because the acceleration a in (18) is in the context of the universe, caused by the vaccum or dark energy
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observational commitment to this field. Keywords: cosmic acceleration, dark energy, dark energy experiments PACS (attributed in current nomenclature to the ``dark energy''). In the words of the Dark Energy Task ...
The Supernova/Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universe's expansion by performing a series of complementary systematics-controlled astr...
National Technical Information Service (NTIS)
In 1998, two groups presented startling evidence that the expansion of the universe is accelerating, and the term "dark energy" was coined as a label for ...
NASA Website
May 19, 2011 ... In fact, dark energy is thought to be pushing the cosmos apart at faster and faster speeds, causing our universe's expansion to accelerate. ...
the cosmic acceleration. For these reasons, the nature of dark energy ranks among the very most compelling of all outstanding problems in physical science. ...
In 1998, high-redshift SNe Ia provided the first and only direct evidencefor an accelerating Universe and the existence of dark energy. ...
the first and only direct evidencefor an accelerating Universe and the existence of dark energy. More recently, ACS and NICMOS on HST have become tools to ...
to indicate that our universe is presently accelerating due to the presence of dark energy. Quintessence represents a possible way to model the dark energy. In these proceedings, we brie y review its main properties. 1 Introduction There is now compelling evidence that dark ...
for the dark energy on the brane has w > 1. Fitting data from type Ia supernova, Sloan Digital Sky Survey. A component that causes the expansion of the universe to accelerate is referred as dark energy. The traditional cosmological constant is a possible candidate of the ...
is often cast in terms of the effective speed of sound for dark energy, e.g., .... the near cancelation of two different effects with opposite signs: ...
Unlike cold dark matter, dark energy exerts a gravitational push (a form of anti -gravity) that is causing the expansion of the universe to accelerate or ...
candidate provides plausible explanations for the accelerating expansion of the Universe, dark energy, both and ultra�high energy (UHE) cosmic rays, dark energy and the accelerating expansion of the cosmos and how matter particles also included ...
The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification of general relativity (modified gravity). In the literature it has been proposed that combining the probes of the cosmic expansion history and growth history can distinguish between ...
Energy Citations Database
The Supernova Acceleration Probe (SNAP) will use Type Ia supernovae (SNe Ia) as distance indicators to measure the effect of dark energy on the expansion history of the Universe. (SNAP's weak-lensing program is described in a separate White Paper.) The ex...
, Brazil Abstract In models of coupled dark energy and dark matter the mass of the dark matter particle depends on the cosmological evolution of the dark energy #12;eld. In this note we exemplify in a simple model is accelerating today. There should ...
EUCLID mission. EUCLID is a mission concept for studying the Dark Energy that is hypothesized to account for the accelerating cosmic expansion. ...
We propose an explanation for the present accelerated expansion of the universe that does not invoke dark energy or a modification of gravity and is firmly rooted in inflationary cosmology.
DOE Information Bridge
The Universe is expanding ever faster - the effect of 'dark energy', most astronomers believe. Surveys of how galaxies were distributed in the past could provide precise clues to what is driving this acceleration.
NASA Astrophysics Data System (ADS)
In this brief WEB note we comment on recent papers related to our paper ''On Acceleration Without Dark Energy''.
Models where the dark matter component of the Universe interacts with the dark energy field have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. In these models the mass of ...
May 2007 Cosmological neutrino mass limit and the dynamics of dark energy Jun-Qing Xia, Gong-Bo Zhao and dark energy with time evolving equation of state. Parameterizing dark energy as w = w0 + w1 #3; z=(1 + z, 10]. This acceleration attributes to a new ...
We explore a model of interacting dark energy where the dark energy density is related by the holographic principle to the Hubble parameter, and the decay of the dark energy into matter occurs at a rate comparable to the current value of the Hubble parameter. We find this ...
################## arXiv:astro�ph/0108103 7 Aug 2001 Dark Energy and the New Cosmology Michael S is dark energy, the causative agent for accelerated expansion. Dark energy is just possibly the most important problem in all of physics. The only ...
for holographic dark energy in a spatially closed universe, gen- eralizing the proposal in hep-th/0403127 that the expansion of our universe is accelerating, due to dark energy with negative pres- sure. Dark energy (or be fair to say that theorists do ...
Cosmological observables are used to construct cosmological models and cosmological models are used to interpert cosmological observations. Statements that the expansion of the Universe is accelerating or that dark energy exists are made within the framework of a particular cosmological model. If the cosmological model is inappropriate ...
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 ...
:06 0:04 #11; = 0:17 +0:87 0:63 #12; 6 Energy and Dark Gravity expansion histories are equivalent under ACCELERATION: DARK ENERGY OR MODIFIED GRAVITY? Sidney Bludman #3; DESY, 22607 Hamburg, Germany (Dated: June 12 a negative pressure constituent in General Relativity (Dark ...
