Cosmological models in R2 gravity with hybrid expansion law

2021 ◽  
pp. 2150143
Author(s):  
Partha Sarathi Debnath ◽  
Bikash Chandra Paul
Keyword(s):  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Cosmological Models ◽  
Model Parameters ◽  
Density Parameter ◽  
Eos Parameter ◽  
Data Set ◽  
Deceleration Phase ◽  
Higher Derivative

In this paper, evolution of a Friedmann–Robertson–Walker universe is studied in a higher derivative theory of gravity. The relativistic solutions admitting hybrid expansion law of the universe are explored here. Hybrid expansion law is a general form of scale factor from which one can recover both the power-law expansion and exponential expansion as a special case. The hybrid expansion law is interesting as it addresses the early deceleration phase and presents accelerating phase satisfactorily. It is found that an inflationary scenario with hybrid expansion law is permitted in the [Formula: see text] gravity fairly well. We consider universe filled with cosmic fluid that describes by an equation of state (EoS) parameter which varies with time. Consequently, we analyze the time variation of energy density parameter, cosmic pressure, equation of state parameter, deceleration parameter and jerk parameter in the cosmological model. The constraints of the model parameters imposed by the cosmological observational data set are determined. The present value of the deceleration parameter [Formula: see text], EoS parameter and the epoch at which the transition of decelerated phase to accelerated phase are estimated. In the higher derivative theory, we obtain some new and interesting cosmological solutions relevant for building cosmological models.

scholarly journals Reconstruction of interaction rate in holographic dark energy model with Hubble horizon as the infrared cut-off

2017 ◽  
Vol 26 (11) ◽  
pp. 1750136 ◽  
Author(s):  
Abdulla Al Mamon
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Energy Equation ◽  
Present Model ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Model Parameters ◽  
Interaction Rate ◽  
Equation Of State Parameter

This work is the reconstruction of the interaction rate of holographic dark energy whose infrared cut-off scale is set by the Hubble length. We have reconstructed the interaction rate between dark matter and the holographic dark energy for a specific parameterization of the effective equation-of-state parameter. We have obtained observational constraints on the model parameters using the latest type Ia supernova (SNIa), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) radiation datasets. We have found that for the present model, the interaction rate increases with expansion and remains positive throughout the evolution. For a comprehensive analysis, we have also compared the reconstructed results of the interaction rate with other well-known holographic dark energy models. The nature of the deceleration parameter, the statefinder parameters and the dark energy equation-of-state parameter have also been studied for the present model. It has been found that the deceleration parameter favors the past decelerated and recent accelerated expansion phase of the universe. It has also been found that the dark energy equation-of-state parameter shows a phantom nature at the present epoch.

Rényi holographic dark energy in the Brans–Dicke cosmology

2020 ◽  
Vol 35 (34) ◽  
pp. 2050281
Author(s):  
Umesh Kumar Sharma ◽  
Vipin Chandra Dubey
Keyword(s):  
Dark Energy ◽  
Stability Analysis ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Density Parameter ◽  
Eos Parameter ◽  
Hubble Horizon ◽  
The Stability

In this paper, we construct a holographic dark energy (HDE) model considering the IR cut-off as Hubble horizon, holographic hypothesis, and using the generalized Rényi entropy, and investigate its cosmological outcomes in Brans–Dicke gravity without interaction. We observe the suitable behavior for the cosmological parameters, involving the deceleration parameter, the equation of state (EoS) parameter, and the density parameter in both flat and non-flat Universes. It is also concluded by the stability analysis that the Rényi holographic dark energy (RHDE) model is classically stable at present and future for the Rényi parameter [Formula: see text] in both flat and non-flat Universe.

scholarly journals GHOST DARK ENERGY IN f(R) MODEL OF GRAVITY

2012 ◽  
Vol 21 (06) ◽  
pp. 1250057 ◽  
Author(s):  
KH. SAAIDI ◽  
A. AGHAMOHAMMADI ◽  
B. SABET ◽  
O. FAROOQ
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dynamical Evolution ◽  
State Parameter ◽  
Jordan Frame ◽  
Density Parameter ◽  
Eos Parameter ◽  
Phantom Divide ◽  
Equation Of State Parameter ◽  
Phantom Divide Line

