular we consider the modification of the usual interpretation of the CMB dipole and its implications for the determination of matter bulk flows on very large scales. We also comment on the possible origin of a dark energy flow and its evolution in different models.

Antonio L. Maroto

2006-09-08T23:59:59.000Z

371

Statefinder Diagnostic for Born-Infeld Type Dark Energy Model

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

Z. G. Huang; H. Q. Lu

2008-02-16T23:59:59.000Z

372

Dark current mechanism of terahertz quantum-well photodetectors

Dark current mechanisms of terahertz quantum-well photodetectors (THz QWPs) are systematically investigated experimentally and theoretically by measuring two newly designed structures combined with samples reported previously. In contrast to previous investigations, scattering-assisted tunneling dark current is found to cause significant contributions to total dark current. A criterion is also proposed to determine the major dark current mechanism at different peak response frequencies. We further determine background limited performance (BLIP) temperatures, which decrease both experimentally and theoretically as the electric field increases. This work gives good description of dark current mechanism for QWPs in the THz region and is extended to determine the transition fields and BLIP temperatures with response peaks from 3 to 12 THz.

Jia, J. Y.; Gao, J. H.; Hao, M. R.; Wang, T. M.; Shen, W. Z.; Zhang, Y. H., E-mail: yuehzhang@sjtu.edu.cn [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Cao, J. C.; Guo, X. G. [Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Schneider, H., E-mail: h.schneider@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, P.O. Box 510119, 01314 Dresden (Germany)

2014-10-21T23:59:59.000Z

373

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

374

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

375

A variety of supersymmetric models give rise to a split mass spectrum characterized by very heavy scalars but sub-TeV gauginos, usually with a wino-like LSP. Such models predict a thermally-produced underabundance of wino-like WIMP dark matter so that non-thermal DM production mechanisms are necessary. We examine the case where theories with a wino-like LSP are augmented by a Peccei-Quinn sector including an axion-axino-saxion supermultiplet in either the SUSY KSVZ or SUSY DFSZ models and with/without saxion decays to axions/axinos. We show allowed ranges of PQ breaking scale f_a for various cases which are generated by solving the necessary coupled Boltzmann equations. We also present results for a model with radiatively-driven naturalness but with a wino-like LSP.

Bae, Kyu Jung; Lessa, Andre; Serce, Hasan

2015-01-01T23:59:59.000Z

376

The World of Dark Shadows Issue 19

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

Multiple Contributors

1978-01-01T23:59:59.000Z

377

Bi-metric Gravity and "Dark Matter"

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

I. T. Drummond

2000-08-18T23:59:59.000Z

378

A Dark Year for Tidal Disruption Events

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

Guillochon, James

2015-01-01T23:59:59.000Z

379

Nuclear Double Beta Decay, Fundamental Particle Physics, Hot Dark Matter, And Dark Energy

Nuclear double beta decay, an extremely rare radioactive decay process, is - in one of its variants - one of the most exciting means of research into particle physics beyond the standard model. The large progress in sensitivity of experiments searching for neutrinoless double beta decay in the last two decades - based largely on the use of large amounts of enriched source material in "active source experiments" - has lead to the observation of the occurrence of this process in nature (on a 6.4 sigma level), with the largest half-life ever observed for a nuclear decay process (2.2 x 10^{25} y). This has fundamental consequences for particle physics - violation of lepton number, Majorana nature of the neutrino. These results are independent of any information on nuclear matrix elements (NME)*. It further leads to sharp restrictions for SUSY theories, sneutrino mass, right-handed W-boson mass, superheavy neutrino masses, compositeness, leptoquarks, violation of Lorentz invariance and equivalence principle in the neutrino sector. The masses of light-neutrinos are found to be degenerate, and to be at least 0.22 +- 0.02 eV. This fixes the contribution of neutrinos as hot dark matter to >=4.7% of the total observed dark matter. The neutrino mass determined might solve also the dark energy puzzle. *(It is briefly discussed how important NME for 0nubb decay really are.)

Hans V. Klapdor-Kleingrothaus; Irina V. Krivosheina

2010-07-15T23:59:59.000Z

380

Dynamical insight into dark-matter haloes

We investigate, using the spherical Jeans equation, self-gravitating dynamical equilibria satisfying a relation rho/sigma_r^3 propto r^-alpha, which holds for simulated dark-matter haloes over their whole resolved radial range. Considering first the case of velocity isotropy, we find that this problem has only one solution with realistic density profile, which occurs only for a critical value of alpha_crit = 35/18 ~= 1.94, which is consistent with the empirical value of 1.9+/-0.05. We extend our analysis in two ways: first we introduce a parameter epsilon to allow for a more general relation rho/\\sigma_r^epsilon propto r^-alpha; second we consider velocity anisotropy. If we assume beta(r) := 1- sigma_theta^2 / sigma_r^2 to be linearly related to the logarithmic density slope gamma(r) := -dln(rho)/dln(r), which is in agreement with simulations, the problem remains analytically tractable and is equivalent to the simpler isotropic case: there exists only one physical solution, which occurs at a critical alpha value. Remarkably, this value of alpha and the density and velocity-dispersion profiles depend only on epsilon and the value beta_0 := beta(r=0), but not on the slope of the linear beta-gamma relation. For epsilon=3, alpha_crit = 35/18 - 2beta_0/9 and the resulting density profile is fully analytic (as are the velocity dispersion and circular speed) with an inner cusp rho propto r^{-(7+10beta_0)/9} and a very smooth transition to a steeper outer power-law asymptote. These models are in excellent agreement with the density, velocity-dispersion and anisotropy profiles of simulated dark-matter haloes over their full resolved radial range. If epsilon=3 is a universal constant, some scatter in beta_0 ~= 0 may account for some diversity in the density profiles. (ABRIDGED)

Walter Dehnen; Dean McLaughlin

2005-06-22T23:59:59.000Z

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.

381

Neutrino constraints on the dark matter total annihilation cross section

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

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

2007-12-15T23:59:59.000Z

382

Cosmological Perturbations in Models of Coupled Dark Energy

Models in which dark energy interacts with dark matter have been proposed in the literature to help explain why dark energy should only come to dominate in recent times. In this paper, we present a dynamical framework to calculate cosmological perturbations for a general quintessence potential and interaction term. Our formalism is built upon the powerful phase-space approach often used to analyse the dynamical attractors in the background. We obtain a set of coupled differential equations purely in terms of dimensionless, bounded variables and apply these equations to calculate perturbations in a number of scenarios. Interestingly, in the presence of dark-sector interactions, we find that dark energy perturbations do not redshift away at late times, but can cluster even on small scales. We also clarify the initial conditions for the perturbations in the dark sector, showing that adiabaticity is no longer conserved in the presence of dark-sector interactions, even on large scales. Some issues of instability in the perturbations are also discussed.

Sirichai Chongchitnan

2009-02-26T23:59:59.000Z

383

Composite dark matter from a model with composite Higgs boson

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

Maxim Yu. Khlopov; Chris Kouvaris

2008-10-10T23:59:59.000Z

384

Diurnal modulation signal from dissipative hidden sector dark matter

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

R. Foot; S. Vagnozzi

2014-12-02T23:59:59.000Z

385

Constraints on particle dark matter from cosmic-ray antiprotons

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

N. Fornengo; L. Maccione; A. Vittino

2015-01-30T23:59:59.000Z

386

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

387

Interaction between DBI-essence and other Dark Energies

The present work considers interaction between DBI-essence and other candidates of dark energies like modified Chaplygin gas, hessence, tachyonic field, and new agegraphic dark energy. The potentials of the fields have been reconstructed under interaction and their evolutions have been viewed against cosmic time $t$ and scalar field $\\phi$. Equation of state parameters have also been obtained. The nature of potentials and the equation of state parameters of the dark energies have been found graphically in presence of interaction (both small and large interaction).

