arXiv subjects

Pratik P. Ray

Publications and source records attributed to Pratik P. Ray.

9 recordsLinked to original sources

arXiv2026

$f(T,\mathcal{L}_m)$ Cosmology Embedded in a Viscous Barotropic Fluid

We examine the cosmological dynamics of a viscous fluid within the framework of $f(T,\mathcal{L}_m)$ gravity by using a barotropic equation of state for cosmic fluid. The modified Friedmann equations are used to construct an analytical Hubble model. Then $H(z)$, Pantheon+SH0ES, DESI DR II BAO, and Cosmic Microwave Background datasets are used in a Bayesian Markov Chain Monte Carlo analysis to constrain its free parameters. Physically viable estimations of the Hubble constant and barotropic equation of state parameter are given by the obtained best-fit values. Based on the constrained parameters, we examine the redshift dependence of deceleration parameter, effective equation of state, dark energy equation of state, the effective pressure and viscous pressure quantities. While the deceleration parameter reveals how the universe evolved from an initially decelerating state to its present accelerating expansion, both equation of state parameters persist in the quintessence regime in the late epoch. Moreover, throughout the cosmic evolution, the viscous and effective pressures stay negative. The observational viability of the suggested viscous $f(T,\mathcal{L}_m)$ cosmological model is supported by the estimated Hubble constant, whose values agree well with the results from independent cosmological observations.

physics.gen-ph↗

arXiv2026

Cosmological Parameters in $f(T)$ Gravity: Theoretical and Observational Analysis

The $f(T)$ gravity is one of the extensions of teleparallel equivalent of general relativity, in which more general functions of the torsion scalar $T$ can be described. With the proposed functional form of $f(T) = \alpha T - \beta u^{-n} + \gamma u^m$, where $u = (-T/6)$, we have analyzed the cosmological parameters using dynamical system analysis and cosmological datasets. The dynamical behavior of this model is analyzed with phase-space analysis by transforming the cosmological equations into an autonomous system. Critical points are identified, and their stability conditions examined, enabling the classifications of the early and late-time evolutionary phases of the Universe. The stability conditions are further demonstrated by phase-portrait diagrams that highlight transitions between radiation, matter, and dark-energy-dominated epochs. Then we used the Markov Chain Monte Carlo statistical technique to constrain the model parameters with the recent observational dataset, such as DESI DR2 BAO, and its combination with the Hubble and Pantheon+SH0ES data. The best-fit values for the model parameters were obtained by data analysis, $m \equiv 0.91^{+0.07}_{-0.09}$ and $n \equiv 0.69^{+0.09}_{-0.08}$, and are well within the stability range obtained ($m<1\land n>-1$) through dynamical system analysis. The combined theoretical and observational analysis shows that the proposed $f(T)$ gravity model successfully reproduces the observed cosmic expansion history of the Universe.

gr-qc↗

arXiv2026

Reconstruction of Accelerating Nonlinear $f(T)$ Gravity Models via Hybrid Scale Factor: Cosmological Dynamics and Bayesian Evidence

This study offers a comprehensive reconstruction of $f(T)$ gravity model with three distinct non-linear as well as novel forms employing a hybrid scale factor to depict the expansion history of the universe starting from early decelerated epoch to late-time accelerated evolution. Model parameters are rigorously constrained using the Monte Carlo Markov Chain (MCMC) analysis with the help of Bayesian statistics and incorporating late-time observations from BAO and Patheon+SH0ES. The investigation of dynamical parameters such as the equation of state parameter and cosmological parameters indicates alignment with an accelerated expansion phase in both the present and late time epochs. Validation is conducted by assessing the energy conditions, verifying the feasibility of the model forms with particular emphasis on the violation of the strong energy condition that indicates dark energy dominance in modified gravity scenarios. This investigation has been instrumental in determining models that remain consistent with cosmological observations and theoretical requirements. The reconstructed forms of the model effectively mimic $\Lambda$CDM at late times, providing significant insights into possible extensions of general relativity and bolstering $f(T)$ gravity theory as a robust explanation for cosmic acceleration.

