Exploring the Universe Expansion History with f(R,T) Gravity: Constraints on Cosmological Parameters

Abstract

This work examines the cosmological implications of two functional forms of $f(R,T)=R+\alpha T^n$ gravity: for two different value of $n$ where $n=1$ and $n\ne 1$, and $\alpha$ and $n$ are free parameters. The modified Friedmann equations are derived, and the cosmic evolution of the Hubble parameter $H(z)$ is determined. Cosmological parameters are estimated through ${\chi }^2$ minimization and MCMC analysis using the emcee algorithm, with model parameters constrained by various observational datasets. Both models reproduce late-time acceleration and remain observationally indistinguishable from $\Lambda$CDM, while allowing small deviations parameterized by $\alpha$ and $n$. The cosmological behavior of the deceleration parameter $q(z)$, the jerk, the snap parameter $s(z)$, and the effective equation of state parameter $\omega$ is also analyzed. The results indicate that the Universe transitioned from deceleration to late-time accelerated expansion, consistent with the $\Lambda$CDM model. Analysis of the energy conditions reveals that the NEC and DEC are satisfied, while the SEC is violated, which explains the transition from a decelerating matter-dominated epoch to the present accelerated phase. These findings indicate that the proposed $f(R,T)$ models are compatible with current observational data and provide a viable alternative to $\Lambda$CDM in describing cosmic acceleration.

12 pages, 20 figures. Published in Physics Letters B ( 2026)

References in corpus (10)

• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• f(R,T) gravity
• The Pantheon+ Analysis: Cosmological Constraints
• Disappearing cosmological constant in f(R) gravity
• Construction of cosmologically viable f(G) gravity models
• Generalized energy conditions in Extended Theories of Gravity
• Bouncing cosmology in modified gravity with higher-order curvature terms
• From Hubble to Snap Parameters: A Gaussian Process Reconstruction
• Curvature dominance DE-model in $f(R)$-gravity
• Energy conditions in $f(Q,L_m)$ gravity