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Binaya K. Bishi

Publications and source records attributed to Binaya K. Bishi.

9 recordsLinked to original sources
arXiv2019

Variable Chaplygin gas cosmologies in f(R, T) gravity with particle creation

A flat FLRW cosmological model with perfect fluid comprising of variable Chaplygin gas has been studied in context of f(R; T) gravity with particle creation. The considered scale factors describe the accelerated expansion of universe due to the effective negative pressure produced during evolution of universe. The role of particle creation pressure on the cosmological parameters have been discussed in detail. By considering well accepted values of free parameters, the late time expansion of the universe with energy conditions have also been studied. The state-finder diagnostic for the considered cases have been studied and the evolution of source function with time have suggested almost constant particle production at late times.

gr-qc↗
arXiv2018

$f(R,T)=f(R)+λT$ gravity models as alternatives to cosmic acceleration

This article presents cosmological models that arise in a subclass of $f(R,T)=f(R)+f(T)$ gravity models, with different $f(R)$ functions and fixed $T$-dependence. That is, the gravitational lagrangian is considered as $f(R,T)=f(R)+λT$, with constant $λ$. Here $R$ and $T$ represent the Ricci scalar and trace of the stress-energy tensor, respectively. The modified gravitational field equations are obtained through the metric formalism for the Friedmann-Lemaître-Robertson-Walker metric with signature $(+,-,-,-)$. We work with $f(R)=R+αR^2-\frac{μ^4}{R}$, $f(R)=R+k\ln(γR)$ and $f(R)=R+me^{[-nR]}$, with $α, μ, k, γ, m$ and $n$ all free parameters, which lead to three different cosmological models for our Universe. For the choice of $λ=0$, this reduces to widely discussed $f(R)$ gravity models. This manuscript clearly describes the effects of adding the trace of the energy-momentum tensor in the $f(R)$ lagrangian. The exact solution of the modified field equations are obtained under the hybrid expansion law. Also we present the Om diagnostic analysis for the discussed models.

gr-qc↗
arXiv2017

Magnetized strange quark matter in $f(R,T)$ gravity with bilinear and special form of time varying deceleration parameter

In this paper, we have studied homogeneous and anisotropic, locally rotationally symmetric (LRS) Bianchi type-I universe model with magnetized strange quark matter (MSQM) distribution and cosmological constant $Λ$ in $f(R,T)$ gravity. The exact solutions of the field equations are obtained under bilinear and special form of time varying deceleration parameter (DP). Firstly we have considered two specific form of bilinear DP with a single parameter of the form: $q=\frac{α(1-t)}{1+t}$ and $q=-\frac{αt}{1+t}$, which leads to a function with constant or linear nature with respect to the choice of constant $α$. Second one is the special form of the DP as $q=-1+\fracβ{1+a^β}$. From obtained results, we could say that in the early universe the magnetic flux has more effects and it gradually reducing its effects in later. For $t\rightarrow \infty$, we get $p\rightarrow -B_c$ and $ρ\rightarrow B_c$. So the strange quark matter along with magnetic epoch gives an idea of accelerated expansion of the universe as per the observations of the type Ia Supernovae.

gr-qc↗
arXiv2017

LRS Bianchi type-I cosmological model with constant deceleration parameter in $f(R,T)$ gravity

A spatially homogeneous anisotropic LRS Bianchi type-I cosmological model is studied in $f(R,T)$ gravity with a special form of Hubble's parameter, which leads to constant deceleration parameter. The parameters involved in the considered form of Hubble parameter can be tuned to match, our models with the $Λ$CDM model. With the present observed value of the deceleration parameter, we have discussed physical and kinematical properties of a specific model. Moreover, we have discussed the cosmological distances for our model.

gr-qc↗
arXiv2017

Magnetized strange quark model with Big Rip singularity in $f(R,T)$ gravity

LRS (Locally Rotationally symmetric) Bianchi type-I magnetized strange quark matter cosmological model have been studied based on $f(R,T)$ gravity. The exact solutions of the field equations are derived with linearly time varying deceleration parameter which is consistent with observational data (from SNIa, BAO and CMB) of standard cosmology. It is observed that the model start with big bang and ends with a Big Rip. The transition of deceleration parameter from decelerating phase to accelerating phase with respect to redshift obtained in our model fits with the recent observational data obtained by Farook et al. in 2017. The well known Hubble parameter $H(z)$ and distance modulus $μ(z)$ are discussed with redshift.

physics.gen-ph↗
arXiv2017

Anisotropic cosmological models in $f(R,T)$ gravity with variable deceleration parameter

The objective of this work enclosed with the study of spatially homogeneous anisotropic Bianchi type-I universe in $f(R,T)$ gravity (where $R$ is the Ricci scalar and $T$ is the trace of stress energy momentum tensor) in two different cases viz. $f(R,T)=R+2f(T)$ and $f(R,T)=f_1(R)+f_2(T)$ with bulk viscosity matter content. In this study, we consider a time varying deceleration parameter, which generates an accelerating universe to obtain the exact solution of the field equations. The physical and kinematical properties of both the models are discussed in detail for the future evolution of the universe. We have explored the nature of WEC, DEC, SEC and energy density for both the cases. We have found that both the models, with bulk viscosity matter component, show an acceleration of the universe. We have also shown that the cosmic jerk parameter is compatible with the three kinematical data sets.

gr-qc↗
arXiv2016

Scalar field and time varying Cosmological constant in $f(R,T)$ gravity for Bianchi type-I Universe

In this article, we have analysed the behaviour of scalar field and cosmological constant in $f(R,T)$ theory of gravity. Here, we have considered the simplest form of $f(R,T)$ i.e. $f(R,T)=R+2f(T)$, where $R$ is the Ricci scalar and $T$ is the trace of the energy momentum tensor and explored the spatially homogeneous and anisotropic Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model. It is assumed that the Universe is filled with two non-interacting matter sources namely scalar field (normal or phantom) with scalar potential and matter contribution due to $f(R,T)$ action. We have discussed two cosmological models according to power law and exponential law of the volume expansion along with constant and exponential scalar potential as sub models. Power law models are compatible with normal (quintessence) and phantom scalar field whereas exponential volume expansion models are compatible with only normal (quintessence) scalar field. The values of cosmological constant in our models are in agreement with the observational results. Finally, we have discussed some physical and kinematical properties of both the models.

gr-qc↗
arXiv2015

Bianchi type-I Universe with Cosmological constant and quadratic equation of state in f(R,T) modified gravity

This article deals with the study of Bianchi type-I universe in the context of f(R,T) gravity. Einstein's field equations in f(R,T) gravity has been solved in presence of cosmological constant ? and quadratic equation of state. Here we have discussed two classes of f(R,T) gravity i.e. f(R,T) = R + 2f(T) and f(R,T) = f_1(R) + f_2(T). A set of models has been taken into consideration based on the plausible relation. Also we have studied the some physical and kinematical properties of the models.

gr-qc↗