Relativistic stars in 4D Einstein-Gauss-Bonnet gravity

Abstract

In the present paper we investigate the structure of relativistic stars in 4D Einstein-Gauss-Bonnet gravity. The mass-radius relations are obtained for realistic hadronic and for strange quark star equations of state, and for a wide range of the Gauss-Bonnet coupling parameter α. Even though the deviations from general relativity for nonzero values of α can be large enough, they are still comparable with the variations due to different modern realistic equations of state if we restrict ourselves to moderate values of α. That is why the current observations of the neutron star masses and radii alone can not impose stringent constraints on the value of the parameter α. Nevertheless some rough constraints on α can be put. The existence of stable stellar mass black holes imposes √(α) ≲ 2.6 km for α > 0 while the requirement that the maximum neutron star mass should be greater than two solar masses gives √(|α|) ≲ 3.9 km for α < 0. We also present an exact solution describing the structure of relativistic stars with uniform energy density in 4D Einstein-Gauss-Bonnet gravity.