We study a correspondence between f(R) model of gravity in the Jordan frame and a phenomenological kind of dark energy (DE), which is known as QCD ghost DE. Since this kind of DE is not stable in the context of Einsteinian theory of gravity and Brans–Dicke model of gravity, we consider two kinds of correspondence between modified gravity and DE. By studding the dynamical evolution of model and finding relevant quantities such as, equation of state parameter, deceleration parameter, dimensionless density parameter, we show that the model can describe the present Universe and also the EoS parameter can cross the phantom divide line without needs to any kinetic energy with negative sign. Furthermore, by obtaining the adiabatic squared sound speed of the model for different cases of interaction, we show that this model is stable. Finally, we fit this model with supernova observational data in a noninteraction case and we find the best values of parameter at 1σ confidence interval as; [Formula: see text], [Formula: see text] and [Formula: see text]. These best-fit values show that DE equation of state parameter, ωd0, can cross the phantom divide line at the present time.

A probe of cosmological models in modified teleparallel gravity

2021 ◽  
pp. 2150208
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Dinesh Chandra Maurya
Keyword(s):  
Hubble Constant ◽  
Teleparallel Gravity ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Model Parameters ◽  
Late Time ◽  
General Function ◽  
Eos Parameter ◽  
Variable Cosmological Term ◽  
Present Universe

In this paper, we have investigated the physical behavior of cosmological models in modified Teleparallel gravity with a general function [Formula: see text] where [Formula: see text] and [Formula: see text] are model parameters and [Formula: see text] is the torsion scalar. We have considered a homogeneous and isotropic Friedman universe filled with perfect fluid. We have derived the deceleration parameter [Formula: see text] in terms of equation of state (EoS) parameter [Formula: see text] and Hubble parameter [Formula: see text]. We have investigated the variation of [Formula: see text] over the observed values of Hubble constant in various observations within the range of redshift [Formula: see text]. Also, we have studied effective energy density [Formula: see text], effective pressure [Formula: see text] and effective EoS parameter [Formula: see text]. We have observed that the second term of [Formula: see text] function behaves just like variable cosmological term [Formula: see text] ([Formula: see text]) at late-time universe and causes the acceleration in expansion and works just like dark energy candidates. Also, we have evaluated the age of the present universe for various stages of matter [Formula: see text] and various [Formula: see text] functions.

Anisotropic Dark Energy Cosmological Model with Cosmic Strings

2020 ◽  
Author(s):  
T. Vinutha ◽  
V.U.M. Rao ◽  
Molla Mengesha
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Model ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Type I ◽  
Field Equations ◽  
Eos Parameter ◽  
Phantom Divide

The present study deals with a spatially homogeneous locally rotationally symmetric (LRS) Bianchi type-I dark energy cosmological model containing one dimensional cosmic string fluid source. The Einstein's field equations are solved by using a relation between the metric potentials and hybrid expansion law of average scale factor. We discuss accelerated expansion of our model through equation of state (ωde) and deceleration parameter (q). We observe that in the evolution of our model, the equation of state parameter starts from matter dominated phase ωde > -1/3 and ultimately attains a constant value in quintessence region (-1 < ωde < -1/3). The EoS parameter of the model never crosses the phantom divide line (ωde = 1). These facts are consistent with recent observations. We also discuss some other physical parameters.