We propose a holographic tachyon model of dark energy with interaction between the components of the dark sector. The correspondence between the tachyon field and the holographic dark energy densities allows the reconstruction of the potential and the dynamics of the tachyon scalar field in a ...
Oct 12, 2009... new ideas about life on other planets and dark energy a mysterious vacuum energy that is accelerating the expansion of the universe. ...
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 resul...
This review on dark energy is intended for a wider audience, beginners as well as experts. It contains important notes on various aspects of dark energy and its alternatives. The section on Newtonian cosmology followed by heuristic arguments to capture the pressure effects allows us to discuss the basic features of ...
. This unexpected acceleration is ascribed to a dark energy that pervades space. Supernova data, combined with other acceleration. On the basis of ob- servations of supernova brightness, of the dark matter that makes galaxies for the nature of the dark ...
We establish a new self-consistent model in order to explain from a unified viewpoint two key features of the cosmological evolution: the inflation in the early Universe and the late-time accelerated expansion. The key element of this new model is the Archimedean-type coupling of the dark matter with dark energy, ...
The expansion of the Universe appears to be accelerating, and the mysterious antigravity 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 ...
PubMed
The expansion of the Universe appears to be accelerating, and the mysterious antigravity 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 ...
The acceleration of the expansion of the universe arises from unknown physical processes involving either new fields in high energy physics or modifications of gravitation theory. It is crucial for our understanding to characterize the properties of the dark energy or gravity through cosmological observations and ...
We investigate several varying-mass dark matter particle models in the framework of phantom cosmology. We examine whether there exist late-time cosmological solutions, corresponding to an accelerating universe and possessing dark energy and dark matter densities of the same order. Imposing ...
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 ...
A so-called "ghost dark energy" was recently proposed to explain the present acceleration of the universe expansion. The energy density of ghost dark energy, which originates from the Veneziano ghost of QCD, is proportional to the Hubble parameter, ?D = ?H, where ? is a ...
We introduce a new form of coupling between dark energy and dark matter that is quadratic in their energy densities. Then we investigate the background dynamics when dark energy is in the form of exponential quintessence. The three types of quadratic coupling all admit ...
In this paper, we use the type Ia supernovae data to constrain the holographic dark energy model proposed by Li. We also apply a cosmic age test to this analysis. We consider in this paper a spatially flat Friedmann-Robertson-Walker universe with a matter component and a holographic dark energy component. The fit ...
A unified treatment of mass varying dark matter coupled to cosmonlike dark energy is shown to result in effective generalized Chaplygin gas (GCG) scenarios. The mass varying mechanism is treated as a cosmon field inherent effect. Coupling dark matter with dark energy allows ...
Neutrinos coupled to an underlying scalar field in the scenario for unification of mass varying dark matter and cosmon-like dark energy is examined. In the presence of a tiny component of mass varying neutrinos, the conditions for the present cosmic acceleration and for the stability issue are reproduced. It is ...
We consider theories in which there exists a nontrivial coupling between the dark matter sector and the sector responsible for the acceleration of the Universe. Such theories can possess an adiabatic regime in which the quintessence field always sits at the minimum of its effective potential, which is set by the local dark matter ...
Using very distant supernovae as standard candles, one can trace the history of cosmic expansion and try to find out what's currently speeding it up.
SNAP, the SuperNova/Acceleration Probe, is an experiment designed to learn the nature of dark energy by precisely measuring the expansion history of the ...
candles," which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds. ...
The Universe seems to be expanding ever faster - a phenomenon generally ascribed to the influence of 'dark energy'. But might the observed acceleration be a trick of the light in an inhomogeneous Universe?
May 2, 2007 ... According to the Assessment of Balance report, lack of balance, .... solar system, the presence of dark energy and the acceleration of an ...
explained by introducing large amounts of dark energy or considering modifications to gravity. I present a Markov chain Monte Carlo analysis of the self-accelerating and normal...
Science.gov Websites
Falsifying Paradigms for Cosmic Acceleration Dragan Huterer University of Michigan Abstract: How can we rule out whole classes of dark energy models? And what quantities, at what...
We investigate the evolution of the viscous dark energy (DE) interacting with the dark matter (DM) in the Einstein cosmology model. By using the linearizing theory of the dynamical system, we find that, in our model, there exists a stable late time scaling solution which corresponds to the accelerating universe. We ...
VAMP (variable-mass particle) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and ...
We investigate the clustering properties of a dynamical dark energy component. In a cosmic mix of a pressureless fluid and a light scalar field, we follow the linear evolution of spherical matter perturbations. We find that the scalar field tends to form underdensities in response to the gravitationally collapsing matter. We thoroughly investigate these ...
SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, whi...
A new paradigm based on an equation of Chandrasekhar points directly to a specific multi-verse(http://arXiv.org/abs/0912.5367 and references there in). Dark energy accelerating the expansion is an essential part of the model -in turn, it shows that dark energy may have caused the expansion to ...
