Phase space analysis in $f(R,L_{m})$ gravity with scalar field

TL;DR

This paper explores the cosmological dynamics of $f(R, \\mathcal{L}_m)$ gravity with scalar fields, revealing stable late-time accelerated expansion and matter-dominated phases through dynamical system analysis.

Contribution

It introduces a detailed dynamical system analysis of $f(R, \\mathcal{L}_m)$ gravity with scalar fields, including stability of critical points and late-time acceleration solutions.

Findings

Existence of matter-dominated and accelerated phases.

Stable late-time de Sitter-like attractors.

Transition from decelerated to accelerated expansion.

Abstract

In this work, we investigate the cosmological dynamics of the $f(R, \mathcal{L}_m)$ gravity framework with a particular focus on the contributions of the scalar field. Considering a functional form that includes linear and exponential dependence on the matter Lagrangian, we perform a detailed dynamical system analysis by introducing appropriate dimensionless variables and constructing the corresponding autonomous system. The critical points are obtained and analyzed, and due to their non-hyperbolic nature, center manifold theory is employed to determine their stability. The analysis reveals the existence of matter-dominated and accelerated phases of the Universe, along with a transition from a decelerated to an accelerated expansion. We further extend the model by incorporating a minimally coupled generalized scalar field with a kinetic term and an exponential self-interacting potential, which enriches the dynamical behavior and leads to stable late-time attractor solutions. The evolution of cosmological parameters, including the deceleration parameter and the effective equation of state, indicates that the model approaches a de Sitter-like phase at late times. These results demonstrate that the $f(R, \mathcal{L}_m)$ gravity framework, with scalar field extensions, provides a viable mechanism to explain the late-time acceleration of the Universe without invoking a cosmological constant.