Gravitational induced particle production through a nonminimal curvature-matter coupling

TL;DR

This paper explores how a nonminimal curvature-matter coupling in gravity can induce particle production, leading to irreversible matter creation, entropy increase, and potentially explaining late-time cosmic acceleration.

Contribution

It reformulates the nonminimal curvature-matter coupling model as a scalar-tensor theory and analyzes particle creation and thermodynamics in a cosmological context.

Findings

Particle creation rates depend on scalar potentials and matter Lagrangian.

The model predicts entropy production during cosmic evolution.

Late-time acceleration may be driven by particle creation processes.

Abstract

We consider the possibility of a gravitationally induced particle production through the mechanism of a nonminimal curvature-matter coupling. An interesting feature of this gravitational theory is that the divergence of the energy-momentum tensor is nonzero. As a first step in our study we reformulate the model in terms of an equivalent scalar-tensor theory, with two arbitrary potentials. By using the formalism of open thermodynamic systems, we interpret the energy balance equations in this gravitational theory from a thermodynamic point of view, as describing irreversible matter creation processes. The particle number creation rates, the creation pressure, and the entropy production rates are explicitly obtained as functions of the scalar field and its potentials, as well as of the matter Lagrangian. The temperature evolution laws of the newly created particles are also obtained. The cosmological implications of the model are briefly investigated, and it is shown that the late-time cosmic acceleration may be due to particle creation processes. Furthermore, it is also shown that due to the curvature--matter coupling, during the cosmological evolution a large amount of comoving entropy is also produced.