Surajit Chattopadhyay; Ujjal Debnath

2010-06-11T23:59:59.000Z

388

Interaction between Tachyon and Hessence (or Hantom) dark energies

In this paper, we have considered that the universe is filled with tachyon, hessence (or hantom) dark energies. Subsequently we have investigated the interactions between tachyon and hessence (hantom) dark energies and calculated the potentials considering the power law form of the scale factor. It has been revealed that the tachyonic potential always decreases and hessence (or hantom) potential increases with corresponding fields. Furthermore, we have considered a correspondence between the hessence (or hantom) dark energy density and new variable modified Chaplygin gas energy density. From this, we have found the expressions of the arbitrary positive constants B0 and C of new variable modified Chaplygin gas.

Surajit Chattopadhyay; Ujjal Debnath

2010-10-07T23:59:59.000Z

389

The Higgs boson, Supersymmetry and Dark Matter: Relations and Perspectives

The discovery of a light Higgs boson at the LHC opens a broad program of studies and measurements to understand the role of this particle in connection with New Physics and Cosmology. Supersymmetry is the best motivated and most thoroughly formulated and investigated model of New Physics which predicts a light Higgs boson and can explain dark matter. This paper discusses how the study of the Higgs boson connects with the search for supersymmetry and for dark matter at the LHC and at a future $e^+e^-$ collider and with dedicated underground dark matter experiments.

Alexandre Arbey; Marco Battaglia; Farvah Mahmoudi

2015-04-20T23:59:59.000Z

390

The Higgs boson, Supersymmetry and Dark Matter: Relations and Perspectives

The discovery of a light Higgs boson at the LHC opens a broad program of studies and measurements to understand the role of this particle in connection with New Physics and Cosmology. Supersymmetry is the best motivated and most thoroughly formulated and investigated model of New Physics which predicts a light Higgs boson and can explain dark matter. This paper discusses how the study of the Higgs boson connects with the search for supersymmetry and for dark matter at the LHC and at a future $e^+e^-$ collider and with dedicated underground dark matter experiments.

Arbey, Alexandre; Mahmoudi, Farvah

2015-01-01T23:59:59.000Z

391

Bianchi Type-I Universe with Wet Dark Fluid

The Bianchi type-I universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state $p=\\gamma (\\rho -\\rho_\\star)$ which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The cases $\\gamma =1$ and $\\gamma =0$ have been also analysed.

T. Singh; R. Chaubey

2010-07-08T23:59:59.000Z

392

Bianchi Type-I Universe with Wet Dark Fluid

The Bianchi type-I universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state $p=\\gamma (\\rho -\\rho_\\star)$ which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The cases $\\gamma =1$ and $\\gamma =0$ have been also analysed.

Singh, T

2010-01-01T23:59:59.000Z

393

Hidden Photon Dark Matter Search with a Large Metallic Mirror

If Dark Matter is composed of hidden-sector photons that kinetically mix with photons of the visible sector, then Dark Matter has a tiny oscillating electric field component. Its presence would lead to a small amount of visible radiation being emitted from a conducting surface, with the photon frequency given approximately by the mass of the hidden photon. Here, we report on experimental efforts that have started recently to search for such hidden photon Dark Matter in the (sub-)eV regime with a prototype mirror for the Auger fluorescence detector at the Karlsruhe Institute for Technology.

Babette Döbrich; Kai Daumiller; Ralph Engel; Marek Kowalski; Axel Lindner; Javier Redondo; Markus Roth

2014-10-01T23:59:59.000Z

394

Dark cores in sunspot penumbral Goran B. Scharmer, Boris V. Gudiksen, Dan Kiselman, Mats G. Lofdahl

............................................................................................................................................................................. Sunspot umbrae--the dark central regions of the spots--are surrounded by brighter filamentary penumbrae are isolated from the bulk of the penumbra and surrounded by dark umbra, show dark cores. The footpoints bright features standing out near the edge of the dark umbra) or penumbral grains (brighter parts

LÃ¶fdahl, Mats

395

Cosmology with dark energy decaying through its chemical-potential contribution

The consideration of dark energy's quanta, required also by thermodynamics, introduces its chemical potential into the cosmological equations. Isolating its main contribution, we obtain solutions with dark energy decaying to matter or radiation. When dominant, their energy densities tend asymptotically to a constant ratio, explaining today's dark energy-dark matter coincidence, and in agreement with supernova redshift data.

J. Besprosvany

2007-12-29T23:59:59.000Z

396

arXiv:astro-ph/0703364v227Aug2007 Electromagnetic dark energy

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

Wright, Francis

397

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

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

Gupta, Vartika; Mukherjee, Amitabha; Lohiya, Daksh

2015-01-01T23:59:59.000Z

398

Planck constraints on holographic dark energy

We perform a detailed investigation on the cosmological constraints on the holographic dark energy (HDE) model by using the Plank data. We find that HDE can provide a good fit to the Plank high-l (l ?> 40) temperature power spectrum, while the discrepancy at l ? 20-40 found in the ?CDM model remains unsolved in the HDE model. The Plank data alone can lead to strong and reliable constraint on the HDE parameter c. At the 68% confidence level (CL), we obtain c = 0.508 ± 0.207 with Plank+WP+lensing, favoring the present phantom behavior of HDE at the more than 2? CL. By combining Plank+WP with the external astrophysical data sets, i.e. the BAO measurements from 6dFGS+SDSS DR7(R)+BOSS DR9, the direct Hubble constant measurement result (H{sub 0} = 73.8 ± 2.4 kms{sup ?1}Mpc{sup ?1}) from the HST, the SNLS3 supernovae data set, and Union2.1 supernovae data set, we get the 68% CL constraint results c = 0.484 ± 0.070, 0.474 ± 0.049, 0.594 ± 0.051, and 0.642 ± 0.066, respectively. The constraints can be improved by 2%-15% if we further add the Plank lensing data into the analysis. Compared with the WMAP-9 results, the Plank results reduce the error by 30%-60%, and prefer a phantom-like HDE at higher significant level. We also investigate the tension between different data sets. We find no evident tension when we combine Plank data with BAO and HST. Especially, we find that the strong correlation between ?{sub m}h{sup 3} and dark energy parameters is helpful in relieving the tension between the Plank and HST measurements. The residual value of ?{sup 2}{sub Plank+WP+HST}??{sup 2}{sub Plank+WP} is 7.8 in the ?CDM model, and is reduced to 1.0 or 0.3 if we switch the dark energy to w model or the holographic model. When we introduce supernovae data sets into the analysis, some tension appears. We find that the SNLS3 data set is in tension with all other data sets; for example, for the Plank+WP, WMAP-9 and BAO+HST, the corresponding ??{sup 2} is equal to 6.4, 3.5 and 4.1, respectively. As a comparison, the Union2.1 data set is consistent with these three data sets, but the combination Union2.1+BAO+HST is in tension with Plank+WP+lensing, corresponding to a large ??{sup 2} that is equal to 8.6 (1.4% probability). Thus, combining internal inconsistent data sets (SNIa+BAO+HST with Plank+WP+lensing) can lead to ambiguous results, and it is necessary to perform the HDE data analysis for each independent data sets. Our tightest self-consistent constraint is c = 0.495 ± 0.039 obtained from Plank+WP+BAO+HST+lensing.

