Sample records for joint dark energy

  1. Exploring Dark Energy with SNAP

    E-Print Network [OSTI]

    Aldering, G.

    2009-01-01T23:59:59.000Z

    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

  2. ITER UltraScaleScientific Joint Dark Energy Mission ComputingCapability

    E-Print Network [OSTI]

    #12;ITER UltraScaleScientific Joint Dark Energy Mission ComputingCapability Linac Coherent Light eRHIC Fusion Energy Contingency Source Upgrade HFIR Second Cold Source Integrated Beam Experiment IntroductionIntroductionIntroductionIntroductionIntroduction 8 Prioritization Process 9 A Benchmark

  3. dark matter dark energy inflation

    E-Print Network [OSTI]

    Hu, Wayne

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

  4. Dark Energy

    E-Print Network [OSTI]

    Norbert Straumann

    2003-11-26T23:59:59.000Z

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

  5. Dark Energy and Dark Matter

    E-Print Network [OSTI]

    Keith A. Olive

    2010-01-27T23:59:59.000Z

    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.

  6. Dark Energy in the Dark Ages

    E-Print Network [OSTI]

    Linder, Eric V.

    2009-01-01T23:59:59.000Z

    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

  7. Dark energy without dark energy

    E-Print Network [OSTI]

    Pedro F. Gonzalez-Diaz

    2006-08-29T23:59:59.000Z

    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.

  8. Dark Energy and Dark Matter Models

    E-Print Network [OSTI]

    Burra G. Sidharth

    2015-01-07T23:59:59.000Z

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

  9. Jelly Bean Universe (Dark Matter / Dark Energy)

    ScienceCinema (OSTI)

    Kurt Riesselmann

    2010-01-08T23:59:59.000Z

    Fermilab's Kurt Riesselmann explains how to make a jelly bean universe to help explain the mysteries of dark matter and dark energy.

  10. The Dark Energy Paradigm

    E-Print Network [OSTI]

    Burra G. Sidharth

    2014-12-30T23:59:59.000Z

    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.

  11. Dark Energy Phenomenology

    E-Print Network [OSTI]

    Martin Kunz; Luca Amendola; Domenico Sapone

    2008-06-08T23:59:59.000Z

    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.

  12. Matter Field, Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Masayasu Tsuge

    2009-03-24T23:59:59.000Z

    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.

  13. Natural Dark Energy

    E-Print Network [OSTI]

    Douglas Scott; Ali Frolop

    2007-03-30T23:59:59.000Z

    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.

  14. Thermodynamics of Dark Energy

    E-Print Network [OSTI]

    Neven Bilic

    2010-09-27T23:59:59.000Z

    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.

  15. Can Dark Matter Decay in Dark Energy?

    E-Print Network [OSTI]

    S. H. Pereira; J. F. Jesus

    2009-02-26T23:59:59.000Z

    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.

  16. Field Flows of Dark Energy

    E-Print Network [OSTI]

    Cahn, Robert N.

    2010-01-01T23:59:59.000Z

    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

  17. Superconducting dark energy

    E-Print Network [OSTI]

    Liang, Shi-Dong

    2015-01-01T23:59:59.000Z

    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...

  18. The Dark Energy Survey

    E-Print Network [OSTI]

    The Dark Energy Survey Collaboration

    2005-10-12T23:59:59.000Z

    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.

  19. Superconducting dark energy

    E-Print Network [OSTI]

    Shi-Dong Liang; Tiberiu Harko

    2015-04-10T23:59:59.000Z

    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.

  20. Dark Energy, or Worse

    ScienceCinema (OSTI)

    Professor Sean Carroll

    2010-01-08T23:59:59.000Z

    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.

  1. Dark Energy, or Worse

    SciTech Connect (OSTI)

    Carroll, Sean (CalTech) [CalTech

    2006-11-13T23:59:59.000Z

    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.

  2. Dark Energy: Taking SidesDark Energy: Taking SidesDark Energy: Taking Sides The University of Chicago

    E-Print Network [OSTI]

    Yamamoto, Hirosuke

    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

  3. The Dark Energy Universe

    E-Print Network [OSTI]

    Burra G. Sidharth

    2015-01-12T23:59:59.000Z

    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.

  4. Dark Energy Survey

    ScienceCinema (OSTI)

    Roodman, Aaron; Nord, Brian; Elliot, Ann

    2014-08-12T23:59:59.000Z

    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.

  5. Dark Energy in the Dark Ages

    E-Print Network [OSTI]

    Eric V. Linder

    2006-04-11T23:59:59.000Z

    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.

  6. UNIFIED THEORY OF DARK ENERGY AND DARK SHOUHONG WANG 2

    E-Print Network [OSTI]

    Wang, Shouhong

    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

  7. Big Mysteries: Dark Energy

    ScienceCinema (OSTI)

    Lincoln, Don

    2014-08-07T23:59:59.000Z

    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.

  8. Big Mysteries: Dark Energy

    SciTech Connect (OSTI)

    Lincoln, Don

    2014-04-15T23:59:59.000Z

    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.

  9. Dark Energy and Electrons

    E-Print Network [OSTI]

    Burra G. Sidharth

    2008-08-05T23:59:59.000Z

    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.

  10. Dark energy and quantum entanglement

    E-Print Network [OSTI]

    Mark Ya. Azbel'

    2005-02-04T23:59:59.000Z

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

  11. Embedding Dark Energy in Supergravity

    E-Print Network [OSTI]

    Philippe Brax

    2007-11-15T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    Collar, Juan I.

    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

  13. A dark energy multiverse

    E-Print Network [OSTI]

    Salvador Robles-Perez; Prado Martin-Moruno; Alberto Rozas-Fernandez; Pedro F. Gonzalez-Diaz

    2007-01-23T23:59:59.000Z

    We present cosmic solutions corresponding to universes filled with dark and phantom energy, all having a negative cosmological constant. All such solutions contain infinite singularities, successively and equally distributed along time, which can be either big bang/crunchs or big rips singularities. Classicaly these solutions can be regarded as associated with multiverse scenarios, being those corresponding to phantom energy that may describe the current accelerating universe.

  14. Alternatives to Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Philip D. Mannheim

    2005-08-01T23:59:59.000Z

    We review the underpinnings of the standard Newton-Einstein theory of gravity, and identify where it could possibly go wrong. In particular, we discuss the logical independence from each other of the general covariance principle, the equivalence principle and the Einstein equations, and discuss how to constrain the matter energy-momentum tensor which serves as the source of gravity. We identify the a priori assumption of the validity of standard gravity on all distance scales as the root cause of the dark matter and dark energy problems, and discuss how the freedom currently present in gravitational theory can enable us to construct candidate alternatives to the standard theory in which the dark matter and dark energy problems could then be resolved. We identify three generic aspects of these alternate approaches: that it is a universal acceleration scale which determines when a luminous Newtonian expectation is to fail to fit data, that there is a global cosmological effect on local galactic motions which can replace galactic dark matter, and that to solve the cosmological constant problem it is not necessary to quench the cosmological constant itself, but only the amount by which it gravitates.

  15. Improved Dark Energy Constraints

    Office of Scientific and Technical Information (OSTI)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItem Not Found Item Not Found TheHot electron dynamics in graphene byI _Improved Dark

  16. On the Nature of Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Yu. A. Baurov; I. F. Malov

    2007-10-16T23:59:59.000Z

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

  17. Weak Lensing: Dark Matter, Dark Energy

    SciTech Connect (OSTI)

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

    2006-02-27T23:59:59.000Z

    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.

  18. Alternatives to Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Mannheim, P D

    2006-01-01T23:59:59.000Z

    We review the underpinnings of the standard Newton-Einstein theory of gravity, and identify where it could possibly go wrong. In particular, we discuss the logical independence from each other of the general covariance principle, the equivalence principle and the Einstein equations, and discuss how to constrain the matter energy-momentum tensor which serves as the source of gravity. We identify the a priori assumption of the validity of standard gravity on all distance scales as the root cause of the dark matter and dark energy problems, and discuss how the freedom currently present in gravitational theory can enable us to construct candidate alternatives to the standard theory in which the dark matter and dark energy problems could then be resolved. We identify three generic aspects of these alternate approaches: that it is a universal acceleration scale which determines when a luminous Newtonian expectation is to fail to fit data, that there is a global cosmological effect on local galactic motions which ca...

  19. Epoch Dependent Dark Energy

    E-Print Network [OSTI]

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

    2009-08-06T23:59:59.000Z

    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.

  20. Dark Energy from "Water"

    E-Print Network [OSTI]

    Holman, R; Holman, Richard; Naidu, Siddartha

    2004-01-01T23:59:59.000Z

    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 $w>0$.

  1. Dark energy and particle mixing

    E-Print Network [OSTI]

    A. Capolupo; S. Capozziello; G. Vitiello

    2008-08-30T23:59:59.000Z

    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.

  2. From Dark Energy and Dark Matter to Dark Metric

    E-Print Network [OSTI]

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

    2008-08-04T23:59:59.000Z

    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.

  3. The Dark Energy Camera

    E-Print Network [OSTI]

    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

    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...

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

    E-Print Network [OSTI]

    Huterer, Dragan

    2009-01-01T23:59:59.000Z

    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

  5. Dark energy and dark matter from cosmological observations

    E-Print Network [OSTI]

    Steen Hannestad

    2005-09-14T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Cheng, Hung

    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

  7. Light Thoughts on Dark Energy

    E-Print Network [OSTI]

    Eric V. Linder

    2004-04-01T23:59:59.000Z

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

  8. Evolving Dark Energy with w =/ -1

    E-Print Network [OSTI]

    Hall, Lawrence J.

    2009-01-01T23:59:59.000Z

    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

  9. Dark Energy - Dark Matter Unification: Generalized Chaplygin Gas Model

    E-Print Network [OSTI]

    Orfeu Bertolami

    2005-04-14T23:59:59.000Z

    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.

  10. Optimizing New Dark Energy Experiments

    SciTech Connect (OSTI)

    Tyson, J. Anthony [University of California, Davis

    2013-08-26T23:59:59.000Z

    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.

  11. Wormhole solutions supported by interacting dark matter and dark energy

    E-Print Network [OSTI]

    Vladimir Folomeev; Vladimir Dzhunushaliev

    2014-03-10T23:59:59.000Z

    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.

  12. Quantum Haplodynamics, Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Harald Fritzsch; Joan Sola

    2014-08-04T23:59:59.000Z

    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.

  13. Combinatorial Dark Energy

    E-Print Network [OSTI]

    Aaron Trout

    2012-08-15T23:59:59.000Z

    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.

  14. Emergent gravity and Dark Energy

    E-Print Network [OSTI]

    T. Padmanabhan

    2008-02-13T23:59:59.000Z

    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.

  15. Dark Energy From Fifth Dimension

    E-Print Network [OSTI]

    H. Alavirad; N. Riazi

    2008-01-21T23:59:59.000Z

    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.

  16. Dark Energy and Dark Matter as Inertial Effects

    E-Print Network [OSTI]

    Serkan Zorba

    2012-10-20T23:59:59.000Z

    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.

  17. Dark energy induced by neutrino mixing

    E-Print Network [OSTI]

    Antonio Capolupo; Salvatore Capozziello; Giuseppe Vitiello

    2006-12-11T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    A. Arbey

    2008-12-18T23:59:59.000Z

    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.

  19. Is Dark Energy Abnormally Weighting?

    E-Print Network [OSTI]

    A. Fuzfa; J. -M. Alimi

    2006-09-05T23:59:59.000Z

    We present a new interpretation of dark energy in terms of an \\textit{Abnormally Weighting Energy} (AWE). This means that dark energy does not couple to gravitation in the same way as ordinary matter, yielding a violation of the weak and strong equivalence principles on cosmological scales. The resulting cosmological mechanism accounts for the Hubble diagram of type Ia supernovae in terms of both cosmic acceleration and variation of the gravitational constant while still accounting for the present tests of general relativity. This explanation allows to build dark energy models (i) without violation of the strong energy condition $p<-\\rho c^2/3$ (ii) with non-negligible direct couplings to gravitation and (iii) natural convergence mechanism toward general relativity.

  20. Correspondence between Ricci and other dark energies

    E-Print Network [OSTI]

    Surajit Chattopadhyay; Ujjal Debnath

    2010-09-26T23:59:59.000Z

    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.

  1. New interactions in the dark sector mediated by dark energy

    E-Print Network [OSTI]

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

    2008-04-10T23:59:59.000Z

    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.

  2. Dark matter, dark energy and gravitational proprieties of antimatter

    E-Print Network [OSTI]

    Dragan Slavkov Hajdukovic

    2009-10-21T23:59:59.000Z

    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.

  3. Redshift drift exploration for interacting dark energy

    E-Print Network [OSTI]

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

    2015-01-01T23:59:59.000Z

    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...

  4. Dark Energy Camera for Blanco

    SciTech Connect (OSTI)

    Binder, Gary A.; /Caltech /SLAC

    2010-08-25T23:59:59.000Z

    In order to make accurate measurements of dark energy, a system is needed to monitor the focus and alignment of the Dark Energy Camera (DECam) to be located on the Blanco 4m Telescope for the upcoming Dark Energy Survey. One new approach under development is to fit out-of-focus star images to a point spread function from which information about the focus and tilt of the camera can be obtained. As a first test of a new algorithm using this idea, simulated star images produced from a model of DECam in the optics software Zemax were fitted. Then, real images from the Mosaic II imager currently installed on the Blanco telescope were used to investigate the algorithm's capabilities. A number of problems with the algorithm were found, and more work is needed to understand its limitations and improve its capabilities so it can reliably predict camera alignment and focus.

  5. Importance of Supernovae at zDark Energy

    E-Print Network [OSTI]

    Linder, E.V.

    2009-01-01T23:59:59.000Z

    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

  6. Dark energy parameterizations and their effect on dark halos

    E-Print Network [OSTI]

    Lamartine Liberato; Rogerio Rosenfeld

    2006-04-19T23:59:59.000Z

    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.

  7. Dark energy and possible alternatives

    E-Print Network [OSTI]

    M. Sami

    2009-01-07T23:59:59.000Z

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

  8. Dark energy and possible alternatives

    E-Print Network [OSTI]

    Sami, M

    2009-01-01T23:59:59.000Z

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

  9. Dark Energy Stars

    E-Print Network [OSTI]

    G. Chapline

    2005-04-13T23:59:59.000Z

    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.

  10. Dark energy and 3-manifold topology

    E-Print Network [OSTI]

    Torsten Asselmeyer-Maluga; Helge Rose

    2007-11-21T23:59:59.000Z

    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.

  11. Agegraphic Chaplygin gas model of dark energy

    E-Print Network [OSTI]

    Ahmad Sheykhi

    2010-02-07T23:59:59.000Z

    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.

  12. Astrophysikalisches Institut Potsdam Probes of Dark Energy

    E-Print Network [OSTI]

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

  13. From Inflation to Dark Energy

    E-Print Network [OSTI]

    Robert Brout

    2005-08-04T23:59:59.000Z

    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.

  14. Joint Announcement | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 Home Page onYouTube YouTube Note: Since the.pdfBreaking ofOil & Gas » MethaneJohnson Controls EnergyJoin the EnergyJoin usJoint

  15. Dark Energy: Is It of Torsion Origin?

    E-Print Network [OSTI]

    M. I. Wanas

    2010-06-10T23:59:59.000Z

    {\\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.

  16. Why we need dark energy

    E-Print Network [OSTI]

    Diego Pavón; Ninfa Radicella

    2012-12-31T23:59:59.000Z

    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.

  17. Dark energy and dark matter as curvature effects

    E-Print Network [OSTI]

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

    2006-03-20T23:59:59.000Z

    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.

  18. Interacting agegraphic tachyon model of dark energy

    E-Print Network [OSTI]

    A. Sheykhi

    2009-11-16T23:59:59.000Z

    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.

  19. From confinement to dark energy

    E-Print Network [OSTI]

    B. Holdom

    2011-02-24T23:59:59.000Z

    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.

  20. Reconstructing Quintom from Ricci Dark Energy

    E-Print Network [OSTI]

    Chao-Jun Feng

    2009-02-11T23:59:59.000Z

    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.

  1. Modelling dark energy 

    E-Print Network [OSTI]

    Jackson, Brendan Marc

    2011-11-23T23:59:59.000Z

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

  2. Material models of dark energy

    E-Print Network [OSTI]

    Jonathan A. Pearson

    2014-09-16T23:59:59.000Z

    We review and develop a new class of "dark energy" models, in which the relativistic theory of solids is used to construct material models of dark energy. These are models which include the effects of a continuous medium with well defined physical properties at the level of linearized perturbations. The formalism is constructed for a medium with arbitrary symmetry, and then specialised to isotropic media (which will be the case of interest for the majority of cosmological applications). We develop the theory of relativistic isotropic viscoelastic media whilst keeping in mind that we ultimately want to observationally constrain the allowed properties of the material model. We do this by obtaining the viscoelastic equations of state for perturbations (the entropy and anisotropic stress), as well as identifying the consistent corner of the theory which has constant equation of state parameter $\\dot{w}=0$. We also connect to the non-relativistic theory of solids, by identifying the two quadratic invariants that are needed to construct the energy-momentum tensor, namely the Rayleigh dissipation function and Lagrangian for perturbations. Finally, we develop the notion that the viscoelastic behavior of the medium can be thought of as a non-minimally coupled massive gravity theory. This also provides a tool-kit for constructing consistent generalizations of coupled dark energy theories.

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

    E-Print Network [OSTI]

    Wang, Shouhong

    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

  4. The Phase Transition of Dark Energy

    E-Print Network [OSTI]

    Wei Wang; Yuanxing Gui; Ying Shao

    2006-12-05T23:59:59.000Z

    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.

  5. Sandia Energy - "Bionic" Liquids from Lignin: Joint BioEnergy...

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

    Liquids from Lignin: Joint BioEnergy Institute Results Pave the Way for Closed-Loop Biofuel Refineries Home Renewable Energy Energy Transportation Energy Biofuels Facilities...

  6. Dark energy from entanglement entropy

    E-Print Network [OSTI]

    Salvatore Capozziello; Orlando Luongo

    2013-03-06T23:59:59.000Z

    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.

  7. Joint Statement on the Global Nuclear Energy Partnership and...

    Office of Environmental Management (EM)

    Joint Statement on the Global Nuclear Energy Partnership and Nuclear Energy Cooperation Joint Statement on the Global Nuclear Energy Partnership and Nuclear Energy Cooperation...

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

    E-Print Network [OSTI]

    R. C. Gupta

    2004-12-07T23:59:59.000Z

    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.

  9. Dark Energy Coupled with Dark Matter in Viscous Fluid Cosmology

    E-Print Network [OSTI]

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

    2014-10-10T23:59:59.000Z

    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.

  10. Strangeness, Cosmological Cold Dark Matter and Dark Energy

    E-Print Network [OSTI]

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

    2005-01-18T23:59:59.000Z

    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.

  11. Spacetime Foam and Dark Energy

    E-Print Network [OSTI]

    Y. Jack Ng

    2008-08-08T23:59:59.000Z

    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.

  12. Dark energy from quantum wave function collapse of dark matter

    E-Print Network [OSTI]

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

    2009-09-03T23:59:59.000Z

    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.

  13. Dark Energy and the New Cosmology

    E-Print Network [OSTI]

    Michael S. Turner

    2001-08-07T23:59:59.000Z

    A successor to the standard hot big-bang cosmology is emerging. It greatly extends the highly successful hot big-bang model. A key element of the New Standard Cosmology is dark energy, the causative agent for accelerated expansion. Dark energy is just possibly the most important problem in all of physics. The only laboratory up to the task of studying dark energy is the Universe itself.

  14. Dark Energy in Global Brane Universe

    E-Print Network [OSTI]

    Yongli Ping; Lixin Xu; Chengwu Zhang; Hongya Liu

    2007-12-20T23:59:59.000Z

    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.

  15. Dark Energy: Is it Q or Lambda ?

    E-Print Network [OSTI]

    Alessandro Melchiorri; Carolina Odman

    2002-12-30T23:59:59.000Z

    New observations of Cosmic Microwave Background Anisotropies, Supernovae luminosity distances and Galaxy Clustering are sharpening our knowledge about dark energy. Here we present the latest constraints.

  16. Statefinder Diagnostic for Dilaton Dark Energy

    E-Print Network [OSTI]

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

    2008-05-07T23:59:59.000Z

    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.

  17. Dark Energy with w>-4/3

    E-Print Network [OSTI]

    Andrei Gruzinov

    2004-05-05T23:59:59.000Z

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

  18. Schwarzschild black hole in dark energy background

    E-Print Network [OSTI]

    Ngangbam Ishwarchandra; Ng. Ibohal; K. Yugindro Singh

    2014-09-27T23:59:59.000Z

    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.

  19. The Fully Quantized Axion and Dark Energy

    E-Print Network [OSTI]

    Dylan Tanner

    2012-12-17T23:59:59.000Z

    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.

  20. Dark Energy and Dark Matter in Stars Physic

    E-Print Network [OSTI]

    Plamen Fiziev

    2014-11-02T23:59:59.000Z

    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.

  1. Investigating Dark Energy with Black Hole Binaries

    E-Print Network [OSTI]

    Laura Mersini-Houghton; Adam Kelleher

    2009-06-08T23:59:59.000Z

    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.

  2. Singularity-free dark energy star

    E-Print Network [OSTI]

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

    2011-08-25T23:59:59.000Z

    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.

  3. Dark energy, cosmological constant and neutrino mixing

    E-Print Network [OSTI]

    A. Capolupo; S. Capozziello; G. Vitiello

    2007-05-02T23:59:59.000Z

    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.

  4. The Quintom Model of Dark Energy

    E-Print Network [OSTI]

    Bo Feng

    2006-02-07T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Stoytcho S. Yazadjiev; Daniela D. Doneva

    2011-12-19T23:59:59.000Z

    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.

  6. Holographic tachyon model of dark energy

    E-Print Network [OSTI]

    M R Setare

    2007-09-11T23:59:59.000Z

    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.

  7. Exploring a new interaction between dark matter and dark energy using the growth rate of structure

    E-Print Network [OSTI]

    Richarte, Martín G

    2015-01-01T23:59:59.000Z

    We present a phenomenological interaction with a scale factor power law form which leads to the appearance of two kinds of perturbed terms, a scale factor spatial variation along with perturbed Hubble expansion rate. We study both the background and the perturbation evolution within the parametrized post-Friedmann scheme, obtaining that the exchange of energy-momentum can flow from dark energy to dark matter in order to keep dark energy and dark matter densities well defined at all times. We combine several measures of the cosmic microwave background (WMAP9+Planck) data, baryon acoustic oscillation measurements, redshift-space distortion data, JLA sample of supernovae, and Hubble constant for constraining the coupling constant and the exponent provided both parametrized the interaction itself. The joint analysis of ${\\rm Planck+WMAP9+BAO}$ ${\\rm +RSD+JLA+HST}$ data seems to favor large coupling constant, $\\xi_c = 0.34403427_{- 0.18907353}^{+ 0.14430125}$ at 1 $\\sigma$ level, and prefers a power law interactio...

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

    SciTech Connect (OSTI)

    Ellis, Richard S.

    2012-09-30T23:59:59.000Z

    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.

  9. Is dark energy an effect of averaging?

    E-Print Network [OSTI]

    Nan Li; Marina Seikel; Dominik J. Schwarz

    2008-01-22T23:59:59.000Z

    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.

  10. Black hole and holographic dark energy

    E-Print Network [OSTI]

    Yun Soo Myung

    2007-04-11T23:59:59.000Z

    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 $\\omega_{\\rm \\Lambda}=-1$.

  11. From the Dark Matter Universe to the Dark Energy Universe

    E-Print Network [OSTI]

    Burra G. Sidharth

    2008-03-30T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Carl H. Gibson

    2012-11-02T23:59:59.000Z

    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.

  13. Interacting Dark Energy: Decay into Fermions

    E-Print Network [OSTI]

    A. de la Macorra

    2007-02-08T23:59:59.000Z

    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.

  14. Dark Energy: Observational Evidence and Theoretical Models

    E-Print Network [OSTI]

    Novosyadlyj, B; Shtanov, Yu; Zhuk, A

    2015-01-01T23:59:59.000Z

    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.

  15. Dark Energy, Inflation and Extra Dimensions

    E-Print Network [OSTI]

    Paul J. Steinhardt; Daniel Wesley

    2008-12-07T23:59:59.000Z

    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.

  16. 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....

  17. Comparing holographic dark energy models with statefinder

    E-Print Network [OSTI]

    Jing-Lei Cui; Jing-Fei Zhang

    2014-04-20T23:59:59.000Z

    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.

  18. Photo Credit: Peter GinterSLAC National Accelerator Laboratory Dark Energy

    E-Print Network [OSTI]

    Osheroff, Douglas D.

    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

  19. Is Hubble's Expansion due to Dark Energy

    E-Print Network [OSTI]

    R. C. Gupta; Anirudh Pradhan

    2010-10-19T23:59:59.000Z

    {\\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'.

  20. Probing the time dependence of dark energy

    SciTech Connect (OSTI)

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

    2012-02-01T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    P. P. Avelino

    2015-03-10T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Avelino, P P

    2015-01-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Kunz, Martin

    2007-01-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Martin Kunz

    2007-10-30T23:59:59.000Z

    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.

  5. Brane-Bulk energy exchange and agegraphic dark energy

    E-Print Network [OSTI]

    Ahmad Sheykhi

    2010-02-06T23:59:59.000Z

    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 $w^{\\mathrm{eff}}_D\\geq-1$.

