Thermodynamics and Bouncing Cosmology in Rastall-like Gravity

TL;DR

This paper investigates a modified Rastall-like gravity theory, exploring its thermodynamic properties and proposing a bouncing cosmological model that avoids the Big Bang singularity through particle production and energy condition violations.

Contribution

It introduces a novel Lagrangian for Rastall-like gravity, linking matter production with thermodynamics and proposing a feasible bouncing universe scenario within this framework.

Findings

Bouncing cosmology is possible in Rastall-like gravity.

Particle production supports the bouncing scenario.

Energy conditions are violated near the bounce, ensuring stability.

Abstract

In this study, we explore the thermodynamic aspects of a modified version of Rastall's gravity theory and its implications for cosmological scenarios. We analyze the role of non-conserved energy-momentum tensor equations and investigate their influence on particle production within an irreversible thermodynamic framework. By introducing a novel Lagrangian, we derive modified field equations and establish their relationship with matter production, both with and without entropy generation. Our analysis focuses on ideal fluid models and extends to spatially flat LFRW cosmologies, providing key equations that govern energy density, pressure, and curvature dynamics. Furthermore, we propose a bouncing cosmological model, in which the universe undergoes cycles of contraction and expansion, avoiding the singularity associated with the Big Bang. Our results indicate that this bouncing scenario is feasible within the Rastall-like gravity framework, supported by particle production processes and stability conditions. The violation of energy conditions near the bounce point further confirms the consistency of this alternative cosmological model. The present work is focused on the theoretical foundations and internal consistency of the model; possible observational implications will be addressed in future investigations. We conclude that the proposed theory offers a coherent phenomenological approach to matter production and provides new insights into non-standard cosmological evolution.