The cosmology of $f(R, L_m)$ gravity: constraining the background and perturbed dynamics

Abstract

This paper delves into the late-time accelerated expansion of the universe and the evolution of cosmic structures within the context of a specific \( f(R, L_m) \) gravity model, formulated as \( f(R, L_m) = \lambda R + \beta L_m^\alpha + \eta \). To study the cosmological viability of the model, we employed the latest cosmic measurement datasets: i) 57 observational Hubble parameter data points (\texttt{OHD}); ii) 1048 distance moduli data points (\texttt{SNIa}); iii) a combined dataset (\texttt{OHD+SNIa}); and large scale structure datasets, including iv) 14 growth rate data points (\texttt{f}); and v) 30 redshift space distortion data points (\texttt{f}$\sigma_8$). These datasets facilitated the constraint of the \( f(R, L_m) \)-gravity model via MCMC simulations, followed by a comparative analysis with the \(\Lambda\)CDM model. A comprehensive statistical analysis has been conducted to evaluate the \( f(R, L_m) \)-gravity model's efficacy in explaining both the accelerated expansion of the universe and the growth of cosmic structures.