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, w ? p/? < -1/3, to an exterior Schwarzschild vacuum solution at a junction interface, situated near to where the event horizon is expected to form. The motivation for ...
The nature of dark energy is of such fundamental importance -- yet such a mystery -- that a dedicated dark energy experiment should be as comprehensive and powerfully incisive as possible. The Supernova/Acceleration Probe robustly controls for a wide variety of systematic uncertainties, ...
################## arXiv:astro�ph/0702239v1 8 Feb 2007 Interacting Dark Energy: Decay into Fermions 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 ...
################## arXiv:astro�ph/0103175 12 Mar 2001 Constraining the properties of dark energy. The presence of dark energy in the Universe is inferred directly from the accelerated expansion of the Universe, and indirectly, from measurements of cosmic microwave background (CMB) anisotropy. ...
################ Revised Version arXiv:hep�th/0702121v5 24 May 2007 Dark energy, in ation dark energy. Assuming the in ation in the early universe and the power-law acceleration phase today we numerical study exploiting the formula well reproduces the observed evolution of ...
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, ...
Understanding the observed cosmic acceleration is widely ranked among the very most compelling of all outstanding problems in physical science. Many believe that nothing short of a revolution will be required in order to integrate the cosmic acceleration (often attributed to ``dark energy'') with our understanding ...
A new model describing the dark sector of the universe is established. The model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an excited state above it as dark matter (DM). The condensate is assumed to have a negative pressure and is embodied as an exotic fluid with Chaplygin equation of state. ...
The acceleration of the expansion of the universe, ascribed to a dark energy, is one of the most intriguing discoveries in science. In addition to precise, systematics controlled data, clear, robust interpretation of the observations is required to reveal the nature of dark energy. Even for the ...
A scalar field is a favorite candidate for the particle responsible for dark energy. However, few theoretical means exist that can simultaneously explain the observed acceleration of the Universe and evade tests of gravity. The chameleon mechanism, whereby the properties of a particle depend upon the local environment, is one possible ...
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 ...
arXiv:0912.3816v1[astro-ph.CO]18Dec2009 Testable dark energy predictions from current data Michael a class of dark energy models, constraints from one set of cosmic acceleration observables make, and the Hubble constant. With a cosmological constant as the dark ...
The dominance of dark energy in the universe has necessitated the introduction of a repulsive gravity source to make q0 negative. The models for dark energy range from a simple ? term to quintessence, Chaplygin gas, etc. We look at the possibility of how change of behaviour of missing energy ...
9/18/09 2:29 PM'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 6http idea of dark energy. According to the new proposition, the universe is not accelerating, Davis. "We're saying that dark energy may not really be the correct explanation." ...
8/24/09 11:48 AMSPACE.com -- 'Big Wave' Theory Offers Alternative to Dark Energy Page 1 of 10http In New? Register: Join Now! 'Big Wave' Theory Offers Alternative to Dark Energy By Clara Moskowitz Staff galaxies to appear to be accelerating away from us. This big wave, initiated after the Big ...
The expansion speed of the Universe is increasing (Glanz 1998). This acceleration is attributed to dark energy which acts almost uniformly everywhere (including the Solar system) and thus essentially influences the Hubble constant. Its current value on a distance of 1 AU is H0 = 10 m/(yr AU). This is quite a large number and thus, the ...
Our universe is observed to be accelerating due to the dominant dark energy with negative pressure. The dark energy equation of state (w) holds a key to understanding the ultimate fate of the universe. The cosmic voids behave like bubbles in the universe so that its shapes must be quite ...
In order to make the increase of Astronomical Unit consistent with observations of the Earth's orbital period variation, an increase of the Solar dark matter as 10-12/yr is needed. This implies that dark matter has an increase ratio, and therefore supports Dirac's multiplicative matter creation, and provides another explanation to the ...
The Next Linear Collider Test Accelerator (NLCTA) being built at SLAC will integrate the new technologies of X-band accelerator structures and RF systems for the Next Linear Collider, demonstrate multibunch beam-loading energy compensation and suppression of higher-order deflecting modes, measure transverse components of the ...
Two cosmological Models for the Poincare Gauge Gravity theory with a non vanishing torsion are proposed. It is shown that the torsion plays an important role in explaining the accelerated expansion of the universe. Some of the cosmological parameters are also expressed in terms of the redshift and the dark energy scenarios are ...
For true insight into the nature of dark energy, measurements of the precision and accuracy of the Supernova/Acceleration Probe (SNAP) are required. Precursor or scaleddown experiments are unavoidably limited, even for distinguishing the cosmological cons...
The SuperNova Acceleration Probe (SNAP) instrument is being designed to collect image and spectroscopic data for the study of dark energy in the universe. In this paper, we describe a distributed architecture for the data acquisition system which interfac...
Only five percent of our universe is composed of visible matter, stars, planets and people; something called "dark matter" makes up about 25 percent and an enormous 70 percent of the universe is pervaded with "dark energy". Scientists had predicted a Big Crunch as the logical opposite of the Big Bang, but far from retracting, the ...
