Bianchi type-I Cosmological Model Research Articles

Perfect Fluid with Heat Flow in f(T) Theory of Gravity

Bianchi Type-I cosmological models have been a subject of extensive research in cosmology due to their simplicity and relevance in understanding the dynamics of the early Universe. In this study, we investigate the dynamics of such models within the framework of f(T) gravity, an alternative theory of gravity that extends teleparallel gravity by introducing a general function of the torsion scalar, T. We focus on the presence of a perfect fluid with heat flow in the cosmic medium. By solving the field equations of f(T) gravity, we obtain exact solutions for the Bianchi Type-I cosmological models. These solutions provide valuable insights into the evolution of the Universe and how it is influenced by the modified gravity theory. Furthermore, we derive cosmological parameters in terms of redshift, offering a convenient way to interpret observational data and connect theoretical predictions to empirical measurements. Our findings not only contribute to a deeper understanding of the dynamics of Bianchi Type-I cosmological models but also provide a foundation for comparing f(T) gravity with standard general relativity in the context of observational cosmology. This research paves the way for further exploration of alternative gravity theories and their implications for the early Universe’s evolution and structure.

Cold dark matter and holographic dark energy in f(R,T) theory of gravity

In this study, we have examined the cosmological model of the locally rotationally symmetric (LRS) Bianchi Type-I universe within the framework of the [Formula: see text] theory of gravity. The [Formula: see text] theory incorporates the Ricci scalar (R) and the trace of the energy–momentum tensor (T) in its formulation. Our investigation focuses on the cold dark matter (CDM) and holographic dark energy (DE) cosmological models, particularly in relation to the occurrence of a big rip singularity. To solve the field equation, we have assumed a specific relationship between the parameters, [Formula: see text] and [Formula: see text], where [Formula: see text] is proportional to [Formula: see text] and m is held constant. We have examined the existence of both the Big Bang and Big Rip singularities within this cosmological model. Additionally, we have analysed the state-finder parameter, which provides insights into the dynamics and evolution of the universe. Furthermore, we have discussed the physical and geometrical parameters of the universe in this context. These parameters help characterize and describe the behavior of the universe, shedding light on its underlying properties and dynamics. Through our investigation, we aim to deepen our understanding of the LRS Bianchi Type-I cosmological model within the [Formula: see text] theory of gravity, exploring the interplay between CDM, holographic DE, singularities, and the various parameters that contribute to the understanding of the universe.

Stability aspects of an LRS Bianchi type-I cosmological model in f(Q) gravity

Stability aspects of an LRS Bianchi type-I cosmological model in f(Q) gravity

Energy Conditions and Statefinder Diagnostic of Cosmological Model with Special Law of Hubble Parameter in f(R, T) Gravity

In this article, we examine the LRS Bianchi type-I cosmological model in the framework of f(R, T) gravity, where R is the Ricci scalar and T is the stress energy momentum tensor in the presence of Domain wall. we used the special law of variation of Hubble’s parameter proposed by Berman (1983) to obtained the exact solution of field equation, corresponds to the model of the universe. The Energy conditions and physical behaviour of the universe has been obtained and their evolution has been discussed using some physical parameter and by means of their graphs. Also, we can use the Statefinder parameter for testing the validity of the model.

LRS Bianchi type-I cosmological model in f(Q,T) theory of gravity with observational constraints

We have investigated LRS Bianchi type-I cosmological model in [Formula: see text] theory of gravity with observational constraints. In [Formula: see text] theory of gravity [Formula: see text] is non-metricity and T is a trace of energy–momentum tensor. Two different functional forms of [Formula: see text] and [Formula: see text] are considered in this work where [Formula: see text], [Formula: see text] and [Formula: see text] are model parameters. We have obtained the best-fit values of constant parameters using least square method for observational constraints using the available datasets like Hubble dataset [Formula: see text], JLA, Pantheon, etc., by applying Root Mean Squared Error (RMSE) formula.

Stability analysis of LRS Bianchi type-I cosmological model with varying $$\Lambda $$

Stability analysis of LRS Bianchi type-I cosmological model with varying $$\Lambda $$

Thermodynamical aspects of Bianchi type-I Universe in quadratic form of [formula omitted] gravity and observational constraints

In this paper, we discuss the Bianchi type-I cosmological model in the framework of symmetric teleparallel gravity say f(Q) gravity in which the non-metricity term Q is responsible for the gravitational interaction. We consider a special form of the f(Q) function which can be cast as f(Q)=λQn, where λ and n both are the dynamical model parameters. Such a choice can be viewed as a hybrid scale factor that leads to a relation between cosmic time and redshift as t=(αt0β)W[βαeβ−ln⁡(1+z)α] which describes a ΛCDM model of the Universe with the expansion evolving from decelerating to an acceleration phase. The best values for the model parameters i.e. α and β that would accord with the most current observational datasets are then estimated. We make use of 57 points from the Hubble dataset, 1048 points from the supernovae of type Ia dataset and 6 points from the BAO dataset. We use the Markov Chain Monte Carlo (MCMC) technique in conjunction with Bayesian analysis and the likelihood function. Further, we study the validity of our model with the investigation of the thermodynamical quantities, energy conditions along with some physical variables such as the EoS, and jerk parameters. Next, our results are discussed in light of current observational data and trends.

