Constraining $f(Q, L_m)$ gravity with bulk viscosity

TL;DR

This paper explores how bulk viscosity affects late-time cosmic acceleration in an extended $f(Q, L_m)$ gravity model, constraining parameters with observational data and showing the model mimics quintessence dark energy.

Contribution

It introduces a specific $f(Q, L_m)$ gravity model with bulk viscosity and derives exact solutions, constraining them with observational datasets to explain cosmic acceleration.

Findings

Deceleration parameter indicates current acceleration.

Effective equation of state resembles quintessence dark energy.

Model behavior confirmed by $Om(z)$ diagnostic.

Abstract

We investigate the influence of bulk viscosity on late-time cosmic acceleration within an extended $f(Q, L_m)$ gravity framework, where the non-metricity $Q$ is non-minimally coupled with the matter Lagrangian $L_m$. Analyzing the function $f(Q, L_m) = \alpha Q + \beta L_m$, we derive exact solutions under non-relativistic matter domination. Using observational datasets ($H(z)$, Pantheon supernovae, and their combination), we constrain the model parameters $H_0$, $\alpha$, $\beta$, and $\zeta$. The deceleration parameter transitions from positive to negative values around redshifts $z_t \approx 0.80$ to $0.99 $, indicating current accelerated expansion. Moreover, the effective equation of state parameter, $\omega_{eff}$, resembles quintessence dark energy ($-1 < \omega_{eff} < -\frac{1}{3}$), with corresponding values from respective datasets. Finally, we use the $Om(z)$ diagnostic, which confirms that our model demonstrates quintessence-like behavior. Our findings underscore the significant role of bulk viscosity in understanding accelerated expansion in the universe within alternative gravity theories.