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A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of general relativity the cause of cosmic acceleration is a highly elastic ( p�-?), very smooth form of energy called �dark ...
There is now strong observational evidence that the expansion of the Universe is accelerating. The standard explanation invokes an unknown "dark energy" component. But such scenarios are faced with serious theoretical problems, which has led to increased interest in models where instead general relativity is modified in a way that ...
I briefly review models of dark energy. These include models of a cosmological constant arising in string theory, dynamical models where a scalar field may be responsible for the observed late time acceleration through to the possibility that we are not fully in control of the gravity sector and the acceleration ...
I briefly review attempts that have been made to model dark energy. These include models of a cosmological constant, dynamical models where a scalar field may be responsible for the observed late time acceleration through to the possibility that we are not fully in control of the gravity sector and the acceleration ...
We argue that the occurrence of late-time acceleration can conveniently be described by first-order general relativity covariantly coupled to fermions. Dark energy arises as a Bardeen-Cooper-Schrieffer condensate of fermions which forms in the early universe. At late times, the gap and chemical potential evolve to have an equation of ...
The most popular way to achieve accelerated expansion of the universe is by introducing a scalar field in which motion of state varies with time. The accelerated expanded universe was first observed by Type Ia supernovae and future confirmed by the latest of CMB (Cosmic Microwave Background). The reason for the accelerated universe is ...
We develop a general program of the unification of a matter-dominated era with an acceleration epoch for scalar-tensor theory or a dark fluid. The general reconstruction of the scalar-tensor theory is fulfilled. The explicit form of the scalar potential for which the theory admits a matter-dominated era, a transition to an ...
We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon-tachyon cosmology by interaction between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling matter Lagrangian in the model rather than being inserted into the formalism as an external ...
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 ...
the term "dark energy" to describe this mysterious phenomenon. Dark energy, combined with dark matter, seem to be the dominant components of the universe. The NASA and DOE Dark...
We consider renormalization group flow applied to the cosmological dynamical equations. A consistency condition arising from energy-momentum conservation links the flow parameters to the cosmological evolution, restricting possible behaviors. Three classes of cosmological fixed points for dark energy plus a barotropic fluid are found: ...
We study the coincidence problem of late cosmic acceleration by assuming that the present ratio between dark matter and dark energy is a slowly varying function of the scale factor. As the dark energy component we consider two different candidates, first a quintessence ...
In the timescape scenario cosmic acceleration is understand as an apparent effect, due to gravitational energy gradients that grow when spatial curvature gradients become significant with the nonlinear growth of cosmic structure. This affects the calibratation of local geometry to the solutions of the volume-average evolution equations corrected by ...
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 ...
Jan 4, 2001 ... What is the difference between Dark Energy and Dark Matter; aren't they ... Dark Energy appears to be, based on the brightness of the most ...
A component of dark energy has been recently proposed to explain the current acceleration of the Universe. Unless some unknown symmetry in Nature prevents or suppresses it, such a field may interact with the pressureless component of dark matter, giving rise to the so-called models of coupled quintessence. In this ...
Exploring the recent expansion history of the universe promises insights into the cosmological model, the nature of dark energy, and potentially clues to high energy physics theories and gravitation. They examine the extent to which precision distance-redshift observations can map out the history, including the ...
Exploring the recent expansion history of the universe promises insights into the cosmological model, the nature of dark energy, and potentially clues to high energy physics theories and gravitation. We examine the extent to which precision distance-redshift observations can map out the history, including the ...
If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the nextgeneration of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From ...
hep-ph/yymmnnn If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the next generation of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark ...
If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the next generation of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From ...
We present a partial unified model for inflation, dark matter and dark energy, based on a global SU (2) � U(1) symmetry, where the corresponding cosmological scalar fields that source such components of the Universe appear as different degrees of freedom of fundamental representations. The protecting symmetry allows to build ...
We propose a model based on a DBI action for the unification of dark matter and dark energy. This is supported by the results of the study of its background behavior at early and late times, and reinforced by the analysis of the evolution of perturbations. We also perform a Bayesian analysis to set observational constraints on the ...
This 47 minute radio broadcast explores dark matter and dark energy of the universe and how the acceleration of the expansion of the universe may be due to a parallel universe according to superstring theory. The show discusses how particle physics experiments are searching for the missing matter of the universe, ...
Supernova observations show that the expansion of the universe has been speeding up. This unexpected acceleration is ascribed to a dark energy that pervades space. Supernova data, combined with other observations, indicate that the universe is about 14 billion years old and is composed of about 30%matter and ...
The paper deals with a spatially homogeneous and anisotropic universe filled with perfect fluid and dark energy components. The two sources are assumed to interact minimally together with a special law of variation for the average Hubble's parameter in order to solve the Einstein's field equations. The law yields two explicit forms of the scale factor ...
