Thermodynamics of the apparent horizon in the generalized energy-momentum-squared cosmology

TL;DR

This paper investigates the thermodynamic behavior of the universe within generalized energy-momentum-squared gravity, deriving conditions for thermodynamic stability and constraining model parameters through analysis of apparent horizon properties.

Contribution

It introduces a generalized framework for analyzing thermodynamics in energy-momentum-squared gravity models, considering power law and exponential forms with stability constraints.

Findings

Thermodynamic parameters are expressed in terms of apparent horizon radius.

Stability conditions significantly restrict model parameter space.

The evolution of Helmholtz free energy indicates stability regions.

Abstract

In this note, we explore the thermodynamic properties of the universe in the background of the generalized energy-momentum-squared gravity. We derive the energy density of matter from the non-standard continuity equation and use it in our analysis. We consider two types of models depending on the nature of coupling between curvature and matter and perform thermodynamic analysis on them using the cosmic apparent horizon. The models are kept as generic as possible from the mathematical point of view in order to gain a wide applicability of the work. In this work we have considered power law and exponential form of models. All the thermodynamic parameters are expressed in terms of the cosmic apparent horizon radius and its time derivatives and their time evolution are studied. By using temperature, heat capacity analysis and the evolution trend of Helmholtz free energy the conditions for thermodynamic stability of the models are derived. It is seen that our stability analysis considerably constrain the parameter space of the model.