  6. Gamma-Ray Bursts and Dark Matter - a joint origin?

    E-Print Network [OSTI]

    Daniel Enstrom

    1998-10-14T23:59:59.000Z

    A scenario is presented where large quark-gluon plasma (QGP) objects escaping the quark-hadron transition in the early Universe account for the baryonic dark matter as well as act as the sources for gamma-ray bursts. Two basic assumptions are made. Firstly, we assume that a QGP consisting of u,d and s quarks is the absolute ground state of QCD and secondly, that the quark-hadron transition in the early Universe was of first order. Both particle physics and astrophysics constraints are discussed, mainly from an observational point of view.

  7. Collapsing Inhomogeneous Dust Fluid in the Background of Dark Energy

    E-Print Network [OSTI]

    Tanwi Bandyopadhyay; Subenoy Chakraborty

    2006-05-11T23:59:59.000Z

    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

  8. Thermodynamical description of the ghost dark energy model

    E-Print Network [OSTI]

    Honarvaryan, M; Moradpour, H

    2015-01-01T23:59:59.000Z

    In this paper, we point out thermodynamical description of ghost dark energy and its generalization to the early universe. Thereinafter, we find expressions for the entropy changes of these dark energy candidates. In addition, considering thermal fluctuations, thermodynamics of the dark energy component interacting with a dark matter sector is addressed. {We will also find the effects of considering the coincidence problem on the mutual interaction between the dark sectors, and thus the equation of state parameter of dark energy.} Finally, we derive a relation between the mutual interaction of the dark components of the universe, accelerated with the either ghost dark energy or its generalization, and the thermodynamic fluctuations.

  9. Particle mixing, flavor condensate and dark energy

    E-Print Network [OSTI]

    Massimo Blasone; Antonio Capolupo; Giuseppe Vitiello

    2009-12-08T23:59:59.000Z

    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.

  10. Neutrino mixing, flavor states and dark energy

    E-Print Network [OSTI]

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

    2007-11-06T23:59:59.000Z

    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.

  11. Effective Theory of Interacting Dark Energy

    E-Print Network [OSTI]

    Gleyzes, Jérôme; Mancarella, Michele; Vernizzi, Filippo

    2015-01-01T23:59:59.000Z

    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.

  12. Dark Energy-Dark Matter Interaction from the Abell Cluster A586

    E-Print Network [OSTI]

    Orfeu Bertolami; Francisco Gil Pedro; Morgan Le Delliou

    2007-12-31T23:59:59.000Z

    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.

  13. Towards Dark Energy from String-Theory

    E-Print Network [OSTI]

    Axel Krause

    2008-03-12T23:59:59.000Z

    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.

  14. Falsification of dark energy by fluid mechanics

    E-Print Network [OSTI]

    Gibson, Carl H

    2012-01-01T23:59:59.000Z

    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 ...

  15. The Logotropic Dark Fluid as a unification of dark matter and dark energy

    E-Print Network [OSTI]

    Chavanis, Pierre-Henri

    2015-01-01T23:59:59.000Z

    We propose a heuristic unification of dark matter and dark energy in terms of a single dark fluid with a logotropic equation of state $P=A\\ln(\\rho/\\rho_P)$, where $\\rho$ is the rest-mass density, $\\rho_P$ is the Planck density, and $A$ is the logotropic temperature. The energy density $\\epsilon$ is the sum of a rest-mass energy term $\\rho c^2$ mimicking dark matter and an internal energy term $u(\\rho)=-P(\\rho)-A$ mimicking dark energy. The logotropic temperature is approximately given by $A \\simeq \\rho_{\\Lambda}c^2/\\ln(\\rho_P/\\rho_{\\Lambda})\\simeq\\rho_{\\Lambda}c^2/[123 \\ln(10)]$, where $\\rho_{\\Lambda}$ is the cosmological density. More precisely, we obtain $A=2.13\\times 10^{-9} \\, {\\rm g}\\, {\\rm m}^{-1}\\, {\\rm s}^{-2}$ that we interpret as a fundamental constant. At the cosmological scale, this model fullfills the same observational constraints as the $\\Lambda$CDM model. However, it has a nonzero velocity of sound and a nonzero Jeans length which, at the beginning of the matter era, is about $\\lambda_J=40.4\\,...

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

    E-Print Network [OSTI]

    Hu, Wayne

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

  17. A Casimir approach to dark energy

    E-Print Network [OSTI]

    Allan Rosencwaig

    2006-06-26T23:59:59.000Z

    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.

  18. Conformal Higgs model: predicted dark energy density

    E-Print Network [OSTI]

    R. K. Nesbet

    2014-11-03T23:59:59.000Z

    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.

  19. Energy from Waste UK Joint Statement on Energy from Waste

    E-Print Network [OSTI]

    Energy from Waste UK Joint Statement on Energy from Waste Read more overleaf Introduction Energy from waste provides us with an opportunity for a waste solution and a local source of energy rolled,itcan onlyaddressaportionofthewastestream andisnotsufficientonitsown. Energy obtained from the combustion of residual waste (Energy from

  20. Braneworlds, Conformal Fields and Dark Energy

    E-Print Network [OSTI]

    Rui Neves

    2006-01-06T23:59:59.000Z

    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.

  1. Joint Center for Energy Storage Research

    SciTech Connect (OSTI)

    Eric Isaacs

    2012-11-30T23:59:59.000Z

    The Joint Center for Energy Storage Research (JCESR) is a major public-private research partnership that integrates U.S. Department of Energy national laboratories, major research universities and leading industrial companies to overcome critical scientific challenges and technical barriers, leading to the creation of breakthrough energy storage technologies. JCESR, centered at Argonne National Laboratory, outside of Chicago, consolidates decades of basic research experience that forms the foundation of innovative advanced battery technologies. The partnership has access to some of the world's leading battery researchers as well as scientific research facilities that are needed to develop energy storage materials that will revolutionize the way the United States and the world use energy.

  2. Alternative Dark Energy Models: An Overview

    E-Print Network [OSTI]

    J. A. S. Lima

    2004-02-04T23:59:59.000Z

    A large number of recent observational data strongly suggest that we live in a flat, accelerating Universe composed of $\\sim$ 1/3 of matter (baryonic + dark) and $\\sim$ 2/3 of an exotic component with large negative pressure, usually named {\\bf Dark Energy} or {\\bf Quintessence}. The basic set of experiments includes: observations from SNe Ia, CMB anisotropies, large scale structure, X-ray data from galaxy clusters, age estimates of globular clusters and old high redshift galaxies (OHRG's). Such results seem to provide the remaining piece of information connecting the inflationary flatness prediction ($\\Omega_{\\rm{T}} = 1$) with astronomical observations. Theoretically, they have also stimulated the current interest for more general models containing an extra component describing this unknown dark energy, and simultaneously accounting for the present accelerating stage of the Universe. An overlook in the literature shows that at least five dark energy candidates have been proposed in the context of general relativistic models. Since the cosmological constant and rolling scalar field models have already been extensively discussed, in this short review we focus our attention to the three remaining candidates, namely: a decaying vacuum energy density (or ${\\bf \\Lambda(t)}$ {\\bf models}), the {\\bf X-matter}, and the so-called {\\bf Chaplygin-type gas}. A summary of their main results is given and some difficulties underlying the emerging dark energy paradigm are also briefly examined.

  3. Cosmological Evolution of Pilgrim Dark Energy

    E-Print Network [OSTI]

    M. Sharif; M. Zubair

    2014-09-26T23:59:59.000Z

    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.

  4. Cosmological Evolution of Pilgrim Dark Energy

    E-Print Network [OSTI]

    Sharif, M

    2015-01-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Giles, C. Lee

    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

  6. Joint Announcement | Department of Energy

    Office of Environmental Management (EM)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742 33Frequently Asked Questions for DOEtheInspection15Department of Energy Join the

  7. Dark goo: Bulk viscosity as an alternative to dark energy

    E-Print Network [OSTI]

    Jean-Sebastien Gagnon; Julien Lesgourgues

    2011-09-16T23:59:59.000Z

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

  8. Dark goo: Bulk viscosity as an alternative to dark energy

    E-Print Network [OSTI]

    Gagnon, Jean-Sebastien

    2011-01-01T23:59:59.000Z

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

  9. Gravitoelectromagnetism and Dark Energy in Superconductors

    E-Print Network [OSTI]

    Clovis Jacinto de Matos

    2006-07-03T23:59:59.000Z

    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.

  10. Wiggly cosmic strings accrete dark energy

    E-Print Network [OSTI]

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

    2005-06-29T23:59:59.000Z

    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.

  11. Dark energy and extending the geodesic equations of motion: connecting the galactic and cosmological length scales

    E-Print Network [OSTI]

    Speliotopoulos, A. D.

    2010-01-01T23:59:59.000Z

    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

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

    E-Print Network [OSTI]

    Speliotopoulos, Achilles D.

    2010-01-01T23:59:59.000Z

    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

  13. Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios

    E-Print Network [OSTI]

    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

    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.).

  14. Thermodynamical description of the interacting new agegraphic dark energy

    E-Print Network [OSTI]

    A. Sheykhi; M. R. Setare

    2010-09-30T23:59:59.000Z

    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.

  15. "Dark energy" as conformal dynamics of space

    E-Print Network [OSTI]

    D. Burlankov

    2006-10-23T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Peter L. Biermann

    2005-10-02T23:59:59.000Z

    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.

  17. Can Holographic dark energy increase the mass of the wormhole?

    E-Print Network [OSTI]

    Surajit Chattopadhyay; Davood Momeni; Aziza Altaibayeva; Ratbay Myrzakulov

    2014-11-26T23:59:59.000Z

    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.

  18. On the similarity of Information Energy to Dark Energy

    E-Print Network [OSTI]

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

    2006-06-19T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Steidel, Chuck

    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

  20. Testable and Untestable Aspects of Dark Energy

    E-Print Network [OSTI]

    Paul H. Frampton

    2005-08-11T23:59:59.000Z

    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.

  1. Using Newton's Law for Dark Energy

    E-Print Network [OSTI]

    Paul Frampton

    2012-09-24T23:59:59.000Z

    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.

  2. Stringy Model of Cosmological Dark Energy

    E-Print Network [OSTI]

    Irina Ya. Aref'eva

    2007-10-16T23:59:59.000Z

    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.

  3. Joint Implementation Network Feed | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to: navigation, searchOf Kilauea Volcano, Hawaii | Wind FarmJeffersonJiminyJoint Implementation

  4. Restoring New Agegraphic Dark Energy in RS II Braneworld

    E-Print Network [OSTI]

    Mubasher Jamil; Kayoomars Karami; Ahmad Sheykhi

    2011-06-14T23:59:59.000Z

    Motivated by recent works [1,2], we investigate new agegraphic model of dark energy in the framework of RS II braneworld. We also include the case of variable gravitational constant in our model. Furthermore, we establish correspondence between the new agegraphic dark energy with other dark energy candidates based on scalar fields.

  5. Insights into Dark Energy: Interplay Between Theory and Observation

    E-Print Network [OSTI]

    Rachel Bean; Sean Carroll; Mark Trodden

    2005-10-03T23:59:59.000Z

    The nature of Dark Energy is still very much a mystery, and the combination of a variety of experimental tests, sensitive to different potential Dark Energy properties, will help elucidate its origins. This white paper briefly surveys the array of theoretical approaches to the Dark Energy problem and their relation to experimental questions.

  6. CAPUT DARK ENERGY TOPICS, 2013 1. The Cosmological Constant

    E-Print Network [OSTI]

    Weijgaert, Rien van de

    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

  7. Dark Energy: The Cosmological Challenge of the T. Padmanabhan

    E-Print Network [OSTI]

    Udgaonkar, Jayant B.

    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

  8. Collapse Dynamics of a Star of Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Subenoy Chakraborty; Tanwi Bandyopadhyay

    2006-09-12T23:59:59.000Z

    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.

  9. An Alternative Approach to Holographic Dark Energy

    E-Print Network [OSTI]

    Simpson, F

    2006-01-01T23:59:59.000Z

    We outline a scenario in which dark energy is associated with the particle horizon. An energy density related to the area of the particle horizon is found to behave in accordance with current observational constraints. The equation of state drops as the particle horizon traverses a closed universe. Depending on the constant of proportionality, either the ensuing inflationary period prevents the particle horizon from vanishing, or it may lead to a sequence of "Big Rips".

  10. The Dark Energy Star and Stability analysis

    E-Print Network [OSTI]

    Piyali Bhar; Farook Rahaman

    2015-01-12T23:59:59.000Z

    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.

  11. Dark matter, dark energy, and dark radiation coupled with a transversal interaction

    E-Print Network [OSTI]

    Luis P. Chimento; Martín G. Richarte

    2012-10-19T23:59:59.000Z

    We investigate a cosmological scenario with three interacting components that includes dark matter, dark energy, and radiation in the spatially flat Friedmann-Robertson-Walker universe. We introduce a 3-dimensional internal space, the interaction vector $\\mathbf{Q}=(Q_{x}, Q_{m}, Q_{r})$ satisfying the constraint plane $Q_{x}+ Q_{m}+ Q_{r}=0$, the barotropic index vector $ \\boldmath ${\\gamma}$=(\\ga_x,\\ga_m,\\ga_r)$ and select a transversal interaction vector $\\mathbf{Q_t}$ in a sense that $\\mathbf{Q_t}\\cdot \\boldmath ${\\gamma}$=0$. We exactly solve the source equation for a linear $\\mathbf{Q_t}$, that depends on the total energy density and its derivatives up to third order, and find all the component energy densities. We obtain a large set of interactions for which the source equation admits a power law solution and show its asymptotic stability by constructing the Lyapunov function. We apply the $\\chi^{2}$ method to the observational Hubble data for constraining the cosmic parameters, and analyze the amount of dark energy in the radiation era for the above linear $\\mathbf{Q_t}$. It turns to be that our model fulfills the severe bound of $\\Omega_{x}(z\\simeq 1100)<0.1$ and is consistent with the future constraints achievable by Planck and CMBPol experiments.

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

    E-Print Network [OSTI]

    R. C. Gupta; Anirudh Pradhan

    2009-07-28T23:59:59.000Z

    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.

  13. Jointly Sponsored Research Program Energy Related Research

    SciTech Connect (OSTI)

    Western Research Institute

    2009-03-31T23:59:59.000Z

    Cooperative Agreement, DE-FC26-98FT40323, Jointly Sponsored Research (JSR) Program at Western Research Institute (WRI) began in 1998. Over the course of the Program, a total of seventy-seven tasks were proposed utilizing a total of $23,202,579 in USDOE funds. Against this funding, cosponsors committed $26,557,649 in private funds to produce a program valued at $49,760,228. The goal of the Jointly Sponsored Research Program was to develop or assist in the development of innovative technology solutions that will: (1) Increase the production of United States energy resources - coal, natural gas, oil, and renewable energy resources; (2) Enhance the competitiveness of United States energy technologies in international markets and assist in technology transfer; (3) Reduce the nation's dependence on foreign energy supplies and strengthen both the United States and regional economies; and (4) Minimize environmental impacts of energy production and utilization. Under the JSR Program, energy-related tasks emphasized enhanced oil recovery, heavy oil upgrading and characterization, coal beneficiation and upgrading, coal combustion systems development including oxy-combustion, emissions monitoring and abatement, coal gasification technologies including gas clean-up and conditioning, hydrogen and liquid fuels production, coal-bed methane recovery, and the development of technologies for the utilization of renewable energy resources. Environmental-related activities emphasized cleaning contaminated soils and waters, processing of oily wastes, mitigating acid mine drainage, and demonstrating uses for solid waste from clean coal technologies, and other advanced coal-based systems. Technology enhancement activities included resource characterization studies, development of improved methods, monitors and sensors. In general the goals of the tasks proposed were to enhance competitiveness of U.S. technology, increase production of domestic resources, and reduce environmental impacts associated with energy production and utilization. This report summarizes the accomplishments of the JSR Program.

  14. Detecting dark energy with wavelets on the sphere

    E-Print Network [OSTI]

    J. D. McEwen

    2007-08-29T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

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

    2009-05-18T23:59:59.000Z

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

  16. Is the evidence for dark energy secure?

    E-Print Network [OSTI]

    Subir Sarkar

    2007-12-05T23:59:59.000Z

    Several kinds of astronomical observations, interpreted in the framework of the standard Friedmann-Robertson-Walker cosmology, have indicated that our universe is dominated by a Cosmological Constant. The dimming of distant Type Ia supernovae suggests that the expansion rate is accelerating, as if driven by vacuum energy, and this has been indirectly substantiated through studies of angular anisotropies in the cosmic microwave background (CMB) and of spatial correlations in the large-scale structure (LSS) of galaxies. However there is no compelling direct evidence yet for (the dynamical effects of) dark energy. The precision CMB data can be equally well fitted without dark energy if the spectrum of primordial density fluctuations is not quite scale-free and if the Hubble constant is lower globally than its locally measured value. The LSS data can also be satisfactorily fitted if there is a small component of hot dark matter, as would be provided by neutrinos of mass 0.5 eV. Although such an Einstein-de Sitter model cannot explain the SNe Ia Hubble diagram or the position of the `baryon acoustic oscillation' peak in the autocorrelation function of galaxies, it may be possible to do so e.g. in an inhomogeneous Lemaitre-Tolman-Bondi cosmology where we are located in a void which is expanding faster than the average. Such alternatives may seem contrived but this must be weighed against our lack of any fundamental understanding of the inferred tiny energy scale of the dark energy. It may well be an artifact of an oversimplified cosmological model, rather than having physical reality.

  17. Kaluza-Klein Cosmology With Modified Holographic Dark Energy

    E-Print Network [OSTI]

    M. Sharif; Farida Khanum

    2011-06-13T23:59:59.000Z

    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.

  18. The physics and identity of dark energy

    E-Print Network [OSTI]

    Tom Gehrels

    2011-01-06T23:59:59.000Z

    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.

  19. Present and future evidence for evolving dark energy

    SciTech Connect (OSTI)

    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

    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.

  20. Present and future evidence for evolving dark energy

    E-Print Network [OSTI]

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

    2006-12-04T23:59:59.000Z

    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.

  1. Dark Energy and Search for the Generalized Second Law

    E-Print Network [OSTI]

    Balendra Kr. Dev Choudhury; Julie Saikia

    2009-06-03T23:59:59.000Z

    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.

  2. Atom-interferometry constraints on dark energy

    E-Print Network [OSTI]

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

    2015-01-01T23:59:59.000Z

    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.

  3. Dark energy as a kinematic effect

    E-Print Network [OSTI]

    Jennen, H

    2015-01-01T23:59:59.000Z

    We present a generalization of teleparallel gravity that is consistent with local spacetime kinematics regulated by the de Sitter group $SO(1,4)$. The mathematical structure of teleparallel gravity is shown to be given by a nonlinear Riemann--Cartan geometry without curvature, which inspires us to build the generalization on top of a de Sitter--Cartan geometry with a cosmological function. The cosmological function is given its own dynamics and naturally emerges nonminimally coupled to the gravitational field in a manner akin to teleparallel dark energy models or scalar-tensor theories in general relativity. New in the theory here presented, the cosmological function gives rise to a kinematic contribution in the deviation equation for the world lines of adjacent free-falling particles. While having its own dynamics, dark energy manifests itself in the local kinematics of spacetime.

  4. Gauss Bonnet dark energy Chaplygin Gas Model

    E-Print Network [OSTI]

    Elahe Karimkhani; Asma Alaii; Abdolhossein Khodam-Mohammadi

    2015-02-27T23:59:59.000Z

    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.

  5. Electromagnetic Dark Energy and Gravitoelectrodynamics of Superconductors

    E-Print Network [OSTI]

    Clovis Jacinto de Matos

    2007-10-29T23:59:59.000Z

    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.

  6. Gauss Bonnet dark energy Chaplygin Gas Model

    E-Print Network [OSTI]

    Karimkhani, Elahe; Khodam-Mohammadi, Abdolhossein

    2015-01-01T23:59:59.000Z

    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.

  7. Cosmological dark energy effects from entanglement

    E-Print Network [OSTI]

    S. Capozziello; O. Luongo; S. Mancini

    2013-02-24T23:59:59.000Z

    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.

  8. An inhomogeneous alternative to dark energy?

    E-Print Network [OSTI]

    Alnes, H; Grøn, Ø; Alnes, Havard; Amarzguioui, Morad; Gron, Oyvind

    2006-01-01T23:59:59.000Z

    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.

  9. An inhomogeneous alternative to dark energy?

    E-Print Network [OSTI]

    Havard Alnes; Morad Amarzguioui; Oyvind Gron

    2006-04-18T23:59:59.000Z

    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.

  10. The Dark Energy Survey Data Processing and Calibration System

    E-Print Network [OSTI]

    Mohr, Joseph J; Bertin, Emmanuel; Daues, Gregory E; Desai, Shantanu; Gower, Michelle; Gruendl, Robert; Hanlon, William; Kuropatkin, Nikolay; Lin, Huan; Marriner, John; Petravick, Don; Sevilla, Ignacio; Swanson, Molly; Tomashek, Todd; Tucker, Douglas; Yanny, Brian

    2012-01-01T23:59:59.000Z

    The Dark Energy Survey (DES) is a 5000 deg2 grizY survey reaching characteristic photometric depths of 24th magnitude (10 sigma) and enabling accurate photometry and morphology of objects ten times fainter than in SDSS. Preparations for DES have included building a dedicated 3 deg2 CCD camera (DECam), upgrading the existing CTIO Blanco 4m telescope and developing a new high performance computing (HPC) enabled data management system (DESDM). The DESDM system will be used for processing, calibrating and serving the DES data. The total data volumes are high (~2PB), and so considerable effort has gone into designing an automated processing and quality control system. Special purpose image detrending and photometric calibration codes have been developed to meet the data quality requirements, while survey astrometric calibration, coaddition and cataloging rely on new extensions of the AstrOmatic codes which now include tools for PSF modeling, PSF homogenization, PSF corrected model fitting cataloging and joint mode...

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

    E-Print Network [OSTI]

    Chen, X S

    2005-01-01T23:59:59.000Z

    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.

  12. Dynamical system analysis for DBI dark energy interacting with dark matter

    E-Print Network [OSTI]

    Nilanjana Mahata; Subenoy Chakraborty

    2015-01-19T23:59:59.000Z

    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.

  13. JOINT DEPARTMENT OF COMMERCE AND DEPARTMENT OF ENERGY SMART CITIES...

    Office of Environmental Management (EM)

    JOINT DEPARTMENT OF COMMERCE AND DEPARTMENT OF ENERGY SMART CITIES - SMART GROWTH BUSINESS DEVELOPMENT MISSION TO CHINA April 12-17, 2015 I. MISSION DESCRIPTION The United States...

  14. Dark Energy: A Universe Out of Nicholas B. Suntzeff. Ph. D.

    E-Print Network [OSTI]

    Boas, Harold P.

    Dark Energy: A Universe Out of Control Nicholas B. Suntzeff. Ph. D. Mitchell into? To me ­ the weirdest #12;The Local Universe · 73% dark energy · 23% dark matter (about 3 H m-3 ourselves?? · And why is Dark Energy ~ Dark Matter #12;Dark Energy There is no picture... So I will wave my

  15. Dark Energy and the False Vacuum

    E-Print Network [OSTI]

    P. Q. Hung

    2006-12-10T23:59:59.000Z

    In this talk, I will present highlights of a recent model of dark energy and dark matter in which the present universe is ``trapped'' in a {\\em false vacuum} described by the potential of an axion-like scalar field (the acceleron) which is related to a new strong interaction gauge sector, $SU(2)_Z$, characterized by a scale $\\Lambda_Z \\sim 3 \\times 10^{-3} eV$. This false vacuum model mimicks the $\\Lambda CDM$ scenario. In addition, there are several additional implications such as a new mechanism for leptogenesis coming from the decay of a ``messenger'' scalar field, as well as a new model of ``low-scale'' inflation whose inflaton is the ``radial'' partner of the acceleron.

  16. Viscous dark energy and phantom evolution

    E-Print Network [OSTI]

    Mauricio Cataldo; Norman Cruz; Samuel Lepe

    2005-06-17T23:59:59.000Z

    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.

  17. DarkStar VI | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand JumpConceptual Model,DOE Facility Database Data and Resources11-DNADalyDanishDarajatDarien,DarkStar VI

  18. Reissner-Nordstrom black hole in dark energy background

    E-Print Network [OSTI]

    Ngangbam Ishwarchandra; Ng. Ibohal; K. Yugindro Singh

    2014-11-29T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    M. R. Setare

    2009-08-03T23:59:59.000Z

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

  20. Joint Center for Energy Storage Research Beyond Lithium-Ion

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

    Joint Center for Energy Storage Research Beyond Lithium-Ion 2012 2017 USE MULTIPLY-CHARGED IONS STORE ENERGY IN CHEMICAL BONDS STORE ENERGY IN LIQUIDS IN THE NEXT FIVE YEARS AT...

