Accelerated expansion of the universe model with parametrization of $q(z)$ in $f(R,L_m)$ theory of gravity

TL;DR

This paper investigates the late-time accelerated expansion of the universe using $f(R,L_m)$ gravity models with a parametrized deceleration parameter, deriving Hubble parameter expressions and fitting model parameters with observational data.

Contribution

It introduces specific non-linear $f(R,L_m)$ models and employs a parametric $q(z)$ to analyze cosmic acceleration, providing new insights into cosmological parameters within this framework.

Findings

Model parameters constrained by observational data.

Derived expressions for Hubble parameter and cosmological parameters.

Estimated the current age of the universe.

Abstract

In this research work, we explore the late-time accelerated expansion of the universe within the framework of modified gravity, specifically $f(R, L_m)$ theory, by considering two non-linear models: $f(R, L_{m}) = \frac{R}{2}+(1+\eta R) L_{m}$ and $f(R, L_{m}) = \frac{R}{2}+ L_{m}^{\eta}$, where $\eta$ is a free parameter. Adopting a parametric form of the deceleration parameter $q(z)$, we derive a quadratic expression for the normalized Hubble parameter. By use of Bayesian statistical analysis with the $\chi^{2}$-minimization approach, we determine the median values of the model parameters for both the cosmic chronometer (CC) and the joint (CC+Pantheon) dataset. Furthermore, we examine the fundamental cosmological parameters: energy density, pressure, the equation of state (EoS) parameter and energy conditions. The cosmographic parameters are thoroughly analyzed and the present age of the universe is estimated based on this model.