Current constraints on the dark energy equation of state parameter, w, are expected to be improved by more than 1 order of magnitude in the next decade. If |w-1| > or approx. 0.01 around the present time, but the dark energy dynamics is sufficiently slow, it is possible that future constraints will rule out ...
In the standard approach to cosmology, the evolution and observations associated with an inhomogeneous universe with density \\rho (\\vec{x}) are modeled by employing a homogeneous cosmological model of density \\left\\langle \\rho (\\vec{x}) \\right\\rangle, where langsdotsdotsdotrang refers to some sort of spatial average. While there is broad agreement that since general relativity is a ...
Edward Hubble in early 1900s observed red shifts for galaxies outside our solar system and found red shifts increasing linearly with distance. Modern telescopes looking at larger distances found a limit for use of red shift for extremely remote galaxies. Two ways of finding distances are (a) the light received (magnitude), and (b) the associated red shift. For very remote galaxies magnitude ...
Structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit or overpredict the development of observed large-scale structures. Traditional approaches to studies of structure formation...
A cosmological theory that predicts a late-time accelerated attractor with a constant dark matter to dark energy ratio can be said to solve the coincidence problem. Such cosmologies are naturally generated in the context of nonstandard gravity theories under conformal transformation because of the resulting ...
Much evidence has accumulated that within the context of general relativistic Friedmann-Robertson-Walker (FRW) cosmology there must exist a new, and gravitationally repulsive, substance in the Universe. The effect of this new type of energy density on the expansion of the Universe is to cause its acceleration, and the name that is given to it is ...
We elaborate on the proposal that the observed acceleration of the Universe is the result of the backreaction of cosmological perturbations, rather than the effect of a negative-pressure dark energy fluid or a modification of general relativity. Through the effective Friedmann equations describing an inhomogeneous Universe after ...
The recent observational evidence for the current cosmic acceleration have stimulated renewed interest in alternative cosmologies, such as scenarios with interaction in the dark sector (dark matter and dark energy). In general, such models contain an unknown negative-pressure ...
With the requirement for particle accelerators getting higher and higher in energy and accelerating gradients many phenomena become more and more dominant. One of them is the dark current, resulted from collective movement of electrons which by quantum effects leave cavity walls and cause additional thermal heatup ...
In the model of quintessino as the dark matter particle, the dark matter and dark energy are unified in one superfield, where the dynamics of the Quintessence drives the Universe acceleration and its superpartner, quintessino, makes up the dark matter of the Universe. This ...
The recently observed acceleration of the expansion of the universe is a topic of intense interest. The favoured causes are the "cosmological constant" or "dark energy". The former, which appears in the Einstein equations as the term [lambda]g[subscript [mu]v], provides an extremely simple, well-defined mechanism for the ...
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The Particle Astrophysics Center was established in fall of 2004. Fermilab director Michael S. Witherell has named Fermilab cosmologist Edward ''Rocky'' Kolb as its first director. The Center will function as an intellectual focus for particle astrophysics at Fermilab, bringing together the Theoretical and Experimental Astrophysics Groups. It also encompasses ...
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/crunches or big rips singularities. Classically these solutions can be regarded as ...
We examine the embedding of dark energy in high energy models based upon supergravity and extend the usual phenomenological setting comprising an observable sector and a hidden supersymmetry breaking sector by including a third sector leading to the acceleration of the expansion of the universe. We find that ...
CTIO > DECam & DES Link to the National Optical Astronomy Observatory's web site Dark Energy Camera (DECam) & the Dark Energy Survey (DES) Dark Energy Survey logo The Dark Energy...
Universal antigravitation, a new physical phenomenon discovered astronomically at distances of 5 to 8 billion light years, manifests itself as cosmic repulsion that acts between distant galaxies and overcomes their gravitational attraction, resulting in the accelerating expansion of the Universe. The source of the antigravitation is not galaxies or any other bodies of nature ...
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}{sub D}=3n{sup 2}m{sub p}{sup 2}/{eta}{sup 2} is replaced with {rho}{sub D}=3n{sup 2{phi}2}/(4{omega}{eta}{sup 2}). We show that ...
We study the sensitivity of weak lensing by large scale structures as a probe of the evolution of dark energy. We explore a two-parameters model of dark energy evolution, inspired by tracking quintessence models. To this end, we compute the likelihood of a few fiducial models with varying and nonvarying equation of ...
We investigate a possible connection between the suppression of the power at low multipoles in the cosmic microwave background (CMB) spectrum and the late time acceleration. We show that, assuming a cosmic IR/UV duality between the UV cutoff and a global infrared cutoff given by the size of the future event horizon, the equation of state of the dark ...
We study a model of scalar field with a general non-minimal kinetic coupling to itself and to the curvature. The cosmological dynamics of this model and the issue of accelerated expansion are analyzed. Solutions giving rise to power-law expansion have been found. By constraining the potential of the model, we obtained a variety of solutions corresponding to phenomenologically ...
