arXiv subjects

Anil Kumar Yadav

Publications and source records attributed to Anil Kumar Yadav.

At least 55 records · Page 3Linked to original sources

arXiv2016

$Λ$-CDM type Heckmann - Suchuking model and union 2.1 compilation

In this paper, we have investigated $Λ$CDM type cosmological model in Heckmann-Schucking space-time, by using 287 high red shift ($ .3 \leq z \leq 1.4$ ) SN Ia data of observed absolute magnitude along with their possible error from Union 2.1 compilation. We have used $χ^{2}$ test to compare Union 2.1 compilation observed data and corresponding theoretical values of apparent magnitude $(m)$. It is found that the best fit value for $(Ω_{m})_0$, $(Ω_Λ)_0$ and $(Ω_σ)_0$ are $0.2940$, $0.7058$ and $0.0002$ respectively and the derived model represents the features of accelerating universe which is consistent with recent astrophysical observations.

gr-qc↗

arXiv2016

A transitioning universe with anisotropic dark energy

In this paper, we present a model of transitioning universe with minimal interaction between perfect fluid and anisotropic dark energy in Bianchi I space-time. The two sources are assumed to minimally interacted and therefore their energy momentum tensors are conserved separately. The explicit expression for average scale factor are considered in hybrid form that gives time varying deceleration parameter which describes both the early and late time physical features of universe. We also discuss the physical and geometrical properties of the model derived in this paper. The solution is interesting physically as it explain accelerating universe as well as singularity free universe.

gr-qc↗

arXiv2015

Some Invariant String Cosmological Models in Cylindrically Symmetric Space-time

In this paper we derive some new invariant solutions of Einstein-Maxwell's field equations for string fluid as source of matter in cylindrically symmetric space-time with Variable Magnetic Permeability. We also discuss the physical and eometrical properties of the models derived in the paper. The solutions, at least one of them, are interesting physically as they can explain the accelerating as well as singularity free Universe.

gr-qc↗

arXiv2014

An optimal system and invariant solutions of dark energy Models in cylindrically symmetric space-time

In this paper, we derive some new invariant solutions of dark energy models in cylindrically symmetric space-time. To quantify the deviation of pressure from isotropy, we introduce three different time dependent skewness parameters along the spatial directions. The matter source consists of dark energy which is minimally interact with perfect fluid. We use symmetry analysis method for solving the non-linear partial differential equations (NLPDEs) which is more powerful than the classical methods of solving NLPDEs. The geometrical and kinematical features of the models and the behaviour of the anisotropy of dark energy, are examined in detail.

gr-qc↗

arXiv2014

$Λ$CDM-type cosmological model and observational constraints

In the present work, we have searched the existence of $Λ$CDM-type cosmological model in anisotropic Heckmann-Schucking space-time. The matter source that is responsible for the present acceleration of the universe consist of cosmic fluid with $p = ωρ$, where $ω$ is the equation of state parameter. The Einstein's field equations have been solved explicitly under some specific choice of parameters that isotropizes the model under consideration. It has been found that the derived model is in good agreement with recent SN Ia observations. Some physical aspects of the model has been discussed in detail.

gr-qc↗

arXiv2013

Noncommutative Wormholes in $f(R)$ Gravity with Lorentzian Distribution

In this paper, we derive some new exact solutions of static wormholes in $f(R)$ gravity supported by the matter possesses Lorentizian density distribution of a particle-like gravitational source. We derive the wormhole's solutions in two possible schemes for a given Lorentzian distribution: assuming an astrophysically viable $F(R)$ function such as a power-law form and discuss several solutions corresponding to different values of the exponent (here $F =\frac{df}{dR}$). In the second scheme, we consider particular form of two shape functions and have reconstructed f(R) in both cases. We have discussed all the solutions with graphical point of view.

gr-qc↗

arXiv2013

Bianchi-V string cosmology with power law expansion in $f(R, T)$ Gravity

In this paper, we search the existence of Bianchi-V string cosmological model in $f(R,T)$ gravity with power law expansion. Einstein's field equations have been solved by taking into account the law of variation of Hubble's parameter that yields the constant value of deceleration parameter (DP). We observe that the massive strings dominate the early universe but they do not survive for long time and finally disappear from the universe. We examine the nature of classical potential and also discuss the physical properties of universe.

physics.gen-ph↗

arXiv2013

Symmetry Group Analysis for perfect fluid Inhomogeneous Cosmological Models in General Relativity

In this paper, we have searched the existence of the similarity solution for plane symmetric inhomogeneous cosmological models in general relativity. The matter source consists of perfect fluid with proportionality relation between expansion scalar and shear scalar. The isovector fields of Einstein's field equation for the models under consideration are derived. A new class of exact solutions of Einstein's field equation have been obtained for inhomogeneous space-time. The physical behaviors and geometric aspects of the derived models have been discussed in detail.

gr-qc↗

arXiv2013

Some Plane Symmetric Inhomogeneous Cosmological Models in the Scalar-Tensor Theory of Gravitation

