P. K. Sahoo

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) = f1(R) + f2(T) with bulk viscosity matter content. In this study, we consider a time varying deceleration parameter (DP), 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.

Bianchi type VI1 cosmological model with wet dark fluid in scale invariant theory of gravitation

In this paper, we have investigated Bianchi type VIh, II and III cosmological model with wet dark fluid in scale invariant theory of gravity, where the matter field is in the form of perfect fluid and with a time dependent gauge function (Dirac gauge). A non-singular model for the universe filled with disorder radiation is constructed and some physical behaviors of the model are studied for the feasible VIh (h=1) space-time.

On Bianchi Type-I Mesonic Cosmological Model In Bimetric Theory

Anisotropic spatially homogeneous Bianchi type-I cosmological model in bimetric theory of gravitation (Rosen, 1973) is considered. It is shown that the Bianchi type-I cosmological model does not exist in case of both meson field and mesonic perfect fluid (with or without mass parameter). Hence only vacuum models can be obtained (Reddy and Venkateswarlu, 1989).

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

Locally rotationally symmetric (LRS) Bianchi type-I magnetized strange quark matter (SQM) cosmological model has 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 begins with big bang and ends with a Big Rip. The transition of the 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. [Astrophys. J. 835, 26 (2017)]. The well-known Hubble parameter H(z) and distance modulus μ(z) are discussed with redshift.

String Cloud and Domain Walls with Quark Matter for Plane Symmetric Cosmological Model in Bimetric Theory

We have studied the plane symmetric cosmological solutions for quark mattercoupled with the string cloud and domain walls in the context ofRosen’s (General Relativity and Gravitation 4:435, 1973) bimetrictheory. It is observed that, in this theory, string cloud and domain wallsdo not exist. As we know that, at the early stage of evolution of theuniverse, domain walls as well as cosmic strings do appear which lead to theformation of galaxies. Thus, it may be said that the bimetric relativitydoes not help to describe the early era of the universe.Pacs04.50+h

Some Bianchi Type Cosmological Models in Bimetric Theory

It is shown that anisotropic spatially homogeneous Bianchi types III and VI0 cosmological models do not exist in Rosens [N. Rosen: Gen. Rel. Grav. 4 (1973) 435] bimetric theory when the source of gravitation is governed by either perfect fluid or mesonic perfect fluid. Hence the vacuum models are constructed.

String Cloud and Domain Walls with Quark Matter in Kink Cosmological Model

We have studied quark matter coupled with string cloud and domain walls in the context of general relativity. For this purpose, we solved Einstein’s field equations for quark matter coupled to the string cloud and domain walls in spherical symmetric kink space-time. It is found that cosmic strings and domain walls do not survive in this space-time. Hence, the space-time in both the cases reduces to Minkowskian and the space-time is flat.

Cosmological constant Λ in f(R,T) modified gravity

In this paper, we have studied the Bianchi type-III cosmological model in the presence of cosmological constant in the context of f(R,T) modified theory of gravity. Here, we have discussed two classes of f(R,T) gravity, i.e. f(R,T) = R + f(T) and f(R,T) = f1(R) + f2(T). In both classes, the modified field equations are solved by the relation expansion scalar θ that is proportional to shear scalar σ which gives A = Cn, where A and C are metric potentials. Also we have discussed some physical and kinematical properties of the models.

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

Abstract In this paper, we have studied homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type-I model with magnetized strange quark matter (MSQM) distribution and cosmological constant Λ in f(R, T) gravity where R is the Ricci scalar and T the trace of matter source. 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 forms of bilinear DP with a single parameter of the form: q = α ( 1 − t ) 1 + t and q = − α t 1 + t , which leads to the constant or linear nature of the function based on the constant α. Second one is the special form of the DP as q = − 1 + β 1 + a β . From the results obtained here, one can observe that in the early universe magnetic flux has more effects and it reduces gradually in the later stage. For t → ∞, we get p → − B c and ρ → Bc. The behaviour of 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.

Two fluid anisotropic dark energy models in a scale invariant theory

Abstract.Some anisotropic Bianchi V dark energy models are investigated in a scale invariant theory of gravity. We consider two non-interacting fluids such as dark energy and a bulk viscous fluid. Dark energy pressure is considered to be anisotropic in different spatial directions. A dynamically evolving pressure anisotropy is obtained from the models. The models favour phantom behaviour. It is observed that, in presence of dark energy, bulk viscosity has no appreciable effect on the cosmic dynamics.