  1. Structure formation in inhomogeneous Early Dark Energy models

    SciTech Connect (OSTI)

    Batista, R.C. [Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Caixa Postal 1524, 59072-970, Natal, Rio Grande do Norte (Brazil); Pace, F., E-mail: rbatista@ect.ufrn.br, E-mail: francesco.pace@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom)

    2013-06-01T23:59:59.000Z

    We study the impact of Early Dark Energy fluctuations in the linear and non-linear regimes of structure formation. In these models the energy density of dark energy is non-negligible at high redshifts and the fluctuations in the dark energy component can have the same order of magnitude of dark matter fluctuations. Since two basic approximations usually taken in the standard scenario of quintessence models, that both dark energy density during the matter dominated period and dark energy fluctuations on small scales are negligible, are not valid in such models, we first study approximate analytical solutions for dark matter and dark energy perturbations in the linear regime. This study is helpful to find consistent initial conditions for the system of equations and to analytically understand the effects of Early Dark Energy and its fluctuations, which are also verified numerically. In the linear regime we compute the matter growth and variation of the gravitational potential associated with the Integrated Sachs-Wolf effect, showing that these observables present important modifications due to Early Dark Energy fluctuations, though making them more similar to the ?CDM model. We also make use of the Spherical Collapse model to study the influence of Early Dark Energy fluctuations in the nonlinear regime of structure formation, especially on ?{sub c} parameter, and their contribution to the halo mass, which we show can be of the order of 10%. We finally compute how the number density of halos is modified in comparison to the ?CDM model and address the problem of how to correct the mass function in order to take into account the contribution of clustered dark energy. We conclude that the inhomogeneous Early Dark Energy models are more similar to the ?CDM model than its homogeneous counterparts.

  2. Dark Energy as the Remnant of Inflation

    E-Print Network [OSTI]

    H. M. Fried; Y. Gabellini

    2013-02-24T23:59:59.000Z

    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.

  3. Meeting Energy Reduction Requirements at Joint Base San Antonio

    E-Print Network [OSTI]

    Dschuden, B.; Thomas, F.

    2013-01-01T23:59:59.000Z

    One Team, One Mission: Your Success! The Premier Joint Base in the Department of Defense! Joint Base San Antonio and Energy Program 18 December 2013 Bruce Dschuden, Frank Thomas JBSA Resource Efficiency Managers ESL-KT-13-12-25 CATEE 2013...: Clean Air Through Energy Efficiency Conference, San Antonio, Texas Dec. 16-18 One Team, One Mission: Your Success! The Premier Joint Base in the Department of Defense! Presenters • Bruce Dschuden, CEM, CSDP, CEA – Sain Engineering Associates • REM...

  4. Machian gravity and a cosmology without dark matter and dark energy

    E-Print Network [OSTI]

    Santanu Das

    2015-04-10T23:59:59.000Z

    The standard model of cosmology is based on the general theory of relativity and demands more than 95\\% of the universe to consist of dark matter and dark energy that has no direct observational evidence till date. The foundation of the concept these dark components are based on a fixed relation between the strength of the gravitational field and the matter density. Alternate models are put forward in past to explain the observations without dark components in the universe. Though they have their own merits and draw backs. In this paper we propose a new cosmological model based on Mach's principle. It provides a similar cosmology as that of the standard cosmological model without any ad-hoc dark matter or dark energy. We show that the theory naturally provides some geometric terms that behave like dark mater and dark energy and dark radiation. The presence of dark radiation provides new observational features in cosmology. We show that the theory is supported by observational data from Big Bang Nucleosynthesis and Cosmic Microwave Background, and provides an explanations for excess number of effective neutrino species and higher Helium mass fraction in the universe. We also calculate the best fit cosmological parameters for our model using Planck+WP data.

  5. Dark Energy: Reason for the Existence of a Classical Universe?

    E-Print Network [OSTI]

    Huang, Peng; Li, Miao; Li, Nan

    2015-01-01T23:59:59.000Z

    Dark energy is investigated from the perspective of quantum cosmology. By treating the existence of a classical universe as a constraint, it is found that the normal ordering ambiguity factor q in Wheeler-DeWitt equation tends to take its value on domain (-1, 3). Furthermore, to ensure the existence of a classical universe, there must be dark energy in the universe. It is in this sense we propose that dark energy is the reason for the existence of a classical universe.

  6. Ricci Dark Energy in Brans-Dicke theory

    E-Print Network [OSTI]

    Chao-Jun Feng

    2008-06-04T23:59:59.000Z

    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.

  7. Constraints of Dark Energy at High Redshift

    E-Print Network [OSTI]

    Qiping Su; Rong-Gen Cai

    2014-08-24T23:59:59.000Z

    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.

  8. An Alternative Approach to Holographic Dark Energy

    E-Print Network [OSTI]

    Fergus Simpson

    2007-03-27T23:59:59.000Z

    Here we consider a scenario in which dark energy is associated with the apparent area of a surface in the early universe. In order to resemble the cosmological constant at late times, this hypothetical reference scale should maintain an approximately constant physical size during an asymptotically de-Sitter expansion. This is found to arise when the particle horizon - anticipated to be significantly greater than the Hubble length - is approaching the antipode of a closed universe. Depending on the constant of proportionality, either the ensuing inflationary period prevents the particle horizon from vanishing, or it may lead to a sequence of "Big Rips".

  9. Generalized equation of state for dark energy

    SciTech Connect (OSTI)

    Barboza, E. M. Jr.; Alcaniz, J. S. [Observatorio Nacional, 20921-400, Rio de Janeiro - RJ (Brazil); Zhu, Z.-H. [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Silva, R. [Departamento de Fisica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal - RN (Brazil); Departamento de Fisica, Universidade do Estado do Rio Grande do Norte, 59610-210, Mossoro - RN (Brazil)

    2009-08-15T23:59:59.000Z

    A generalized parametrization w{sub {beta}}(z) for the dark energy equation of state is proposed and some of its cosmological consequences are investigated. We show that in the limit of the characteristic dimensionless parameter {beta}{yields}+1, 0 and -1 some well-known equation of state parametrizations are fully recovered whereas for other values of {beta} the proposed parametrization admits a wider and new range of cosmological solutions. We also discuss possible constraints on the w{sub {beta}}(z) parameters from current observational data.

  10. Neutron Interferometry constrains dark energy chameleon fields

    E-Print Network [OSTI]

    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

    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 $\\varphi^n$.

  11. Neutron Interferometry constrains dark energy chameleon fields

    E-Print Network [OSTI]

    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

    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 $\\varphi^n$.

  12. Probing Dark Energy with Atom Interferometry

    E-Print Network [OSTI]

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

    2014-08-06T23:59:59.000Z

    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.

  13. Inflation and New Agegraphic Dark Energy

    E-Print Network [OSTI]

    Cheng-Yi Sun; Rui-Hong Yue

    2011-04-23T23:59:59.000Z

    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.

  14. 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...

  15. Statefinder diagnosis and the interacting ghost model of dark energy

    E-Print Network [OSTI]

    M. Malekjani; A. Khodam-Mohammadi

    2012-02-19T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    G. M. Kremer

    2007-04-03T23:59:59.000Z

    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.

  17. A unifying description of dark energy

    E-Print Network [OSTI]

    Jérôme Gleyzes; David Langlois; Filippo Vernizzi

    2015-01-22T23:59:59.000Z

    We review and extend a novel approach that we introduced recently, to describe general dark energy or scalar-tensor models. Our approach relies on an ADM formulation based on the hypersurfaces where the underlying scalar field is uniform. The advantage of this approach is that it can describe in the same language and in a minimal way a vast number of existing models, such as quintessence models, $F(R)$ theories, scalar tensor theories, their Horndeski extensions and beyond. It also naturally includes Horava-Lifshitz theories. As summarized in this review, our approach provides a unified treatment of the linear cosmological perturbations about a FLRW universe, obtained by a systematic expansion of our general action up to quadratic order. This shows that the behaviour of these linear perturbations is generically characterized by five time-dependent functions. We derive the full equations of motion in the Newtonian gauge, and obtain in particular the equation of state for dark energy perturbations, in the Horndeski case, in terms of these functions. Our unifying description thus provides the simplest and most systematic way to confront theoretical models with current and future cosmological observations.

  18. Counting voids to probe dark energy

    E-Print Network [OSTI]

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

    2015-01-01T23:59:59.000Z

    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...

  19. LISA as a dark energy probe

    E-Print Network [OSTI]

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

    2009-04-20T23:59:59.000Z

    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.

  20. Dark Energy from Casimir Energy on Noncommutative Extra Dimensions

    E-Print Network [OSTI]

    S. Fabi; B. Harms; G. Karatheodoris

    2006-07-20T23:59:59.000Z

    We study the possibility that dark energy is a manifestation of the Casimir energy on extra dimensions with the topology of $S^2$. We consider our universe to be $M^4 \\times S^2$ and modify the geometry by introducing noncommutativity on the extra dimensions only, i.e. replacing $S^2$ with the fuzzy version $S_{F}^2$. We find the energy density as a function of the size of the representation $M+1$ of the algebra of $S_{F}^2$, and we calculate its value for the $M+1=2$ case. The value of the energy density turns out to be positive, i.e. provides dark energy, and the size of the extra dimensions agrees with the experimental limit. We also recover the correct commutative limit as the noncommutative parameter goes to zero.

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

    E-Print Network [OSTI]

    P. M. Sutter; P. M. Ricker

    2008-10-03T23:59:59.000Z

    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.

  2. Could Dark Matter Interactions be an Alternative to Dark Energy ?

    E-Print Network [OSTI]

    S. Basilakos; M. Plionis

    2009-08-05T23:59:59.000Z

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

  3. Interacting Dark Matter as an Alternative to Dark Energy

    E-Print Network [OSTI]

    Spyros Basilakos; Manolis Plionis

    2009-11-12T23:59:59.000Z

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

  4. Interacting Dark Matter as an Alternative to Dark Energy

    E-Print Network [OSTI]

    Basilakos, Spyros

    2009-01-01T23:59:59.000Z

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

  5. From Dark Energy to Dark Matter via Non-Minimal Coupling

    E-Print Network [OSTI]

    A. Borowiec

    2008-12-23T23:59:59.000Z

    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.

  6. The dynamics of universe for exponential decaying dark energy

    E-Print Network [OSTI]

    Bostan, Nilay

    2015-01-01T23:59:59.000Z

    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.

  7. Dark energy rest frame and the CMB dipole

    E-Print Network [OSTI]

    Antonio L. Maroto

    2006-09-08T23:59:59.000Z

    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.

  8. 9/24/09 2:12 PMErasing Dark Energy SEEDMAGAZINE.COM Page 1 of 23http://seedmagazine.com/content/article/erasing_dark_energy/

    E-Print Network [OSTI]

    Temple, Blake

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

  9. Evolution of the horizons for dark energy universe

    E-Print Network [OSTI]

    Ritabrata Biswas; Nairwita Mazumder; Subenoy Chakraborty

    2011-06-12T23:59:59.000Z

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

  10. Spherical Collapse Model And Dark Energy(I)

    E-Print Network [OSTI]

    Ding-fang Zeng; Yi-hong Gao

    2005-05-09T23:59:59.000Z

    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.

  11. Baryon Acoustic Oscillation Intensity Mapping of Dark Energy

    E-Print Network [OSTI]

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

    2007-01-01T23:59:59.000Z

    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.

  12. Analysis of Generalized Ghost Version of Pilgrim Dark Energy

    E-Print Network [OSTI]

    M. Sharif; Abdul Jawad

    2014-08-18T23:59:59.000Z

    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.

  13. Dodging the dark matter degeneracy while determining the dynamics of dark energy

    E-Print Network [OSTI]

    Busti, Vinicius C

    2015-01-01T23:59:59.000Z

    One of the key issues in cosmology is to establish the nature of dark energy, and to determine whether the equation of state evolves with time. When estimating this from distance measurements there is a degeneracy with the matter density. We show that there exists a simple function of the dark energy equation of state and its first derivative which is independent of this degeneracy at all redshifts, and so is a much more robust determinant of the evolution of dark energy than just its derivative. We show that this function can be well determined at low redshift from supernovae using Gaussian Processes, and that this method is far superior to a variety of parameterisations which are also subject to priors on the matter density. This shows that parametrised models give very biased constraints on the evolution of dark energy.

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

    E-Print Network [OSTI]

    Bjoern Malte Schaefer

    2008-03-14T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Eingorn, Maxim

    2015-01-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    V. E. Kuzmichev; V. V. Kuzmichev

    2004-05-24T23:59:59.000Z

    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}.

  17. Interacting holographic dark energy models: A general approach

    E-Print Network [OSTI]

    S. Som; A. Sil

    2014-12-01T23:59:59.000Z

    Dark energy models inspired by the cosmological holographic principle are studied in homogeneous isotropic spacetime with a general choice for the dark energy density $\\rho_d=3(\\alpha H^2+\\beta\\dot{H})$. Special choices of the parameters enable us to obtain three different holographic models, including the holographic Ricci dark energy(RDE) model. Effect of interaction between dark matter and dark energy on the dynamics of those models are investigated for different popular forms of interaction. It is found that crossing of phantom divide can be avoided in RDE models for $\\beta>0.5$ irrespective of the presence of interaction. A choice of $\\alpha=1$ and $\\beta=2/3$ leads to a varying $\\Lambda$-like model introducing an IR cutoff length $\\Lambda^{-1/2}$. It is concluded that among the popular choices an interaction of the form $Q\\propto H\\rho_m$ suits the best in avoiding the coincidence problem in this model.

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

    E-Print Network [OSTI]

    Kh. Saaidi; A. Aghamohammadi

    2010-10-12T23:59:59.000Z

    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.

  19. Interaction between Tachyon and Hessence (or Hantom) dark energies

    E-Print Network [OSTI]

    Surajit Chattopadhyay; Ujjal Debnath

    2010-10-07T23:59:59.000Z

    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.

  20. Entropic-force dark energy reconsidered

    E-Print Network [OSTI]

    Spyros Basilakos; Joan Sola

    2014-05-21T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Xiang-Song Chen

    2005-06-07T23:59:59.000Z

    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 $f_\\sigma>1$.

  2. The Unified Equation of State for Dark Matter and Dark Energy

    E-Print Network [OSTI]

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

    2005-04-05T23:59:59.000Z

    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.

  3. Spectroscopic Needs for Imaging Dark Energy Experiments

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

    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

    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

  4. Spectroscopic Needs for Imaging Dark Energy Experiments

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

    Newman, Jeffrey A.; Slosar, Anze; Abate, Alexandra; Abdalla, Filipe B.; Allam, Sahar; Allen, Steven W.; Ansari, Reza; Bailey, Stephen; Barkhouse, Wayne A.; Beers, Timothy C.; et al

    2015-03-01T23:59:59.000Z

    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 setsmore »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 m

  5. Planck constraints on holographic dark energy

    SciTech Connect (OSTI)

    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

    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.

  6. Interaction between DBI-essence and other Dark Energies

    E-Print Network [OSTI]

    Surajit Chattopadhyay; Ujjal Debnath

    2010-06-11T23:59:59.000Z

    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).

  7. The Dark Energy Regulated by Emergent Conformal Symmetry

    E-Print Network [OSTI]

    Yongsung Yoon

    2013-08-28T23:59:59.000Z

    We have found a mechanism which regulates the dark energy in our universe. With an emergent conformal symmetry, the dark energy density is regulated to the order of a conformal anomaly parameter in the conformally coupled gravity. In the late time cosmological evolution, we have obtained a set of exact cosmological equations which deviate from the Friedmann equations significantly. Based on the recent observational cosmic expansion data, it is shown that the dark energy density is about 1/4 of the matter density at present, which is quite smaller than determined by General Relativity. The jerk parameter at present is also determined as a definite value 0.47.

  8. Vacuum quantum fluctuation energy in expanding universe and dark energy

    E-Print Network [OSTI]

    Shun-Jin Wang

    2014-10-27T23:59:59.000Z

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

  9. Dark Energy and Some Alternatives: a Brief Overview

    E-Print Network [OSTI]

    J. S. Alcaniz

    2006-08-29T23:59:59.000Z

    The high-quality cosmological data, which became available in the last decade, have thrusted upon us a rather preposterous composition for the universe which poses one of the greatest challenges theoretical physics has ever faced: the so-called dark energy. By focusing our attention on specific examples of dark energy scenarios, we discuss three different candidates for this dark component, namely, a decaying vacuum energy or time-varying cosmological constant [$\\Lambda(t)$], a rolling homogeneous quintessence field ($\\Phi$), and modifications in gravity due to extra spatial dimensions. As discussed, all these candidates [along with the vacuum energy or cosmological constant ($\\Lambda$)] seem somewhat to be able to explain the current observational results, which hampers any definitive conclusion on the actual nature of the dark energy.

  10. Dark Energy and Some Alternatives: a Brief Overview

    E-Print Network [OSTI]

    Alcaniz, J S

    2006-01-01T23:59:59.000Z

    The high-quality cosmological data, which became available in the last decade, have thrusted upon us a rather preposterous composition for the universe which poses one of the greatest challenges theoretical physics has ever faced: the so-called dark energy. By focusing our attention on specific examples of dark energy scenarios, we discuss three different candidates for this dark component, namely, a decaying vacuum energy or time-varying cosmological constant [$\\Lambda(t)$], a rolling homogeneous quintessence field ($\\Phi$), and modifications in gravity due to extra spatial dimensions. As discussed, all these candidates [along with the vacuum energy or cosmological constant ($\\Lambda$)] seem somewhat to be able to explain the current observational results, which hampers any definitive conclusion on the actual nature of the dark energy.

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

    E-Print Network [OSTI]

    George F. R. Ellis

    2008-11-21T23:59:59.000Z

    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 $\\Lambda$.

  12. Darke County, Ohio: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand JumpConceptual Model,DOE Facility Database Data and Resources11-DNADalyDanishDarajatDarien,DarkStar

  13. Gravitational Field Equations and Theory of Dark Matter and Dark Energy

    E-Print Network [OSTI]

    Tian Ma; Shouhong Wang

    2012-07-11T23:59:59.000Z

    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.

  14. 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItem NotEnergy,ARMFormsGasReleaseSpeechesHall A ThisFermilab'sSpace and

  15. Cooling the dark energy camera instrument

    SciTech Connect (OSTI)

    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

    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.

  16. Axion-dilaton cosmology and dark energy

    SciTech Connect (OSTI)

    Catena, Riccardo; Moeller, Jan, E-mail: catena@sissa.it, E-mail: janmoe@mail.desy.de [Deutsches Elektronen-Synchrotron DESY, Theory Group, Notkestrasse 85, D-22603 Hamburg (Germany)

    2008-03-15T23:59:59.000Z

    We discuss a class of flat FRW cosmological models based on D = 4 axion-dilaton gravity universally coupled to cosmological background fluids. In particular, we investigate the possibility of recurrent acceleration, which was recently shown to be generically realized in a wide class of axion-dilaton models, but in the absence of cosmological background fluids. We observe that, once we impose the existence of radiation- and matter-dominated earlier stages of cosmic evolution, the axion-dilaton dynamics is altered significantly with respect to the case of pure axion-dilaton gravity. Explicit computations are done considering a universal metric coupling between the dilaton and the matter fields. As a result we find that during the matter-dominated epoch the scalar fields remain either frozen, due to the large expansion rate, or enter a cosmological scaling regime. In both cases, oscillations of the effective equation of state around the acceleration boundary value are impossible. Models which enter an oscillatory stage in the low redshift regime, on the other hand, are disfavored by observations. We also comment on the viability of the axion-dilaton system as a candidate for dynamical dark energy. In a certain subclass of models, an intermediate scaling regime is succeeded by eternal acceleration. We also briefly discuss the issue of dependence on initial conditions.

  17. Axion-Dilaton Cosmology and Dark Energy

    E-Print Network [OSTI]

    Riccardo Catena; Jan Möller

    2007-09-12T23:59:59.000Z

    We discuss a class of flat FRW cosmological models based on D=4 axion-dilaton gravity universally coupled to cosmological background fluids. In particular, we investigate the possibility of recurrent acceleration, which was recently shown to be generically realized in a wide class of axion-dilaton models, but in absence of cosmological background fluids. We observe that, once we impose the existence of radiation -and matter- dominated earlier stages of cosmic evolution, the axion-dilaton dynamics is altered significantly with respect to the case of pure axion-dilaton gravity. During the matter dominated epoch the scalar fields remain either frozen, due to the large expansion rate, or enter a cosmological scaling regime. In both cases, oscillations of the effective equation of state around the acceleration boundary value are impossible. Models which enter an oscillatory stage in the low redshift regime, on the other hand, are disfavored by observations. We also comment on the viability of the axion-dilaton system as a candidate for dynamical dark energy. In a certain subclass of models, an intermediate scaling regime is succeeded by eternal acceleration. We also briefly discuss the issue of dependence on initial conditions.

  18. The Dark Energy Survey Data Management System

    E-Print Network [OSTI]

    Sevilla, I; Bertin, E; Carlson, A; Daues, G; Desai, S; Gower, M; Gruendl, R; Hanlon, W; Jarvis, M; Kessler, R; Kuropatkin, N; Lin, H; Marriner, J; Mohr, J; Petravick, D; Sheldon, E; Swanson, M E C; Tomashek, T; Tucker, D; Yang, Y; Yanny, B

    2011-01-01T23:59:59.000Z

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

  19. The Dark Energy Survey Data Management System

    SciTech Connect (OSTI)

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

    2011-09-01T23:59:59.000Z

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

  20. Joint Statement on Future U.S.-Russia Nuclear Energy and Nonproliferat...

    Energy Savers [EERE]

    Joint Statement on Future U.S.-Russia Nuclear Energy and Nonproliferation Collaboration Following Russian Delegation Visit to the United States Joint Statement on Future...

  1. Dark Energy and Large-Scale Structure of the Universe

    E-Print Network [OSTI]

    Yu. Kulinich; B. Novosyadlyj

    2004-12-14T23:59:59.000Z

    The evolution of matter density perturbations in two-component model of the Universe consisting of dark energy (DE) and dust-like matter (M) is considered. We have analyzed it for two kinds of DE with $\\omega\

  2. Stable dark energy stars: An alternative to black holes?

    E-Print Network [OSTI]

    Lobo, F S N

    2008-01-01T23:59:59.000Z

    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.

  3. Effect of phantom dark energy on the holographic thermalization

    E-Print Network [OSTI]

    Zeng, Xiao-Xiong; Li, Li-Fang

    2015-01-01T23:59:59.000Z

    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.

  4. Stable dark energy stars: An alternative to black holes?

    E-Print Network [OSTI]

    Francisco S. N. Lobo

    2006-12-05T23:59:59.000Z

    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.

  5. Particle mixing as possible explanation of the dark energy conundrum

    E-Print Network [OSTI]

    Antonio Capolupo; Giuseppe Vitiello

    2009-01-28T23:59:59.000Z

    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.

  6. Cosmological viability conditions for f(T) dark energy models

    SciTech Connect (OSTI)

    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

    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.

  7. 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...

  8. Effect of phantom dark energy on the holographic thermalization

    E-Print Network [OSTI]

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

    2015-03-16T23:59:59.000Z

    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.

  9. arXiv:astro-ph/0703364v227Aug2007 Electromagnetic dark energy

    E-Print Network [OSTI]

    Wright, Francis

    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

  10. Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies

    E-Print Network [OSTI]

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

    2007-04-03T23:59:59.000Z

    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.

  11. New agegraphic dark energy model with generalized uncertainty principle

    E-Print Network [OSTI]

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

    2008-08-07T23:59:59.000Z

    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 $n_c=2.799531478$.

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

    ScienceCinema (OSTI)

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

    2011-06-08T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Prabir Rudra; Ujjal Debnath

    2014-05-29T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    B. A. Trubnikov

    2008-12-09T23:59:59.000Z

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

  15. Cosmological Perturbations in Models of Coupled Dark Energy

    E-Print Network [OSTI]

    Sirichai Chongchitnan

    2009-02-26T23:59:59.000Z

    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.

  16. Interacting Dark Energy in Ho?ava-Lifshitz Cosmology

    E-Print Network [OSTI]

    M R Setare

    2009-12-02T23:59:59.000Z

    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.

  17. Reconstruction of the dark matter-vacuum energy interaction

    E-Print Network [OSTI]

    Wang, Yuting; Wands, David; Pogosian, Levon; Crittenden, Robert G

    2015-01-01T23:59:59.000Z

    An interaction between the vacuum energy and dark matter is an intriguing possibility which may offer a way of solving the cosmological constant problem. Adopting a general prescription for momentum exchange between the two dark components, we reconstruct the temporal evolution of the coupling strength between dark matter and vacuum energy, $\\alpha(a)$ in a non-parametric Bayesian approach using the combined observational datasets from the cosmic microwave background, supernovae and large scale structure. An evolving interaction between the vacuum energy and dark matter removes some of the tensions between different types of datasets, and is favoured at $\\sim95\\%$ CL if we include the baryon acoustic oscillations measurements of the BOSS Lyman-$\\alpha$ forest sample.

  18. DOD-DOE Workshop on Joint Energy Activities

    SciTech Connect (OSTI)

    None

    1980-01-01T23:59:59.000Z

    The general conditions for DOD-DOE interactions were delineated in an October 1978, Memorandum of Understanding (MOU) that identified two basic goals: improving energy efficiency and availability within DOD, and utilizing DOD and DOE expertise and facilities to carry out projects of mutual interest. There has been considerable interaction between DOD and DOE, including a number of proposed joint initiatives but a systematic and coordinated approach for nurturing, maintaining, and expanding these relationships has not been developed. A DOD-DOE Workshop on Joint Energy Activities was held on March 10-12, 1980. The workshop was structured into five working groups - Mobility Fuels, Conservation, Fossil Fuels for Fixed Facilities, Solar and Renewable Energy Sources, and Special Projects - with DOD and DOE cochairmen for each. Over a hundred DOD and DOE management, program, and policymaking representatives were brought together by the workshop Steering Committee to identify specific programs for inclusion in an overall plan for implementing the MOU and to deal with fundamental issues and problems of maintaining future communications. The workshop accomplished its goals, these being to: (1) improve communication among the appropriate key DOD and DOE personnel at all levels and promote information exchange; (2) review ongoing and already-proposed joint DOD and DOE programs; (3) initiate a coordinated, systematic effort to establish joint DOD-DOE energy-security programs; and (4) propose specific programs and projects of mutual interest for inclusion in a follow-on joint-implementation plan.

