Observational analysis of late-time acceleration in f(Q,Lm) gravity

Abstract

In this study, we explored late-time cosmology within an extended class of theories based on f(Q,Lm) gravity. This theory generalizes f(Q) gravity by incorporating a non-minimal coupling between the non-metricity Q and the matter Lagrangian Lm, analogous to the f(Q,T) theory. The coupling between Q and Lm leads to the non-conservation of the matter energy-momentum tensor. We first investigated a cosmological model defined by the functional form f(Q,Lm)=αQ+βLmn, where α, β, and n are constants. The derived Hubble parameter H(z)=H0(1+z)3n2(2n−1) indicates that n significantly influences the scaling of H(z) over cosmic history, with n>2 suggesting accelerated expansion. We also examined the simplified case of n=1, leading to the linear form f(Q,Lm)=αQ+βLm, consistent with a universe dominated by non-relativistic matter. Using various observational datasets, including H(z) and Pantheon, we constrained the model parameters. Our analysis showed that the f(Q,Lm) model aligns well with observational results and exhibits similar behavior to the ΛCDM model. The results, with q0=−0.22±0.01 across all datasets, indicate an accelerating universe, highlighting the model's potential as an alternative to ΛCDM.