scholarly journals A Study on Some Special Forms of Holographic Ricci Dark Energy in Fractal Universe

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Surajit Chattopadhyay ◽  
Antonio Pasqua ◽  
Sudipto Roy
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Deceleration Parameter ◽  
Hubble Parameter ◽  
Equations Of State ◽  
State Parameter ◽  
Ricci Dark Energy ◽  
Energy Models

We have considered the modified and the extended holographic Ricci dark energy models (MHRDE and EHRDE) in fractal universe. We have assumed a time-like fractal profile v=t−β, where β=4(1−α). We have reconstructed the Hubble parameter H, the energy density, the equations of state parameter w, and the deceleration parameter q for both MHRDE and EHRDE.

scholarly journals Analysis off(R)Theory Corresponding to NADE and NHDE

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
M. Sharif ◽  
M. Zubair
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Future Evolution ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Effective Description

We develop the connection off(R)theory with new agegraphic and holographic dark energy models. The functionf(R)is reconstructed regarding thef(R)theory as an effective description for these dark energy models. We show the future evolution offand conclude that these functions represent distinct pictures of cosmological eras. The cosmological parameters such as equation of state parameter, deceleration parameter, statefinder diagnostic, andw−w′analysis are investigated which assure the evolutionary paradigm off.

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.

scholarly journals DARK ENERGY MODELS WITH VARIABLE EQUATION OF STATE PARAMETER

2010 ◽  
Vol 19 (04) ◽  
pp. 475-487 ◽  
Author(s):  
UTPAL MUKHOPADHYAY ◽  
SAIBAL RAY ◽  
FAROOK RAHAMAN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Five Dimensions ◽  
Energy Models ◽  
Variable Λ ◽  
Equation Of State Parameter ◽  
Variable Equation

Two phenomenological variable Λ models, viz.Λ ~ (ȧ/a)2 and Λ ~ ρ, have been studied under the assumption that the equation of state parameter ω is a function of time. The selected Λ models are found to be equivalent both in four and five dimensions. The possibility of signature flip of the deceleration parameter is also shown.

scholarly journals INTERACTING MODIFIED HOLOGRAPHIC RICCI DARK ENERGY MODEL AND STATEFINDER DIAGNOSIS IN FLAT UNIVERSE

2014 ◽  
Vol 23 (03) ◽  
pp. 1450024 ◽  
Author(s):  
PRASEETHA PANKUNNI ◽  
TITUS K. MATHEW
Keyword(s):  
Dark Energy ◽  
Equations Of State ◽  
State Parameter ◽  
Chaplygin Gas ◽  
De Sitter ◽  
Ricci Dark Energy ◽  
Future Evolution ◽  
Standard Models ◽  
The Universe ◽  
Far Future

In this paper, we have considered the modified holographic Ricci dark energy interacting with dark matter through a nongravitational coupling. We took three phenomenological forms for the interaction term Q in the model, where, in general, it is proportional to the Hubble parameter and densities of the dark sectors, that Q = ρde+ρm, ρmand ρde, respectively. We have obtained analytical solutions for the three interacting models, and studied the evolutions of equations of state parameter and deceleration parameter. The results are compared with the observationally constrained values for the best parameters of the model. In general, we have shown that the equation of state of models are showing a de Sitter type behavior, in the far future evolution of the universe. We have also done the statefinder analysis of the model to discriminate it from other standard models of dark energy and have shown that the present r–s values of the models were in the range of the r–s value of the Chaplygin gas model of dark energy.

Anisotropic universe and reconstructing f(R, T) theory from holographic Ricci dark energy

2017 ◽  
Vol 95 (5) ◽  
pp. 524-534 ◽  
Author(s):  
V. Fayaz ◽  
H. Hossienkhani ◽  
Z. Zarei ◽  
M. Ganji ◽  
N. Azimi
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Equations Of State ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Anisotropic Universe ◽  
Density Parameter ◽  
Type I ◽  
Ricci Dark Energy ◽  
Bianchi Type I

In this work, we regard f(R, T) gravity as an effective description of the acceleration of the universe and reconstruct the function f(R, T) from the holographic Ricci dark energy by considering a Bianchi type I universe. So the connection gives us an opportunity to redefine the Hubble parameter, the pressure, the equations of state parameter, and the energy density parameter representation by considering Bianchi type I models for holographic Ricci dark energy. We wrap up the evolution of the accelerated expansion of the anisotropic universe, which is faster than the evolution of the FRW and ΛCDM models.