We investigate the possibility 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. We build a transient mechanism in which gravitation is pushed away from general relativity (GR) by a Born-Infeld (BI) gauge interaction acting as an ...
We investigate the possibility 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. We build a transient mechanism in which gravitation is pushed away from general relativity by a Born-Infeld gauge interaction acting as an abnormally ...
Astrophysical observations provide robust evidence that our current picture of fundamental physics is incomplete. The discovery in 1998 that the expansion of the Universe is accelerating (apparently due to gravitational repulsion between regions of empty space!) presents us with a profound challenge, at the interface between gravity and quantum mechanics. This ...
A new cosmological scenario driven by a slow rolling homogeneous scalar field whose exponential potential V(Phi) has a quadratic dependence on the field Phi in addition to the standard linear term is discussed. The derived equation of state for the field predicts a transient accelerating phase, in which the Universe was decelerated in the past, began to ...
The presently accelerating universe may keep accelerating forever, eventually run into the event horizon problem, and thus be in conflict with the superstring idea. On the other hand, the current accelerating phase as well as the fate of the universe may be swayed by a negative cosmological constant, which dictates a big crunch. Based ...
The question of the nature of the dark matter in the Universe remains one of the most outstanding unsolved problems in basic science. One of the best motivated particle physics candidates is the lightest supersymmetric particle, assumed to be the lightest neutralino - a linear combination of the supersymmetric partners of the photon, the Z boson and neutral scalar Higgs ...
Interactions between dark matter and dark energy with a given equation of state are known to modify the cosmic dynamics. On the other hand, the strength of these interactions is subject to strong observational constraints. Here we discuss a model in which the transition from decelerated to accelerated expansion of ...
Is Dark Energy justified as an alternative to the cosmological constant LAMBDA in order to explain the acceleration of the cosmic expansion? It turns out that a straightforward dimensional analysis of Einstein equation provides us with clear evidences that the geometrical nature of LAMBDA is the only viable source to this phenomenon, ...
A large number of observations suggest that our universe entered at low redshifts a stage with accelerated expansion rate. Many models, Dark Energy (DE) models, able to explain this departure from conventional cosmology have been proposed. These models are conceptually very different, either introducing some new component with ...
How the field excitations play the role of dark energy is explored. There has been the suggestion by Sahni and Wang (1999) that quintessence with rapidly oscillating modes can provide repulsive gravity and drive the cosmic acceleration. A specific model of oscillating quintessence in this scenario with less fine tuning is presented by ...
We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase-plane of w and ...
The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model including the evolution of EoS parameter w ?, energy density ?? and deceleration parameter q are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a ...
We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase plane of w and w', the ...
InflationInflation xx Dark MatterDark Matter xx Dark EnergyDark Energy CC��dric Pahuddric Pahud Kofman, Linde and Starobinsky (1994 & 1997) #12;Unification scenarioUnification scenario Dark Energy Dark Matter Inflation V() ~ ...
The elementary physics battle-tested principles of Lorentz invariance, Einstein equivalence principle and the boson commutation and fermion anti-commutation rules of quantum field theory explain gravitationally repulsive dark energy as virtual bosons and gravitationally attractive dark matter as virtual fermion-antifermion pairs. The ...
May 3, 2011 ... Dark Energy: The amount of dark energy in your universe, as a percentage of the critical density. Unlike cold dark matter, dark energy ...
A model of dark matter and dark energy based on the concept of gravitational polarization is investigated. We propose an action in standard general relativity for describing, at some effective or phenomenological level, the dynamics of a dipolar medium, i.e. one endowed with a dipole moment vector, and polarizable in a gravitational ...
Dec 22, 2008 ... About 10 years ago, scientists reached the astonishing conclusion that our universe is accelerating apart at ever-increasing speeds, stretching ...
This report discusses the following topics: identifying the universe's dark matter; computer simulations of cosmic ray acceleration; the interiors of uranus and neptune; seismic imaging of the deep structure of northern California; and geochemical tracing of lead contaminants in the environment.
An impressive amount of different astrophysical data converges towards the picture of a spatially flat Universe undergoing today a phase of accelerated expansion. The nature of the dark energy dominating the energy content of the Universe is still unknown, and a lot of different scenarios are viable candidates to ...
Aims: The interacting dark matter (IDM) scenario allows for the acceleration of the Universe without dark energy. Methods: We constrain the IDM model by using the newly revised observational data including H(z) data and Union2 SNe Ia via the Markov chain Monte Carlo method. Results: When mimicking the ?CDM model, ...
It is now widely accepted that most of mass-energy in the universe is unobserved except by its gravitational effects. Baryons make only about 4% of the total, with ''dark matter'' making up about 23% and the ''dark energy'' responsible for the ...
Consistency relations between growth of structure and expansion history observables exist for any physical explanation of cosmic acceleration. We perform MCMC likelihood exploration of these relations, using future SNAP supernova and Planck CMB data to derive the expected variation in the growth and distance functions and the Hubble parameter under different classes of models ...
