scholarly journals Mapping the Dark Energy Equation of State

2005 ◽  
Vol 216 ◽  
pp. 59-66
Author(s):  
Eric V. Linder
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Cosmic Microwave Background ◽  
Structure Formation ◽  
Energy Equation ◽  
Microwave Background ◽  
Redshift Surveys ◽  
Expansion Of The Universe ◽  
The Universe

The acceleration of the expansion of the universe has deep implications for structure formation, the composition of the universe, and its fate. Roughly 70% of the energy density is in a dark energy, whose nature remains unknown. Mapping the expansion history through supernovae, mapping the geometry of the universe and formation of structure through redshift surveys, and mapping the distance to recombination through the cosmic microwave background provide complementary, precise probes of the equation of state of the dark energy. Together these next generation maps of the cosmos can reveal not only the value today, but the redshift variation, of the equation of state, providing a critical clue to the underlying physics.

scholarly journals PARAMETRIZATION OF THE DARK ENERGY EQUATION OF STATE

2007 ◽  
Vol 16 (10) ◽  
pp. 1581-1591 ◽  
Author(s):  
VINOD B. JOHRI ◽  
P. K. RATH
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Comparative Study ◽  
Energy Equation ◽  
Critical Evaluation ◽  
Density Parameter ◽  
Dark Energy Density ◽  
History Of ◽  
The Universe

A comparative study of various parametrizations of the dark energy equation of state is made. Astrophysical constraints from LSS, CMB and BBN are laid down to test the physical viability and cosmological compatibility of these parametrizations. A critical evaluation of the four-index parametrizations reveals that Hannestad–Mörtsell as well as Lee parametrizations are simple and transparent in probing the evolution of the dark energy during the expansion history of the universe and they satisfy the LSS, CMB and BBN constraints on the dark energy density parameter.

scholarly journals CAN THE EXISTENCE OF DARK ENERGY BE DIRECTLY DETECTED?

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3426-3436 ◽  
Author(s):  
MARTIN L. PERL
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Energy Density ◽  
Total Mass ◽  
Mass Density ◽  
Mass Energy ◽  
Dark Energy Density ◽  
Astronomical Observations ◽  
Expansion Of The Universe ◽  
The Universe

Over the last decade, astronomical observations show that the acceleration of the expansion of the universe is greater than expected from our understanding of conventional general relativity, the mass density of the visible universe, the size of the visible universe and other astronomical measurements. The additional expansion has been attributed to a variety of phenomenon that have been given the general name of dark energy. Dark energy in the universe seems to comprise a majority of the energy in the visible universe amounting to about three times the total mass energy. But locally the dark energy density is very small. However it is not zero. In this paper I describe the work of others and myself on the question of whether dark energy density can be directly detected. This is a work-in-progress and I have no answer at present.

ENTROPY CORRECTED HOLOGRAPHIC DARK ENERGY f(T) GRAVITY MODEL

2014 ◽  
Vol 29 (02) ◽  
pp. 1450015 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Statefinder Parameters ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Evolution Trajectory

This paper is devoted to study the power-law entropy corrected holographic dark energy (ECHDE) model in the framework of f(T) gravity. We assume infrared (IR) cutoff in terms of Granda–Oliveros (GO) length and discuss the constructed f(T) model in interacting as well as in non-interacting scenarios. We explore some cosmological parameters like equation of state (EoS), deceleration, statefinder parameters as well as ωT–ωT′ analysis. The EoS and deceleration parameters indicate phantom behavior of the accelerated expansion of the universe. It is mentioned here that statefinder trajectories represent consistent results with ΛCDM limit, while evolution trajectory of ωT–ωT′ phase plane does not approach to ΛCDM limit for both interacting and non-interacting cases.