Li, Miao; Zhang, Zhenhui [Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Xiao-Dong [Korea Institute for Advanced Study, Hoegiro 87, Dongdaemun-Gu, Seoul 130-722 (Korea, Republic of); Ma, Yin-Zhe [Department of Physics and Astronomy, University of British Columbia, Vancouver, V6T 1Z1, BC Canada (Canada); Zhang, Xin, E-mail: mli@itp.ac.cn, E-mail: xiaodongli@kias.re.kr, E-mail: mayinzhe@phas.ubc.ca, E-mail: zhangxin@mail.neu.edu.cn, E-mail: zhangzhh@itp.ac.cn [College of Sciences, Northeastern University, Shenyang 110004 (China)

2013-09-01T23:59:59.000Z

399

Spectroscopic Needs for Imaging Dark Energy Experiments

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

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, etc. – rather than to make the moments themselve

Newman, Jeffrey A. [Univ. of Pittsburgh and PITT PACC, PA (United States). Dept of Physics and Astronomy; Slosar, Anze [Brookhaven National Laboratory (BNL), Upton, NY (United States); Abate, Alexandra [Univ. of Arizona, Tucson, AZ (United States); Abdalla, Filipe B. [Univ. College London (United Kingdom); Allam, Sahar [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Allen, Steven W. [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Ansari, Reza [LAL Univ. Paris-Sud, Orsay (France); Bailey, Stephen [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Barkhouse, Wayne A. [Univ. of North Dakota, Grand Forks, ND (United States); Beers, Timothy C. [National Optical Astronomy Observations, Tucson, AZ (United States); Blanton, Michael R. [New York Univ., NY (United States); Brodwin, Mark [Univ. of Missouri at Kansas City, Kansas City, MO (United States); Brownstein, Joel R. [Univ. of Utah, Salt Lake City, UT (United States); Brunner, Robert J. [Illinois Univ., Urbana, IL (United States); Carrasco-Kind, Matias [Illinois Univ., Urbana, IL (United States); Cervantes-Cota, Jorge [Inst. Nacional de Investigaciones Nucleares (ININ), Escandon (Mexico); Chisari, Nora Elisa [Princeton Univ., Princeton, NJ (United States); Colless, Matthew [Australian National Univ., Canberra (Australia). Research School of Astronomy and Astrophysics; Comparat, Johan [Campus of International Excellence UAM and CSIC, Madrid (Spain); Coupon, Jean [Univ. of Geneva (Switzerland). Astronomical Observatory; Cheu, Elliott [Univ. of Arizona, Tucson, AZ (United States); Cunha, Carlos E. [Stanford Univ., Stanford, CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology; de la Macorra, Alex [UNAM, Mexico City (Mexico). Dept. de Fisica Teorica and Inst. Avanzado de Cosmologia; Dell’Antonio, Ian P. [Brown Univ., Providence, RI (United States); Frye, Brenda L. [Univ. of Arizona, Tucson, AZ (United States); Gawiser, Eric J. [State Univ. of New Jersey, Piscataway, NJ (United States); Gehrels, Neil [NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Grady, Kevin [NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Hagen, Alex [Penn State Univ., University Park, PA (United States); Hall, Patrick B. [York Univ., Toronto, ON (Canada); Hearin, Andrew P. [Yale Univ., New Haven, CT (United States); Hildebrandt, Hendrik [Argelander-Inst. fuer Astronomie, Bonn (Germany); Hirata, Christopher M. [Ohio State Univ., Columbus, OH (United States); Ho, Shirley [Carnegie Mellon Univ., Pittsburgh, PA (United States). McWilliams Center for Cosmology; Honscheid, Klaus [Ohio State Univ., Columbus, OH (United States); Huterer, Dragan [Univ. of Michigan, Ann Arbor, MI (United States); Ivezic, Zeljko [Univ. of Washington, Seattle, WA (United States); Kneib, Jean -Paul [Laboratoire d'Astrophysique, Ecole Polytechnique Federale de Lausanne (EPFL) (Swizerland); Laboratoire d'Astrophysique de Marseille (France); Kruk, Jeffrey W. [NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Lahav, Ofer [Univ. College London, Bloomsbury (United Kingdom); Mandelbaum, Rachel [Carnegie Mellon Univ., Pittsburgh, PA (United States). McWilliams Center for Cosmology; Marshall, Jennifer L. [Texas A and M Univ., College Station, TX (United States); Matthews, Daniel J. [Univ. of Pittsburgh and PITT PACC, PA (United States). Dept of Physics and Astronomy; Menard, Brice [Johns Hopkins Univ., Baltimore, MD (United States); Miquel, Ramon [Univ. Autonoma de Barcelona (Spain). Inst. de Fisica d'Altes Energies (IFAE); Moniez, Marc [Univ. Paris-Sud, Orsay (France); Moos, H. W. [Johns Hopkins Univ., Baltimore, MD (United States); Moustakas, John [Siena College, Loudonville, NY (United States); Papovich, Casey [Texas A and M Univ., College Station, TX (United States); Peacock, John A. [Univ. of Edinburgh (United Kingdom). Inst. for Astronomy, Royal Observatory; Park, Changbom [Korea Inst. for Advanced Study, Seoul (Korea, Republic of); Rhodes, Jason [Jet Propulsion Lab./Caltech, Pasadena, CA (United States)

2015-03-01T23:59:59.000Z

400

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

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.

401

Cosmological viability conditions for f(T) dark energy models

Recently f(T) modified teleparallel gravity where T is the torsion scalar has been proposed as the natural gravitational alternative for dark energy. We perform a detailed dynamical analysis of these models and find conditions for the cosmological viability of f(T) dark energy models as geometrical constraints on the derivatives of these models. We show that in the phase space exists two cosmologically viable trajectory which (i) The universe would start from an unstable radiation point, then pass a saddle standard matter point which is followed by accelerated expansion de sitter point. (ii) The universe starts from a saddle radiation epoch, then falls onto the stable matter era and the system can not evolve to the dark energy dominated epoch. Finally, for a number of f(T) dark energy models were proposed in the more literature, the viability conditions are investigated.

Setare, M.R.; Mohammadipour, N., E-mail: rezakord@ipm.ir, E-mail: N.Mohammadipour@uok.ac.ir [Department of Science, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

2012-11-01T23:59:59.000Z

402

Effect of phantom dark energy on the holographic thermalization

Gravitational collapse of a shell of charged dust surrounded by the phantom dark energy is probed by the minimal area surface, which is dual to probe the thermalization in the boundary quantum field by expectation values of Wilson loop in the framework of the AdS/CFT correspondence. We investigated mainly the effect of the phantom dark energy parameter and chemical potential on the thermalization. The result shows that the smaller the phantom dark energy parameter is, the easier the plasma thermalizes as the chemical potential is fixed, and the larger the chemical potential is, the harder the plasma thermalizes as the dark energy parameter is fixed. We get the fitting function of the thermalization curve and with it, the thermalization velocity and thermalization acceleration are discussed.

Zeng, Xiao-Xiong; Li, Li-Fang

2015-01-01T23:59:59.000Z

403

Neutrino masses, leptogenesis, and sterile neutrino dark matter

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

Takanao Tsuyuki

2014-07-20T23:59:59.000Z

404

Light Dark Matter Detection Prospects at Neutrino Experiments

We consider the prospects for the detection of relatively light dark matter through direct annihilation to neutrinos. We specifically focus on the detection possibilities of water Cherenkov and liquid scintillator neutrino detection devices. We find in particular that liquid scintillator detectors may potentially provide excellent detection prospects for dark matter in the 4-10 GeV mass range. These experiments can provide excellent corroborative checks of the DAMA/LIBRA annual modulation signal, but may yield results for low mass dark matter in any case. We identify important tests of the ratio of electron to muon neutrino events (and neutrino versus anti-neutrino events), which discriminate against background atmospheric neutrinos. In addition, the fraction of events which arise from muon neutrinos or anti-neutrinos ($R_{\\mu}$ and $R_{\\bar \\mu}$) can potentially yield information about the branching fractions of hypothetical dark matter annihilations into different neutrino flavors. These results apply to n...

Kumar, Jason; Smith, Stefanie

2009-01-01T23:59:59.000Z

405

a1 decreases dark: Topics by E-print Network

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

intermediate-luminosity elliptical galaxies inferred to have an unusually diffuse dark matter halo. We use the chi2-made-to-measure particle code NMAGIC to construct axisymmetric...

406

asymmetric mirror dark: Topics by E-print Network

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

17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 GeV Scale Asymmetric Dark Matter from Mirror Universe: Direct Detection and LHC Signatures HEP - Experiment (arXiv)...

407

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

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

ancient starlight found its way to a mountaintop in Chile, where the newly-constructed Dark Energy Camera - the most powerful sky-mapping machine ever created - captured and...

