Anisotropic Cosmological Model in a Modified Theory of Gravitation

Abstract

Current observations indicate that, on a large enough scale, the universe is homogeneous and isotropic. However, this does not preclude the possibility of some anisotropy having occurred during the early stages of the evolution of the universe, which could then have been damped out later. This idea has aroused interest in the Bianchi models, which are homogeneous but anisotropic. Secondly, there is much interest in modified gravity these days due to the problems that the usual ΛCDM model faces in general relativity. Hence, in this paper, a study was conducted on the Bianchi type-I cosmological model in f(R,T)-modified gravity. Following some ideas from cosmography, a specific form of the deceleration parameter was assumed, leading to a model that exhibited a transition from early deceleration to late-time acceleration. The derived model approached isotropy at late times. The physical properties of the model were discussed, and expressions for the various parameters of the model were derived. It is also possible to make progress towards solving the cosmological constant problem, since in this model in f(R,T) gravity, a variable cosmological-type parameter arose, which was large early on but decreased to a constant value in later times.

FLRW Transit Cosmological Model in F (R,T) Gravity

“…Some theorist working in this area have attempted to study it by constructing the cosmological models using geometrical parameters, such as a parametrization of the deceleration parameter, Hubble parameter or scale factor which can provide the transition from past deceleration to present acceleration [21][22][23][24]. Most of these models have been studied in homogeneous and isotropic background [25][26][27][28][29][30][31][32][33], but some studies also have been considered in homogeneous but anisotropic background [34][35][36][37][38][39][40].…”

FLRW Transit Cosmological Model in f (R, T) Gravity

“…Some theorists working in this area have attempted to study it by constructing cosmological models using geometrical parameters, such as the parametrization of the deceleration parameter, Hubble parameter, or scale factor, which can provide the transition from past deceleration to present acceleration [53][54][55][56]. Most of these models have been studied in homogeneous and isotropic backgrounds [57][58][59][60][61][62][63][64][65], but some studies have also been considered in homogeneous but anisotropic backgrounds [66][67][68][69][70][71][72].…”

Bulk Viscous Flat FLRW Model with Observational Constraints in f(T, B) Gravity

“…It is defined by the antisymmetric connection of the non-holonomic basis, which is called the curvature-less Weitzenbock connection [13,14]. In literature, there are various modified theories influenced by teleparallelism that have yielded a variety of intriguing findings in cosmology and astrophysics [15,16] like f (R) theory [8,17,18], f (T) theory [19][20][21][22], f (T, B) theory [23][24][25], f (R, T) theory [26][27][28][29][30][31], f (Q, T) theory [32,33], f (G) theory [34], f (R, G) theory [35], f (Q) theory [18,[36][37][38], F(R, T, Q, τ) theory [39], etc. Recently, Mardan et al [40] have investigated the conformally flat spherically symmetric fluid distribution with a generalized polytropic equation of state in f (R) gravity.…”