Stellar Structure Equations in Extended Palatini Gravity

TL;DR

This paper derives stellar structure equations within extended Palatini gravity theories, generalizing the Tolman-Oppenheimer-Volkoff equations and analyzing how these modifications affect stellar and vacuum solutions compared to General Relativity.

Contribution

It formulates the TOV equations for a broad class of Palatini gravity theories with a general function of R and Ricci tensor squared, extending previous models.

Findings

Recover standard TOV equations in GR limit

Exterior solutions are Schwarzschild-de Sitter type

Interior solutions may exhibit modifications from GR

Abstract

We consider static spherically symmetric stellar configurations in Palatini theories of gravity in which the Lagrangian is an unspecified function of the form $f(R,R_{\mu\nu}R^{\mu\nu})$. We obtain the Tolman-Oppenheimer-Volkov equations corresponding to this class of theories and show that they recover those of $f(R)$ theories and General Relativity in the appropriate limits. We show that the exterior vacuum solutions are of Schwarzschild-de Sitter type and comment on the possible expected modifications, as compared to GR, of the interior solutions.