408

Interacting Dark Energy in Ho?ava-Lifshitz Cosmology

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

M R Setare

2009-12-02T23:59:59.000Z

409

axino dark matter: Topics by E-print Network

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

5times104gev. At higher treh and lower mass, axinos could constitute warm dark matter. In the scenario with axinos as relics, the gravitino problem finds a natural...

410

DMTPC: A dark matter detector with directional sensitivity

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

Battat, James

411

Cosmic-ray electron signatures of dark matter

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

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

2009-02-15T23:59:59.000Z

412

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

413

Search for Dark Matter Satellites Using the FERMI-LAT

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

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

2012-08-16T23:59:59.000Z

414

Interacting holographic dark energy model in non-flat universe

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

M R Setare

2006-10-14T23:59:59.000Z

415

Cosmological viability conditions for $f(T)$ dark energy models

Recently $f(T)$ modified teleparallel gravity where T is the torsion scalar has been proposed as the natural gravitational alternative for dark energy. We perform a detailed dynamical analysis of these models and find conditions for the cosmological viability of $f(T)$ dark energy models as geometrical constraints on the derivatives of these models. We show that in the phase space exists two cosmologically viable trajectory which (i) The universe would start from an unstable radiation point, then pass a saddle standard matter point which is followed by accelerated expansion de sitter point. (ii) The universe starts from a saddle radiation epoch, then falls onto the stable matter era and the system can not evolve to the dark energy dominated epoch. Finally, for a number of $f(T)$ dark energy models were proposed in the more literature, the viability conditions are investigated.

M. R. Setare; N. Mohammadipour

2012-11-06T23:59:59.000Z

416

A dark energy model resulting from a Ricci symmetry revisited

Observations of supernovae of type Ia require dark energy (some unknown exotic \\emph{`matter'} of negative pressure) to explain their unexpected faintness. Whereas the simplest and most favoured candidate of dark energy, the Einsteinian cosmological constant, is about 120 orders of magnitude smaller than the theoretically predicted value. Motivated by this problem, a number of models of dynamically decaying dark energy have been proposed by considering different phenomenological laws or potentials of the scalar field, which are more or less ad-hoc. However, it is more advisable to consider the symmetry properties of spacetime rather than the ad-hoc assumptions. In this view, we consider a model of Robertson-Walker cosmology emerging from a Ricci symmetry which provides consistently an evolving dark energy. We test the model for the recent supernovae Ia data, as well as, the ultracompact radio sources data compiled by Jackson and Dodgson. The model fits the data very well.

R. G. Vishwakarma

2008-01-18T23:59:59.000Z

417

Navigation without vision: bumblebee orientation in complete darkness

to isolate navigation mechanisms used in naturally dark situations, such as in the nest. Using infrared video altogether (such as here) can this question be answered unambiguously. To estimate direction, honeybees

Chittka, Lars

418

On extended sign-changeable interactions in the dark sector

We extend the cosmological couplings proposed in Sun et al. and Wei, where they suggested interactions with change of signs along the cosmological evolution. Our extension liberates the changes of sign of the interaction from the deceleration parameter and from the relation of energy densities of the dark sector and considers the presence of non interactive matter. In three cases we obtain the general solutions and the results obtained in models fitted with Hubble's function and SNe Ia data, are analyzed regarding the problem of the cosmological coincidence, the problem of the crisis of the cosmological age and the magnitude of the energy density of dark energy at early universe. Also we graphically study the range of variation of, the actual dark matter density parameter, the effective equation of state of the dark energy and the redshift of transition to the accelerated regimen, generated by variations at order $1\\sigma$ in the coupling parameters.

Mónica Forte

2014-09-23T23:59:59.000Z

419

Design and Construction of Prototype Dark Matter Detectors

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

Peter Fisher

2012-03-23T23:59:59.000Z

420

Making the Dark Matter Connection Between Particle Physics and Cosmology

be explained within the Standard Model of particle physics. However, models which extend the Standard Model, such as supersymmetry, can explain dark matter. This dissertation investigates the signals of some supersymmetry models in the context of collider...

Krislock, Abram Michael

2012-10-19T23:59:59.000Z

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

Effect of phantom dark energy on the holographic thermalization

Gravitational collapse of a shell of charged dust surrounded by the phantom dark energy is probed by the minimal area surface, which is dual to probe the thermalization in the boundary quantum field by expectation values of Wilson loop in the framework of the AdS/CFT correspondence. We investigated mainly the effect of the phantom dark energy parameter and chemical potential on the thermalization. The result shows that the smaller the phantom dark energy parameter is, the easier the plasma thermalizes as the chemical potential is fixed, and the larger the chemical potential is, the harder the plasma thermalizes as the dark energy parameter is fixed. We get the fitting function of the thermalization curve and with it, the thermalization velocity and thermalization acceleration are discussed.

Xiao-Xiong Zeng; Xin-Yun Hu; Li-Fang Li

2015-03-16T23:59:59.000Z

422

Detecting the invisible universe with neutrinos and dark matter

Recent work in astrophysics has show that most of the matter in the universe is non-luminous. This work investigates two searches for non-luminous matter: hot dark matter formed from cosmic relic neutrinos from the Big ...

Kaboth, Asher C. (Asher Cunningham)

2012-01-01T23:59:59.000Z

423

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

424

The Unification and Cogeneration of Dark Matter and Baryonic Matter

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

S. M. Barr

2011-09-18T23:59:59.000Z

425

The Unification and Cogeneration of Dark Matter and Baryonic Matter

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

Barr, S M

2011-01-01T23:59:59.000Z

426

From massive gravity to dark matter density II

As previously observed the massless limit of massive gravity leads to a modification of general relativity. Here we study spherically symmetric solutions of the modified field equations which contain normal matter together with a dark energy density. If the dark density profile is assumed to be known, the whole problem is reduced to a linear first order differential equation which can be solved by quadratures.

G. Scharf

2009-02-18T23:59:59.000Z

427

Direct Search for Low Mass Dark Matter Particles with CCDs

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

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

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

2012-05-15T23:59:59.000Z

428

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

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

Kh. Saaidi; A. Aghamohammadi

2010-10-12T23:59:59.000Z

429

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

430

Dark energy models with variable equation of state parameter

The dark energy models with variable equation of state parameter $\\omega$ is investigated by using law of variation of Hubble's parameter that yields the constant value of deceleration parameter. The equation of state parameter $\\omega$ is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical significance of the dark energy models has also been discussed.

Anil Kumar Yadav; Farook Rahaman; Saibal Ray

2010-09-24T23:59:59.000Z

431

New agegraphic dark energy model with generalized uncertainty principle

We investigate the new agegraphic dark energy models with generalized uncertainty principle (GUP). It turns out that although the GUP affects the early universe, it does not change the current and future dark energy-dominated universe significantly. Furthermore, this model could describe the matter-dominated universe in the past only when the parameter $n$ is chosen to be $n>n_c$, where the critical value determined to be $n_c=2.799531478$.

Yong-Wan Kim; Hyung Won Lee; Yun Soo Myung; Mu-In Park

2008-08-07T23:59:59.000Z

432

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

433

Polytropic gas scalar field models of dark energy

In this work we investigate the polytropic gas dark energy model in the non flat universe. We first calculate the evolution of EoS parameter of the model as well as the cosmological evolution of Hubble parameter in the context of polytropic gas dark energy model. Then we reconstruct the dynamics and the potential of the tachyon and K-essence scalar field models according to the evolutionary behavior of polytropic gas model.

Mohammad Malekjani

2012-06-04T23:59:59.000Z

434

Gif Lectures on direct detection of Dark Matter

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

Eric Armengaud

2010-03-11T23:59:59.000Z

435

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

436

Can dark matter be a Bose-Einstein condensate?

