Evaporation/Antievaporation and energy conditions in alternative gravity

TL;DR

This paper investigates how evaporation and antievaporation phenomena in Nariai solutions are driven by modifications to energy conditions in extended gravity theories, with examples in $f(R)$ and Gauss-Bonnet gravity.

Contribution

It demonstrates that evaporation and antievaporation originate from deformations of energy conditions due to extra degrees of freedom in extended gravity models.

Findings

Energy conditions are deformed by extra degrees of freedom.

Evaporation and antievaporation linked to energy condition modifications.

Explicit examples provided in $f(R)$ and Gauss-Bonnet gravity.

Abstract

We discuss the evaporation and antievaporation instabilities of Nariai solution in extended theories of gravity. These phenomena were explicitly shown in several different extensions of General Relativity, suggesting that a universal cause is behind them. We show that evaporation and antievaporation are originated from deformations of energy conditions on the Nariai horizon. Energy conditions get new contributions from the extra propagating degrees of freedom, which can provide extra focalizing or antifocalizing terms in the Raychanduri equation. We also show two explicit examples in $f(R)$-gravity and Gauss-Bonnet gravity.