Consistency relations between growth of structure and expansion history observables exist for any physical explanation of cosmic acceleration, be it a cosmological constant, scalar field quintessence, or a general component of dark energy that is smooth relative to dark matter on small scales. The high-quality ...
If general relativity is the correct theory of physics on large scales, then there is a differential equation that relates the Hubble expansion function, inferred from measurements of angular diameter distance and luminosity distance, to the growth rate of large scale structure. For a dark energy fluid without couplings or an unusual sound speed, ...
In this Letter, the cosmological dynamics of a modified holographic dark energy which is derived from the UV/IR duality by considering the black hole mass in higher dimensions as UV cutoff, is investigated in Dvali-Gabadadze-Porrati (DGP) brane world model. We choose Hubble horizon and future event horizon as IR cutoff respectively. And the two branches of ...
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 behavior of a dust-dominated inhomogeneous Lemaitre-Tolman-Bondi universe ...
Observations indicate that the expansion of the Universe is accelerating, which is attributed to a `dark energy' component that opposes gravity. There is a purely geometric test of the expansion of the Universe (the Alcock-Paczynski test), which would provide an independent way of investigating the abundance () and equation of state () ...
These two radio broadcasts discusse new evidence supporting the existence of dark energy from the Chandra X-ray Observatory and Darwin and his theory of evolution. First, The new observatory data from measured distances between galactic clusters suggest the universe started accelerating 6 billion years ago and that the amount of ...
At the turn of the 20th Century, the Universe was thought to consist of our solar system, the Sun, planets, satellites and comets, floating under the Milky Way. The astronomers were ignorant of the existence of galaxies, clusters, quasars and black holes. Over the last ten years the Cosmology has made remarkable progress in our understanding of the composition of the Universe: 23 per cent is in an ...
-relativistic dark matter constituent that interacts directly with dark energy is also considered, where the dark]; the nature of the responsible entity, called dark energy, still remains unknown. The simplest explanation matter and dark ...
We review the problem of dark energy, including a survey of theoretical models and some aspects of numerical studies.
Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable consequences in many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has ...
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 ...
The accelerating expansion of the universe presents an exciting, fundamental challenge to the standard models of particle physics and cosmology. I highlight some of the outstanding challenges in both developing theoretical models and interpreting without bias the observational results from precision cosmology experiments in the next decade that will return data to help reveal ...
We show that intermediate mass black holes conjectured to be the early precursors of supermassive black holes and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high center-of-mass energies in the case of Kerr black holes. While the ejecta from such ...
Astronomers have detected and probed dark energy by applying a powerful, new method that uses images of galaxy clusters made by NASA's Chandra X-ray Observatory. The results trace the transition of the expansion of the Universe from a decelerating to an accelerating phase several billion years ago, and give intriguing clues about the ...
We give a brief review of the known effects of a dynamical vacuum cosmological component, the dark energy, on the anisotropies of the cosmic microwave background (CMB). We distinguish between a "classic" class of observables, used so far to constrain the average of the dark energy abundance in the redshift interval ...
Two new one-parameter tracking behavior dark energy representations {omega}={omega}{sub 0}/(1+z) and {omega}={omega}{sub 0}e{sup z/(1+z)}/(1+z) are used to probe the geometry of the Universe and the property of dark energy. The combined type Ia supernova, Sloan Digital Sky Survey, and Wilkinson Microwave Anisotropy ...
Oscillations of the $F(R)$ dark energy around the phantom divide line, $\\omega_{DE}=-1$, both during the matter era and also in the de Sitter epoch are investigated. The analysis during the de Sitter epoch is carried out by expanding the modified equations of motion around the de Sitter solution. It is seen that the dark ...
The acceleration of the Universe can be explained either through dark energy or through the modification of gravity on large scales. In this paper we investigate modified gravity models and compare their observable predictions with dark energy models. Modifications of general relativity are ...
We discuss a cosmology in which cold dark matter particles decay into relativistic particles. We argue that such decays could lead naturally to a bulk viscosity in the cosmic fluid. For decay lifetimes comparable to the present Hubble age, this bulk viscosity enters the cosmic energy equation as an effective negative pressure. We investigate whether this ...
The authors discuss a cosmology in which cold dark-matter particles decay into relativistic particles. They argue that such decays could lead naturally to a bulk viscosity in the cosmic fluid. for decay lifetimes comparable to the present hubble age, this bulk viscosity enters the cosmic energy equation as an effective negative pressure. They investigate ...
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 = ThdSh + WdV, at the apparent horizon. In addition, the generalized second law of thermodynamics can be fulfilled in a region enclosed by the ...
The coincidence problem of late cosmic acceleration constitutes a serious riddle with regard to our understanding of the evolution of the Universe. Here we argue that this problem may someday be solved - or better understood - by expressing the Hubble expansion rate as a function of the ratio of densities (dark matter/dark ...
