Non-minimal Gravitational Coupling of Phantom and Big Rip Singularity

TL;DR

This paper explores a non-minimal coupling between matter and geometry in gravity, showing how energy transfer depends on the matter's equation of state and can prevent the universe's catastrophic Big Rip singularity.

Contribution

It introduces a model with arbitrary Ricci scalar-dependent coupling, analyzing its thermodynamic implications and potential to avoid cosmic doomsday scenarios.

Findings

Energy transfer direction depends on matter's equation of state.

Phantom fluids can lose energy, potentially avoiding Big Rip.

Non-minimal coupling influences cosmic evolution.

Abstract

We consider a non-minimal coupling of a perfect fluid matter system with geometry, which the coupling function is taken to be an arbitrary function of the Ricci scalar. Due to such a coupling, the matter stress tensor is no longer conserved and there is an energy transfer between the two components. By solving the conservation equation and applying the second law of thermodynamics, we show that direction of the energy transfer depends on the equation of state of the matter fluid. In particular, a phantom fluid should loose energy with expansion of the universe. This energy reduction can avoid the universe to end with a cosmic doomsday.