Late-time cosmology in f(Q,Lm) gravity: Analytical solutions and observational fits

Abstract

In this study, we examined the late-time cosmic expansion of the universe within the framework of $f(Q,L_m)$ gravity, where $Q$ denotes the non-metricity and $L_m$ represents the matter Lagrangian. We analyzed a linear $f(Q,L_m)$ model of the form $f(Q,L_m)=-\alpha Q+2L_m+\beta$. Using MCMC methods, we constrained the model parameters $H_0$, $\alpha$, and $\beta$ with various datasets, including $H\left(z\right)$, Pantheon+SH0ES, and BAO data. For the $H\left(z\right)$ dataset, we found $H_0=67.90\pm 0.66$, $\alpha =0.1072_{-0.0069}^{+0.0054}$, and $\beta =-1988.2\pm 1.0$. For the Pantheon+SH0ES dataset, $H_0=70.05\pm 0.68$, $\alpha =0.0916_{-0.0033}^{+0.0028}$, and $\beta =-1988.3\pm 1.0$. For the BAO dataset, $H_0=68.1\pm 1.0$, $\alpha =0.1029_{-0.0052}^{+0.0041}$, and $\beta =-1988.24\pm 0.99$. Moreover, the energy density remains positive and approaches zero in the distant future, and the deceleration parameter indicates a transition from deceleration to acceleration, with transition redshifts of $z_t=0.60$, $z_t=0.78$, and $z_t=0.66$ for the respective datasets. These findings align with previous observational studies and contribute to our understanding of the universe’s expansion dynamics.