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

C. G. Boehmer; T. Harko

2007-06-21T23:59:59.000Z

437

The galactic halo in mixed dark matter cosmologies

A possible solution to the small scale problems of the cold dark matter (CDM) scenario is that the dark matter consists of two components, a cold and a warm one. We perform a set of high resolution simulations of the Milky Way halo varying the mass of the WDM particle (m{sub WDM}) and the cosmic dark matter mass fraction in the WDM component ( f-bar {sub W}). The scaling ansatz introduced in combined analysis of LHC and astroparticle searches postulates that the relative contribution of each dark matter component is the same locally as on average in the Universe (e.g. f{sub W,s}un = f-bar {sub W}). Here we find however, that the normalised local WDM fraction (f{sub W,s}un / f-bar {sub W}) depends strongly on m{sub WDM} for m{sub WDM} < 1 keV. Using the scaling ansatz can therefore introduce significant errors into the interpretation of dark matter searches. To correct this issue a simple formula that fits the local dark matter densities of each component is provided.

Anderhalden, D.; Diemand, J.; Schneider, A. [Institute for Theoretical Physics, University of Zürich, Winterthurerst. 190, 8057 Zürich (Switzerland); Bertone, G. [GRAPPA Institute, University of Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands); Macciò, A.V., E-mail: donninoa@physik.uzh.ch, E-mail: diemand@physik.uzh.ch, E-mail: gf.bertone@gmail.com, E-mail: maccio@mpia.de, E-mail: aurel@physik.uzh.ch [Max-Planck-Insitute for Astronomy, Königstuhl 17, 69117 Heidelberg (Germany)

2012-10-01T23:59:59.000Z

438

Equivalent Neutrinos, Light WIMPs, and the Chimera of Dark Radiation

According to conventional wisdom, in the standard model (SM) of particle physics and cosmology the effective number of neutrinos is Neff=3 (more precisely, 3.046). In extensions of the standard model allowing for the presence of DeltaNnu equivalent neutrinos (or dark radiation), Neff is generally >3. The canonical results are reconsidered here, revealing that a measurement of Neff>3 can be consistent with DeltaNnu=0 (dark radiation without dark radiation). Conversely, a measurement consistent with Neff=3 is not inconsistent with the presence of dark radiation (DeltaNnu>0). In particular, if there is a light WIMP that annihilates to photons after the SM neutrinos have decoupled, the photons are heated beyond their usual heating from e+- annihilation, reducing the late time ratio of neutrino and photon temperatures (and number densities), leading to Neff3 even in the absence of equivalent neutrinos or dark radiation. A measurement of Neff>3 is thus no guarantee of the presence of equivalent neutrinos or dark ra...

Steigman, Gary

2013-01-01T23:59:59.000Z

439

Equivalent Neutrinos, Light WIMPs, and the Chimera of Dark Radiation

According to conventional wisdom, in the standard model (SM) of particle physics and cosmology the effective number of neutrinos is Neff=3 (more precisely, 3.046). In extensions of the standard model allowing for the presence of DeltaNnu equivalent neutrinos (or dark radiation), Neff is generally >3. The canonical results are reconsidered here, revealing that a measurement of Neff>3 can be consistent with DeltaNnu=0 (dark radiation without dark radiation). Conversely, a measurement consistent with Neff=3 is not inconsistent with the presence of dark radiation (DeltaNnu>0). In particular, if there is a light WIMP that annihilates to photons after the SM neutrinos have decoupled, the photons are heated beyond their usual heating from e+- annihilation, reducing the late time ratio of neutrino and photon temperatures (and number densities), leading to Neff3 even in the absence of equivalent neutrinos or dark radiation. A measurement of Neff>3 is thus no guarantee of the presence of equivalent neutrinos or dark radiation. In the presence of light WIMPs and/or equivalent neutrinos there are degeneracies among the light WIMP mass and its nature (fermion or boson, as well as its couplings to neutrinos or photons), the number and nature (fermion or boson) of the equivalent neutrinos, and their decoupling temperature (the strength of their interactions with the SM particles). There's more to a measurement of Neff than meets the eye.

Gary Steigman

2013-03-18T23:59:59.000Z

440

Dark Matter; Modification of f(R) or Wimps Miracle

The identity of dark matter is one of the key outstanding problems in both particle and astrophysics. In this thesis, I review some candidates of dark matter, especially WIMPs (weakly interacting massive particles) which is one of the best candidate so it is called that WIMPs miracle. In addition of this, there are also some theories of modification of gravity, by changing the law of gravity, it could be possible that the dark matter observations are explained. Until the dark matter particle is detected, there is some room for uncertainty. So we should consider every part of the problem and solve it. Dark matter problem is covering a large area so every possibility is important. So f(R) gravity is also reviewed in this thesis and some theories are considered as a possible solution of dark matter problem. Finally we highlight that, even in the case of WIMPs or another particles solution, f(R) gravity is also can be used for this problem. However, last words will be said by experiments.

A. Övgün

2013-01-23T23:59:59.000Z

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

A FLUKA Study of $\\beta$-delayed Neutron Emission for the Ton-size DarkSide Dark Matter Detector

In the published cosmogenic background study for a ton-sized DarkSide dark matter search, only prompt neutron backgrounds coincident with cosmogenic muons or muon induced showers were considered, although observation of the initiating particle(s) was not required. The present paper now reports an initial investigation of the magnitude of cosmogenic background from $\\beta$-delayed neutron emission produced by cosmogenic activity in DarkSide. The study finds a background rate for $\\beta$-delayed neutrons in the fiducial volume of the detector on the order of < 0.1 event/year. However, detailed studies are required to obtain more precise estimates. The result should be compared to a radiogenic background event rate from the PMTs inside the DarkSide liquid scintillator veto of 0.2 events/year.

Empl, Anton

2014-01-01T23:59:59.000Z

442

In this note we address the well-known cosmic coincidence problem in the framework of the \\textit{f(R,T)} gravity. In order to achieve this, an interaction between dark energy and dark matter is considered. A constraint equation is obtained which filters the \\textit{f(R,T)} models that produce a stationary scenario between dark energy and dark matter. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of chosen interaction terms. As an illustration three widely known models of \\textit{f(R,T)} gravity are taken into consideration and used in the setup designed to study the problem. The study reveals that, the realization of the coincidence scenario is almost impossible for the popular models of $f(R,T)$ gravity, thus proving to be a major setback for these models.

Rudra, Prabir

2015-01-01T23:59:59.000Z

443

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

444

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

445

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

446

Dark Matter Constraints on Composite Higgs Models

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

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

2015-01-01T23:59:59.000Z

447

Cooling the dark energy camera instrument

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

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

2008-06-01T23:59:59.000Z

448

Searching a Dark Photon with HADES

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

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

2013-11-01T23:59:59.000Z

449

Searching a Dark Photon with HADES

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

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

2013-01-01T23:59:59.000Z

450

Possible solution of dark matter, the solution of dark energy and Gell-Mann as great theoretician

This talk discusses the formation of primordial intermediate-mass black holes, in a double-inflationary theory, of sufficient abundance possibly to provide all of the cosmological dark matter. There follows my, hopefully convincing, explanation of the dark energy problem, based on the observation that the visible universe is well approximated by a black hole. Finally, I discuss that Gell-Mann is among the five greatest theoreticians of the twentieth century.

Paul Howard Frampton

2010-07-02T23:59:59.000Z

451

DarkLight: A Search for Dark Forces at the Jefferson Laboratory Free-Electron Laser Facility

We give a short overview of the DarkLight detector concept which is designed to search for a heavy photon A' with a mass in the range 10 MeV/c^2 < m(A') < 90 MeV/c^2 and which decays to lepton pairs. We describe the intended operating environment, the Jefferson Laboratory free electon laser, and a way to extend DarkLight's reach using A' --> invisible decays.