  19. The Dark Energy Survey Data Management System

    E-Print Network [OSTI]

    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

    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.

  20. The Dark Energy Survey Data Management System

    SciTech Connect (OSTI)

    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

    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.

  1. A Quantum Cosmology: No Dark Matter, Dark Energy nor Accelerating Universe

    E-Print Network [OSTI]

    Reginald T Cahill

    2007-09-18T23:59:59.000Z

    We show that modelling the universe as a pre-geometric system with emergent quantum modes, and then constructing the classical limit, we obtain a new account of space and gravity that goes beyond Newtonian gravity even in the non-relativistic limit. This account does not require dark matter to explain the spiral galaxy rotation curves, and explains as well the observed systematics of black hole masses in spherical star systems, the bore hole $g$ anomalies, gravitational lensing and so on. As well the dynamics has a Hubble expanding universe solution that gives an excellent parameter-free account of the supernovae and gamma-ray-burst red-shift data, without dark energy or dark matter. The Friedmann-Lema\\^{i}tre-Robertson-Walker (FLRW) metric is derived from this dynamics, but is shown not satisfy the General Relativity based Friedmann equations. It is noted that General Relativity dynamics only permits an expanding flat 3-space solution if the energy density in the pressure-less dust approximation is non-zero. As a consequence dark energy and dark matter are required in this cosmological model, and as well the prediction of a future exponential accelerating Hubble expansion. The FLRW $\\Lambda$CDM model data-based parameter values, $\\Omega_\\Lambda=0.73$, $\\Omega_{DM}=0.27$, are derived within the quantum cosmology model, but are shown to be merely artifacts of using the Friedmann equations in fitting the red-shift data.

  2. $?$CDM coupled to radiation. Dark energy and Universe acceleration

    E-Print Network [OSTI]

    Renat R. Abbyazov; Sergey V. Chervon; Volker Müller

    2014-09-02T23:59:59.000Z

    Recently the Chiral Cosmological Model (CCM) coupled to cold dark matter (CDM) has been investigated as $\\sigma$CDM model to study the observed accelerated expansion of the Universe. Dark sector fields (as Dark Energy content) coupled to cosmic dust were considered as the source of Einstein gravity in Friedmann-Robertson-Walker (FRW) cosmology. Such model had a beginning at the matter-dominated era. The purposes of our present investigation are two folds: to extend > of the $\\sigma$CDM for earlier times to radiation-dominated era and to take into account variation of the exponential potential via variation of the interaction parameter $\\lambda $. We use Markov Chain Monte Carlo (MCMC) procedure to investigate possible values of initial conditions constrained by the measured amount of the dark matter, dark energy and radiation component today. Our analysis includes dark energy contribution to critical density, the ratio of the kinetic and potential energies, deceleration parameter, effective equation of state and evolution of DE equation of state with variation of coupling constant $\\lambda $. A comparison with the $\\Lambda$CDM model was performed. A new feature of the model is the existence of some values of potential coupling constant, leading to a $\\sigma$CDM solution without transit into accelerated expansion epoch.

  3. Dark Energy Regulation with Approximate Emergent Conformal Symmetry

    E-Print Network [OSTI]

    Yongsung Yoon

    2013-08-28T23:59:59.000Z

    A cosmic potential which can relax the vacuum energy is proposed in a framework of scalar-tensor gravity. In the phase of the gravity scalar field around the evolution with an approximate emergent conformal symmetry, we have obtained a set of cosmological equations with the dark energy regulated to the order of a conformal anomaly parameter. Through a role of the cosmic potential, the vacuum energy which could be generated in matter Lagrangian does not contribute to the dark energy in the phase.

  4. QCD nature of dark energy at finite temperature: cosmological implications

    E-Print Network [OSTI]

    K. Azizi; N. Katirci

    2015-06-23T23:59:59.000Z

    The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras.It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.

  5. QCD nature of dark energy at finite temperature: cosmological implications

    E-Print Network [OSTI]

    Azizi, K

    2015-01-01T23:59:59.000Z

    The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras.It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.

  6. Bulk-Brane Interaction and Holographic Dark Energy

    E-Print Network [OSTI]

    M R Setare

    2006-12-14T23:59:59.000Z

    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.

  7. Phenomenology of hybrid scenarios of neutrino dark energy

    SciTech Connect (OSTI)

    Antusch, Stefan; Dutta, Koushik [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, D-80805 Muenchen (Germany)] [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, D-80805 Muenchen (Germany); Das, Subinoy, E-mail: antusch@mppmu.mpg.de, E-mail: subinoy@nyu.edu, E-mail: koushik@mppmu.mpg.de [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)] [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

    2008-10-15T23:59:59.000Z

    We study the phenomenology of hybrid scenarios of neutrino dark energy, where in addition to a so-called mass-varying neutrino (MaVaN) sector a cosmological constant (from a false vacuum) is driving the accelerated expansion of the universe today. For general power law potentials we calculate the effective equation of state parameter w{sub eff}(z) in terms of the neutrino mass scale. Due to the interaction of the dark energy field ('acceleron') with the neutrino sector, w{sub eff}(z) is predicted to become smaller than -1 for z>0, which could be tested in future cosmological observations. For the scenarios considered, the neutrino mass scale additionally determines which fraction of the dark energy is dynamical, and which originates from the 'cosmological-constant-like' vacuum energy of the false vacuum. On the other hand, the field value of the 'acceleron' field today as well as the masses of the right-handed neutrinos, which appear in the seesaw-type mechanism for small neutrino masses, are not fixed. This, in principle, allows us to realize hybrid scenarios of neutrino dark energy with a 'high-scale' seesaw where the right-handed neutrino masses are close to the GUT scale. We also comment on how MaVaN hybrid scenarios with 'high-scale' seesaw might help to resolve stability problems of dark energy models with non-relativistic neutrinos.

  8. Testing the Cosmic Coincidence Problem and the Nature of Dark Energy

    E-Print Network [OSTI]

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

    2001-05-18T23:59:59.000Z

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

  9. Determination of Dark Energy and Dark Matter from the values of Redshift for the present time, Planck and Trans-Planck epochs of the Big-Bang model

    E-Print Network [OSTI]

    Asger G. Gasanalizade; Ramin A. Hasanalizade

    2015-02-20T23:59:59.000Z

    As an alternative to the Standard cosmology model we have developed a new modified Freundlich's (quantum relativity) redshift (MFRS) mechanisms, which provide a precise solutions of the Dark Energy and Dark Matter problems. We apply the joint solution of three MFRS equations for concordances quantize bounce Planck hierarchy steps. Simultaneous scaling solutions of MFRS equations in logarithmic scale appropriate to three cosmological epoch's, yields a currently testable predictions regarding the Dark Matter {\\Omega}_{DM} = 0.25, and Dark Energy {\\Omega}_{DE} = 0.75. These predictions coincides with the recent observational data from WMAP and other a key supernovae SNe Ia findings. Thus, the presence of Dark Matter and Dark Energy had already been not only detected observationally, but also confirmed theoretically with the very compelling accuracy. From the WMAP7 and our predicted ages we find a value of the Hubble constant H_0 = 65.6 km * s^{-1} Mpc^{-1} which is excellent agreement with the Planck 2013 results XVI. Compared with the "holographic scenario" results, we find an important coincidence between our new and "holographic" parameters. We discuss the connection hierarchy between the multiverse masses and examine the status of the cosmic acceleration. The product of the age of the Universe into the cosmic acceleration in each cosmological epochs --including present day are constant and precisely corresponds to an possible observable-geophysical parameter g_U = 9.50005264_{265} (exact) * (m/s^2). For the derived by WMAP7 age of the Universe t_{W7} = 13.75(13) * 10^9 yr, we find the relevant acceleration a_{W7} = 6.91(65) * 10^{-10} m/s^2. The predicted value of t_0 = 9.0264_9(51) * 10^2 Gyr is consistent with the background acceleration. a_0 = 1.05246_4(61) * 10^{-11} m/s^2.

  10. A dark energy model alternative to generalized Chaplygin gas

    E-Print Network [OSTI]

    Hoavo Hova; Huanxiong Yang

    2010-11-22T23:59:59.000Z

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

  11. A dark energy model alternative to generalized Chaplygin gas

    E-Print Network [OSTI]

    Hova, Hoavo

    2010-01-01T23:59:59.000Z

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

  12. Dark energy in some integrable and nonintegrable FRW cosmological models

    E-Print Network [OSTI]

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

    2011-09-14T23:59:59.000Z

    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.

  13. JCESR | Joint Center for Energy Storage Research

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

    want. More Sandia: High Density Storage JCESR Partner Sandia discusses high density energy storage for electric vehicles and the grid More JCESR and NASA team up JCESR and...

  14. Joint Energy Management and Resource Allocation in Rechargeable Sensor Networks

    E-Print Network [OSTI]

    Sinha, Prasun

    Joint Energy Management and Resource Allocation in Rechargeable Sensor Networks Ren-Shiou Liu CSE, The Ohio State University Email: rsliu@cse.ohio-state.edu Prasun Sinha CSE, The Ohio State University Email: prasun@cse.ohio-state.edu Can Emre Koksal ECE, The Ohio State University Email: koksal

  15. Large-scale stable interacting dark energy model: Cosmological perturbations and observational constraints

    E-Print Network [OSTI]

    Yun-He Li; Xin Zhang

    2014-04-20T23:59:59.000Z

    Dark energy might interact with cold dark matter in a direct, nongravitational way. However, the usual interacting dark energy models (with constant $w$) suffer from some catastrophic difficulties. For example, the $Q\\propto\\rho_{\\rm c}$ model leads to an early-time large-scale instability, and the $Q\\propto\\rho_{\\rm de}$ model gives rise to the future unphysical result for cold dark matter density (in the case of a positive coupling). In order to overcome these fatal flaws, we propose in this paper an interacting dark energy model (with constant $w$) in which the interaction term is carefully designed to realize that $Q\\propto\\rho_{\\rm de}$ at the early times and $Q\\propto\\rho_{\\rm c}$ in the future, simultaneously solving the early-time superhorizon instability and future unphysical $\\rho_{\\rm c}$ problems. The concrete form of the interaction term in this model is $Q=3\\beta H \\frac{\\rho_{\\rm{de}}\\rho_{\\rm{c}}}{\\rho_{\\rm{de}}+\\rho_{\\rm{c}}}$, where $\\beta$ is the dimensionless coupling constant. We show that this model is actually equivalent to the decomposed new generalized Chaplygin gas (NGCG) model, with the relation $\\beta=-\\alpha w$. We calculate the cosmological perturbations in this model in a gauge-invariant way and show that the cosmological perturbations are stable during the whole expansion history provided that $\\beta>0$. Furthermore, we use the Planck data in conjunction with other astrophysical data to place stringent constraints on this model (with eight parameters), and we find that indeed $\\beta>0$ is supported by the joint constraint at more than 1$\\sigma$ level. The excellent theoretical features and the support from observations all indicate that the decomposed NGCG model deserves more attention and further investigation.

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

    E-Print Network [OSTI]

    Martiros Khurshudyan

    2013-01-31T23:59:59.000Z

    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.

  17. A low-$z$ test for interacting dark energy

    E-Print Network [OSTI]

    Goncalves, R S; Alcaniz, J S

    2015-01-01T23:59:59.000Z

    A non-minimal coupling between the dark matter and dark energy components may offer a way of solving the so-called coincidence problem. In this paper we propose a low-$z$ test for such hypothesis using measurements of the gas mass fraction $f_{\\rm{gas}}$ in relaxed and massive galaxy clusters. The test applies to any model whose dilution of dark matter is modified with respect to the standard $a^{-3}$ scaling, as usual in interacting models, where $a$ is the cosmological scale factor. We apply the test to current $f_{\\rm{gas}}$ data and perform Monte Carlo simulations to forecast the necessary improvements in number and accuracy of upcoming observations to detect a possible interaction in the cosmological dark sector. Our results show that improvements in the present relative error $\\sigma_{\\rm{gas}}/f_{\\rm{gas}}$ are more effective to achieve this goal than an increase in the size of the $f_{\\rm{gas}}$ sample.

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

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

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

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

    E-Print Network [OSTI]

    Ujjal Debnath

    2015-03-06T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Debnath, Ujjal

    2015-01-01T23:59:59.000Z

    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...

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

    E-Print Network [OSTI]

    Ujjal Debnath

    2015-02-08T23:59:59.000Z

    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.

  2. Dynamics of interacting phantom and quintessence dark energies

    E-Print Network [OSTI]

    M. Umar Farooq; Mubasher Jamil; Ujjal Debnath

    2011-04-20T23:59:59.000Z

    We present models, in which phantom energy interacts with two different types of dark energies including variable modified Chaplygin gas (VMCG) and new modified Chaplygin gas (NMCG). We then construct potentials for these cases. It has been shown that the potential of the phantom field decreases from a higher value with the evolution of the Universe.

  3. Joint Implementation Network (JIN) | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are8COaBulkTransmissionSitingProcess.pdfGetecGtelInteriasIowa: Energy Resources Jump to: navigation,Ohio:Joice,

  4. Gamesa Santana Joint Venture | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual Siteof Energy 2,AUDIT REPORTEnergyFarms A SUK Place: Newport, Wales, United

  5. Nome Joint Utility Systems | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual SiteofEvaluatingGroup |JilinLuOpen EnergyNelsoniXInformation NobleNobles

  6. Climate Leaders Joint Venture | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnualProperty EditCalifornia:PowerCER.png El CER esDatasetCity ofClarkEnergy

  7. What We Know About Dark Energy From Supernovae

    ScienceCinema (OSTI)

    Alex Filippenko

    2010-01-08T23:59:59.000Z

    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.

  8. Fine-structure constant constraints on dark energy

    E-Print Network [OSTI]

    Martins, C J A P

    2015-01-01T23:59:59.000Z

    We use astrophysical and atomic clock tests of the stability of the fine-structure constant $\\alpha$, together with Type Ia supernova and Hubble parameter data, to constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, $\\zeta$, to the electromagnetic sector) the $\\alpha$ variation. We show how current data tightly constrains a combination of $\\zeta$ and the dark energy equation of state $w_0$. At the $95\\%$ confidence level and marginalizing over $w_0$ we find $|\\zeta|<5\\times10^{-6}$, with the atomic clock tests dominating the constraints. The forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.

  9. Dark Energy Cosmology with the Alternative Cosmic Microwave Background Data

    E-Print Network [OSTI]

    Hao Wei

    2011-04-19T23:59:59.000Z

    Recently, in a series of works by Liu and Li (L&L), they claimed that there exists a timing asynchrony of $-25.6\\,$ms between the spacecraft attitude and radiometer output timestamps in the original raw WMAP time-ordered data (TOD). L&L reprocessed the WMAP data while the aforementioned timing asynchrony has been corrected, and they obtained an alternative CMB map in which the quadrupole dropped to nearly zero. In the present work, we try to see the implications to dark energy cosmology if L&L are right. While L&L claimed that there is a bug in the WMAP pipeline which leads to significantly different cosmological parameters, an interesting question naturally arises, namely, how robust is the current dark energy cosmology with respect to systematic errors and bugs? So, in this work, we adopt the alternative CMB data of L&L as a strawman to study the robustness of dark energy predictions.

  10. A new equation of state for dark energy

    E-Print Network [OSTI]

    Dragan Slavkov Hajdukovic

    2009-11-04T23:59:59.000Z

    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.

  11. Status of the Dark Energy Survey Camera (DECam) Project

    SciTech Connect (OSTI)

    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

    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.

  12. Joint Implementation Network (JIN) | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to: navigation, searchOf Kilauea Volcano, Hawaii | Wind FarmJeffersonJiminy

  13. Malibu Joint Venture | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to: navigation, searchOfRose Bend < MHKconvertersource History ViewMali[1] "USAID'sMalibu

  14. Joint Statement by Energy Ministers of G8, The People's Republic...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    energy consumption plan to achieve global energy security, climate change mitigation and sustainable development. Joint Statement by Energy Ministers of G8, The People's Republic...

  15. DOE Announces Funding for U.S.-India Joint Clean Energy Research...

    Office of Environmental Management (EM)

    for U.S.-India Joint Clean Energy Research and Development Center DOE Announces Funding for U.S.-India Joint Clean Energy Research and Development Center May 16, 2011 - 12:00am...

  16. Dark energy and non-linear power spectrum

    E-Print Network [OSTI]

    Sang Gyu Biern; Jinn-Ouk Gong

    2015-06-29T23:59:59.000Z

    We investigate the effects of homogeneous general dark energy on the non-linear matter perturbation in fully general relativistic context. The equation for the density contrast contains even at linear order new contributions which are non-zero for general dark energy. Taking into account the next-leading-order corrections, we derive the total power spectrum in real and redshift spaces. We find that the observable galaxy power spectrum deviates from the LambdaCDM spectrum, which is nearly identical to that in the Einstein-de Sitter universe, and the relative difference is about 10% on a scale of the baryon acoustic oscillations.

  17. Viscous Dark Energy in $f(T)$ Gravity

    E-Print Network [OSTI]

    M. Sharif; Shamaila Rani

    2014-05-18T23:59:59.000Z

    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.

  18. Majorana neutrino superfluidity and stability of neutrino dark energy

    SciTech Connect (OSTI)

    Bhatt, Jitesh R.; Sarkar, Utpal [Physical Research Laboratory, Ahmedabad 380009 (India)

    2009-08-15T23:59:59.000Z

    We demonstrate that Majorana neutrinos can form Cooper pairs due to long-range attractive forces and show BCS superfluidity in a class of mass varying neutrino dark energy models. We describe the condensates for Majorana neutrinos and estimate the value of the gap, critical temperature, and Pippard coherence length for a simple neutrino dark energy model. In the strong coupling regime bosonic degree of freedom can become important, and Bose-Einstein condensate may govern the dynamics for the mass varying neutrino models. Formation of the condensates can significantly alter the instability scenario in the mass varying neutrino models.

  19. A conjecture on the origin of dark energy

    E-Print Network [OSTI]

    Shan Gao

    2011-07-16T23:59:59.000Z

    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.

  20. Quantisation of the holographic Ricci dark energy model

    E-Print Network [OSTI]

    Albarran, Imanol

    2015-01-01T23:59:59.000Z

    While general relativity is an extremely robust theory to describe the gravitational interaction in our Universe, it is expected to fail close to singularities like the cosmological ones. On the other hand, it is well known that some dark energy models might induce future singularities; this can be the case for example within the setup of the Holographic Ricci Dark Energy model (HRDE). On this work, we perform a cosmological quantisation of the HRDE model and obtain under which conditions a cosmic doomsday can be avoided within the quantum realm. We show as well that this quantum model not only avoid future singularities but also the past Big Bang.

  1. The Dark Energy Equation of State using Alternative High-z Cosmic Tracers

    E-Print Network [OSTI]

    M. Plionis; R. Terlevich; S. Basilakos; F. Bresolin; E. Terlevich; J. Melnick; R. Chavez

    2010-01-18T23:59:59.000Z

    We propose to use alternative cosmic tracers to measure the dark energy equation of state and the matter content of the Universe [w(z) & Omega_m]. Our proposed method consists of two components: (a) tracing the Hubble relation using HII galaxies which can be detected up to very large redshifts, z~4, as an alternative to supernovae type Ia, and (b) measuring the clustering pattern of X-ray selected AGN at a median redshift of z~1. Each component of the method can in itself provide interesting constraints on the cosmological parameters, especially under our anticipation that we will reduce the corresponding random and systematic errors significantly. However, by joining their likelihood functions we will be able to put stringent cosmological constraints and break the known degeneracies between the dark energy equation of state (whether it is constant or variable) and the matter content of the universe and provide a powerful and alternative route to measure the contribution to the global dynamics and the equation of state of dark energy. A preliminary joint analysis of X-ray selected AGN (based on the largest to-date XMM survey; the 2XMM) and the currently largest SNIa sample (Hicken et al.), using as priors a flat universe and the WMAP5 normalization of the power-spectrum, provides: Omega_m=0.27+-0.02 and w=-0.96+-0.07. Equivalent and consistent results are provided by the joint analysis of X-ray selected AGN clustering and the latest Baryonic Acoustic Oscillation measures, providing: Omega_m=0.27+-0.02 and w=-0.97+-0.04.

  2. Dark Energy from Quantum Uncertainty of Distant Clocks

    E-Print Network [OSTI]

    M. J. Luo

    2015-05-04T23:59:59.000Z

    The observed cosmic acceleration was attributed to an exotic dark energy in the framework of classical general relativity. The dark energy behaves very similar with vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a complete wrong result and leads to a severe fine-tuning. To solve the problem, the exact meaning of time in quantum mechanics is reexamined. We abandon the standard interpretation of time in quantum mechanics that time is just a global parameter, replace it by a quantum dynamical variable playing the role of physical clock. We find that synchronization of two spatially separated clocks can not be precisely realized at quantum level. There is an intrinsic quantum uncertainty of distant simultaneity, which implies an apparent vacuum energy fluctuation and gives an observed dark energy density $\\rho_{de}=\\frac{6}{\\pi}L_{P}^{-2}L_{H}^{-2}$ at tree level approximation, where $L_{P}$ and $L_{H}$ are the Planck and Hubble scale cutoffs. The fraction of the dark energy is given by $\\Omega_{de}=\\frac{2}{\\pi}$, which does not evolve with the internal clock time. The "dark energy" as a quantum cosmic variance is always seen comparable with the matter energy density by an observer using the internal clock time. The corrected distance-redshift relation of cosmic observations due to the distant clock effect are also discussed, which again gives a redshift independent fraction $\\Omega_{de}=\\frac{2}{\\pi}$. The theory is consistent with current cosmic observations.

  3. Thermodynamics of viscous dark energy in an RSII braneworld

    E-Print Network [OSTI]

    M. R. Setare; A. Sheykhi

    2011-03-05T23:59:59.000Z

    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.

  4. General Coordinate Transformations as the Origins of Dark Energy

    E-Print Network [OSTI]

    V. G. J. Rodgers; Takeshi Yasuda

    2006-01-17T23:59:59.000Z

    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.

  5. Italy Joint Statement | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your Density Isn't YourTransport(FactDepartment ofLetter Report: I11IG002RTC3 | 12/1/2014 |Is5:It's that time

  6. Einstein-Aether Theory as an Alternative to Dark Energy Model?

    E-Print Network [OSTI]

    Meng, Xin-He

    2011-01-01T23:59:59.000Z

    In the Einstein-aether theory by taking a special form of the ${\\cal F}({\\cal K})$ (a free function in this theory) the possibility of Einstein-aether theory as an alternative to dark energy model is discussed in details, that is, taking a special Aether field as a dark energy candidate. We compute the joint statistic constraints on this special model's parameters by using the recent type Ia supernovae (SNe Ia) data, the Cosmic Microwave Background (CMB) shift parameter data, and the Baryonic Acoustic Oscillations (BAOs) data traced by the Sloan Digital Sky Survey (SDSS). Furthermore, we analyze other constrains from the observational Hubble parameter data (OHD). The comparison with the standard cosmological model (cosmological constant $\\Lambda$ Cold Dark Matter ($\\Lambda$CDM) model) is clearly shown with new features; also we discuss an interesting relation between the coupling constant M in this model and the possible existence of a special accelerate scale in the MOdified Newtonian Dynamics (MOND) model i...

  7. Unification of Gravitation, Gauge Field and Dark Energy

    E-Print Network [OSTI]

    Xin-Bing Huang

    2005-08-26T23:59:59.000Z

    This paper is composed of two correlated topics: 1. unification of gravitation with gauge fields; 2. the coupling between the daor field and other fields and the origin of dark energy. After introducing the concept of ``daor field" and discussing the daor geometry, we indicate that the complex daor field has two kinds of symmetry transformations. Hence the gravitation and SU(1,3) gauge field are unified under the framework of the complex connection. We propose a first-order nonlinear coupling equation of the daor field, which includes the coupling between the daor field and SU(1,3) gauge field and the coupling between the daor field and the curvature, and from which Einstein's gravitational equation can be deduced. The cosmological observations imply that dark energy cannot be zero, and which will dominate the doom of our Universe. The real part of the daor field self-coupling equation can be regarded as Einstein's equation endowed with the cosmological constant. It shows that dark energy originates from the self-coupling of the space-time curvature, and the energy-momentum tensor is proportional to the square of coupling constant \\lambda. The dark energy density given by our scenario is in agreement with astronomical observations. Furthermore, the Newtonian gravitational constant G and the coupling constant \\epsilon of gauge field satisfy G= \\lambda^{2}\\epsilon^{2}.

  8. New holographic dark energy model inspired by the DGP braneworld

    E-Print Network [OSTI]

    Sheykhi, A; Ghaffari, S

    2015-01-01T23:59:59.000Z

    The energy density of the holographic dark energy is based on the area law of entropy, and thus any modification of the area law leads to a modified holographic energy density. Inspired by the entropy expression associated with the apparent horizon of a Friedmann-Robertson-Walker (FRW) Universe in DGP braneworld, we propose a new model for the holographic dark energy in the framework of DGP brane cosmology. We investigate the cosmological consequences of this new model and calculate the equation of state parameter by choosing the Hubble radius, $L = H^{-1}$, as the system's IR cutoff. Our study show that, due to the effects of the extra dimension (bulk), the identification of IR-cutoff with Hubble radius, can reproduce the present acceleration of the Universe expansion. This is in contrast to the ordinary holographic dark energy in standard cosmology which leads to the zero equation of state parameter in the case of choosing the Hubble radius as system's IR cutoff in the absence of interaction between dark ma...

