Curvature singularities, tidal forces and the viability of Palatini f(R) gravity

TL;DR

This paper examines the presence of curvature singularities in Palatini f(R) gravity near the surfaces of certain stellar objects, questioning its viability as an alternative to General Relativity.

Contribution

It provides a detailed analysis of the physical implications of curvature singularities in Palatini f(R) gravity for stellar models.

Findings

Curvature singularities occur near the surface of polytropic stars with 3/2<Gamma<2.

Singularities lead to divergent tidal forces, challenging the physical viability of the theory.

The results suggest fundamental issues with Palatini f(R) gravity as an alternative gravitational model.

Abstract

In a previous paper we showed that static spherically symmetric objects which, in the vicinity of their surface, are well-described by a polytropic equation of state with 3/2<Gamma<2 exhibit a curvature singularity in Palatini f(R) gravity. We argued that this casts serious doubt on the validity of Palatini f(R) gravity as a viable alternative to General Relativity. In the present paper we further investigate this characteristic of Palatini f(R) gravity in order to clarify its physical interpretation and consequences.