Balewski, Jan; Bernauer, J.; Bertozzi, William; Bessuille, Jason; Buck, B.; Cowan, Ray; Dow, K.; Epstein, C.; Fisher, Peter; Gilad, Shalev; Ihloff, Ernest; Kahn, Yonatan; Kelleher, Aidan; Kelsey, J.; Milner, Richard; Moran, C.; Ou, Longwu; Russell, R.; Schmookler, Barak; Thaler, J.; Tschalar, C.; Vidal, Christopher; Winnebeck, A.; Benson, Stephen [JLAB; Gould, Christopher [JLAB; Biallas, George [JLAB; Boyce, James [JLAB; Coleman, James [JLAB; Douglas, David [JLAB; Ent, Rolf [JLAB; Evtushenko, Pavel [JLAB; Fenker, Howard [JLAB; Gubeli, Joseph [JLAB; Hannon, Fay [JLAB; Huang, Jia [JLAB; Jordan, Kevin [JLAB; Legg, Robert [JLAB; Marchlik, Matthew [JLAB; Moore, Steven [JLAB; Neil, George [JLAB; Shinn, Michelle D [JLAB; Tennant, Christopher [JLAB; Walker, Richard [JLAB; Williams, Gwyn [JLAB; Zhang, Shukui [JLAB; Freytsis, M.; Fiorito, Ralph; O'Shea, P.; Alarcon, Ricardo; Dipert, R.; Ovanesyan, G.; Gunter, Thoth; Kalantarians, Narbe; Kohl, M.; Albayrak, Ibrahim; Horn, Tanja; Gunarathne, D. S.; Martoff, C. J.; Olvitt, D. L.; Surrow, Bernd; Lia, X.; Beck, Reinhard; Schmitz, R.; Walther, D.; Brinkmann, K.; Zaunig, H.

2014-05-01T23:59:59.000Z

452

"Lehigh After Dark" Funding Lehigh after Dark is a university-supported program that aims to expand the vibrant and exciting social and recreational environment at Lehigh. The Lehigh After Dark fund supports community on Thursday, Friday, and Saturday nights. Funding parameters: New as well as existing events

Gilchrist, James F.

453

Pantry and Fabric Pests in the Home

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

Merchant, Michael E.; Brown, Wizzie

2008-10-22T23:59:59.000Z

454

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

455

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

456

Merger Rates of Dark-Matter Haloes

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

Eyal Neistein; Avishai Dekel

2008-05-22T23:59:59.000Z

457

The Dark Energy Survey Data Management System

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

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

2008-07-16T23:59:59.000Z

458

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

459

Using Tidal Tails to Probe Dark Matter Halos

We use simulations of merging galaxies to explore the sensitivity of the morphology of tidal tails to variations of the halo mass distributions in the parent galaxies. Our goal is to constrain the mass of dark halos in well-known merging pairs. We concentrate on prograde encounters between equal mass galaxies which represent the best cases for creating tidal tails, but also look at systems with different relative orientations, orbital energies and mass ratios. As the mass and extent of the dark halo increase in the model galaxies, the resulting tidal tails become shorter and less massive, even under the most favorable conditions for producing these features. Our simulations imply that the observed merging galaxies with long tidal tails ($\\sim 50-100$ kpc) such as NGC 4038/39 (the Antennae) and NGC 7252 probably have halo:disk+bulge mass ratios less than 10:1. These results conflict with the favored values of the dark halo mass of the Milky Way derived from satellite kinematics and the timing argument which give a halo:disk+bulge mass ratio of $\\sim 30:1$. However, the lower bound of the estimated dark halo mass in the Milky Way (mass ratio $\\sim 10:1$) is still consistent with the inferred tidal tail galaxy masses. Our results also conflict with the expectations of $\\Omega=1$ cosmologies such as CDM which predict much more massive and extended dark halos.

John Dubinski; J. Christopher Mihos; Lars Hernquist

1995-09-04T23:59:59.000Z

460

Non-relativistic effective theory of dark matter direct detection

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

JiJi Fan; Matthew Reece; Lian-Tao Wang

2010-12-10T23:59:59.000Z

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.

461

Non-relativistic effective theory of dark matter direct detection

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

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

2010-11-01T23:59:59.000Z

462

Complementarity of Dark Matter Searches in the pMSSM

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

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

2014-05-26T23:59:59.000Z

463

Gamma-ray probes of dark matter substructure

The substructure content of dark matter halos is interesting because it can be affected by complex galaxy physics and dark matter particle physics. However, observing the small scale structure of dark matter is a challenge. The subhalo abundance (mass function, minimum mass) and morphology (density profile, subhalo shape, subsubstructure) contain information about complex astrophysics (halo formation processes) and new exotic fundamental physics (dark matter interactions). Indirect detection of dark matter annihilation radiation (DMAR) in gamma rays may be the most direct method for observing small scale structure. I outline the ways in which gamma rays may probe halo substructure. If substructure is bountiful, it may be responsible for the eventual discovery of DMAR, for instance in galaxy clusters or the diffuse gamma-ray background. Otherwise, the observation of DMAR in places without much substructure, such as the Galactic center, would lead to strict limits on the properties of small scale structure. Properties of the gamma-ray angular power spectrum will also provide information or constraints on Milky Way halo substructure.

Campbell, Sheldon [Department of Physics and Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210 (United States)

2014-06-24T23:59:59.000Z

464

Influence of Dark Matter on Light Propagation in Solar System

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

Hideyoshi Arakida

2009-11-17T23:59:59.000Z

465

DARK MATTER AS AN ACTIVE GRAVITATIONAL AGENT IN CLOUD COMPLEXES

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

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

2012-04-01T23:59:59.000Z

466

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

467

Growth of Cosmic Structure: Probing Dark Energy Beyond Expansion

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

The quantity and quality of cosmic structure observations have greatly accelerated in recent years, and further leaps forward will be facilitated by imminent projects. These will enable us to map the evolution of dark and baryonic matter density fluctuations over cosmic history. The way that these fluctuations vary over space and time is sensitive to several pieces of fundamental physics: the primordial perturbations generated by GUT-scale physics; neutrino masses and interactions; the nature of dark matter and dark energy. We focus on the last of these here: the ways that combining probes of growth with those of the cosmic expansion such as distance-redshift relations will pin down the mechanism driving the acceleration of the Universe.

Huterer D.; May M.; Kirkby, D.; Bean, R.; Connolly, A.; Dawson, K; Dodelson, S.; Evrard, A.; Jain, B.; Jarvis, M.; Linder, E.; Mandelbaum, R.; Raccanelli, A.; Reid, B; Rozo, E.; Schmidt, F.; Sehgal, N.; Slosar, A.; Van Engelen, A.; Wu, H-Y.; Zhao, G.

2015-03-01T23:59:59.000Z

468

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

469

Circumscribing late dark matter decays model-independently

A number of theories, spanning a wide range of mass scales, predict dark matter candidates that have lifetimes much longer than the age of the Universe, yet may produce a significant flux of gamma rays in their decays today. We constrain such late-decaying dark matter scenarios model-independently by utilizing gamma-ray line emission limits from the Galactic Center region obtained with the SPI spectrometer on INTEGRAL, and the determination of the isotropic diffuse photon background by SPI, COMPTEL, and EGRET observations. We show that no more than {approx}5% of the unexplained MeV background can be produced by late dark matter decays either in the Galactic halo or cosmological sources.

Yueksel, Hasan; Kistler, Matthew D. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States) and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States)

2008-07-15T23:59:59.000Z

470

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

471

Composite Goldstone Dark Matter: Experimental Predictions from the Lattice

We study, via first principles lattice simulations, the nonperturbative dynamics of $SU(2)$ gauge theory with two fundamental Dirac flavors. The model can be used simultaneously as a template for composite Goldstone boson dark matter and for breaking the electroweak symmetry dynamically. We compute the form factor, allowing us to estimate the associated electromagnetic charge radius. Interestingly we observe that the form factor obeys vector meson dominance even for the two color theory. We finally compare the model predictions with dark matter direct detection experiments. We find that the composite Goldstone boson dark matter cross sections is constrained by the most stringent direct-detection experiments. Our results are a foundation for quantitative new composite dynamics relevant for model building, and are of interest to current experiments.