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

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

    High-Powered Dark Energy Camera Can See Billions of Light Years Away High-Powered Dark Energy Camera Can See Billions of Light Years Away August 21, 2014 - 10:19am Addthis Stars...

  10. United States -Japan Joint Nuclear Energy Action Plan

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

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOn AprilA group current C3E AmbassadorsUS-EU-Japan-Japan Joint Nuclear Energy Action Plan

  11. United States -Japan Joint Nuclear Energy Action Plan | Department of

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

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOn AprilA group current C3E AmbassadorsUS-EU-Japan-Japan Joint Nuclear Energy Action

  12. U.S. Department of Energy Joint Genome Institute

    Office of Scientific and Technical Information (OSTI)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItem Not FoundInformation DOEInformation Summary Big*The LA:UR-Energy Joint

  13. The Graviton and the Nature of Dark Energy

    E-Print Network [OSTI]

    A. Zee

    2004-03-05T23:59:59.000Z

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

  14. agegraphic dark energy: Topics by E-print Network

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

    agegraphic dark energy 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 Agegraphic Chaplygin gas model...

  15. A cosmographic analysis of holographic dark energy models

    E-Print Network [OSTI]

    Supriya Pan; Subenoy Chakraborty

    2014-11-10T23:59:59.000Z

    The present work deals with a detailed study of interacting holographic dark energy model for three common choices of the interaction term. Also, two standard choices of IR cut-off, namely, Ricci length scale and radius of the event horizon are considered here. Finally, the cosmographic parameters are presented both analytically and graphically.

  16. Inflation, Dark Energy, and the Fate of the Universe

    SciTech Connect (OSTI)

    Linde, Andrei (Stanford University) [Stanford University

    2003-11-12T23:59:59.000Z

    Inflationary theory, which describes an accelerated expansion of the early universe, gradually becomes a standard cosmological paradigm. It solves many complicated problems of the usual big bang theory, explains the origin of galaxies, and makes several predictions, which, so far, are in a good agreement with cosmological observations. Recently we learned that few billion years ago the universe entered the second stage of acceleration, driven by mysterious 'dark energy'. According to the simplest version of inflationary theory, the universe is an eternally existing self-reproducing fractal consisting of different balloons of exponentially large size. The universe as a whole can be immortal, but the fate of each of these balloons, including the one in which we live now, depends on the properties of dark energy. According to some of the theories of dark energy, our part of the universe will continue its accelerated expansion forever. Other theories predict that eventually our part of the universe will become ten-dimensional and stop accelerating. Still another possibility is that our part of the universe will collapse. I will describe recent developments in inflationary theory and the theory of dark energy, and discuss the possibility to find our fate by cosmological observations.

  17. Evolution of entropic dark energy and its phantom nature

    E-Print Network [OSTI]

    Mathew, Titus K; J, Shejeelammal

    2015-01-01T23:59:59.000Z

    Assuming the form of the entropic dark energy as arises form the surface term in the Einstein-Hilbert's action, it's evolution were analyzed in an expanding flat universe. The model parameters were evaluated by constraining model using the Union data on Type Ia supernovae. We found that the model predicts an early decelerated phase and a later accelerated phase at the background level. The evolution of the Hubble parameter, dark energy density, equation of state parameter and deceleration parameter were obtained. The model is diagnosed with $Om$ parameter. The model is hardly seems to be supporting the linear perturbation growth for the structure formation. We also found that the entropic dark energy shows phantom nature for redshifts $z<0.257.$ During the phantom epoch, the model predicts big-rip effect at which both the scale factor of expansion and the dark energy density become infinitely large and the big rip time is found to be around 36 Giga Years from now.

  18. Cosmological Analysis of Pilgrim Dark Energy in Loop Quantum Cosmology

    E-Print Network [OSTI]

    Jawad, Abdul

    2015-01-01T23:59:59.000Z

    The proposal of pilgrim dark energy is based on speculation that phantom-like dark energy (with strong enough resistive force) can prevent black hole formation in the universe. We explore this phenomenon in loop quantum cosmology framework by taking Hubble horizon as an infra-red cutoff in pilgrim dark energy. We evaluate the cosmological parameters such as Hubble, equation of state parameter, squared speed of sound and also cosmological planes like $\\omega_{\\vartheta}-\\omega'_{\\vartheta}$ and $r-s$ on the basis of pilgrim dark energy parameter ($u$) and interacting parameter ($d^2$). It is found that values of Hubble parameter lies in the range $74^{+0.005}_{-0.005}$. It is mentioned here that equation state parameter lies within the ranges $-1\\mp0.00005$ for $u=2, 1$ and $(-1.12,-1), (-5,-1)$ for $u=-1,-2$, respectively. Also, $\\omega_{\\vartheta}-\\omega'_{\\vartheta}$ planes provide $\\Lambda$CDM limit, freezing and thawing regions for all cases of $u$. It is also interesting to mention here that $\\omega_{\\va...

  19. Reconstructing $f(R)$ Theory from Ricci Dark Energy

    E-Print Network [OSTI]

    Chao-Jun Feng

    2008-12-11T23:59:59.000Z

    In this letter, we regard the $f(R)$ theory as an effective description for the acceleration of the universe and reconstruct the function $f(R)$ from the Ricci dark energy, which respects holographic principle of quantum gravity. By using different parameter $\\alpha$ in RDE, we show the behaviors of reconstructed $f(R)$ and find they are much different in the future.

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

    E-Print Network [OSTI]

    Piyali Bagchi Khatua; Shuvendu Chakraborty; Ujjal Debnath

    2011-05-08T23:59:59.000Z

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

  1. Axionic dark energy and a composite QCD axion

    SciTech Connect (OSTI)

    Kim, Jihn E. [Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747 (Korea, Republic of)] [Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747 (Korea, Republic of); Nilles, Hans Peter, E-mail: jekim@ctp.snu.ac.kr, E-mail: nilles@th.physik.uni-bonn.de [Bethe Center for Theoretical Physics and Physikalisches Institut, Universitaet Bonn, D-53115, Bonn (Germany)

    2009-05-15T23:59:59.000Z

    We discuss the idea that the model-independent (MI) axion of string theory is the source of quintessential dark energy. The scenario is completed with a composite QCD axion from hidden sector squark condensation that could serve as dark matter candidate. The mechanism relies on the fact that the hidden sector anomaly contribution to the composite axion is much smaller than the QCD anomaly term. This intuitively surprising scenario is based on the fact that below the hidden sector scale {Lambda}{sub h} there are many light hidden sector quarks. Simply, by counting engineering dimensions the hidden sector instanton potential can be made negligible compared to the QCD anomaly term.

  2. Growth of Cosmic Structure: Probing Dark Energy Beyond Expansion

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

    Huterer, Dragan; Kirkby, David; Bean, Rachel; Connolly, Andrew; Dawson, Kyle; Dodelson, Scott; Evrard, August; Jain, Bhuvnesh; Jarvis, Michael; Linder, Eric; et al

    2015-03-01T23:59:59.000Z

    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 expansionmore »such as distance-redshift relations will pin down the mechanism driving the acceleration of the Universe.« less

  3. Growth of Cosmic Structure: Probing Dark Energy Beyond Expansion

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

    Huterer, Dragan [University of Michigan, Department of Physics Ann Harbor, MI (United States); Kirkby, David [UC Irvine, Department of Physics and Astronomy, CA (United States); Bean, Rachel [Cornell University, Department of Astronomy, Ithaca, NY (United States); Connolly, Andrew [University of Washington, Department of Astronomy, Seattle, WA (United States); Dawson, Kyle [University of Utah, Department of Physics & Astronomy, Salt Lake City, UT (United States); Dodelson, Scott [Fermi National Accelerator Laboratory, Fermilab Center for Particle Astrophysics, Batavia, IL (United States); University of Chicago, Department of Physics & Astrophysics, Chicago, IL (United States); Evrard, August [University of Michigan, Department of Physics Ann Harbor, MI (United States); Jain, Bhuvnesh [University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, PA (United States); Jarvis, Michael [University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, PA (United States); Linder, Eric [Lawrence Berkeley National Laboratory, Physics Division, Berkeley, CA (United States); Mandelbaum, Rachel [Carnegie Mellon University, Department of Physics, Pittsburgh, PA (United States); May, Morgan [Brookhaven National Laboratory (BNL), Upton, NY (United States); Raccanelli, Alvise [California Institute of Technology, NASA Jet Propulsion Laboratory, Pasadena, CA (United States); Reid, Beth [Lawrence Berkeley National Laboratory, Physics Division, Berkeley, CA (United States); Rozo, Eduardo [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Schmidt, Fabian [Princeton University, Department of Astrophysical Sciences, Princeton, NJ (United States); Max-Planck-Insitute for Astrophysics, Garching (Germany); Sehgal, Neelima [Stony Brook University, NY (United States); Slosar, Anze [Brookhaven National Laboratory (BNL), Upton, NY (United States); Van Engelen, Alex [Stony Brook University, NY (United States); Wu, Hao-Yi [University of Michigan, Department of Physics, Ann Harbor, MI (United States); Zhao, Gongbo [Chinese Academy of Science, National Astronomy Observatories, Beijing (China)

    2015-03-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    M. R. Setare

    2009-07-28T23:59:59.000Z

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

  5. arXiv:astro-ph/0512327v27Mar2006 Laboratory tests on dark energy

    E-Print Network [OSTI]

    Beck, Christian

    arXiv:astro-ph/0512327v27Mar2006 Laboratory tests on dark energy Christian Beck School of the currently observed dark energy in the universe is completely unclear, and many different theoretical models co-exist. Nevertheless, if dark energy is produced by vac- uum fluctuations then there is a chance

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

    E-Print Network [OSTI]

    Sirianni, Marco

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

  7. Holographic Dark Energy with Time Varying n^2 Parameter in Non-Flat Universe

    E-Print Network [OSTI]

    Bushra Majeed; Mubasher Jamil; Azad A. Siddiqui

    2014-11-01T23:59:59.000Z

    We consider a holographic dark energy model, with a varying parameter, n, which evolves slowly with time. We obtain the differential equation describing evolution of the dark energy density parameter, $\\Omega_d$, for the flat and non-flat FRW universes. The equation of state parameter in this generalized version of holographic dark energy depends on n.

  8. Resource Letter: Dark Energy and the Accelerating Universe

    E-Print Network [OSTI]

    Eric V. Linder

    2007-05-28T23:59:59.000Z

    This Resource Letter provides a guide to the literature on dark energy and the accelerating universe. It is intended to be of use to researchers, teachers, and students at several levels. Journal articles, books, and websites are cited for the following topics: Einstein's cosmological constant, quintessence or dynamical scalar fields, modified cosmic gravity, relations to high energy physics, cosmological probes and observations, terrestrial probes, calculational tools and parameter estimation, teaching strategies and educational resources, and the fate of the universe.

  9. On the nature of dark energy. Is the Casimir force a manifestation of this exotic kind of energy?

    E-Print Network [OSTI]

    P. Brovetto; V. Maxia; M. Salis

    2009-05-25T23:59:59.000Z

    Topics concerning dark energy and the accelerating expansion of universe are briefly reported. Arguments about the quantum fluctuations of vacuum are examined in order to decide if the Casimir force really is a laboratory evidence of dark energy.

  10. DOC-DOE Joint China Mission Statement | Department of Energy

    Office of Environmental Management (EM)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742 33 111 1,613PortsmouthBartlesvilleAbout » Contact UsDepartment of EnergyandJoint China Mission

  11. Joint DOE-Rosatom Statement | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your Density Isn't YourTransport(FactDepartment ofLetter Report: I11IG002RTC3 | ofproposalof Energy usJoint

  12. Joint Fuel Cell Bus Workshop Summary Report | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your Density Isn't YourTransport(FactDepartment ofLetter Report: I11IG002RTC3 | ofproposalof Energy usJointFuel

  13. U.S.-Japan Joint Statement | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your DensityEnergy U.S.-China Electric Vehicle and Battery Technology Workshop U.S.-China Electric-Japan Joint

  14. Alvan Blanch Green Fuels joint venture | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to:Ezfeedflag JumpID-fTriWildcat Place:Alvan Blanch Green Fuels joint venture Jump to:

  15. Testing the cosmological constant as a candidate for dark energy

    SciTech Connect (OSTI)

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

    2003-12-03T23:59:59.000Z

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

  16. Illuminating Dark Photons with High-Energy Colliders

    E-Print Network [OSTI]

    David Curtin; Rouven Essig; Stefania Gori; Jessie Shelton

    2015-02-27T23:59:59.000Z

    High-energy colliders offer a unique sensitivity to dark photons, the mediators of a broken dark U(1) gauge theory that kinetically mixes with the Standard Model (SM) hypercharge. Dark photons can be detected in the exotic decay of the 125 GeV Higgs boson, h -> Z Z_D -> 4l, and in Drell-Yan events, pp -> Z_D -> ll. If the dark U(1) is broken by a hidden-sector Higgs mechanism, then mixing between the dark and SM Higgs bosons also allows the exotic decay h -> Z_D Z_D -> 4l. We show that the 14 TeV LHC and a 100 TeV proton-proton collider provide powerful probes of both exotic Higgs decay channels. In the case of kinetic mixing alone, direct Drell-Yan production offers the best sensitivity to Z_D, and can probe epsilon >~ 9 x 10^(-4) (4 x 10^(-4)) at the HL-LHC (100 TeV pp collider). The exotic Higgs decay h -> Z Z_D offers slightly weaker sensitivity, but both measurements are necessary to distinguish the kinetically mixed dark photon from other scenarios. If Higgs mixing is also present, then the decay h -> Z_D Z_D can allow sensitivity to the Z_D for epsilon >~ 10^(-9) - 10^(-6) (10^(-10) - 10^(-7)) for the mass range 2 m_mu updating previous work in the literature. Electroweak precision measurements at LEP, Tevatron, and the LHC exclude epsilon as low as 3 x 10^(-2). Sensitivity can be improved by up to a factor of ~2 with HL-LHC data, and an additional factor of ~4 with ILC/GigaZ data.

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

    E-Print Network [OSTI]

    Hans V. Klapdor-Kleingrothaus; Irina V. Krivosheina

    2010-07-15T23:59:59.000Z

    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.)

  18. On the internal consistency of holographic dark energy models

    SciTech Connect (OSTI)

    Horvat, R, E-mail: horvat@lei3.irb.hr [Rudjer Boskovic Institute, POB 180, 10002 Zagreb (Croatia)] [Rudjer Boskovic Institute, POB 180, 10002 Zagreb (Croatia)

    2008-10-15T23:59:59.000Z

    Holographic dark energy (HDE) models, underpinned by an effective quantum field theory (QFT) with a manifest UV/IR connection, have become convincing candidates for providing an explanation of the dark energy in the universe. On the other hand, the maximum number of quantum states that a conventional QFT for a box of size L is capable of describing relates to those boxes which are on the brink of experiencing a sudden collapse to a black hole. Another restriction on the underlying QFT is that the UV cut-off, which cannot be chosen independently of the IR cut-off and therefore becomes a function of time in a cosmological setting, should stay the largest energy scale even in the standard cosmological epochs preceding a dark energy dominated one. We show that, irrespective of whether one deals with the saturated form of HDE or takes a certain degree of non-saturation in the past, the above restrictions cannot be met in a radiation dominated universe, an epoch in the history of the universe which is expected to be perfectly describable within conventional QFT.

  19. 9/18/09 2:07 PMSPACE.com --'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 8http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html

    E-Print Network [OSTI]

    Temple, Blake

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

  20. 8/24/09 11:48 AMSPACE.com --'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 10http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html#comments

    E-Print Network [OSTI]

    Temple, Blake

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

  1. System Architecture of the Dark Energy Survey Camera Readout Electronics

    SciTech Connect (OSTI)

    Shaw, Theresa; /FERMILAB; Ballester, Otger; Cardiel-Sas, Laia; Castilla, Javier; /Barcelona, IFAE; Chappa, Steve; /Fermilab; de Vicente, Juan; /Madrid, CIEMAT; Holm, Scott; Huffman, Dave; Kozlovsky, Mark; /Fermilab; Martinez, Gustavo; /Madrid, CIEMAT; Moore, Todd; /Madrid, CIEMAT /Fermilab /Illinois U., Urbana /Fermilab

    2010-05-27T23:59:59.000Z

    The Dark Energy Survey makes use of a new camera, the Dark Energy Camera (DECam). DECam will be installed in the Blanco 4M telescope at Cerro Tololo Inter-American Observatory (CTIO). DECam is presently under construction and is expected to be ready for observations in the fall of 2011. The focal plane will make use of 62 2Kx4K and 12 2kx2k fully depleted Charge-Coupled Devices (CCDs) for guiding, alignment and focus. This paper will describe design considerations of the system; including, the entire signal path used to read out the CCDs, the development of a custom crate and backplane, the overall grounding scheme and early results of system tests.

  2. A divergence-free parametrization for dynamical dark energy

    E-Print Network [OSTI]

    Akarsu, Ozgur; Vazquez, J Alberto

    2015-01-01T23:59:59.000Z

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

  3. Semi-dynamical perturbations of unified dark energy

    E-Print Network [OSTI]

    Lombriser, Lucas

    2015-01-01T23:59:59.000Z

    Linear cosmological perturbations of a large class of modified gravity and dark energy models can be unified in the effective field theory of cosmic acceleration, encompassing Horndeski scalar-tensor theories and beyond. The fully available model space inherent to this formalism cannot be constrained by measurements in the quasistatic small-scale regime alone. To facilitate the analysis of modifications from the concordance model beyond this limit, we introduce a semi-dynamical treatment extrapolated from the evolution of perturbations at a pivot scale of choice. At small scales, and for Horndeski theories, the resulting modifications recover a quasistatic approximation but account for corrections to it near the Hubble scale. For models beyond Horndeski gravity, we find that the velocity field and time derivative of the spatial metric potential can generally not be neglected, even in the small-scale limit. We test the semi-dynamical approximation against the linear perturbations of a range of dark energy and ...

  4. Possible Measurable Effects of Dark Energy in Rotating Superconductors

    E-Print Network [OSTI]

    Clovis Jacinto de Matos; Christian Beck

    2007-07-12T23:59:59.000Z

    We discuss recent laboratory experiments with rotating superconductors and show that three so far unexplained experimentally observed effects (anomalous acceleration signals, anomalous gyroscope signals, Cooper pair mass excess) can be physically explained in terms of a possible interaction of dark energy with Cooper pairs. Our approach is based on a Ginzburg-Landau-like model of electromagnetic dark energy, where gravitationally active photons obtain mass in the superconductor. We show that this model can account simultaneously for the anomalous acceleration and anomalous gravitomagnetic fields around rotating superconductors measured by Tajmar et al. and for the anomalous Cooper pair mass in superconductive Niobium, measured by Cabrera and Tate. It is argued that these three different physical effects are ultimately different experimental manifestations of the simultaneous spontaneous breaking of gauge invariance, and of the principle of general covariance in superconductive materials.

  5. Higher signal harmonics, LISA's angular resolution, and dark energy

    E-Print Network [OSTI]

    K. G. Arun; Bala R. Iyer; B. S. Sathyaprakash; Siddhartha Sinha; Chris Van Den Broeck

    2007-10-24T23:59:59.000Z

    It is generally believed that the angular resolution of the Laser Interferometer Space Antenna (LISA) for binary supermassive black holes (SMBH) will not be good enough to identify the host galaxy or galaxy cluster. This conclusion, based on using only the dominant harmonic of the binary SMBH signal, changes substantially when higher signal harmonics are included in assessing the parameter estimation problem. We show that in a subset of the source parameter space the angular resolution increases by more than a factor of 10, thereby making it possible for LISA to identify the host galaxy/galaxy cluster. Thus, LISA's observation of certain binary SMBH coalescence events could constrain the dark energy equation of state to within a few percent, comparable to the level expected from other dark energy missions.

  6. Thermodynamic of universe with a varying dark energy component

    E-Print Network [OSTI]

    Ebadi, E

    2015-01-01T23:59:59.000Z

    We consider a FRW universe filled by a dark energy candidate together with other possible sources which may include the baryonic and non-baryonic matters. Thereinafter, we consider a situation in which the cosmos sectors do not interact with each other. By applying the first law of thermodynamics on the apparent horizon of the FRW universe, we show that the dark energy candidate may modify the apparent horizon entropy and thus the Bekenstein limit. Moreover, we generalize our study to the models in which the cosmos sectors have a mutual interaction. Our final result indicates that the mutual interaction between the cosmos sectors may add an additional term to the apparent horizon entropy leading to modify the Bekenstein limit. Relationships with previous works have been addressed throughout the paper. Finally, we investigate the validity of the second law of thermodynamics and its generalization form in the interacting and non-interacting cosmos.

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

    E-Print Network [OSTI]

    V. Majernik

    2003-11-06T23:59:59.000Z

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

  8. Joint Environmental Management System (EMS) | Department of Energy

    Office of Environmental Management (EM)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742 33 111 1,613 122Commercial602 1,39732on ArmedManufacturing |Time-BasedIrvingDupuyJoin us forofJoint

  9. Solder Joints of Power Electronics | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your Density Isn'tOriginEducationVideo »UsageSecretary ofSmallConfidential,2Cycle SelectionDepartment of11Joints

  10. Solder Joints of Power Electronics | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 DataDepartment of Energy Your Density Isn'tOriginEducationVideo »UsageSecretary ofSmallConfidential,2Cycle SelectionDepartment of11Joints09

  11. Mutually interacting Tachyon dark energy with variable $G$ and $?$

    E-Print Network [OSTI]

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

    2014-05-20T23:59:59.000Z

    In this paper we consider Tachyonic scalar field as dark energy with interaction between components in the case of variable $G$ and $\\Lambda$. We assume a flat Universe with specific form of scale factor and study cosmological parameters numerically and graphically. Statefinder analysis also performed as well. In the special choice of interaction parameters we succeed to obtain analytical expression of densities. We find that our model will be stable in the late stage but there is an instability at the early Universe.

  12. Solar System Constraints on Gauss-Bonnet Dark Energy

    E-Print Network [OSTI]

    Stephen C. Davis

    2007-08-15T23:59:59.000Z

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

  13. Holographic dark energy with non-minimal coupling

    E-Print Network [OSTI]

    L. N. Granda; L. D. Escobar

    2009-10-03T23:59:59.000Z

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

  14. Analysis of Generalized Ghost Pilgrim Dark Energy in Non-flat FRW Universe

    E-Print Network [OSTI]

    Abdul Jawad

    2014-12-11T23:59:59.000Z

    This work is based on pilgrim dark energy conjecture which states that phantom-like dark energy possesses the enough resistive force to preclude the formation of black hole. The non-flat geometry is considered which contains the interacting generalized ghost pilgrim dark energy with cold dark matter. Some well-known cosmological parameters (evolution parameter ($\\omega_{\\Lambda}$) and squared speed of sound) and planes ($\\omega_{\\Lambda}$-$\\omega_{\\Lambda}'$ and statefinder) are constructed in this scenario. The discussion of these parameters is totally done through pilgrim dark energy parameter ($u$) and interacting parameter ($d^2$). It is interesting to mention here that the analysis of evolution parameter supports the conjecture of pilgrim dark energy. Also, this model remains stable against small perturbation in most of the cases of $u$ and $d^2$. Further, the cosmological planes correspond to $\\Lambda$CDM limit as well as different well-known dark energy models.

  15. Studies of inflation and dark energy with coupled scalar fields

    E-Print Network [OSTI]

    Vu, Susan

    2015-01-01T23:59:59.000Z

    Currently there is no definitive description for the accelerated expansion of the Universe at both early and late times; we know these two periods as the epochs of inflation and dark energy. Contained within this Thesis are two studies of inflation and one in the context of dark energy. The first study involves two noncanonical kinetic terms each in a two-field scenario, and their effects on the generation of isocurvature modes. As a result, these terms affect the isocurvature perturbations produced, and consequently the Cosmic Microwave Background. In the following study, the impact of a sharp transition upon the effective Planck mass is considered in both a single-field and two-field model. A feature in the primordial power spectrum arising from these transitions is found in single-field models, but not for two-field models. The final model discussed is on the subject of dark energy. A type of nonconformal coupling is examined namely the "disformal" coupling; in this scenario a scalar field is disformally c...

  16. Dark Energy Generated by Warped Cosmic Strings

    E-Print Network [OSTI]

    Reinoud Jan Slagter

    2014-07-29T23:59:59.000Z

    If we live on the weak brane in a warped 5D bulk spacetime, gravitational waves and brane fluctuations can be generated by a part of the 5D Weyl tensor and carries information of the gravitational field outside the brane. We consider the U(1) self-gravitating scalar-gauge field on the warped spacetime without bulk matter. It turns out that "branons" can be formed dynamically, due to the modified energy-momentum tensor components of the cosmic string. It turns out that the parameter $\\alpha$, i.e., the gauge-to-scalar mass, changes from a value $>1$ to a value $wave energy. It is the time-dependent part of the warp factor which triggers this extraordinary behavior.

