Eddington-inspired Born Infeld gravity theory as an anisotropic equation of state on stars

Abstract

We show that the first-order expansion of parameter κ of Eddington - inspired Born Infeld (EiBI) theory of gravity yields a Tolman-Oppenheimer-Volkoff (TOV) equation for anisotropic stars which is equivalent to the one of general relativity (GR) theory. It is also evidence that, for the non-relativistic limit, the radial pressure gradient of the corresponding first-order GR-like expansion of EiBI theory is exactly the same as the one of EiBI theory. We also investigate the mass-radius relation of neutron stars predicted by first-order GR-like expansion of EiBI theory. The results are compared to the exact one to see how good the corresponding expansion.