LRS Bianchi type-I cosmological models with periodic time varying deceleration parameter in f(R,T) gravity

In this research, we examine a spatially homogeneous anisotropic locally rotationally symmetric (LRS) Bianchi type-I cosmological model in [Formula: see text] gravity, for some choices of the function [Formula: see text] (arXiv:1104.2669 [gr-qc]). The precise solutions of the field equations are introduced for the periodic-time varying deceleration parameter that can adjust to meet the [Formula: see text]CDM model. We have reviewed the physical and dynamic characteristics of these models to understand the accelerated expansion of the Universe in the current era. Furthermore, SNe Ia union data (arXiv:0811.2379 [astro-ph]), SN Ia with BAO and CMB observations (arXiv:1203.3213 [astro-ph.CO]) and OHD[Formula: see text]JLA data (arXiv:1711.03437 [astro-ph.CO]) are used to estimate the statefinder diagnostics to get the geometric dynamics of the Universe at distinct stages and also to find the luminosity distance, angular-diameter distance, and distance modulus. We have also investigated the transit points for the deceleration parameter (q) in the framework of these three observations within the range of redshift [Formula: see text].

Microscopic Body Cosmological Model

In this paper we study Bianchi type-I cosmological model in presence of microscopic body in self-creation theory. We solve field equation by using relation B  Am ,C  An and equation of state of microscopic body. Also we discuss physical and kinematical properties and discussed stability of obtained model.

Stability analysis of anisotropic Bianchi type-I cosmological model in teleparallel gravity

In this work, we study a cosmological model of Bianchi type-I Universe in teleparallel gravity for a perfect fluid. To obtain the cosmological solution of the model, we assume that the deceleration parameter (DP) is a linear function of the Hubble parameter H i.e. q = −1 + βH (where β as a positive constant). Consequently, we get a model of our Universe, where it goes from the initial phase of deceleration to the current phase of acceleration. We have discussed some physical and geometric properties such as Hubble parameter, DP, energy density, pressure, and equation of state parameter and study their behavior graphically in terms of redshift and compare it with observational data such as Type Ia supernovae. We also discussed the behavior of other parameters such as the jerk parameter, statefinder parameters and we tested the validity of the model by studying the stability analysis and energy conditions.

Bianchi Type-I Anisotropic Universe with Metric Potential in Saez-Ballester Theory of Gravitation

Bianchi Type-I cosmological model in the presence of Saez-Ballester theory gravitation is studied. An exact solution of the field equation is given by considering the cosmological model yield a metric potential included with a real number. The relation between the deceleration parameter and Hubble parameter and average scale factor is used in that cosmological model. The effect of the viscosity on the entropy of the universe is utilized by energy momentum tensor with bulk viscous terms in a conservative manner. We obtained a formula for calculating the entropy of the universe in terms of viscosity and used it to compare to the study. Also, various physical and kinematical properties have been discussed.

On a Bianchi type-I space-time with bulk viscosity in f(R,T) gravity

In this paper, we present a spatially homogeneous and anisotropic Bianchi type-I cosmological model with a viscous bulk fluid in [Formula: see text] gravity where [Formula: see text] and [Formula: see text] are the Ricci scalar and trace of the energy-momentum tensor, respectively. The field equations are solved explicitly using the hybrid law of the scale factor, which is related to the average Hubble parameter and gives a time-varying deceleration parameter (DP). We found the deceleration parameter describing two phases in the universe, the early deceleration phase [Formula: see text] and the current acceleration phase [Formula: see text]. We have calculated some physical and geometric properties and their graphs, whether in terms of time or redshift. Note that for our model, the bulk viscous pressure [Formula: see text] is negative and the energy density [Formula: see text] is positive. The energy conditions and the [Formula: see text] analysis for our spatially homogeneous and anisotropic Bianchi type-I model are also discussed.