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.

scholarly journals DARK ENERGY IN GLOBAL BRANE UNIVERSE

2007 ◽  
Vol 16 (10) ◽  
pp. 1633-1640 ◽  
Author(s):  
YONGLI PING ◽  
LIXIN XU ◽  
CHENGWU ZHANG ◽  
HONGYA LIU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Exact Solutions ◽  
Deceleration Parameter ◽  
Mass Density ◽  
Density Parameter ◽  
Dark Energy Density ◽  
Friedmann Equations

We discuss the exact solutions of brane universes and the results indicate that 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 that the new term varies with the redshift z. Finally, the evolutions of the mass density parameter Ω2, dark energy density parameter Ωx and deceleration parameter q2 are studied.

scholarly journals THE EFFECT OF DIFFERENT OBSERVATIONAL DATA IN CONSTRAINING COSMOLOGICAL PARAMETERS

2012 ◽  
Vol 10 ◽  
pp. 85-94 ◽  
Author(s):  
YUNGUI GONG ◽  
QING GAO ◽  
ZONG-HONG ZHU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Data ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Model Parameters ◽  
Type Ia Supernova ◽  
Equation Of State Parameter ◽  
Type Ia

We use the SNLS3 compilation of 472 type Ia supernova data, the baryon acoustic oscillation measurement of distance, and the cosmic microwave background radiation data from the seven year Wilkinson Microwave Anisotropy Probe to study the effect of their different combinations on the fittings of cosmological parameters. Neither BAO nor WMAP7 data alone gives good constraint on the equation of state parameter of dark energy, but both WMAP7 data and BAO data help type Ia supernova data break the degeneracies among the model parameters, hence tighten the constraint on the variation of equation of state parameter wa, and WMAP7 data does the job a little better. Although BAO and WMAP7 data provide reasonably good constraints on Ωm and Ωk, it is not able to constrain the dynamics of dark energy, we need SNe Ia data to probe the property of dark energy, especially the variation of the equation of state parameter of dark energy. For the SNLS SNe Ia data, the nuisance parameters α and β are consistent for all different combinations of the above data. Their impacts on the fittings of cosmological parameters are minimal. ΛCDM model is consistent with current observational data.

scholarly journals Sign-changeable interacting agegraphic dark energy in Brans–Dicke cosmology

2020 ◽  
Vol 98 (7) ◽  
pp. 643-649
Author(s):  
M. Abdollahi Zadeh ◽  
A. Sheykhi
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
The State ◽  
Evolutionary Equation ◽  
Model Parameters ◽  
Late Time ◽  
Frw Universe ◽  
Agegraphic Dark Energy ◽  
Deceleration Phase ◽  
The Universe

We explore a spatially homogeneous and isotropic Friedmann–Robertson–Walker (FRW) universe that is filled with agegraphic dark energy (ADE) with mutual interaction with pressureless dark matter in the background of Brans–Dicke (BD) theory. We consider both original and a new type of ADE (NADE) and further assume that the sign of the interaction term can change during the history of the universe. We obtain the equation of the state parameter, the deceleration parameter, and the evolutionary equation for the sign-changeable interacting ADE and NADE in BD cosmology. We find that in both models, the equation of the state parameter, wD, cannot cross the phantom line, although they can predict the universe evolution from the early deceleration phase to the late time acceleration, compatible with observations. We also investigate the sound stability of these models and find out that both models cannot show a signal of stability for different model parameters.

scholarly journals Λ-CDM UNIVERSE: A PHENOMENOLOGICAL APPROACH WITH MANY POSSIBILITIES

2008 ◽  
Vol 17 (02) ◽  
pp. 301-309 ◽  
Author(s):  
UTPAL MUKHOPADHYAY ◽  
SAIBAL RAY ◽  
S. B. DUTTA CHOUDHURY
Keyword(s):  
Equation Of State ◽  
Phenomenological Model ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Phenomenological Approach ◽  
Time Dependent ◽  
Equation Of State Parameter ◽  
Dependent Form ◽  
Age Of The Universe ◽  
The Universe

A time-dependent phenomenological model of Λ, viz. [Formula: see text], is selected to investigate the Λ-CDM cosmology. The time-dependent form of the equation-of-state parameter ω is derived and it has been possible to obtain the sought-for flip of sign of the deceleration parameter q. The present age of the Universe, calculated for some specific values of the parameters, agrees very well with the observational data.

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