Ari Hietanen; Randy Lewis; Claudio Pica; Francesco Sannino

2014-09-15T23:59:59.000Z

472

Dark energy in some integrable and nonintegrable FRW cosmological models

One of the greatest challenges in cosmology today is to determine the nature of dark energy, the sourse of the observed present acceleration of the Universe. Besides the vacuum energy, various dark energy models have been suggested. The Friedmann - Robertson - Walker (FRW) spacetime plays an important role in modern cosmology. In particular, the most popular models of dark energy work in the FRW spacetime. In this work, a new class of integrable FRW cosmological models is presented. These models induced by the well-known Painlev$\\acute{e}$ equations. Some nonintegrable FRW models are also considered. These last models are constructed with the help of Pinney, Schr$\\ddot{o}$dinger and hypergeometric equations. Scalar field description and two-dimensional generalizations of some cosmological models are presented. Finally some integrable and nonintegrable $F(R)$ and $F(G)$ gravity models are constructed.

Kuralay Esmakhanova; Nurgissa Myrzakulov; Gulgasyl Nugmanova; Yerlan Myrzakulov; Leonid Chechin; Ratbay Myrzakulov

2011-09-14T23:59:59.000Z

473

Bulk-Brane Interaction and Holographic Dark Energy

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

M R Setare

2006-12-14T23:59:59.000Z

474

General Coordinate Transformations as the Origins of Dark Energy

In this note we demonstrate that the algebra associated with coordinate transformations might contain the origins of a scalar field that can behave as an inflaton and/or a source for dark energy. We will call this particular scalar field the diffeomorphism scalar field. In one dimension, the algebra of coordinate transformations is the Virasoro algebra while the algebra of gauge transformations is the Kac-Moody algebra. An interesting representation of these algebras corresponds to certain field theories that have meaning in any dimension. In particular the so called Kac-Moody sector corresponds to Yang-Mills theories and the Virasoro sector corresponds to the diffeomorphism field theory that contains the scalar field and a rank-two symmetric, traceless tensor. We will focus on the contributions of the diffeomorphism scalar field to cosmology. We show that this scalar field can, qualitatively, act as a phantom dark energy, an inflaton, a dark matter source, and the cosmological constant Lambda.

V. G. J. Rodgers; Takeshi Yasuda

2006-01-17T23:59:59.000Z

475

A new equation of state for dark energy

In the contemporary Cosmology, dark energy is modeled as a perfect fluid, having a very simple equation of state: pressure is proportional to dark energy density. As an alternative, I propose a more complex equation of state, with pressure being function of three variables: dark energy density, matter density and the size of the Universe. One consequence of the new equation is that, in the late-time Universe, cosmological scale factor is linear function of time; while the standard cosmology predicts an exponential function.The new equation of state allows attributing a temperature to the physical vacuum, a temperature proportional to the acceleration of the expansion of the Universe. The vacuum temperature decreases with the expansion of the Universe, approaching (but never reaching) the absolute zero.

Dragan Slavkov Hajdukovic

2009-11-04T23:59:59.000Z

476

A Dark Energy model combining DGP gravity and Chaplygin gas

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

Matts Roos

2007-04-06T23:59:59.000Z

477

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

478

Right-handed Neutrinos as Superheavy Dark Matter

We propose that right-handed neutrinos are very long-lived dark matter. The long lifetime is realized by the separation of the wavefunction of right-handed neutrinos and that of other fermions in an extra dimension. Such long-lived and superheavy dark matter can naturally explain observed ultra high energy cosmic rays above the GZK cutoff (5 * 10^{19} eV) and huge amounts of cold dark matter simultaneously. Furthermore, the exponentially suppressed Yukawa couplings of right-handed neutrinos leads to the high predictablilty on the mass parameter of the neutrinoless double beta decay, as all the models which predict very small neutrino mass of one generation.

Yosuke Uehara

2002-01-04T23:59:59.000Z

479

Status of the Dark Energy Survey Camera (DECam) Project

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

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

2012-06-29T23:59:59.000Z

480

Isospin-Violating Dark Matter and Neutrinos From the Sun

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

Shao-Long Chen; Yue Zhang

2011-06-20T23:59:59.000Z

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.

481

EFFECT OF DARK MATTER HALO SUBSTRUCTURES ON GALAXY ROTATION CURVES

In this paper, the effect of halo substructures on galaxy rotation curves is investigated using a simple model of dark matter clustering. A dark matter halo density profile is developed based only on the scale-free nature of clustering that leads to a statistically self-similar distribution of the substructures at the galactic scale. A semi-analytical method is used to derive rotation curves for such a clumpy dark matter density profile. It is found that the halo substructures significantly affect the galaxy velocity field. Based on the fractal geometry of the halo, this self-consistent model predicts a Navarro-Frenk-White-like rotation curve and a scale-free power spectrum of the rotation velocity fluctuations.

Roy, Nirupam, E-mail: nroy@aoc.nrao.ed [NRAO, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States)

2010-11-01T23:59:59.000Z

482

First Results from the DarkSide-50 Dark Matter Experiment at Laboratori Nazionali del Gran Sasso

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4+-0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422+-67) kg d exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1x10^-44 cm^2 for a WIMP mass of 100 GeV/c^2.

P. Agnes; T. Alexander; A. Alton; K. Arisaka; H. O. Back; B. Baldin; K. Biery; G. Bonfini; M. Bossa; A. Brigatti; J. Brodsky; F. Budano; L. Cadonati; F. Calaprice; N. Canci; A. Candela; H. Cao; M. Cariello; P. Cavalcante; A. Chavarria; A. Chepurnov; A. G. Cocco; L. Crippa; D. D'Angelo; M. D'Incecco; S. Davini; M. De Deo; A. Derbin; A. Devoto; F. Di Eusanio; G. Di Pietro; E. Edkins; A. Empl; A. Fan; G. Fiorillo; K. Fomenko; G. Forster; D. Franco; F. Gabriele; C. Galbiati; A. Goretti; L. Grandi; M. Gromov; M. Y. Guan; Y. Guardincerri; B. Hackett; K. Herner; E. V. Hungerford; Al. Ianni; An. Ianni; C. Jollet; K. Keeter; C. Kendziora; S. Kidner; V. Kobychev; G. Koh; D. Korablev; G. Korga; A. Kurlej; P. X. Li; B. Loer; P. Lombardi; C. Love; L. Ludhova; S. Luitz; Y. Q. Ma; I. Machulin; A. Mandarano; S. Mari; J. Maricic; L. Marini; C. J. Martoff; A. Meregaglia; E. Meroni; P. D. Meyers; R. Milincic; D. Montanari; A. Monte; M. Montuschi; M. E. Monzani; P. Mosteiro; B. Mount; V. Muratova; P. Musico; A. Nelson; S. Odrowski; M. Okounkova; M. Orsini; F. Ortica; L. Pagani; M. Pallavicini; E. Pantic; L. Papp; S. Parmeggiano; R. Parsells; K. Pelczar; N. Pelliccia; S. Perasso; A. Pocar; S. Pordes; D. Pugachev; H. Qian; K. Randle; G. Ranucci; A. Razeto; B. Reinhold; A. Renshaw; A. Romani; B. Rossi; N. Rossi; S. D. Rountree; D. Sablone; P. Saggese; R. Saldanha; W. Sands; S. Sangiorgio; E. Segreto; D. Semenov; E. Shields; M. Skorokhvatov; O. Smirnov; A. Sotnikov; C. Stanford; Y. Suvorov; R. Tartaglia; J. Tatarowicz; G. Testera; A. Tonazzo; E. Unzhakov; R. B. Vogelaar; M. Wada; S. Walker; H. Wang; Y. Wang; A. Watson; S. Westerdale; M. Wojcik; A. Wright; X. Xiang; J. Xu; C. G. Yang; J. Yoo; S. Zavatarelli; A. Zec; C. Zhu; G. Zuzel

2015-02-27T23:59:59.000Z

483

A Comprehensive Search for Dark Matter Annihilation in Dwarf Galaxies

We present a new formalism designed to discover dark matter annihilation occurring in the Milky Way's dwarf galaxies. The statistical framework extracts all available information in the data by simultaneously combining observations of all the dwarf galaxies and incorporating the impact of particle physics properties, the distribution of dark matter in the dwarfs, and the detector response. The method performs maximally powerful frequentist searches and produces confidence limits on particle physics parameters. Probability distributions of test statistics under various hypotheses are constructed exactly, without relying on large sample approximations. The derived limits have proper coverage by construction and claims of detection are not biased by imperfect background modeling. We implement this formalism using data from the Fermi Gamma-ray Space Telescope to search for an annihilation signal in the complete sample of Milky Way dwarfs whose dark matter distributions can be reliably determined. We find that the observed data is consistent with background for each of the dwarf galaxies individually as well as in a joint analysis. The strongest constraints are at small dark matter particle masses. Taking the median of the systematic uncertainty in dwarf density profiles, the cross section upper limits are below the pure s-wave weak scale relic abundance value (2.2 x 10^-26 cm^3/s) for dark matter masses below 26 GeV (for annihilation into b quarks), 29 GeV (tau leptons), 35 GeV (up, down, strange, charm quarks and gluons), 6 GeV (electrons/positrons), and 114 GeV (two-photon final state). For dark matter particle masses less than 1 TeV, these represent the strongest limits obtained to date using dwarf galaxies.

