Skyrmions and pion stars in the $U(1)$ gauged Einstein-Skyrme model

Abstract

We consider topological and non-topological regular soliton solutions in the Einstein-Maxwell-Skyrme theory. We analyze the properties of these solutions and determine their domains of existence. The dependence of the solutions on the gauge coupling and on the strength of the effective gravitational coupling are examined. Topologically trivial localized field configurations, \textit{pion stars}, are shown to exist, as non-linear gravitational bound states of the Skyrme field. Both spherically-symmetric and axially-symmetric pion stars are considered. We find that these solutions share many features with the usual (mini-)boson stars. In particular they also exhibit a spiraling behavior and do not possess a flat space limit.