Viability of nonminimally coupled f (R) gravity

TL;DR

This paper investigates the physical viability of nonminimally coupled f(R) gravity theories by analyzing stability conditions and addressing misconceptions about their behavior, contrasting with recent claims of pathologies.

Contribution

It provides a detailed stability analysis of nonminimally coupled f(R) gravity, clarifying misconceptions and establishing conditions for their physical viability.

Findings

Nonminimally coupled f(R) models can be stable under certain conditions.

Contradicts recent claims of pathologies by correcting the analogy with k-essence.

Identifies criteria to avoid tachyon and ghost instabilities.

Abstract

In this work we explore the viability of nonminimally coupled matter- curvature gravity theories, namely the conditions required for the absence of tachyon instabilities and ghost degrees of freedom. We contrast our finds with recent claims of a pathological behaviour of this class of models, which resorted to, in our view, an incorrect analogy with k-essence.