  17. Is dark energy an artifact of decoherence?

    E-Print Network [OSTI]

    Chris Fields

    2015-02-19T23:59:59.000Z

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

  18. Is dark energy an artifact of decoherence?

    E-Print Network [OSTI]

    Fields, Chris

    2015-01-01T23:59:59.000Z

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

  19. Berkeley Algorithms Help Researchers Understand 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWP TWPAlumniComplex historianBenefits of BES BasicBenefitsBerkeley

  20. Evidence for Dark Energy | GE Global Research

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Science (SC) Environmental Assessments (EA) /Email Announcements12:25 p.m.Experiments with

  1. Dark Energy: A Missing Physical Ingredient

    E-Print Network [OSTI]

    Wanas, M I

    2008-01-01T23:59:59.000Z

    Recent observation of supernovae type Ia show clearly that there is a large scale repulsive force in the Universe. Neither of the four known fundamental interactions can account for this repulsive force. Gravity is known to be the interaction responsible for the large scale structure and evolution of the Universe. The problem with gravity is that it gives rise to a force which is attractive only. Gravity theories, including General Relativity, deals with gravity as an attractive force. Although this is consistent with our experience in the solar system and other similar astrophysical systems, gravity theories fail to account for SN type Ia observation. So, we are in a real problem concerning the interpretation of these observation. This problem is only ten years old. In order to go out of this problematic situation, scientists have suggested the existence of a type of energy in the Universe that is responsible for the above mentioned repulsive force. They have given this type of energy the exotic term {\\it "D...

  2. A topological origin for Dark Energy

    E-Print Network [OSTI]

    Espiro, J Lorca

    2015-01-01T23:59:59.000Z

    Cosmology struggles with the theoretical problems generated by the observed value and recent emergence of a cosmological constant, in the standard model of cosmology, i.e. the concordance model. We propose to provide a more natural explanation for its value than the conventional quantum vacuum energy in the guise of topological invariants. Introducing topological classes densities as Lagrange multipliers, an effective cosmological constant is generated. General Relativity is reestablished by cancelling the torsion thus generated, which provides constraints on the invariants and yield the form of the effective cosmological constant. As it is divided by the total volume of spacetime, its small value compared to the Planck scale is therefore natural. It also provides a direct measurement of the global Euler number.

  3. Calibrated Ultra Fast Image Simulations for the Dark Energy Survey

    E-Print Network [OSTI]

    Bruderer, Claudio; Refregier, Alexandre; Amara, Adam; Berge, Joel; Gamper, Lukas

    2015-01-01T23:59:59.000Z

    Weak lensing by large-scale structure is a powerful technique to probe the dark components of the universe. To understand the measurement process of weak lensing and the associated systematic effects, image simulations are becoming increasingly important. For this purpose we present a first implementation of the $\\textit{Monte Carlo Control Loops}$ ($\\textit{MCCL}$; Refregier & Amara 2014), a coherent framework for studying systematic effects in weak lensing. It allows us to model and calibrate the shear measurement process using image simulations from the Ultra Fast Image Generator (UFig; Berge et al. 2013). We apply this framework to a subset of the data taken during the Science Verification period (SV) of the Dark Energy Survey (DES). We calibrate the UFig simulations to be statistically consistent with DES images. We then perform tolerance analyses by perturbing the simulation parameters and study their impact on the shear measurement at the one-point level. This allows us to determine the relative im...

  4. Introduction to Modified Gravity and Gravitational Alternative for Dark Energy

    E-Print Network [OSTI]

    Nojiri, S

    2006-01-01T23:59:59.000Z

    We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of such theories may pass the Solar System tests. On the same time, it is demonstrated that they have quite rich cosmological structure: they may naturally describe the effective (cosmological constant, quintessence or phantom) late-time era with a possible transition from decceleration to acceleration thanks to gravitational terms which increase with scalar curvature decrease. The possibility to explain the coincidence problem as the manifestation of the universe expansion in such models is mentioned. The late (phantom or quintessence) universe filled with dark fluid with inhomogeneous equation of state (where inhomogeneous terms are originated from the modif...

  5. Darke Rural Electric Coop, Inc | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual SiteofEvaluating A Potential Microhydro Site Jump(RedirectedDalian XinyangDanishDaofu CoDarke

  6. Does f(R,T) gravity admit a stationary scenario between dark energy and dark matter in its framework?

    E-Print Network [OSTI]

    Rudra, Prabir

    2015-01-01T23:59:59.000Z

    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.

  7. Dynamics of interacting dark energy model in Einstein and Loop Quantum Cosmology

    E-Print Network [OSTI]

    Songbai Chen; Bin Wang; Jiliang Jing

    2008-11-10T23:59:59.000Z

    We investigate the background dynamics when dark energy is coupled to dark matter in the universe described by Einstein cosmology and Loop Quantum Cosmology. We introduce a new general form of dark sector coupling, which presents us a more complicated dynamical phase space. Differences in the phase space in obtaining the accelerated scaling attractor in Einstein cosmology and Loop Quantum Cosmology are disclosed.

  8. JETC: Joint Energy Thermal and Cooling Management for Memory and CPU Subsystems in Servers

    E-Print Network [OSTI]

    Simunic, Tajana

    JETC: Joint Energy Thermal and Cooling Management for Memory and CPU Subsystems in Servers Raid In this work we propose a joint energy, thermal and cooling management technique (JETC) that significantly re- duces per server cooling and memory energy costs. Our analysis shows that decoupling the optimization

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

    E-Print Network [OSTI]

    Paul Howard Frampton

    2010-07-02T23:59:59.000Z

    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.

  10. Coincidences of Dark Energy with Dark Matter -- Clues for a Simple Alternative?

    E-Print Network [OSTI]

    HongSheng Zhao

    2007-10-21T23:59:59.000Z

    A rare coincidence of scales in standard particle physics is needed to explain why $\\Lambda$ or the negative pressure of cosmological dark energy (DE) coincides with the positive pressure $P_0$ of random motion of dark matter (DM) in bright galaxies. Recently Zlosnik et al. (2007) propose to modify the Einsteinian curvature by adding a non-linear pressure from a medium flowing with a four-velocity vector field $U^\\mu$. We propose to check whether a smooth extension of GR with a simple kinetic Lagrangian of $U^\\mu$ can be constructed, and whether the pressure can bend space-time sufficiently to replace the roles of a $w=-1$ DE, $w=0$ Cold DM and heavy neutrinos in explaining anomalous accelerations at all scales. As a specific proof of concept we find a Vector-for-$\\Lambda$ model (${\\mathbf V\\Lambda}$-model) and its variants. With essentially {\\it no free parameters}, these appear broadly consistent with the solar system, gravitational potentials in dwarf spiral galaxies and the bullet cluster of galaxies, early universe with inflation, structure formation and BBN, and late acceleration with a 1:3 ratio of DM:DE.

  11. Coincidences of Dark Energy with Dark Matter -- Clues for a Simple Alternative?

    E-Print Network [OSTI]

    Zhao, HongSheng

    2007-01-01T23:59:59.000Z

    A rare coincidence of scales in standard particle physics is needed to explain why $\\Lambda$ or the negative pressure of cosmological dark energy (DE) coincides with the positive pressure $P_0$ of random motion of dark matter (DM) in bright galaxies. Recently Zlosnik et al. (2007) propose to modify the Einsteinian curvature by adding a non-linear pressure from a medium flowing with a four-velocity vector field $U^\\mu$. We propose to check whether a smooth extension of GR with a simple kinetic Lagrangian of $U^\\mu$ can be constructed, and whether the pressure can bend space-time sufficiently to replace the roles of a $w=-1$ DE, $w=0$ Cold DM and heavy neutrinos in explaining anomalous accelerations at all scales. As a specific proof of concept we find a Vector-for-$\\Lambda$ model (${\\mathbf V\\Lambda}$-model) and its variants. With essentially {\\it no free parameters}, these appear broadly consistent with the solar system, gravitational potentials in dwarf spiral galaxies and the bullet cluster of galaxies, ear...

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

    E-Print Network [OSTI]

    A. T. Filippov

    2009-05-29T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  14. Joint Statement between U.S. Department of Energy and Republic...

    Office of Environmental Management (EM)

    between U.S. Department of Energy and Republic of Korea's Ministry of Trade, Industry, and Energy Joint Statement between U.S. Department of Energy and Republic of Korea's Ministry...

  15. Casimir Energy, Holographic Dark Energy and Electromagnetic Metamaterial Mimicking de Sitter

    E-Print Network [OSTI]

    Miao Li; Rong-Xin Miao; Yi Pang

    2010-05-13T23:59:59.000Z

    We compute the Casimir energy of the photon field in a de Sitter space and find it to be proportional to the size of the horizon, the same form of the holographic dark energy. We suggest to make metamaterials to mimic de Sitter space in laboratory and measure the predicted Casimir energy.

  16. Sudden Future Singularity models as an alternative to Dark Energy?

    E-Print Network [OSTI]

    Hoda Ghodsi; Martin A. Hendry; Mariusz P. Dabrowski; Tomasz Denkiewicz

    2011-03-11T23:59:59.000Z

    Current observational evidence does not yet exclude the possibility that dark energy could be in the form of phantom energy. A universe consisting of a phantom constituent will be driven toward a drastic end known as the `Big Rip' singularity where all the matter in the universe will be destroyed. Motivated by this possibility, other evolutionary scenarios have been explored by Barrow, including the phenomena which he called Sudden Future Singularities (SFS). In such a model it is possible to have a blow up of the pressure occurring at sometime in the future evolution of the universe while the energy density would remain unaffected. The particular evolution of the scale factor of the universe in this model that results in a singular behaviour of the pressure also admits acceleration in the current era. In this paper we will present the results of our confrontation of one example class of SFS models with the available cosmological data from high redshift supernovae, baryon acoustic oscillations (BAO) and the cosmic microwave background (CMB). We then discuss the viability of the model in question as an alternative to dark energy.

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

    E-Print Network [OSTI]

    Ahmad Sheykhi

    2009-12-19T23:59:59.000Z

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

  18. Berkeley India Joint Leadership on Energy and Environment | Open Energy

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual Siteof EnergyInnovation in Carbonof Alternative Sources of Funding:

  19. Holographic dark energy with varying gravitational constant in Ho?ava-Lifshitz cosmology

    SciTech Connect (OSTI)

    Setare, M.R. [Department of Physics, University of Kurdistan, Pasdaran Ave., Sanandaj (Iran, Islamic Republic of); Jamil, Mubasher, E-mail: rezakord@ipm.ir, E-mail: mjamil@camp.nust.edu.pk [Center for Advanced Mathematics and Physics, National University of Sciences and Technology, Rawalpindi, 46000 (Pakistan)

    2010-02-01T23:59:59.000Z

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

  20. The Dark Energy Survey: Prospects for Resolved Stellar Populations

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

    Rossetto, Bruno M; Santiago, Basilio X; Girardi, Leo; Camargo, Julio I.B.; Balbinot, Eduardo; da Costa, Luiz N; Yanny, Brian; Maia, Marcio A.G.; Makler, Martin; Ogando, Ricardo L.C.; et al

    2011-05-06T23:59:59.000Z

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

  1. Can Massive Gravitons be an Alternative to Dark Energy?

    E-Print Network [OSTI]

    Marcio E. S. Alves; Oswaldo D. Miranda; Jose C. N. de Araujo

    2010-08-24T23:59:59.000Z

    In this work, we explore some cosmological implications of the model proposed by M. Visser in 1998. In his approach, Visser intends to take in account mass for the graviton by means of an additional bimetric tensor in the Einstein's field equations. Our study has shown that a consistent cosmological model arises from Visser's approach. The most interesting feature is that an accelerated expansion phase naturally emerges from the cosmological model, and we do not need to postulate any kind of dark energy to explain the current observational data for distant type Ia supernovae (SNIa).

  2. Modified GBIG Scenario as a Successful Alternative for Dark Energy

    E-Print Network [OSTI]

    Nozari, Kourosh

    2009-01-01T23:59:59.000Z

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

  3. Can Massive Gravitons be an Alternative to Dark Energy?

    E-Print Network [OSTI]

    Alves, Marcio E S; de Araujo, Jose C N

    2009-01-01T23:59:59.000Z

    In this work, we explore some cosmological implications of the model proposed by M. Visser in 1998. In his approach, Visser intends to take in account mass for the graviton by means of an additional bimetric tensor in the Einstein's field equations. Our study has shown that a consistent cosmological model arises from Visser's approach. The most interesting feature is that an accelerated expansion phase naturally emerges from the cosmological model, and we do not need to postulate any kind of dark energy to explain the current observational data for distant type Ia supernovae (SNIa).

  4. Modified GBIG Scenario as an Alternative for Dark Energy

    E-Print Network [OSTI]

    Kourosh Nozari; Narges Rashidi

    2009-09-02T23:59:59.000Z

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

  5. Nonlocal String Tachyon as a Model for Cosmological Dark Energy

    SciTech Connect (OSTI)

    Aref'eva, Irina Ya. [Steklov Mathematical Institute, Russian Academy of Sciences, Gubkin st. 8, Moscow, 119991 (Russian Federation)

    2006-03-29T23:59:59.000Z

    There are many different phenomenological models describing the cosmological dark energy and accelerating Universe by choosing adjustable functions. In this paper we consider a specific model of scalar tachyon field which is derived from the NSR string field theory and study its cosmological applications. We find that in the effective field theory approximation the equation of state parameter w < -1, i.e. one has a phantom Universe. It is shown that due to nonlocal effects there is no quantum instability that the usual phantom models suffer from. Moreover due to a flip effect of the potential the Universe does not enter to a future singularity.

  6. Attaining the Photometric Precision Required by Future Dark Energy Projects

    SciTech Connect (OSTI)

    Stubbs, Christopher

    2013-01-21T23:59:59.000Z

    This report outlines our progress towards achieving the high-precision astronomical measurements needed to derive improved constraints on the nature of the Dark Energy. Our approach to obtaining higher precision flux measurements has two basic components: 1) determination of the optical transmission of the atmosphere, and 2) mapping out the instrumental photon sensitivity function vs. wavelength, calibrated by referencing the measurements to the known sensitivity curve of a high precision silicon photodiode, and 3) using the self-consistency of the spectrum of stars to achieve precise color calibrations.

  7. The Dark Energy Survey: Prospects for Resolved Stellar Populations

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

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

    2011-05-06T23:59:59.000Z

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

  8. High-resolution temporal constraints on the dynamics of dark energy

    E-Print Network [OSTI]

    Gong-Bo Zhao; Dragan Huterer; Xinmin Zhang

    2008-05-18T23:59:59.000Z

    We use the recent type Ia supernova, cosmic microwave background and large-scale structure data to shed light on the temporal evolution of the dark energy equation of state $w(z)$ out to redshift one. We constrain the most flexible parametrization of dark energy to date, and include the dark energy perturbations consistently throughout. Interpreting our results via the principal component analysis, we find no significant evidence for dynamical dark energy: the cosmological constant model is consistent with data everywhere between redshift zero and one at 95% C.L.

  9. Dark Energy Models and Laws of Thermodynamics in Bianchi I Model

    E-Print Network [OSTI]

    M. Sharif; Rabia Saleem

    2013-02-20T23:59:59.000Z

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

  10. New infrared cut-off for the holographic scalar fields models of dark energy

    E-Print Network [OSTI]

    L. N. Granda; A. Oliveros

    2008-10-23T23:59:59.000Z

    Introducing a new infrared cut-off for the holographic dark-energy, we study the correspondence between the quintessence, tachyon, K-essence and dilaton energy density with this holographic dark energy density in the flat FRW universe. This correspondence allows to reconstruct the potentials and the dynamics for the scalar fields models, which describe accelerated expansion.

  11. Hydro-Gravitational-Dynamics of Planets and Dark Energy

    E-Print Network [OSTI]

    Carl H. Gibson; Rudolph E. Schild

    2008-08-24T23:59:59.000Z

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

  12. Dark matter, dark energy and the time evolution of masses in the Universe

    E-Print Network [OSTI]

    Joan Sola

    2014-09-03T23:59:59.000Z

    The traditional "explanation" for the observed acceleration of the universe is the existence of a positive cosmological constant. However, this can hardly be a truly convincing explanation, as an expanding universe is not expected to have a static vacuum energy density. So, it must be an approximation. This reminds us of the so-called fundamental "constants" of nature. Recent and past measurements of the fine structure constant and of the proton-electron mass ratio suggest that basic quantities of the standard model, such as the QCD scale parameter $\\Lambda_{QCD}$, might not be conserved in the course of the cosmological evolution. The masses of the nucleons and of the atomic nuclei would be time-evolving. This can be consistent with General Relativity provided the vacuum energy itself is a dynamical quantity. Another framework realizing this possibility is QHD (Quantum Haplodynamics), a fundamental theory of bound states. If one assumes that its running couplings unify at the Planck scale and that such scale changes slowly with cosmic time, the masses of the nucleons and of the DM particles, including the cosmological term, will evolve with time. This could explain the dark energy of the universe.

  13. Avoiding Boltzmann Brain domination in holographic dark energy models

    E-Print Network [OSTI]

    R. Horvat

    2015-02-23T23:59:59.000Z

    In a spatially infinite and eternal universe approaching ultimately a de Sitter (or quasi-de Sitter) regime, structure can form by thermal fluctuations as such a space is thermal. The models of Dark Energy invoking holographic principle fit naturally into such a category, and spontaneous formation of isolated brains in otherwise empty space seems the most perplexing, creating the paradox of Boltzmann Brains (BB). It is thus appropriate to ask if such models can be made free from domination by Boltzmann Brains. Here we consider only the simplest model, but adopt both the local and the global viewpoint in the description of the Universe. In the former case, we find that if a parameter $c$, which modulates the Dark Energy density, lies outside the exponentially narrow strip around the most natural $c = 1$ line, the theory is rendered BB-safe. In the later case, the bound on $c$ is exponentially stronger, and seemingly at odds with those bounds on $c$ obtained from various observational tests.

  14. DARK ENERGY FROM THE LOG-TRANSFORMED CONVERGENCE FIELD

    SciTech Connect (OSTI)

    Seo, Hee-Jong [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Sato, Masanori [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Chiba 277-8582 (Japan); Dodelson, Scott, E-mail: hee-jongseo@lbl.gov [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

    2012-03-20T23:59:59.000Z

    A logarithmic transform of the convergence field improves 'the information content', i.e., the overall precision associated with the measurement of the amplitude of the convergence power spectrum, by improving the covariance matrix properties. The translation of this improvement in the information content to that in cosmological parameters, such as those associated with dark energy, requires knowing the sensitivity of the log-transformed field to those cosmological parameters. In this paper, we use N-body simulations with ray tracing to generate convergence fields at multiple source redshifts as a function of cosmology. The gain in information associated with the log-transformed field does lead to tighter constraints on dark energy parameters, but only if shape noise is neglected. The presence of shape noise quickly diminishes the advantage of the log-mapping, more quickly than we would expect based on the information content. With or without shape noise, using a larger pixel size allows for a more efficient log-transformation.

  15. Testing Loop Quantum Gravity and Electromagnetic Dark Energy in Superconductors

    E-Print Network [OSTI]

    Clovis Jacinto de Matos

    2009-08-06T23:59:59.000Z

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

  16. Observational constraints on holographic dark energy with varying gravitational constant

    SciTech Connect (OSTI)

    Lu, Jianbo; Xu, Lixin [Institute of Theoretical Physics, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian, 116024 (China); Saridakis, Emmanuel N. [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Setare, M.R., E-mail: lvjianbo819@163.com, E-mail: msaridak@phys.uoa.gr, E-mail: rezakord@ipm.ir, E-mail: lxxu@dlut.edu.cn [Department of Science of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of)

    2010-03-01T23:59:59.000Z

    We use observational data from Type Ia Supernovae (SN), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and observational Hubble data (OHD), and the Markov Chain Monte Carlo (MCMC) method, to constrain the cosmological scenario of holographic dark energy with varying gravitational constant. We consider both flat and non-flat background geometry, and we present the corresponding constraints and contour-plots of the model parameters. We conclude that the scenario is compatible with observations. In 1? we find ?{sub ?0} = 0.72{sup +0.03}{sub ?0.03}, ?{sub k0} = ?0.0013{sup +0.0130}{sub ?0.0040}, c = 0.80{sup +0.19}{sub ?0.14} and ?{sub G}?G'/G = ?0.0025{sup +0.0080}{sub ?0.0050}, while for the present value of the dark energy equation-of-state parameter we obtain w{sub 0} = ?1.04{sup +0.15}{sub ?0.20}.

  17. Avoiding Boltzmann Brain domination in holographic dark energy models

    E-Print Network [OSTI]

    Horvat, R

    2015-01-01T23:59:59.000Z

    In a spatially infinite and eternal universe approaching ultimately a de Sitter (or quasi-de Sitter) regime, structure can form by thermal fluctuations as such a space is thermal. The models of Dark Energy invoking holographic principle fit naturally into such a category, and spontaneous formation of isolated brains in otherwise empty space seems the most perplexing, creating the paradox of Boltzmann Brains (BB). It is thus appropriate to ask if such models can be made free from domination by Boltzmann Brains. Here we consider only the simplest model, but adopt both the local and the global viewpoint in the description of the Universe. In the former case, we find that if a parameter $c$, which modulates the Dark Energy density, lies outside the exponentially narrow strip around the most natural $c = 1$ line, the theory is rendered BB-safe. In the later case, the bound on $c$ is exponentially stronger, and seemingly at odds with those bounds on $c$ obtained from various observational tests.

  18. Probing the imprint of interacting dark energy on very large scales

    E-Print Network [OSTI]

    Duniya, Didam; Maartens, Roy

    2015-01-01T23:59:59.000Z

    The observed galaxy power spectrum acquires relativistic corrections from lightcone effects, and these corrections grow on very large scales. Future galaxy surveys in optical, infrared and radio bands will probe increasingly large wavelength modes and reach higher redshifts. In order to exploit the new data on large scales, an accurate analysis requires inclusion of the relativistic effects. This is especially the case for primordial non-Gaussianity and for extending tests of dark energy models to horizon scales. Here we investigate the latter, focusing on models where the dark energy interacts non-gravitationally with dark matter. Interaction in the dark sector can also lead to large-scale deviations in the power spectrum. If the relativistic effects are ignored, the imprint of interacting dark energy will be incorrectly identified and thus lead to a bias in constraints on interacting dark energy on very large scales.

  19. Thermodynamical description of interacting entropy-corrected new agegraphic dark energy

    E-Print Network [OSTI]

    Kayoomars Karami; Ahmad Sheykhi; Mubasher Jamil; F. Felegary; M. M. Soltanzadeh

    2011-02-16T23:59:59.000Z

    To explain the accelerating universe driven by dark energy, a so-called "entropy-corrected new agegraphic dark energy" (ECNADE), was recently proposed with the help of quantum corrections to the entropy-area relation in the framework of loop quantum cosmology. Using this definition, we study its thermodynamical features including entropy and energy conservation. We discuss the thermodynamical interpretation of the interaction between ECNADE and dark matter in a non-flat universe bounded by the apparent horizon. We obtain a relation between the interaction term of the dark components and thermal fluctuation.

  20. The Parameterized Post-Friedmannian Framework for Interacting Dark Energy Theories

    E-Print Network [OSTI]

    Skordis, C; Copeland, E J

    2015-01-01T23:59:59.000Z

    We present the most general parametrisation of models of dark energy in the form of a scalar field which is explicitly coupled to dark matter. We follow and extend the Parameterized Post-Friedmannian approach, previously applied to modified gravity theories, in order to include interacting dark energy. We demonstrate its use through a number of worked examples and show how the initially large parameter space of free functions can be significantly reduced and constrained to include only a few non-zero coefficients. This paves the way for a model-independent approach to classify and test interacting dark energy theories.

  1. Neutrinos and dark energy after Planck and BICEP2: data consistency tests and cosmological parameter constraints

    E-Print Network [OSTI]

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

    2014-10-17T23:59:59.000Z

    The detection of the B-mode polarization of the cosmic microwave background (CMB) by the BICEP2 experiment implies that the tensor-to-scalar ratio $r$ should be involved in the base standard cosmology. In this paper, we extend the $\\Lambda$CDM+$r$+neutrino/dark radiation models by replacing the cosmological constant with the dynamical dark energy with constant $w$. Four neutrino plus dark energy models are considered, i.e., the $w$CDM+$r+\\sum m_\

  2. A Strategy to Measure the Dark Energy Equation of State using the HII galaxy Hubble Relation & X-ray AGN Clustering: Preliminary Results

    E-Print Network [OSTI]

    M. Plionis; R. Terlevich; S. Basilakos; F. Bresolin; E. Terlevich; J. Melnick; R. Chavez

    2011-06-22T23:59:59.000Z

    We explore the possibility of setting stringent constraints to the Dark Energy equation of state using alternative cosmic tracers like: (a) the Hubble relation using HII galaxies, which can be observed at much higher redshifts (z~3.5) than those currently traced by SNIa samples, and (b) the large-scale structure using the clustering of X-ray selected AGN,which have a redshift distribution peaking at z~1. We use extensive Monte-Carlo simulations to define the optimal strategy for the recovery of the dark-energy equation of state using the high redshift (z~2) Hubble relation, but accounting also for the effects of gravitational lensing, which for such high redshifts can significantly affect the derived cosmological constraints. Based on a "Figure of Merit" analysis, we provide estimates for the number of 2energy equation of state by using the joint likelihood of the X-ray AGN clustering and of the Hubble relation cosmological analyses. A preliminary joint analysis using the X-ray AGN clustering of the 2XMM survey and the Hubble relation of the Constitution SNIa set provide: Omega_m= 0.31+-0.01 and w=-1.06+-0.05. We also find that the joint SNIa-2XMM analysis provides significantly more stringent cosmological constraints, increasing the Figure of Merit by a factor ~2, with respect to that of the joint SNIa-BAO analysis.

