Constraining anisotropic universe under $f(R,T)$ theory of gravity

TL;DR

This work investigates an anisotropic Bianchi type V universe within $f(R,T)$ gravity with a nonminimal matter-geometry coupling, solved using a power-law scale factor and constrained by $H(z)$, BAO, and Pantheon data. The model yields $H_0$ values near 68–69 km s$^{-1}$ Mpc$^{-1}$ and an age of about $14.3$–$14.9$ Gyr, broadly aligning with Planck ΛCDM expectations, while predicting SEC violation at late times to account for acceleration. Energy conditions indicate NEC, WEC, and DEC are satisfied; the cosmological diagnostics Om$(z)$, state finder, and jerk parameter provide supportive but data-dependent insights into the expansion history. Overall, the anisotropic $f(R,T)$ framework with the chosen coupling and a power-law expansion can be compatible with current observations, offering an alternative route to explain cosmic acceleration without a cosmological constant.

Abstract

We try to find the possibility of a Bianchi V universe in the modified gravitational field theory of $f(R,T)$. We have considered a Lagrangian model in the connection between the trace of the energy-momentum tensor $T$ and the Ricci scalar $R$. In order to solve the field equations a power law for the scaling factor was also considered. To make a comparison of the model parameters with the observational data, we put constraints on the model under the datasets of the Hubble parameter, Baryon Acoustic Oscillations, Pantheon, joint datasets of Hubble parameter + Pantheon, and collective datasets of the Hubble parameter + Baryon Acoustic Oscillations + Pantheon. The outcomes for the Hubble parameter in the present epoch are reasonably acceptable, especially since our estimation of this $H_0$ is remarkably consistent with various recent Planck Collaboration studies that utilize the $Λ$-CDM model.

Figures (18)

• Figure 1: $1D$ marginalized distribution and $2D$ contour diagrams for the present $f(R,T)$ model parameters with the $H(z)$ dataset.
• Figure 2: $1D$ marginalized distribution and $2D$ contour diagrams for the present $f(R,T)$ model parameters with the BAO dataset.
• Figure 3: $1D$ marginalized distribution and $2D$ contour diagrams for the present $f(R,T)$ model parameters with the Pantheon dataset.
• Figure 4: $1D$ marginalized distribution and $2D$ contour diagrams for the present $f(R,T)$ model parameters with the combined $H(z)$ and Pantheon dataset.
• Figure 5: $1D$ marginalized distribution and $2D$ contour diagrams for the present $f(R,T)$ model parameters with the combined $H(z)$, BAO and Pantheon dataset.