Alex Geringer-Sameth; Savvas M. Koushiappas; Matthew G. Walker

2014-10-08T23:59:59.000Z

484

Dark radiation from the axino solution of the gravitino problem

Current observations of the cosmic microwave background could confirm an increase in the radiation energy density after primordial nucleosynthesis but before photon decoupling. We show that, if the gravitino problem is solved by a light axino, dark (decoupled) radiation emerges naturally in this period leading to a new upper bound on the reheating temperature T_R < 10^{11} GeV. In turn, successful thermal leptogenesis might predict such an increase. The Large Hadron Collider could endorse this opportunity. At the same time, axion and axino can naturally form the observed dark matter.

Jasper Hasenkamp

2011-12-13T23:59:59.000Z

485

Dark matter annihilation and the PAMELA, FERMI, and ATIC anomalies

If dark matter annihilation accounts for the tantalizing excess of cosmic ray electron/positrons, as reported by the PAMELA, ATIC, HESS, and FERMI observatories, then the implied annihilation cross section must be relatively large. This results, in the context of standard cosmological models, in very small relic dark matter abundances that are incompatible with astrophysical observations. We explore possible resolutions to this apparent conflict in terms of nonstandard cosmological scenarios; plausibly allowing for large cross sections, while maintaining relic abundances in accord with current observations.

El Zant, A. A.; Okada, H. [Centre for Theoretical Physics, British University in Egypt, El Sherouk City, Postal No, 11837, Post Office Box 43 (Egypt); Khalil, S. [Centre for Theoretical Physics, British University in Egypt, El Sherouk City, Postal No, 11837, Post Office Box 43 (Egypt); Department of Mathematics, Ain Shams University, Faculty of Science, Cairo, 11566 (Egypt)

2010-06-15T23:59:59.000Z

486

A new test of the light dark matter hypothesis

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

Celine Boehm; Joseph Silk

2007-08-21T23:59:59.000Z

487

Carbon Nanotubes Potentialities in Directional Dark Matter Searches

We propose a new solution to the problem of dark matter directional detection based on large parallel arrays of carbon nanotubes. The phenomenon of ion channeling in single wall nanotubes is simulated to calculate the expected number of recoiling carbon ions, due to the hypothetical scattering with dark matter particles, subsequently being driven along their longitudinal extension. As shown by explicit calculation, the relative orientation of the carbon nanotube array with respect to the direction of motion of the Sun has an appreciable effect on the channeling probability of the struck ion and this provides the required detector anisotropic response.

L. M. Capparelli; G. Cavoto; D. Mazzilli; A. D. Polosa

2014-12-28T23:59:59.000Z

488

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

2006-06-19T23:59:59.000Z

489

A conjecture on the origin of dark energy

The physical origin of holographic dark energy (HDE) is investigated. The main existing explanations, namely the UV/IR connection argument of Cohen et al, Thomas' bulk holography argument, and Ng's spacetime foam argument, are shown to be not satisfactory. A new explanation of the HDE model is then proposed based on the ideas of Thomas and Ng. It is suggested that the dark energy might originate from the quantum fluctuations of spacetime limited by the event horizon of the universe. Several potential problems of the explanation are also discussed.

Shan Gao

2011-07-16T23:59:59.000Z

490

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

491

Muon g-2 Anomaly and Dark Leptonic Gauge Boson

One of the major motivations to search for a dark gauge boson of MeV-GeV scale is the long-standing muon g-2 anomaly. Because of active searches such as fixed target experiments and rare meson decays, the muon g-2 favored parameter region has been rapidly reduced. With the most recent data, it is practically excluded now in the popular dark photon model. We overview the issue and investigate a potentially alternative model based on the gauged lepton number or U(1)_L, which is under different experimental constraints.

Lee, Hye-Sung [W& M

2014-11-01T23:59:59.000Z

492

Dark matter candidate in an extended type III seesaw scenario

The type III seesaw mechanism for neutrino mass generation usually makes use of at least two $Y = 0$, $SU(2)_L$ lepton triplets. We augment such a model with a third triplet and a sterile neutrino, both of which are odd under a conserved $\\Z_2$ symmetry. With all new physics confined to the $\\Z_2$-odd sector, whose low energy manifestation is in some higher-dimensional operators, a fermionic dark matter candidate is found to emerge. We identify the region of the parameter space of the scenario, which is consistent with all constraints from relic density and direct searches, and allows a wide range of masses for the dark matter candidate.

Chaudhuri, Avinanda; Mukhopadhyaya, Biswarup; Rakshit, Subhendu

2015-01-01T23:59:59.000Z

493

Viscous Dark Energy in $f(T)$ Gravity

We study the bulk viscosity taking dust matter in the generalized teleparallel gravity. We consider different dark energy models in this scenario along with a time dependent viscous model to construct the viscous equation of state parameter for these dark energy models. We discuss the graphical representation of this parameter to investigate the viscosity effects on the accelerating expansion of the universe. It is mentioned here that the behavior of the universe depends upon the viscous coefficients showing the transition from decelerating to accelerating phase. It leads to the crossing of phantom divide line and becomes phantom dominated for specific ranges of these coefficients.

M. Sharif; Shamaila Rani

2014-05-18T23:59:59.000Z

494

The Hubble Web: The Dark Matter Problem and Cosmic Strings

I propose a reinterpretation of cosmic dark matter in which a rigid network of cosmic strings formed at the end of inflation. The cosmic strings fulfill three functions: At recombination they provide an accretion mechanism for virializing baryonic and warm dark matter into disks. These cosmic strings survive as configurations which thread spiral and elliptical galaxies leading to the observed flatness of rotation curves and the Tully-Fisher relation. We find a relationship between the rotational velocity of the galaxy and the string tension and discuss the testability of this model.

Alexander, Stephon [Departments of Physics and Astronomy, Institute for Gravity and Geometry, Pennsylvania State University, University Park, PA 16802 (United States)

2009-07-06T23:59:59.000Z

495

The Hubble Web: The Dark Matter Problem and Cosmic Strings

I propose a reinterpretation of cosmic dark matter in which a rigid network of cosmic strings formed at the end of inflation. The cosmic strings fulfill three functions: At recombination they provide an accretion mechanism for virializing baryonic and warm dark matter into disks. These cosmic strings survive as configurations which thread spiral and elliptical galaxies leading to the observed flatness of rotation curves and the Tully-Fisher relation. We find a relationship between the rotational velocity of the galaxy and the string tension and discuss the testability of this model.

Stephon Alexander

2007-02-27T23:59:59.000Z

496

Disformal couplings and the dark sector of the universe

Interactions between dark matter and dark energy, allowing both conformal and and disformal couplings, are studied in detail. We discuss the background evolution, anisotropies in the cosmic microwave background and large scale structures. One of our main findings is that a large conformal coupling is not necessarily disallowed in the presence of a general disformal term. On the other hand, we find that negative disformal couplings very often lead to instabilities in the scalar field. Studying the background evolution and linear perturbations only, our results show that it is observationally challenging to disentangle disformal from purely conformal couplings.

van de Bruck, C

2015-01-01T23:59:59.000Z