scholarly journals TACHYON FIELD-INSPIRED DARK ENERGY AND SUPERNOVAE CONSTRAINTS

2008 ◽  
Vol 17 (12) ◽  
pp. 2325-2335 ◽  
Author(s):  
JIE REN ◽  
XIN-HE MENG
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Function Method ◽  
State Parameter ◽  
Data Sets ◽  
Tachyon Field ◽  
Shift Parameter ◽  
Energy Models ◽  
Equation Of State Parameter

The tachyon field in cosmology is studied in this paper by applying the generating function method to obtain exact solutions. The equation of state parameter of the tachyon field is [Formula: see text], which can be expressed as a function in terms of the redshift z. Based on these solutions, we propose some tachyon-inspired dark energy models to explore the properties of the corresponding cosmological evolution. The explicit relations between the Hubble parameter and redshift enable us to test the models with SNe Ia data sets easily. In this paper, we employ the SNe Ia data with the parameter [Formula: see text] measured from the SDSS and the shift parameter [Formula: see text] from WMAP observations to constrain the parameters in our models.

Variable deceleration parameter and dark energy models

2016 ◽  
Vol 13 (05) ◽  
pp. 1650055 ◽  
Author(s):  
Binaya K. Bishi
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Linear Relation ◽  
Bianchi Type ◽  
State Parameter ◽  
Momentum Tensor ◽  
Field Equations ◽  
Variable Deceleration Parameter ◽  
Energy Models ◽  
Expansion Scalar

This paper deals with the Bianchi type-III dark energy model and equation of state parameter in a first class of [Formula: see text] gravity. Here, [Formula: see text] and [Formula: see text] represents the Ricci scalar and trace of the energy momentum tensor, respectively. The exact solutions of the modified field equations are obtained by using (i) linear relation between expansion scalar and shear scalar, (ii) linear relation between state parameter and skewness parameter and (iii) variable deceleration parameter. To obtain the physically plausible cosmological models, the variable deceleration parameter with the suitable substitution leads to the scale factor of the form [Formula: see text], where [Formula: see text] and [Formula: see text] are arbitrary constants. It is observed that our models are accelerating for [Formula: see text] and for [Formula: see text], transition phase from deceleration to acceleration. Further, we have discussed physical properties of the models.

scholarly journals FORMATION OF DARK MATTER HALOES IN A HOMOGENEOUS DARK ENERGY UNIVERSE

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1397-1403
Author(s):  
L. MARASSI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
State Parameter ◽  
Mass Function ◽  
Accelerated Expansion ◽  
X Ray ◽  
Energy Models ◽  
Dark Energy Component ◽  
Standard Press

Several independent cosmological tests have shown evidences that the energy density of the universe is dominated by a dark energy component, which causes the present accelerated expansion. The large scale structure formation can be used to probe dark energy models, and the mass function of dark matter haloes is one of the best statistical tools to perform this study. We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model, proposed in the work of Percival (2005), using an observational flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our analysis, the standard Press–Schechter (PS) approach (where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function), and the PL (power–law) mass function (where we apply a non-extensive q-statistical distribution to the primordial density field). We conclude that the PS mass function cannot explain at the same time the X-ray and the CMB data (even at 99% confidence level), and the PS best fit dark energy equation of state parameter is ω = -0.58, which is distant from the cosmological constant case. The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data; we also note that the ω parameter is very sensible to modifications in the PL free parameter, q, suggesting that the PL mass function could be a powerful tool to constrain dark energy models.

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

2010 ◽  
Vol 691 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Jingfei Zhang ◽  
Li Zhang ◽  
Xin Zhang
Keyword(s):  
Dark Energy ◽  
Ricci Dark Energy ◽  
Energy Models

scholarly journals Do we come from a quantum anomaly?

2019 ◽  
Vol 28 (14) ◽  
pp. 1944002 ◽  
Author(s):  
Spyros Basilakos ◽  
Nick E. Mavromatos ◽  
Joan Solà Peracaula
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Hubble Parameter ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Quantum Anomaly ◽  
Inflationary Phase ◽  
Axion Field ◽  
The Universe

We present a string-based picture of the cosmological evolution in which (CP-violating) gravitational anomalies acting during the inflationary phase of the universe cause the vacuum energy density to “run” with the effective Hubble parameter squared, [Formula: see text], thanks to the axion field of the bosonic string multiplet. This leads to baryogenesis through leptogenesis with massive right-handed neutrinos. The generation of chiral matter after inflation helps in cancelling the anomalies in the observable radiation- and matter-dominated eras. The present era inherits the same “running vacuum” structure triggered during the inflationary time by the axion field. The current dark energy is thus predicted to be mildly dynamical, and dark matter should be made of axions. Paraphrasing Carl Sagan [ https://www.goodreads.com/author/quotes/10538.Carl_Sagan .]: we are all anomalously made from starstuff.

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