# Particle creation and decay in nonminimally coupled models of gravity

## TL;DR

This paper challenges the assumption that nonminimal coupling in extended gravity models leads to particle creation, suggesting instead it causes momentum changes unless significant inhomogeneities occur, affecting cosmological matter density evolution.

## Contribution

It provides a new perspective on nonminimal coupling effects, arguing they alter particle momentum rather than cause creation or decay under typical conditions.

## Key findings

- Nonminimal coupling results in particle momentum changes over cosmological timescales.
- Particle creation or decay requires significant microscopic inhomogeneities.
- The impact on matter density evolution is phenomenologically described.

## Abstract

In extended models of gravity a nonminimal coupling to matter has been assumed to lead to irreversible particle creation. In this paper we challenge this assumption. We argue that a non-minimal coupling of the matter and gravitational sectors results in a change in particle-momentum on a cosmological timescale, irrespective of particle creation or decay. We further argue that particle creation or decay associated with a non-minimal coupling to gravity could only happen as a result of significant deviations from a homogeneous Friedmann-Robertson-Walker geometry on microscopic scales, and provide a phenomenological description of the impact of particle creation or decay on the cosmological evolution of the density of the matter fields.