Compact stars in Eddington inspired gravity

TL;DR

This paper explores a new Eddington-inspired gravity theory that differs from General Relativity inside matter, leading to non-singular collapse, stable compact stars, and strong observational constraints on the theory.

Contribution

It introduces a viable one-parameter gravity theory that avoids singularities and supports stable compact stars, with implications for dark matter models and observational tests.

Findings

Avoids singularities in dust collapse

Supports stable, pressureless stars

Imposes strong constraints on the theory's parameter

Abstract

A new, Eddington inspired theory of gravity was recently proposed by Banados and Ferreira. It is equivalent to General Relativity in vacuum, but differs from it inside matter. This viable, one parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar.