Upper bound on the gravitational masses of stable spatially regular charged compact objects

Abstract

In a very interesting paper, Andr\'easson has recently proved that the gravitational mass of a spherically symmetric compact object of radius $R$ and electric charge $Q$ is bounded from above by the relation $\sqrt{M}\leq{{\sqrt{R}}\over{3}}+\sqrt{{{R}\over{9}}+{{Q^2}\over{3R}}}$. In the present paper we prove that, in the dimensionless regime ${{Q}/{M}}<\sqrt{{9/8}}$, a stronger upper bound can be derived on the masses of physically realistic ({\it stable}) self-gravitating horizonless compact objects: $M<{{R}\over{3}}+{{2Q^2}\over{3R}}$.