Neutron stars in the symmetron model

Abstract

Screening mechanisms are often deployed by dark energy models in order to conceal the effects of their new degrees of freedom from the scrutiny of terrestrial and solar system experiments. However, extreme properties of nuclear matter may lead to a partial failure of screening mechanisms inside the most massive neutron stars observed in Nature, opening up the possibility of probing these theories with neutron star observations. In this work we explore equilibrium and stability properties of neutron stars in two variants of the symmetron model. We show that around sufficiently compact neutron stars, the symmetron is amplified with respect to its background, cosmological value by several orders of magnitude, and that properties of such unscreened stars are sensitive to corrections to the leading linear coupling between the symmetron and matter.