gr-qc↗

arXiv2025

Reconstructing $f(T)$ Gravity From Hubble Parameterization Constraints

In this paper, we have presented the cosmological model of the Universe that represents late time cosmic acceleration in torsion based gravitational theory, the $f(T)$ gravity. A well motivated parametrization for the Hubble parameter has been introduced and the free parameters involved are constrained using the cosmological datasets. With the constrained values of the free parameters, other geometrical parameters such as deceleration parameter, jerk parameter, and snap parameter are analyzed and confronted with the prescribed value of the cosmological observations. In addition, the dynamical parameters are analyzed in some non-linear form of $f(T)$ and the energy conditions are also studied and confirmed with the violation of the strong energy condition. The obtained cosmological model provides late time phantom behavior of the Universe.

gr-qc↗

arXiv2021

Cosmological models with Big rip and Pseudo rip Scenarios in extended theory of gravity

In this paper, we have presented the big rip and pseudo rip cosmological models in an extended theory of gravity. The matter field is considered to be that of perfect fluid. The geometrical parameters are adjusted in such a manner that it matches the prescriptions given by cosmological observations, to be specific to the range of Hubble tension $(H_{0})$. The models favor phantom behavior. The violation of strong energy conditions are shown in both the models, as it has become essential in an extended gravity. The representative values of the coupling parameter are significant on the evolution of the universe.

gr-qc↗

arXiv2021

Stability analysis of two-fluid dark energy models

In this paper, we have studied the stability of the cosmological models with dark energy and combination of matter fields and dark energy in an anisotropic space time. The pressure anisotropy along the spatial directions are derived and its stability in each direction has been examined. The four models presented here, show its stability on certain spatial direction. The role of matter field on the stability analysis has been obtained. The positive and negative value of cosmic string completely changed the stability behaviour of the model. The presence of a magnetic field disturbs the stability aspects of the models at least in an early epoch.

gr-qc↗

arXiv2018

Anisotropic cosmological models with two fluids

In this paper, aniostropic dark energy cosmological models have been constructed in a Bianchi-V space-time with the energy momentum tensor consisting of two non-interacting fluids namely bulk viscous fluid and dark energy fluid. Two different models are constructed based on the power law cosmology and de Sitter universe. The constructed model also embedded with different pressure gradients along different spatial directions. The variable equation of state (EoS) parameter, skewness parameters for both the models are obtained and analyzed. The physical properties of the models obtained with the use of scale factors of power law and de Sitter law are also presented.

gr-qc↗

arXiv2017

Dark Energy Cosmological Models with General forms of Scale Factor

In this paper, we have constructed dark energy models in an anisotropic Bianchi-V space-time and studied the role of anisotropy in the evolution of dark energy. We have considered anisotropic dark energy fluid with different pressure gradients along different spatial directions. In order to obtain a deterministic solution, we have considered three general forms of scale factor. The different forms of scale factors considered here produce time varying deceleration parameters in all the cases that simulates the cosmic transition. The variable equation of state (EoS) parameter, skewness parameters for all the models are obtained and analyzed. The physical properties of the models are also discussed.

physics.gen-ph↗

arXiv2017

Accelerating Dark Energy Cosmological Model in Two Fluid with Hybrid Scale Factor

In this paper, we have investigated the anisotropic behavior of the accelerating universe in Bianchi V space time in the frame work of General Relativity (GR). The matter field we have considered is of two non interacting fluids i.e. the usual string fluid and dark energy (DE) fluid. In order to represent the pressure anisotropy, the skewness parameters are introduced along three different spatial directions. To achieve a physically realistic solutions to the field equations, we have considered a scale factor, known as hybrid scale factor, which is generated by a time varying deceleration parameter. This simulates a cosmic transition from early deceleration to late time acceleration. It is observed that the string fluid dominates the universe at early deceleration phase but does not affect nature of cosmic dynamics substantially at late phase where as, the DE fluid dominates the universe in present time, which is in accordance with the observations results. Hence, we analysed here the role of two fluids in the transitional phases of universe with respect to time which depicts the reason behind the cosmic expansion and DE. The role of DE with variable equation of state parameter (EoS), skewness parameters also discussed along with physical and geometrical properties.

gr-qc↗