OBSERVATIONAL COSMOLOGY 2004: WHAT THE DATA SAY ABOUT DARK ENERGY AND THE CONTENTS OF THE UNIVERSE

2005 ◽  
Vol 20 (14) ◽  
pp. 2931-2942
Author(s):  
JOSEPH FOWLER
Keyword(s):  
Dark Energy ◽  
Background Radiation ◽  
Current Data ◽  
Observational Cosmology ◽  
Microwave Background ◽  
Hubble Expansion ◽  
Microwave Background Radiation ◽  
Expansion Of The Universe ◽  
Cosmological Data ◽  
The Universe

The latest cosmological data point to a model of the universe that is self-consistent but deeply weird. It seems that most matter in our universe is non-baryonic and hidden from direct view. Meanwhile, a repulsive "dark energy" causes the expansion of the universe to proceed at an accelerating rate. Sources of current data include studies of the distribution of matter in the universe, the anisotropies of the cosmic microwave background radiation, and the Hubble expansion law as probed by distant supernovae. In the near future, we can hope that measurements like these will begin to illuminate the nature of dark energy, starting with the question of whether it behaves like a cosmological constant or shows a more complicated evolution.

A study on the modified holographic Ricci dark energy in logarithmic f(T) gravity

2013 ◽  
Vol 91 (4) ◽  
pp. 351-354 ◽  
Author(s):  
Antonio Pasqua ◽  
Surajit Chattopadhyay
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Modified Gravity ◽  
State Parameter ◽  
Ricci Dark Energy ◽  
Equation Of State Parameter ◽  
Interaction Term ◽  
The Universe

In this paper, we have studied and investigated the behavior of a modified holographic Ricci dark energy (DE) model interacting with pressureless dark matter (DM) under the theory of modified gravity, dubbed logarithmic f(T) gravity. We have chosen the interaction term between DE and DM in the form Q = 3γHρm and investigated the behavior of the torsion, T, the Hubble parameter, H, the equation of state parameter, ωDE, the energy density of DE, ρDE, and the energy density contribution due to torsion, ρT, as functions of the redshift, z. We have found that T increases with the redshift, z, H increases with the evolution of the universe, ωDE has a quintessence-like behavior, and both energy densities increase going from higher to lower redshifts.

THREE COMPONENTS EVOLUTION IN A SIMPLE BIG BOUNCE COSMOLOGICAL MODEL

2005 ◽  
Vol 14 (05) ◽  
pp. 883-891 ◽  
Author(s):  
LIXIN XU ◽  
HONGYA LIU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Model ◽  
Accelerated Expansion ◽  
Ricci Flat ◽  
Bouncing Cosmology ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Three Components ◽  
Big Bounce

We consider a five-dimensional Ricci flat Bouncing cosmology and assume that the four-dimensional universe is permeated smoothly by three minimally coupled matter components: CDM + baryons ρm, radiation ρr and dark energy ρx. Evolutions of these three components are studied and it is found that dark energy dominates before the bounce, and pulls the universe contracting. In this process, dark energy decreases while radiation and the matter increases. After the bounce, the radiation and matter dominates alternatively and then decreases with the expansion of the universe. At present, the dark energy dominates again and pushes the universe accelerating. In this model, we also obtain that the equation of state (EOS) of dark energy at present time is wx0≈-1.05 and the redshift of the transition from decelerated expansion to accelerated expansion is zT≈0.37, which are compatible with the current observations.

scholarly journals CONSTRAINTS ON DARK ENERGY AND COSMIC TOPOLOGY

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1625-1630
Author(s):  
MARCELO J. REBOUÇAS
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Equation ◽  
Cosmological Parameters ◽  
Set Constraints ◽  
Spatial Topology ◽  
Locally Homogeneous ◽  
Topology Of The Universe ◽  
The Universe

A non-trivial spatial topology of the Universe is a potentially observable attribute, which can be probed through the circles-in-the-sky for all locally homogeneous and isotropic universes with no assumptions on the cosmological parameters. We show how one can use a possible circles-in-the-sky detection of the spatial topology of globally homogeneous universes to set constraints on the dark energy equation of state parameters.

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