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34 pages, 556 KB

Open AccessArticle

Finsler-Randers-Bianchi Type-V Cosmological Model and Modified

f (R, T)

Gravity in Lyra Geometry

by Sachin Kumar, Praduman Kumar Dwivedi, Chayan Kumar Mishra, Ioannis Ampazis and Panayiotis C. Stavrinos

Universe 2026, 12(4), 100; https://doi.org/10.3390/universe12040100 - 31 Mar 2026

Viewed by 978

Abstract

In this research paper, we investigate a Finsler-Randers spacetime in the context of a Bianchi type-V model of universe within the framework of Lyra geometry, employing a modified

f (R, T)

gravity theory that incorporates a cosmological constant

Λ

[...] Read more.

In this research paper, we investigate a Finsler-Randers spacetime in the context of a Bianchi type-V model of universe within the framework of Lyra geometry, employing a modified

f (R, T)

gravity theory that incorporates a cosmological constant

Λ

. We have derived the corresponding anisotropic Friedmann equations for the Finsler–Randers Bianchi type-V model of universe with modified

f (R, T)

gravity in Lyra geometry, including the contributions of the cosmological constant and Randers anisotropic terms

b_{0} (t)

and obtained analytical solutions. Further, we have examined the behavior of various dynamical parameters, commonly used in cosmological analysis, both geometrical and graphical interpretations have been provided. Furthermore, we have derived the Raychaudhuri equation in terms of the cosmological constant as a function of the cosmic time t. Our analysis reveals that the shear scalar

σ^{2}

and the scalar expansion

θ

decrease with cosmic time and tend to zero at late times, indicating the isotropization of the universe in the presence of the cosmological constant; however, the Hubble parameter approaches a constant value rather than vanishing, while the energy density

ρ

, pressure

P

, and the Lyra gauge function

β

remain finite and non-zero even at large cosmic times. Ultimately, we conclude that the universe described by this framework exhibits continuous acceleration, as indicated by the negative value of the deceleration parameter q. Full article

(This article belongs to the Special Issue Celebrating the 110th Anniversary of General Relativity: Advances, Challenges and Perspectives)

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18 pages, 872 KB

Open AccessArticle

Hyperbolic Scenario of Accelerating Universe in Modified Gravity

by Raja Azhar Ashraaf Khan, Rishi Kumar Tiwari, Jumi Bharali, Amine Bouali, G. Dilara Açan Yildiz and Ertan Güdekli

Symmetry 2023, 15(6), 1238; https://doi.org/10.3390/sym15061238 - 9 Jun 2023

Cited by 2 | Viewed by 2356

Abstract

Throughout this study, locally rotationally symmetric (LRS) Bianchi type-V space-time is pondered with Tsallis holographic dark energy (THDE) with the Granda–Oliveros (GO) cut-off in the Sáez–Ballester (SB) theory of gravity. A parameterization of the deceleration parameter

(q)

has been suggested: [...] Read more.

(q)

has been suggested:

q = α - \frac{β}{H^{2}}

. The proposed deceleration parameterization demonstrates the Universe’s phase transition from early deceleration to current acceleration. Markov chain Monte Carlo (MCMC) was utilized to have the best-fit value for our model parameter and confirm that the model satisfies the recent observational data. Additional parameters such as deceleration parameter q with cosmographic parameters jerk, snap, and lerk have also been observed physically and graphically. The constructed model is differentiated from other dark energy models using statefinder pair analysis. Some important features of the model are discussed physically and geometrically. Full article

(This article belongs to the Special Issue Application of Symmetry in Gravity Researches)

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17 pages, 1100 KB

Open AccessArticle

Quintessence Behavior of an Anisotropic Bulk Viscous Cosmological Model in Modified f(Q)-Gravity

by Anirudh Pradhan, Archana Dixit and Dinesh Chandra Maurya

Symmetry 2022, 14(12), 2630; https://doi.org/10.3390/sym14122630 - 12 Dec 2022

Cited by 47 | Viewed by 2359

Abstract

In this article, we consider an anisotropic viscous cosmological model having LRS Bianchi type I spacetime with

f (Q)

gravity. We investigate the modified

f (Q)

gravity with form

f (Q) = α Q^{2} + β

[...] Read more.

In this article, we consider an anisotropic viscous cosmological model having LRS Bianchi type I spacetime with

f (Q)

gravity. We investigate the modified

f (Q)

gravity with form

f (Q) = α Q^{2} + β

, where Q is the non-metricity scalar and

α

β

are the positive constants. From the modified Einstein’s field equation having the viscosity coefficient

ξ (t) = ξ_{0} H

, the scale factor is derived as

a (t) = 2 s i n h (\frac{m + 2}{6} \sqrt{\frac{ξ_{0}}{α (2 m + 1)}} t)

. We apply the observational constraints on the apparent magnitude

m (z)

using the

χ^{2}

test formula with the observational data set such as JLA, Union 2.1 compilation and obtained the best approximate values of the model parameters

m, α, H_{0}, ξ_{0}

. We find a transit universe which is accelerating at late times. We also examined the bulk viscosity equation of state (EoS) parameter

ω_{v}

and derived its current value satisfying

ω_{v} < - 1 / 3

, which shows the dark energy dominating universe evolution having a cosmological constant, phantom, and super-phantom evolution stages. It tends to the

Λ

cold dark matter (

Λ

CDM) value (

ω_{v} = - 1

) at late times. We also estimate the current age of the universe as

t_{0} \approx 13.6

Gyrs and analyze the statefinder parameters with

(s, r) \to (0, 1)

t \to \infty

. Full article

(This article belongs to the Special Issue Symmetry in Gravity Research)

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