Spinor fields in -gravity

We present a tetrad–affine approach to gravity coupled to spinor fields of spin-. After deriving the field equations, we derive the conservation law of the spin density, showing that the latter ensures the vanishing of the antisymmetric part of the Einstein-like equations, just as it happens in theories with torsion and metricity. We then focus on Bianchi type-I cosmological models proposing a general procedure to solve the corresponding field equations and providing analytical solutions in the case of gravitational Lagrangian functions of the kind . At late time such solutions are seen to isotropize and, depending on the value of the exponent n, they can undergo an accelerated expansion of the spatial scale factors.

Higher Dimensional Bianchi Type-I Cosmological Models With Massive String in General Relativity

Here we studied Bianchi type-I cosmological models with massive strings in general relativity in five dimensional space time. Out of the two different cases obtained here, one case leads to a five dimensional Bianchi type-I string cosmological model in general relativity while the other yields the vacuum Universe in general relativity in five dimensional space time. The physical and geometrical properties of the model Universe are studied and compared with the present day’s observational findings. It is observed that our model is anisotropic, expanding, shearing, and decelerates at an early stage and then accelerates at a later time. The model expands along x, y, and z axes and the extra dimension contracts and becomes unobservable at t → ∞. We also observed that the sum of the energy density (ρ) and the string tension density (λ) vanishes (ρ + λ = 0).

Interacting anisotropic dark energy with hybrid expansion in [formula omitted] gravity

This paper investigates the locally rotationally symmetric(LRS) Bianchi type-I cosmological models in f(R,T) gravity, where R is the Ricci scalar and T is the trace of the energy momentum tensor. We find the solutions of the field equations of Bianchi type-I space time by assuming the Hybrid Expansion Law(HEL) for the average scale factor and a particular form of the functional f(R,T)=R+2f(T) where f(T)=μT. It is observed that the Universe with hybrid expansion becomes anisotropic in the early phase, later transforms into isotropic Universe at late epoch. Energy conditions of the model have been investigated. It is observed that strong energy condition is violated which is in agreement with present observation. The derived model also overlaps with ΛCDM at late epoch. We presented both geometrical and physical behaviors of the derived model.

Anisotropic Cosmological Model in a Modified Theory of Gravitation

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.

Some dark energy cosmological models in [formula omitted] gravity

In this paper, locally rotationally symmetric Bianchi type-I cosmological models in f(R,ϕ) theory of gravity have been investigated, where R and ϕ are Ricci scalar and scalar potential function, respectively. Some exact solutions pertaining to the dark energy and the cosmic expansion have been found by implementing the power law model f(R,ϕ)=λRm+1+βϕl+1, with λ,m, β and l being the arbitrary real constants, such that m,β≠−1 for the sake of non-triviality. Some important physical attributes like the pressure, energy density, equation of the state parameter, skewness parameter and energy conditions have been studied and analysed graphically. It has been concluded that both of the models are favorable for cosmic expansion. Furthermore, expansion of universe may be justified in f(R,ϕ) gravity under these models.

Bianchi type-I cosmological model with Tsallis holographic dark energy in f(R,T) theory of gravity

Objectives: In the f(R, T) theory of gravity, to examine the Bianchi type-I model with dark matter and Tsallis holographic dark energy (THDE). Method: To acquire exact solutions of the field equations, we used THDE density and two separate volumetric expansions. The model’s physical properties are compared to current observational evidence. Findings/ Novelty: The universe is in accelerating stage for both volumetric expansion models and it reaches isotropy at a delayed time, according to the study of the deceleration parameter. In addition, our model acts as a lambda model. Keywords: Bianchi type-I; THDE; f(R T) gravity; Isotropy; Lambda model

Bianchi type-I bulk viscous cosmological model with inhomogeneous equation of state

In the present paper we investigate Bianchi type-I Cosmological model with inhomogeneous equation of state (EoS) in the presence of variable bulk viscous fluid(ζ) in the framework of general theory of relativity. In order to find exact solutions of the Einstein’s field equations, we have assumed a special law of variation for Hubble parameter H i. e. . The nature of model is discussed for α ≠ 0 and α = 0. Some physical and kinematical aspects of model are also discussed for both the conditions.

Dynamics of Bulk Viscous String Cosmological Model in f(R,G) Theory of Gravity

Existing investigations dedicated to the self-propelling investigation of dynamics of bulk viscous string in LRS Bianchi type-I cosmological model within the circumstance of alternative theory of gravity with Langrangian be the impulsive perform of Ricci scalar R and Gouss-Bonnet invariant G , say f(R,G) gravity. Exact solutions of the field equations correspond to special law of variation which provides singular model. Also some physical and kinematical aspects and its behavior with the present day universe of the cosmological model have been discussed.