It is shown that the recently detected acceleration of the Uuniverse can be understood by considering a modification of the teleparallel equivalent of general relativity, with no need of dark energy. The solution also exhibits phases dominated by matter and radiation as expected in the standard cosmological evolution. We perform a ...
The discovery of the cosmic acceleration has made it clear that we have very little direct information on the global properties of our universe. The main goal of research in the next decade should be the reconstruction of the space-time metric at the background level and at first order. This will be a crucial step on the road to understanding the nature of ...
We study general properties of attractors for scalar-field dark energy scenarios which possess cosmological scaling solutions. In all such models there exists a scalar-field dominant solution with an energy fraction {omega}{sub {phi}}=1 together with a scaling solution. A general analytic formula is given to derive fixed points ...
We construct a consistent model of gravity where the tensor graviton mode is massive, while linearized equations for scalar and vector metric perturbations are not modified. The Friedmann equation acquires an extra dark-energy component leading to accelerated expansion. The mass of the graviton can be as large as approximately (10(15) cm)(-1), being ...
Disformal Dark Energy Disformal Quintessence Conclusions Disformal Dark Energy and Disformal�arregui Disformal Dark Energy #12;Disformal Dark Energy Disformal Quintessence Conclusions Outline 1 Disformal Dark ...
... DARK-FIELD STUDY OF REAR-SIDE DENSITY STRUCTURE IN LASER.ACCELERATED FOILS The ablative acceleration of thin foil targets ...
DTIC Science & Technology
Cosmology is undergoing a revolution. With recent precise measurements of the cosmic microwave background radiation, large galaxy redshift surveys, better measurements of the expansion rate of the Universe and a host of other astrophysical observations, there is now a standard, highly constrained cosmological model. It is not a cosmology that was predicted. Unidentified dark ...
Novel physics founded on a dual and commensurate space-time universe explicates the nature of dark matter and energy [see APS 2007 Spring Meeting]. Its governing principles also illuminate how the dark matter and energy become unobservable, why the dark energy still ...
We study the dynamics of the scalar field Friedmann-Lemaitre-Robertson-Walker flat cosmological models within the framework of the unified dark matter (UDM) scenario. In this model we find that the main cosmological functions such as the scale factor of the Universe, the scalar field, the Hubble flow, and the equation of state parameter are defined in terms of hyperbolic ...
Recent evidence suggests that most of the energy in the universe consists of some form of dark energy that is gravitationally self-repulsive and that is causing the expansion rate of the universe to accelerate. We review the evidence, including recent measurements of the cosmic microwave background by the DASI, ...
Structure formation processes are discussed in the BEC(Bose-Einstein Condensation) cosmological model, in which, the boson dark matter (DM) gradually condensates into the uniform dark energy (DE) with negative pressure. This global condensate itself yields the accelerated expansion of the Universe. On the other ...
We consider Double Quintessence models for which the Dark Energy sector consists of two coupled scalar fields. We study, in particular, the possibility to have a transient acceleration in these models. In both Double Quintessence models studied here, it is shown that, if acceleration occurs, it is necessarily ...
Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy ...
Observations exploring the contemporary cosmic acceleration have sparked interest in dark energy models possessing equations of state with w<-1. We review how the cosmic expansion history of a Dvali-Gabadadze-Porrati (DGP) braneworld model with a standard brane cosmological constant can mimic that of ordinary 4D gravity with ...
In the present work a procedure is build up, that allows obtaining dark matter (DM) and cosmic acceleration in our 4D universe embedded in a 5D manifold. Both, DM and the factor causing cosmic acceleration, as well ordinary matter are induced in the 4D space-time by a warped, but empty from matter, 5D bulk. The procedure is carried out ...
For true insight into the nature of dark energy, measurements of the precision and accuracy of the Supernova/Acceleration Probe (SNAP) are required. Precursor or scaled-down experiments are unavoidably limited, even for distinguishing the cosmological constant. They can pave the way for, but should not delay, SNAP by developing ...
Unexpected discoveries? A cutaway view of SNAP's image plane showing CCD and HgCdTe detector arrays noise HgCdTe infrared devices: high QE from 0.9�1.7 �m low noise Integral Field 0.35�1.7 �m Spectrograph
Non-accelerator Particle Physics and Neutrino Physics Research programs of: Prof. Martin connect particle physics with astrophysics and cosmology Some questions: - What particles constitute "dark? #12;The techniques: Laboratory experiments, in the style of particle physics � High energy detectors: Prof Wojcicki
This report is a compilation of papers reflecting current trends in non-accelerator particle physics, corresponding to talks that its author was invited to present at the Workshop on Tibet Cosmic Ray Experiment and Related Physics Topics held in Beijing, ...
We study cosmological constraints on the various accelerating models of the universe using the time evolution of the cosmological redshift of distant sources. The important characteristic of this test is that it directly probes the expansion history of the universe. In this work we analyze the various models of the universe which can explain the late time ...
If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a "dark energy." However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the inhomogeneous Universe, the averaged ...