  3. Supernova constraints on multi-coupled dark energy

    SciTech Connect (OSTI)

    Piloyan, Arpine [Yerevan State University, Alex Manoogian 1, Yerevan 0025 (Armenia); Marra, Valerio; Amendola, Luca [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Baldi, Marco, E-mail: arpine.piloyan@ysu.am, E-mail: valerio.marra@me.com, E-mail: marco.baldi5@unibo.it, E-mail: l.amendola@thphys.uni-heidelberg.de [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale C. Berti-Pichat 6/2, I-40127, Bologna (Italy)

    2013-07-01T23:59:59.000Z

    The persisting consistency of ever more accurate observational data with the predictions of the standard ?CDM cosmological model puts severe constraints on possible alternative scenarios, but still does not shed any light on the fundamental nature of the cosmic dark sector. As large deviations from a ?CDM cosmology are ruled out by data, the path to detect possible features of alternative models goes necessarily through the definition of cosmological scenarios that leave almost unaffected the background and — to a lesser extent — the linear perturbations evolution of the universe. In this context, the Multi-coupled DE (McDE) model was proposed by Baldi [9] as a particular realization of an interacting Dark Energy field characterized by an effective screening mechanism capable of suppressing the effects of the coupling at the background and linear perturbation level. In the present paper, for the first time, we challenge the McDE scenario through a direct comparison with real data, in particular with the luminosity distance of Type Ia supernovae. By studying the existence and stability conditions of the critical points of the associated background dynamical system, we select only the cosmologically consistent solutions, and confront their background expansion history with data. Confirming previous qualitative results, the McDE scenario appears to be fully consistent with the adopted sample of Type Ia supernovae, even for coupling values corresponding to an associated scalar fifth-force about four orders of magnitude stronger than standard gravity. Our analysis demonstrates the effectiveness of the McDE background screening, and shows some new non-trivial asymptotic solutions for the future evolution of the universe. Clearly, linear perturbation data and, even more, nonlinear structure formation properties are expected to put much tighter constraints on the allowed coupling range. Nonetheless, our results show how the background expansion history might be highly insensitive to the fundamental nature and to the internal complexity of the dark sector.

  4. Interacting Dark Energy Model: Exact Analytic Solution and Equivalent Scenario for MCG and Scalar field

    E-Print Network [OSTI]

    Supriya Pan; Subenoy Chakraborty

    2014-04-02T23:59:59.000Z

    Dark energy models have got tremendous enthusiasm recently both from theoretical and observational point of view. In the present work we assume that the universe at present is dominated by dark matter (DM) and dark energy (DE) which do not evolve separately but interact non-gravitationally with one another and are equivalent to a single dark fluid. We construct explicit solutions for two choices of the equation of state parameter for DE and results are analyzed both graphically as well as analytically. The modified chaplygin gas (MCG) model is shown to be compatible with this effective single dark fluid as well as different interacting holographic dark energy (HDE) models characterized by various IR cut off lengths. Finally, we establish the equivalence between HDE with different scalar field models.

  5. Non-relativistic high-energy physics: top production and dark matter annihilation

    E-Print Network [OSTI]

    Beneke, Martin

    2015-01-01T23:59:59.000Z

    Non-relativistic physics is often associated with atomic physics and low-energy phenomena of the strong interactions between nuclei and quarks. In this review we cover three topics in contemporary high-energy physics at or close to the TeV scale, where non-relativistic dynamics plays an important if not defining role. We first discuss in detail the third-order corrections to top-quark pair production in electron-positron collisions in the threshold region, which plays a major role at a future high-energy e+ e- collider. Threshold effects are also relevant in the production of heavy particles in hadronic collisions, where in addition to the Coulomb force soft gluon radiation contributes to enhanced quantum corrections. We review the joint resummation of non-relativistic and soft gluon effects for pair production of top quarks and supersymmetric particles to next-to-next-to-leading logarithmic accuracy. The third topic deals with pair annihilation of dark matter particles within the framework of the Minimal Sup...

  6. Introduction to Modified Gravity and Gravitational Alternative for Dark Energy

    E-Print Network [OSTI]

    S. Nojiri; S. D. Odintsov

    2006-03-31T23:59:59.000Z

    We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of such theories may pass the Solar System tests. On the same time, it is demonstrated that they have quite rich cosmological structure: they may naturally describe the effective (cosmological constant, quintessence or phantom) late-time era with a possible transition from decceleration to acceleration thanks to gravitational terms which increase with scalar curvature decrease. The possibility to explain the coincidence problem as the manifestation of the universe expansion in such models is mentioned. The late (phantom or quintessence) universe filled with dark fluid with inhomogeneous equation of state (where inhomogeneous terms are originated from the modified gravity) is also described.

  7. Dark Energy and Tachyon Field in Bianchi Type-V Space-time

    E-Print Network [OSTI]

    J. Sadeghi; H. Farahani

    2014-04-15T23:59:59.000Z

    In this paper, we consider Bianchi type-V space-time and study a cosmological model of dark energy based on Tachyon scalar field. We assumed three different kinds of matter without possibility of interaction with scalar dark energy. Assuming power law Hubble parameter in terms of scale factor we obtain evolution of scalar field, scalar potential and equation of state parameter.

  8. Dark energy and dust matter phases from an exact $f(R)$-cosmology model

    E-Print Network [OSTI]

    S. Capozziello; P. Martin-Moruno; C. Rubano

    2008-04-28T23:59:59.000Z

    We show that dust matter-dark energy combined phases can be achieved by the exact solution derived from a power law $f(R)$ cosmological model. This example answers the query by which a dust-dominated decelerated phase, before dark-energy accelerated phase, is needed in order to form large scale structures.

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

    ScienceCinema (OSTI)

    Linder, Eric

    2011-04-28T23:59:59.000Z

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

  10. Puzzles of the dark energy in the universe - phantom

    E-Print Network [OSTI]

    Mariusz P. Dabrowski

    2014-12-30T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    Temple, Blake

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

  12. 2009 ASME WIND ENERGY SYMPOSIUM Static and Fatigue Testing of Thick Adhesive Joints for

    E-Print Network [OSTI]

    1 2009 ASME WIND ENERGY SYMPOSIUM Static and Fatigue Testing of Thick Adhesive Joints for Wind as wind blade size has increased. Typical blade joints use paste adhesives several millimeters thick aircraft, which are also of relevance to wind blades in many instances. The strengths of lap-shear and many

  13. Structure formation in modified gravity models alternative to dark energy

    E-Print Network [OSTI]

    Kazuya Koyama

    2006-01-10T23:59:59.000Z

    We study structure formation in phenomenological models in which the Friedmann equation receives a correction of the form $H^{\\alpha}/r_c^{2-\\alpha}$, which realize an accelerated expansion without dark energy. In order to address structure formation in these model, we construct simple covariant gravitational equations which give the modified Friedmann equation with $\\alpha=2/n$ where $n$ is an integer. For $n=2$, the underlying theory is known as a 5D braneworld model (the DGP model). Thus the models interpolate between the DGP model ($n=2, \\alpha=1$) and the LCDM model in general relativity ($n \\to \\infty, \\alpha \\to 0$). Using the covariant equations, cosmological perturbations are analyzed. It is shown that in order to satisfy the Bianchi identity at a perturbative level, we need to introduce a correction term $E_{\\mu \

  14. Structure formation in modified gravity models alternative to dark energy

    E-Print Network [OSTI]

    Koyama, K

    2006-01-01T23:59:59.000Z

    We study structure formation in phenomenological models in which the Friedmann equation receives a correction of the form $H^{\\alpha}/r_c^{2-\\alpha}$, which realize an accelerated expansion without dark energy. In order to address structure formation in these model, we construct simple covariant gravitational equations which give the modified Friedmann equation with $\\alpha=2/n$ where $n$ is an integer. For $n=2$, the underlying theory is known as a 5D braneworld model (the DGP model). Thus the models interpolate between the DGP model ($n=2, \\alpha=1$) and the LCDM model in general relativity ($n \\to \\infty, \\alpha \\to 0$). Using the covariant equations, cosmological perturbations are analyzed. It is shown that in order to satisfy the Bianchi identity at a perturbative level, we need to introduce a correction term $E_{\\mu \

  15. Non-Abelian condensates as alternative for dark energy

    E-Print Network [OSTI]

    Gal'tsov, Dmitri V

    2009-01-01T23:59:59.000Z

    We review basic features of cosmological models with large-scale classical non-Abelian Yang-Mills (YM) condensates. There exists a unique SU(2) YM configuration (generalizable to larger gauge groups) compatible with homogeneity and isotropy of the three-space which is parameterized by a single scalar field. In the past various aspects of Einstein-Yang-Mills (EYM) cosmology were discussed in the context of the Early Universe. Due to conformal invariance, solvable EYM FRW models exist both on the classical and quantum levels. To develop the YM model for dark energy one has to find mechanisms of the conformal symmetry breaking. We discuss the Born-Infeld generalization and some phenomenological models motivated by quantum corrections exploring possibility of transient DE and phantom regimes.

  16. Non-Abelian condensates as alternative for dark energy

    E-Print Network [OSTI]

    Dmitri V. Gal'tsov

    2008-12-31T23:59:59.000Z

    We review basic features of cosmological models with large-scale classical non-Abelian Yang-Mills (YM) condensates. There exists a unique SU(2) YM configuration (generalizable to larger gauge groups) compatible with homogeneity and isotropy of the three-space which is parameterized by a single scalar field. In the past various aspects of Einstein-Yang-Mills (EYM) cosmology were discussed in the context of the Early Universe. Due to conformal invariance, solvable EYM FRW models exist both on the classical and quantum levels. To develop the YM model for dark energy one has to find mechanisms of the conformal symmetry breaking. We discuss the Born-Infeld generalization and some phenomenological models motivated by quantum corrections exploring possibility of transient DE and phantom regimes.

  17. Exploring holographic dark energy model with Sandage-Loeb test

    E-Print Network [OSTI]

    Hongbao Zhang; Wuhan Zhong; Zong-Hong Zhu; Song He

    2007-11-14T23:59:59.000Z

    Taking into account that Sandage-Loeb test is unique in its coverage of the redshift desert and available in the near future, we explore the cosmic time evolution behavior of the source redshift for holographic dark energy model, an important competing cosmological model. As a result, we find that Sandage-Loeb test can provide a extremely strong bound on $\\Omega^0_m$, while its constraint on another dimensionless parameter $\\lambda$ is weak. In addition, it is proposed here for the first time that we can also constrain various cosmological model by measuring the value of $z_{max}$ at which the peak of redshift velocity occurs. Combining this new proposed method with the traditional Sandage-Loeb test, we should be able to provide a better constraint on $\\lambda$, at least from the theoretical perspective.

  18. Planck 2015 results. XIV. Dark energy and modified gravity

    E-Print Network [OSTI]

    Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Battye, R; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Désert, F -X; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Heavens, A; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huang, Z; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Lewis, A; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Ma, Y -Z; Macías-Pérez, J F; Maggio, G; Mandolesi, N; Mangilli, A; Marchini, A; Martin, P G; Martinelli, M; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Narimani, A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Pearson, T J; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rowan-Robinson, M; Rubiño-Martín, J A; Rusholme, B; Salvatelli, V; Sandri, M; Santos, D; Savelainen, M; Savini, G; Schaefer, B M; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Viel, M; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; White, M; Yvon, D; Zacchei, A; Zonca, A

    2015-01-01T23:59:59.000Z

    We study the implications of Planck data for models of dark energy (DE) and modified gravity (MG), beyond the cosmological constant scenario. We start with cases where the DE only directly affects the background evolution, considering Taylor expansions of the equation of state, principal component analysis and parameterizations related to the potential of a minimally coupled DE scalar field. When estimating the density of DE at early times, we significantly improve present constraints. We then move to general parameterizations of the DE or MG perturbations that encompass both effective field theories and the phenomenology of gravitational potentials in MG models. Lastly, we test a range of specific models, such as k-essence, f(R) theories and coupled DE. In addition to the latest Planck data, for our main analyses we use baryonic acoustic oscillations, type-Ia supernovae and local measurements of the Hubble constant. We further show the impact of measurements of the cosmological perturbations, such as redshif...

  19. Mega-masers, Dark Energy and the Hubble Constant

    SciTech Connect (OSTI)

    Lo, Fred K. Y.

    2007-10-15T23:59:59.000Z

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

  20. 9/18/09 2:09 PM'Big Wave' Theory Offers Alternative to Dark Energy -Physical Science Page 1 of 3http://scienceblips.dailyradar.com/story/big_wave_theory_offers_alternative_to_dark_energy/

    E-Print Network [OSTI]

    Temple, Blake

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

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

    E-Print Network [OSTI]

    Temple, Blake

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

  2. A Simple Asymptotically Optimal Joint Energy Allocation and Routing Scheme in Rechargeable

    E-Print Network [OSTI]

    Sinha, Prasun

    1 A Simple Asymptotically Optimal Joint Energy Allocation and Routing Scheme in Rechargeable Sensor problem for a sensor network with energy replenishment. Each sensor node consumes energy in its battery be replenished from renewable energy sources, the energy allocation should be carefully designed in order

  3. The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Energy, LLC, on behalf of the U.S. Department of Energy's

    E-Print Network [OSTI]

    The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Energy, LLC, on behalf of the Alliance for Sustainable Energy, LLC. The Joint Institute for Strategic Energy Analysis 15013 Denver West

  4. Low Energy Nuclear Recoil Response in Xenon Gas for Low Mass Dark Matter WIMP Search

    E-Print Network [OSTI]

    Sofka, Clement James

    2014-04-16T23:59:59.000Z

    Massive Particles (WIMPs) and dark energy. Initial cosmological considerations suggested that WIMPs were some type of Standard Model (SM) particle, but even the best-case estimates lead to matter energy densities that come up well short without a...

  5. New Camera Sheds Light on Dark Energy | Department of 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's Possible for Renewable Energy:Nanowire Solar541,9337, 2011R - 445 CU - 2 3 1

  6. New Camera Sheds Light on Dark Energy | Department of Energy

    Office of Environmental Management (EM)

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742 33Frequently Asked QuestionsDepartment ofDepartment of Energy New Air andEnergyDepartment

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

    E-Print Network [OSTI]

    Basilakos, S

    2008-01-01T23:59:59.000Z

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

  8. Sudden Future Singularity models as an alternative to Dark Energy?

    E-Print Network [OSTI]

    Ghodsi, Hoda; Dabrowski, Mariusz P; Denkiewicz, Tomasz

    2011-01-01T23:59:59.000Z

    Current observational evidence does not yet exclude the possibility that dark energy could be in the form of phantom energy. A universe consisting of a phantom constituent will be driven toward a drastic end known as the `Big Rip' singularity where all the matter in the universe will be destroyed. Motivated by this possibility, other evolutionary scenarios have been explored by Barrow, including the phenomena which he called Sudden Future Singularities (SFS). In such a model it is possible to have a blow up of the pressure occurring at sometime in the future evolution of the universe while the energy density would remain unaffected. The particular evolution of the scale factor of the universe in this model that results in a singular behaviour of the pressure also admits acceleration in the current era. In this paper we will present the results of our confrontation of one example class of SFS models with the available cosmological data from high redshift supernovae, baryon acoustic oscillations (BAO) and the c...

  9. Dark River, Minnesota: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand JumpConceptual Model,DOE Facility Database Data and Resources11-DNADalyDanishDarajatDarien,

  10. alternative dark energy: Topics by E-print Network

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

    universe with the local Big Bang and everlasting expansion is demonstrated. Dark matter can be essentially contributed by the non-relativistic massive neutrinos, which have...

  11. The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Energy, LLC, on behalf of the U.S. Department of Energy's

    E-Print Network [OSTI]

    The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Analysis is operated by the Alliance for Sustainable Energy, LLC, on behalf of the U.S. Department Energy, LLC. The Joint Institute for Strategic Energy Analysis 15013 Denver West Parkway Golden, Colorado

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

    E-Print Network [OSTI]

    A. E. Shalyt-Margolin

    2010-04-16T23:59:59.000Z

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

  13. Holographic thermalization and gravitational collapse in the spacetime dominated by quintessence dark energy

    E-Print Network [OSTI]

    Xiao-Xiong Zeng; De-You Chen; Li-Fang Li

    2014-12-21T23:59:59.000Z

    In this paper, the thermalization has been studied holographically. Explicitly in the gravity side, we consider the gravitational collapse of a thin shell of dust in a spacetime dominated by quintessence dark energy. With the thermalization probes such as the normalized geodesic length and minimal area surface, we study the effect of the state parameter for the quintessence dark energy on the thermalization. Our results show that the smaller the state parameter of quintessence is, the harder the plasma to thermalize. We also investigate the thermalization velocity and thermalization acceleration. We hope our results here can shed light on the nature of the quintessence dark energy.

  14. How CMB and large-scale structure constrain chameleon interacting dark energy

    E-Print Network [OSTI]

    Boriero, Daniel; Wong, Yvonne Y Y

    2015-01-01T23:59:59.000Z

    We explore a chameleon type of interacting dark matter-dark energy scenario in which a scalar field adiabatically traces the minimum of an effective potential sourced by the dark matter density. We discuss extensively the effect of this coupling on cosmological observables, especially the parameter degeneracies expected to arise between the model parameters and other cosmological parameters, and then test the model against observations of the cosmic microwave background (CMB) anisotropies and other cosmological probes. We find that the chameleon parameters $\\alpha$ and $\\beta$, which determine respectively the slope of the scalar field potential and the dark matter-dark energy coupling strength, can be constrained to $\\alpha < 0.17$ and $\\beta < 0.19$ using CMB data alone. The latter parameter in particular is constrained only by the late Integrated Sachs-Wolfe effect. Adding measurements of the local Hubble expansion rate $H_0$ tightens the bound on $\\alpha$ by a factor of two, although this apparent i...

  15. Testing models of vacuum energy interacting with cold dark matter

    E-Print Network [OSTI]

    Li, Yun-He; Zhang, Xin

    2015-01-01T23:59:59.000Z

    We test the models of vacuum energy interacting with cold dark matter, and try to probe the possible deviation from the $\\Lambda$CDM model using current observations. We focus on two specific models, $Q=3\\beta H\\rho_{\\Lambda}$ and $Q=3\\beta H\\rho_c$. The data combinations come from the Planck 2013 data, the baryon acoustic oscillations measurements, the Type-Ia supernovae data, the Hubble constant measurement, the redshift space distortions data and the galaxy weak lensing data. For the $Q=3\\beta H\\rho_c$ model, we find that it can be tightly constrained by all the data combinations, while for the $Q=3\\beta H\\rho_{\\Lambda}$ model there still exist significant degeneracies between parameters. The tightest constraints for the coupling constant are $\\beta=-0.026^{+0.036}_{-0.053}$ (for $Q=3\\beta H\\rho_{\\Lambda}$) and $\\beta=-0.00045\\pm0.00069$ (for $Q=3\\beta H\\rho_c$) at $1\\sigma$ level. For all the fit results, we find that the null interaction $\\beta=0$ is always consistent with data. Our work completes the di...

  16. Utility of observational Hubble parameter data on dark energy evolution

    E-Print Network [OSTI]

    Meng, Xiao-Lei; Li, Shi-Yu; Zhang, Tong-Jie

    2015-01-01T23:59:59.000Z

    Aiming at exploring the nature of dark energy, we use thirty-six observational Hubble parameter data (OHD) in the redshift range $0 \\leqslant z \\leqslant 2.36$ to make a cosmological model-independent test of the two-point $Omh^2(z_{2};z_{1})$ diagnostic. In $\\Lambda$CDM, we have $Omh^2 \\equiv \\Omega_{m}h^2$, where $\\Omega_{m}$ is the matter density parameter at present. We bin all the OHD into four data points to mitigate the observational contaminations. By comparing with the value of $\\Omega_{m}h^2$ which is constrained tightly by the Planck observations, our results show that in all six testing pairs of $Omh^2$ there are two testing pairs are consistent with $\\Lambda$CDM at $1\\sigma$ confidence level (CL), whereas for another two of them $\\Lambda$CDM can only be accommodated at $2\\sigma$ CL. Particularly, for remaining two pairs, $\\Lambda$CDM is not compatible even at $2\\sigma$ CL. Therefore it is reasonable that although deviations from $\\Lambda$CDM exist for some pairs, cautiously, we cannot rule out th...

  17. New holographic Chaplygin gas model of dark energy

    E-Print Network [OSTI]

    M. Malekjani; A. Khodam-Mohammadi

    2010-11-20T23:59:59.000Z

    In this work, we investigate the holographic dark energy model with new infrared cut-off (new HDE model) proposed by Granda and Oliveros. Using this new definition for infrared cut-off, we establish the correspondence between new HDE model and standard Chaplygin gas (SCG), generalized Chaplygin gas (GCG) and modified Chaplygin gas (MCG) scalar field models in non-flat universe. The potential and dynamics for these scalar field models, which describe the accelerated expansion of the universe are reconstructed. According to the evolutionary behavior of new HDE model, we derive the same form of dynamics and potential for different SCG, GCG and MCG models. We also calculate the squared sound speed of new HDE model as well as for SCG, GCG and MCG models and investigate the new HDE Chaplygin gas models from the viewpoint of linear perturbation theory. All results in non-flat universe are also discussed in the limiting case of flat universe, i.e. $k=0$.

  18. Search for dark energy potentials in quintessence theory

    E-Print Network [OSTI]

    Muromachi, Yusuke; Okada, Daiki; Hara, Tetsuya; Itoh, Yutaka

    2015-01-01T23:59:59.000Z

    The time evolution of the equation of state $w$ for quintessence models with a scalar field as dark energy is studied up to the third derivative ($d^3w/da^3$) with respect to scale factor $a$, in order to predict the future observations and specify the scalar potential parameters with the observables. The third derivative of $w$ for general potential $V$ was derived and applied to several types of potential. They are the inverse power-law ($V=M^{4+\\alpha}/Q^{\\alpha}$), exponential ($V=M^4\\exp{(\\beta M/Q)}$), mixed ( $V=M^{4+\\gamma}\\exp{(\\beta M/Q)}/Q^{\\gamma}$), cosine ($V=M^4(\\cos (Q/f)+1)$) and the Gaussian types ($V=M^4\\exp(-Q^2/\\sigma^2)$), which are prototypical potentials for the freezing and thawing models. If the parameter number for a potential form is $ n$, it is necessary to find at least for $n+2$ independent observations to identify the potential form and the evolution of scalar field ($Q$ and $ \\dot{Q} $). Such observations would be the values of $ \\Omega_Q, w, dw/da. \\cdots $, and $ dw^n/da^n$....

  19. Statefinder hierarchy exploration of the extended Ricci dark energy

    E-Print Network [OSTI]

    Yu, Fei; Zhang, Jing-Fei; Zhang, Xin

    2015-01-01T23:59:59.000Z

    We apply the statefinder hierarchy plus the fractional growth parameter to explore the extended Ricci dark energy (ERDE) model, in which there are two independent coefficients $\\alpha$ and $\\beta$. By adjusting them, we plot evolution trajectories of some typical parameters, including Hubble expansion rate $E$, deceleration parameter $q$, the third and fourth order hierarchy $S_3^{(1)}$ and $S_4^{(1)}$ and fractional growth parameter $\\epsilon$, respectively, as well as several combinations of them. For the case of variable $\\alpha$ and constant $\\beta$, in the low-redshift region the evolution trajectories of $E$ are in high degeneracy and that of $q$ separate somewhat. However, the $\\Lambda$CDM model is confounded with ERDE in both of these two cases. $S_3^{(1)}$ and $S_4^{(1)}$, especially the former, perform much better. They can differentiate well only varieties of cases within ERDE except $\\Lambda$CDM in the low-redshift region. For high-redshift region, combinations $\\{S_n^{(1)},\\epsilon\\}$ can break t...

  20. Modeling the Transfer Function for the Dark Energy Survey

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

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

    2015-03-10T23:59:59.000Z

    We present a forward-modelling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function -- a mapping from cosmological and astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator, Berge et al. 2013) and catalogs representative of the DES data. In this work we simulate the 244 deg2 coadd images and catalogs in 5 bands for the DES Science Verification (SV) data. The simulation output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples, star/galaxy classification and proximity effects on object detection, are then used to demonstrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modelling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies which is sufficiently realistic and highly controllable.

  1. Modeling the Transfer Function for the Dark Energy Survey

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

    Chang, C.; Busha, M. T.; Wechsler, R. H.; Refregier, A.; Amara, A.; Rykoff, E.; Becker, M. R.; Bruderer, C.; Gamper, L.; Leistedt, B.; et al

    2015-03-10T23:59:59.000Z

    We present a forward-modelling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function -- a mapping from cosmological and astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator, Berge et al. 2013) and catalogs representative of the DES data. In this work we simulate the 244 deg2 coadd images and catalogs in 5 bands for the DES Science Verification (SV) data. The simulationmore »output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples, star/galaxy classification and proximity effects on object detection, are then used to demonstrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modelling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies which is sufficiently realistic and highly controllable.« less

  2. Modelling the Transfer Function for the Dark Energy Survey

    SciTech Connect (OSTI)

    Chang, C.