The present study deals with the inhomogeneous plane symmetric models in scalar - tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed.

gr-qc↗

arXiv2012

Anisotropic massive strings in scalar-tensor theory of gravitation

We present the model of anisotropic universe with string fluid as source of matter within the framework of scalar-tensor theory of gravitation. Exact solution of field equations are obtained by applying Berman's law of variation of Hubble's parameter which yields a constant value of DP. The nature of classical potential is examined for the model under consideration. It has been also found that the massive strings dominate in early universe and at long last disappear from universe. This is in agreement with current astronomical observations. The physical and dynamical properties of model are also discussed.

gr-qc↗

arXiv2012

Magnetized dark energy and the late time acceleration

In the present work we have searched the existence of the late time acceleration of the Universe. The matter source that is responsible for the late time acceleration of the Universe consists of cosmic fluid with the equation of state parameter $ω=\frac{p}ρ$ and uniform magnetic field of energy density $ρ_{B}$. The study is done here under the framework of spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-I cosmological model in the presence of magnetized dark energy. To get the deterministic model of the Universe, we assume that the shear scalar $(σ)$ in the model is proportional to expansion scalar $(θ)$. This condition leads to $A=B^{n}$, where $A$ and $B$ are metric functions and $n$ is a positive constant giving the proportionality condition between shear and expansion scalar. It has been found that the isotropic distribution of magnetized dark energy leads to the present accelerated expansion of the Universe and the derived model is in good agreement with the recent astrophysical observations. The physical behavior of the Universe has been discussed in details.

physics.gen-ph↗

arXiv2012

Transit universe with time varying $G$ and decaying $Λ$

We present the model of transit universe from early deceleration phase to current acceleration phase under the framework of general relativity in presence of gravitational coupling $G(t)$ and cosmological terms $Λ(t)$. The Einstein's field equations have been solved by considering time dependent deceleration parameter (DP) which renders the scale factor $a = (t^{n}e^{kt})^{\frac{1}{m}}$ where $m$, $n$ and $k$ are positive constants. The cosmological term $(Λ(t))$ is found to be positive and a decreasing function of time which supports the result obtained from supernovae Ia observations. The geometrical and kinematical features of the model are examined in detail.

physics.gen-ph↗

arXiv2012

Bianchi-V string cosmological model and late time acceleration

In the present work we have searched the existence of the late time acceleration of the universe with string fluid as source of matter in Bianchi V space-time. To get the deterministic solution, we choose the scale factor as increasing function of time that yields a time dependent deceleration parameter, representing a model which generates a transition of universe from early decelerating phase to recent accelerating phase. The study reveals that strings dominate the early universe and eventually disappear from the universe for sufficiently large times i. e. at present epoch. The same is observed by current astronomical observations. The physical behaviour of universe has been discussed in detail.

physics.gen-ph↗

arXiv2012

Dark energy model with variable $q$ and $ω$ in LRS Bianchi-II space-time

The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein's field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(σ^{1}_{1})$ and expansion scalar $(\vartheta)$, which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.

physics.gen-ph↗

arXiv2012

Cosmological constant dominated transit universe from early deceleration to current acceleration phase in Bianchi-V space-time

The paper presents the transition of universe from early decelerating phase to current accelerating phase with viscous fluid and time dependent cosmological constant $(Λ)$ as source of matter in Bianchi-V space-time. To study the transit behaviour of universe, we have assumed the scale factor as increasing function of time which generates a time dependent deceleration parameter (DP). The study reveals that the cosmological term does not change its fundamental nature for $ξ$ = constant and $ξ=ξ(t)$, where $ξ$ is the coefficient of bulk viscosity. The $Λ(t)$ is found to be positive and is decreasing function of time. The same is observed by recent supernovae observations. The physical behaviour of universe has been discussed in detail.

physics.gen-ph↗

arXiv2011

Cylindrically Symmetric Inhomogeneous Universes with a Cloud of Strings

Cylindrically symmetric inhomogeneous string cosmological models are investigated in presence of string fluid as a source of matter. To get the three types of exact solutions of Einstein's field equations we assume $A = f(x)k(t)$, $B = g(x)\ell(t)$ and $C = h(x)\ell(t)$. Some physical and geometric aspects of the models are discussed.

gr-qc↗

arXiv2011

LRS Bianchi-I Anisotropic Cosmological Model with Dominance of Dark Energy

The present study deals with spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with dominance of dark energy. To get the deterministic model of Universe, we assume that the shear scalar $(σ)$ in the model is proportional to expansion scalar $(θ)$. This condition leads to $A=B^{n}$, where $A$,\;$B$ are metric potential and $n$ is positive constant. It has been found that the anisotropic distribution of dark energy leads to the present accelerated expansion of Universe. The physical behavior of the Universe has been discussed in detail.

physics.gen-ph↗

arXiv2011

Singularity-free dark energy star

We propose a model for an anisotropic dark energy star where we assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density. We discuss various physical features of our model and show that the model satisfies all the regularity conditions and stable as well as singularity-free.

gr-qc↗