    2014-10-31T23:59:59.000Z

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

  3. Automated Transient Identification in the Dark Energy Survey

    E-Print Network [OSTI]

    Goldstein, D A; Fischer, J A; Foley, R J; Gupta, R R; Kessler, R; Kim, A G; Nichol, R C; Nugent, P; Papadopoulos, A; Sako, M; Smith, M; Sullivan, M; Thomas, R C; Wester, W; Wolf, R C; Abdalla, F B; Banerji, M; Benoit-Lévy, A; Bertin, E; Brooks, D; Rosell, A Carnero; Castander, F J; da Costa, L N; Covarrubias, R; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Eifler, T F; Neto, A Fausti; Finley, D A; Flaugher, B; Fosalba, P; Frieman, J; Gerdes, D; Gruen, D; Gruendl, R A; James, D; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Maia, M A G; Makler, M; March, M; Marshall, J L; Martini, P; Merritt, K W; Miquel, R; Nord, B; Ogando, R; Plazas, A A; Romer, A K; Roodman, A; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Walker, A R

    2015-01-01T23:59:59.000Z

    We describe an algorithm for identifying point-source transients and moving objects on reference-subtracted optical images containing artifacts of processing and instrumentation. The algorithm makes use of the supervised machine learning technique known as Random Forest. We present results from its use in the Dark Energy Survey Supernova program (DES-SN), where it was trained using a sample of 898,963 signal and background events generated by the transient detection pipeline. After reprocessing the data collected during the first DES-SN observing season (Sep. 2013 through Feb. 2014) using the algorithm, the number of transient candidates eligible for human scanning decreased by a factor of 13.4, while only 1 percent of the artificial Type Ia supernovae (SNe) injected into search images to monitor survey efficiency were lost, most of which were very faint events. Here we characterize the algorithm's performance in detail, and we discuss how it can inform pipeline design decisions for future time-domain imaging...

  4. The Random Energy Model in a Magnetic Field and Joint SourceChannel Coding

    E-Print Network [OSTI]

    Merhav, Neri

    the ensemble performance (random coding exponents) of joint source­channel codes to the free energy of the REM to the free energies in the various phases of the phase diagram. While the above­described relation takes to the free energy of the REM in its different phases. The outline of this paper is as follows. In Section 2

  5. The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable Energy, LLC, on behalf of the U.S. Department of Energy's

    E-Print Network [OSTI]

    The Joint Institute for Strategic Energy Analysis is operated by the Alliance for Sustainable/TP-6A50-60052 February 2014 #12;The Joint Institute for Strategic Energy Analysis is operated Institute for Strategic Energy Analysis 15013 Denver West Parkway Golden, CO 80401 303-275-3000 · www

  6. Galaxy clusters and structure formation in quintessence versus phantom dark energy universe

    E-Print Network [OSTI]

    Zacharias Roupas; Minos Axenides; George Georgiou; Emmanuel N. Saridakis

    2014-04-13T23:59:59.000Z

    The self-gravitating gas in the Newtonian limit is studied in the presence of dark energy with a linear and constant equation of state. Entropy extremization associates to the isothermal Boltzmann distribution an effective density that includes `dark energy particles', which either strengthen or weaken mutual gravitational attraction, in case of quintessence or phantom dark energy, respectively, that satisfy a linear equation of state. Stability is studied for microcanonical (fixed energy) and canonical (fixed temperature) ensembles. Compared to the previously studied cosmological constant case, in the present work it is found that quintessence increases, while phantom dark energy decreases the instability domain under gravitational collapse. Thus, structures are more easily formed in a quintessence rather than in a phantom dominated Universe. Assuming that galaxy clusters are spherical, nearly isothermal and in hydrostatic equilibrium we find that dark energy with a linear and constant equation of state, for fixed radius, mass and temperature, steepens their total density profile. In case of a cosmological constant, this effect accounts for a 1.5% increase in the density contrast, that is the center to edge density ratio of the cluster. We also propose a method to constrain phantom dark energy.

  7. Power Law Entropy Corrected New-Agegraphic Dark Energy in Ho?ava-Lifshitz Cosmology

    E-Print Network [OSTI]

    K. Karami; A. Sheykhi; Mubasher Jamil; R. Myrzakulov; S. Ghaffari; A. Abdolmaleki

    2012-03-31T23:59:59.000Z

    We investigate the new agegraphic dark energy (NADE) model with power-law corrected entropy in the framework of Ho\\v{r}ava-Lifshitz cosmology. For a non-flat universe containing the interacting power-law entropy-corrected NADE (PLECNADE) with dark matter, we obtain the differential equation of the evolution of density parameter as well as the deceleration parameter. To study parametric behavior, we used an interesting form of state parameter as function of redshift $\\omega_{\\Lambda}(z)=\\omega_0+\\omega_1 z$. We found that phantom crossing occurs for the state parameter for a non-zero coupling parameter, thus supporting interacting dark energy model.

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

    E-Print Network [OSTI]

    M. R. Setare; Mubasher Jamil

    2010-08-27T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    Santos, Emilio

    2010-01-01T23:59:59.000Z

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

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

    E-Print Network [OSTI]

    Emilio Santos

    2009-12-30T23:59:59.000Z

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

  11. Utilizing the Updated Gamma-Ray Bursts and Type Ia Supernovae to Constrain the Cardassian Expansion Model and Dark Energy

    E-Print Network [OSTI]

    Wei, Jun-Jie; Wu, Xue-Feng

    2015-01-01T23:59:59.000Z

    We update gamma-ray burst (GRB) luminosity relations among certain spectral and light-curve features with 139 GRBs. The distance modulus of 82 GRBs at $z>1.4$ can be calibrated with the sample at $z\\leq1.4$ by using the cubic spline interpolation method from the Union2.1 Type Ia supernovae (SNe Ia) set. We investigate the joint constraints on the Cardassian expansion model and dark energy with 580 Union2.1 SNe Ia sample ($z<1.4$) and 82 calibrated GRBs data ($1.4dark energy models in which the equation of state $w(z)$ is parametrized as $w(z)=w_{0}$ and $w(z)=w_{0}+w_{1}z/(1+z)$, respectively. Based on o...

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

    E-Print Network [OSTI]

    Ariadna Montiel; Nora Bretón

    2012-02-14T23:59:59.000Z

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

  13. Contact Term, its Holographic Description in QCD and Dark Energy

    E-Print Network [OSTI]

    Ariel R. Zhitnitsky

    2012-08-01T23:59:59.000Z

    In this work we study the well known contact term, which is the key element in resolving the so-called $U(1)_A$ problem in QCD. We study this term using the dual Holographic Description. We argue that in the dual picture the contact term is saturated by the D2 branes which can be interpreted as the tunnelling events in Minkowski space-time. We quote a number of direct lattice results supporting this identification. We also argue that the contact term receives a Casimir -like correction $\\sim (\\Lqcd R)^{-1}$ rather than naively expected $\\exp(-\\Lqcd R)$ when the Minkowski space-time ${\\cal R}_{3,1}$ is replaced by a large but finite manifold with a size $R$. Such a behaviour is consistent with other QFT-based computations when power like corrections are due to nontrivial properties of topological sectors of the theory. In holographic description such a behaviour is due to massless Ramond-Ramond (RR) field living in the bulk of multidimensional space when power like corrections is a natural outcome of massless RR field. In many respects the phenomenon is similar to the Aharonov -Casher effect when the "modular electric field" can penetrate into a superconductor where the electric field is exponentially screened. The role of "modular operator" from Aharonov -Casher effect is played by large gauge transformation operator $\\cal{T}$ in 4d QCD, resulting the transparency of the system to topologically nontrivial pure gauge configurations. We discuss some profound consequences of our findings. In particular, we speculate that a slow variation of the contact term in expanding universe might be the main source of the observed Dark Energy.

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

    E-Print Network [OSTI]

    James G. Gilson

    2010-07-20T23:59:59.000Z

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

  15. JOINT SOURCE-CHANNEL CODING AND POWER ALLOCATION FOR ENERGY EFFICIENT WIRELESS VIDEO COMMUNICATIONS

    E-Print Network [OSTI]

    Kuzmanovic, Aleksandar

    utilization of transmission energy is a critical design consideration [5]. Besides FEC, adjustmentJOINT SOURCE-CHANNEL CODING AND POWER ALLOCATION FOR ENERGY EFFICIENT WIRELESS VIDEO COMMUNICATIONS F. Zhai, Y. Eisenberg, T. N. Pappas, R. Berry, and A. K. Katsaggelos Department of Electrical

  16. The European Joint Undertaking for ITER and the Development of Fusion Energy

    E-Print Network [OSTI]

    1 The European Joint Undertaking for ITER and the Development of Fusion Energy (Fusion for Energy Agreement · Last meeting of negotiators took place in Jeju, China in November 2005 · Meeting of legal experts in Barcelona last week resolved most remaining issues #12;3 Tentative ITER Timetable · Political

  17. Ultra low energy results and their impact to dark matter and low energy neutrino physics

    E-Print Network [OSTI]

    E. Bougamont; P. Colas; J. Derre; I. Giomataris; G. Gerbier; M. Gros; P. Magnier; X. F. Navick; P. Salin; I. Savvidis; G. Tsiledakis; J. D. Vergados

    2010-10-20T23:59:59.000Z

    We present ultra low energy results taken with the novel Spherical Proportional Counter. The energy threshold has been pushed down to about 25 eV and single electrons are clearly collected and detected. To reach such performance low energy calibration systems have been successfully developed: - A pulsed UV lamp extracting photoelectrons from the inner surface of the detector - Various radioactive sources allowing low energy peaks through fluorescence processes. The bench mark result is the observation of a well resolved peak at 270 eV due to carbon fluorescence which is unique performance for such large-massive detector. It opens a new window in dark matter and low energy neutrino search and may allow detection of neutrinos from a nuclear reactor or from supernova via neutrino-nucleus elastic scattering

  18. Distinguishing interacting dark energy from wCDM with CMB, lensing, and baryon acoustic oscillation data

    E-Print Network [OSTI]

    Valiviita, Jussi

    2015-01-01T23:59:59.000Z

    We employ the Planck 2013 CMB temperature anisotropy and lensing data, and baryon acoustic oscillation (BAO) data to constrain a phenomenological $w$CDM model, where dark matter and dark energy interact. We assume time-dependent equation of state parameter for dark energy, and treat dark matter and dark energy as fluids whose energy-exchange rate is proportional to the dark-matter density. The CMB data alone leave a strong degeneracy between the interaction rate and the physical CDM density parameter today, $\\omega_c$, allowing a large interaction rate $|\\Gamma| \\sim H_0$. However, as has been known for a while, the BAO data break this degeneracy. Moreover, we exploit the CMB lensing potential likelihood, which probes the matter perturbations at redshift $z \\sim 2$ and is very sensitive to the growth of structure, and hence one of the tools for discerning between the $\\Lambda$CDM model and its alternatives. However, we find that in the non-phantom models ($w_{\\mathrm{de}}>-1$), the constraints remain unchange...

  19. Scaling Dark Energy in a Five-Dimensional Bouncing Cosmological Model

    E-Print Network [OSTI]

    Lixin Xu; Hongya Liu

    2005-12-31T23:59:59.000Z

    We consider a 5-dimensional Ricci flat bouncing cosmological model in which the 4-dimensional induced matter contains two components at late times - the cold dark matter (CDM)+baryons and dark energy. We find that the arbitrary function $f(z)$ contained in the solution plays a similar role as the potential $V(\\phi)$ in quintessence and phantom dark energy models. To resolve the coincidence problem, it is generally believed that there is a scaling stage in the evolution of the universe. We analyze the condition for this stage and show that a hyperbolic form of the function $f(z)$ can work well in this property. We find that during the scaling stage (before $z\\approx 2$), the dark energy behaves like (but not identical to) a cold dark matter with an adiabatic sound speed $c_{s}^{2}\\approx 0$ and $p_{x}\\approx 0$. After $z\\approx 2$, the pressure of dark energy becomes negative. The transition from deceleration to acceleration happens at $z_{T}\\approx 0.8$ which, as well as other predictions of the $5D$ model, agree with current observations.

  20. Dynamical 3-Space: Supernovae and the Hubble Expansion - Older Universe and End of Dark Energy

    E-Print Network [OSTI]

    Reginald T Cahill

    2007-06-05T23:59:59.000Z

    We apply the new dynamics of 3-space to cosmology by deriving a Hubble expansion solution. This dynamics involves two constants; G and alpha - the fine structure constant. This solution gives an excellent parameter-free fit to the recent supernova and gamma-ray burst data without the need for `dark energy' or `dark matter'. The data and theory together imply an older age for the universe of some 14.7Gyrs. Various problems such as fine tuning, the event horizon problem etc are now resolved. A brief review discusses the origin of the 3-space dynamics and how that dynamics explained the bore hole anomaly, spiral galaxy flat rotation speeds, the masses of black holes in spherical galaxies, gravitational light bending and lensing, all without invoking `dark matter' or `dark energy'. These developments imply that a new understanding of the universe is now available.

  1. Joint Statement of the U.S.-Iraq Joint Coordinating Committee on Energy |

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    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 Home Page onYouTube YouTube Note: Since the.pdfBreaking ofOil & Gas » MethaneJohnson Controls EnergyJoinChina, India and

  2. Dynamical Systems analysis of an interacting dark energy model in the Brane Scenario

    E-Print Network [OSTI]

    Biswas, Sujay Kr

    2015-01-01T23:59:59.000Z

    In this paper, we investigate the background dynamics in brane cosmology when dark energy is coupled to dark matter by a suitable interaction. Here we consider an homogeneous and isotropic Friedmann-Robertson-Walker (FRW) brane model and the evolution equations are reduced to an autonomous system by suitable transformation of variables. The nature of critical points are analyzed by evaluating the eigenvalues of linearized Jacobi matrix. Finally, the classical stability of the model is also studied.

  3. Accretion of Dark Energy onto Higher Dimensional Charged BTZ Black Hole

    E-Print Network [OSTI]

    Ujjal Debnath

    2014-09-15T23:59:59.000Z

    In this work, we have studied the accretion of $(n+2)$-dimensional charged BTZ black hole (BH). The critical point and square speed of sound have been obtained. The mass of the BTZ BH has been calculated and we have observed that the mass of the BTZ BH is related with square root of the energy density of dark energy which accretes onto BH in our accelerating FRW universe. We have assumed modified Chaplygin gas (MCG) as a candidate of dark energy which accretes onto BH and we have found the expression of BTZ BH mass. Since in our solution of MCG, this model generates only quintessence dark energy (not phantom) and so BTZ BH mass increases during the whole evolution of the accelerating universe. Next we have assumed 5 kinds of parametrizations of well known dark energy models. These models generate both quintessence and phantom scenarios i.e., phantom crossing models. So if these dark energies accrete onto the BTZ BH, then in quintessence stage, BH mass increases upto a certain value (finite value) and then decreases to a certain finite value for phantom stage during whole evolution of the universe. We have shown these results graphically.

  4. Modified Regge calculus as an explanation of dark energy

    E-Print Network [OSTI]

    W. M. Stuckey; T. J. McDevitt; M. Silberstein

    2012-01-26T23:59:59.000Z

    Using Regge calculus, we construct a Regge differential equation for the time evolution of the scale factor $a(t)$ in the Einstein-de Sitter cosmology model (EdS). We propose two modifications to the Regge calculus approach: 1) we allow the graphical links on spatial hypersurfaces to be large, as in direct particle interaction when the interacting particles reside in different galaxies, and 2) we assume luminosity distance $D_L$ is related to graphical proper distance $D_p$ by the equation $D_L = (1+z)\\sqrt{\\overrightarrow{D_p}\\cdot \\overrightarrow{D_p}}$, where the inner product can differ from its usual trivial form. The modified Regge calculus model (MORC), EdS and $\\Lambda$CDM are compared using the data from the Union2 Compilation, i.e., distance moduli and redshifts for type Ia supernovae. We find that a best fit line through $\\displaystyle \\log{(\\frac{D_L}{Gpc})}$ versus $\\log{z}$ gives a correlation of 0.9955 and a sum of squares error (SSE) of 1.95. By comparison, the best fit $\\Lambda$CDM gives SSE = 1.79 using $H_o$ = 69.2 km/s/Mpc, $\\Omega_{M}$ = 0.29 and $\\Omega_{\\Lambda}$ = 0.71. The best fit EdS gives SSE = 2.68 using $H_o$ = 60.9 km/s/Mpc. The best fit MORC gives SSE = 1.77 and $H_o$ = 73.9 km/s/Mpc using $R = A^{-1}$ = 8.38 Gcy and $m = 1.71\\times 10^{52}$ kg, where $R$ is the current graphical proper distance between nodes, $A^{-1}$ is the scaling factor from our non-trival inner product, and $m$ is the nodal mass. Thus, MORC improves EdS as well as $\\Lambda$CDM in accounting for distance moduli and redshifts for type Ia supernovae without having to invoke accelerated expansion, i.e., there is no dark energy and the universe is always decelerating.

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

    E-Print Network [OSTI]

    Rahul Ghosh; Surajit Chattopadhyay; Ujjal Debnath

    2011-10-22T23:59:59.000Z

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

  6. A closer look at interacting dark energy with statefinder hierarchy and growth rate of structure

    E-Print Network [OSTI]

    Yin, Lu; Cui, Jing-Lei; Li, Yun-He; Zhang, Xin

    2015-01-01T23:59:59.000Z

    We investigate the interacting dark energy models by using the diagnostics of statefinder hierarchy and growth rate of structure. We wish to explore the deviations from $\\Lambda$CDM and to differentiate possible degeneracies in the interacting dark energy models with the geometrical and structure growth diagnostics. We consider two interacting forms for the models, i.e., $Q_1=\\beta H\\rho_c$ and $Q_2=\\beta H\\rho_{de}$, with $\\beta$ being the dimensionless coupling parameter. Our focus is the I$\\Lambda$CDM model that is a one-parameter extension to $\\Lambda$CDM by considering a direct coupling between the vacuum energy ($\\Lambda$) and cold dark matter (CDM), with the only additional parameter $\\beta$. But we begin with a more general case by considering the I$w$CDM model in which dark energy has a constant $w$ (equation-of-state parameter). For calculating the growth rate of structure, we employ the "parametrized post-Friedmann" theoretical framework for interacting dark energy to numerically obtain the $\\epsil...

  7. Primordial non-Gaussianity and Dark Energy constraints from Cluster Surveys

    SciTech Connect (OSTI)

    Sefusatti, Emiliano; Vale, Chris; /Fermilab; Kadota, Kenji; /Fermilab /Minnesota U., Theor. Phys. Inst.; Frieman, Joshua; /Fermilab /KICP, Chicago /Chicago U., Astron.

    2006-09-01T23:59:59.000Z

    Galaxy cluster surveys will be a powerful probe of dark energy. At the same time, cluster abundances is sensitive to any non-Gaussianity of the primordial density field. It is therefore possible that non-Gaussian initial conditions might be misinterpreted as a sign of dark energy or at least degrade the expected constraints on dark energy parameters. To address this issue, we perform a likelihood analysis of an ideal cluster survey similar in size and depth to the upcoming South Pole Telescope/Dark Energy Survey (SPT-DES).We analyze a model in which the strength of the non-Gaussianity is parameterized by the constant f{sub NL}; this model has been used extensively to derive Cosmic Microwave Background (CMB) anisotropy constraints on non-Gaussianity, allowing us to make contact with those works. We find that the constraining power of the cluster survey on dark energy observables is not significantly diminished by non-Gaussianity provided that cluster redshift information is included in the analysis. We also find that even an ideal cluster survey is unlikely to improve significantly current and future CMB constraints on non-Gaussianity. However, when all systematics are under control, it could constitute a valuable cross check to CMB observations.

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

    E-Print Network [OSTI]

    Donato Bini; Andrea Geralico; Daniele Gregoris; Sauro Succi

    2014-08-23T23:59:59.000Z

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

  9. Thermodynamical description of modified generalized Chaplygin gas model of dark energy

    E-Print Network [OSTI]

    H. Ebadi; H. Moradpour

    2015-04-15T23:59:59.000Z

    We consider a universe filled by a modified generalized Chaplygin gas together with a pressureless dark matter component. We get a thermodynamical interpretation for the modified generalized Chaplygin gas confined to the apparent horizon of FRW universe, whiles dark sectors do not interact with each other. Thereinafter, by taking into account a mutual interaction between the dark sectors of the cosmos, we find a thermodynamical interpretation for interacting modified generalized Chaplygin gas. Additionally, probable relation between the thermal fluctuations of the system and the assumed mutual interaction is investigated. Finally, we show that if one wants to solve the coincidence problem by using this mutual interaction, then the coupling constants of the interaction will be constrained. The corresponding constraint is also addressed. Moreover, the thermodynamic interpretation of using either a generalized Chaplygin gas or a Chaplygin gas to describe dark energy is also addressed throughout the paper.

  10. UT tower goes dark to conserve energy by KVUE.com

    E-Print Network [OSTI]

    Johnston, Daniel

    UT tower goes dark to conserve energy by KVUE.com Posted on November 22, 2013 at 5:12 PM Updated, but the first time the tower turned off its lights for the initiative. In previous initiatives, the UT Energy Friday, Nov 22 at 5:51 PM AUSTIN -- The University of Texas tower will remain unlit Friday night

  11. Experimental High Energy Physics Research: Direct Detection of Dark Matter

    SciTech Connect (OSTI)

    Witherell, Michael S.

    2014-10-02T23:59:59.000Z

    The grant supported research on an experimental search for evidence of dark matter interactions with normal matter. The PI carried out the research as a member of the LUX and LZ collaborations. The LUX research team collected a first data set with the LUX experiment, a large liquid xenon detector installed in the Sanford Underground Research Facility (SURF). The first results were published in Physical Review Letters on March 4, 2014. The journal Nature named the LUX result a scientific highlight of the year for 2013. In addition, the LZ collaboration submitted the full proposal for the Lux Zeplin experiment, which has since been approved by DOE-HEP as a second-generation dark matter experiment. Witherell is the Level 2 manager for the Outer Detector System on the LUX-Zeplin experiment.

  12. Dark Matter Theory

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

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

  13. Intermittency in the Joint Cascade of Energy and Helicity

    E-Print Network [OSTI]

    Qiaoning Chen; Shiyi Chen; Gregory L. Eyink; Darryl D. Holm

    2002-03-28T23:59:59.000Z

    The statistics of the energy and helicity fluxes in isotropic turbulence are studied using high resolution direct numerical simulation. The scaling exponents of the energy flux agree with those of the transverse velocity structure functions through refined similarity hypothesis, consistent with Kraichnan's prediction \\cite{Kr74}. The helicity flux is even more intermittent than the energy flux and its scaling exponents are closer to those of the passive scalar. Using Waleffe's helical decomposition, we demonstrate that the existence of positive mean helicity flux inhibits the energy transfer in the negative helical modes, a non-passive effect.

  14. United States and Japan Sign Joint Nuclear Energy Action Plan...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of a global nuclear energy infrastructure as envisioned in GNEP to develop innovative nuclear reactor and fuel cycle technologies. GNEP seeks to bring about a significant,...

  15. 2010_Nuclear_Security_Joint_Statement.pdf | Department of Energy

    Energy Savers [EERE]

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directed off Energy.gov. Are you sure you wantJoin us for|IdahotheWhat is theBrian LarsenEnergy 0

  16. U.S. - Pakistan Joint Press Statement | Department of Energy

    Energy Savers [EERE]

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual Siteof Energy 2, 2015 -Helicopter Accident at RatonU.S. - China Energy Cooperation U.S. --

  17. JETC: Joint Energy, Thermal and Cooling Management for CPU and Memory

    E-Print Network [OSTI]

    Simunic, Tajana

    JETC: Joint Energy, Thermal and Cooling Management for CPU and Memory Subsystems in Servers Raid Ayoub, Rajib Nath, Tajana Rosing, UCSD 2052.002 Observation Model of Thermal Coupling Between CPU: No Memory Management NCM: No CPU Migration DLB: Dynamic Load Balancing DTM-CM+PI: Dynamic Thermal Management

  18. Cosmology in presence of dark energy in an emergent gravity scenario

    E-Print Network [OSTI]

    Gangopadhyay, Debashis

    2015-01-01T23:59:59.000Z

    We obtain the analogues of the Friedman equations in an emergent gravity scenario in the presence of dark energy. The background metric is taken to be Friedman-Lemaitre-Robertson-Walker (FLRW). We show that if $\\dot\\phi ^{2}$ is the dark energy density (in units of the critical density) then (a) for total energy density greater than the pressure (non-relativistic scenario, matter domination) the deceleration parameter $q(t)\\approx\\frac {1}{2} [1 + 27 \\dot\\phi ^{2}+...] > \\frac{1}{2}$ (b) for total energy density equal to 3 times the pressure (relativistic case, radiation domination), the deceleration parameter $q(t)\\approx 1 + 18\\dot\\phi ^{2} +... > 1$ and (c) for total energy density equal to the negative of the pressure (dark energy scenario), the deceleration parameter $q(t)dark energy right from the beginning of the universe where the time parameter $t\\equiv \\frac{t}{t_{0}}$, $t_{0}$ being the p...

  19. Washington Joint Aquatic Resources Permit Application | Open Energy

    Open Energy Info (EERE)

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere IRaghuraji Agro IndustriesTown ofNationwide PermitInformationIsland: Energy

  20. Statement from Energy Secretary Ernest Moniz on the Joint Comprehensive

    Energy Savers [EERE]

    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 onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directed off Energy.gov. Are you sure you wantJoin us for|Idaho | Department