Boson Stars: Gravitational Equilibria of Self-Interacting Scalar Fields

Abstract

Spherically symmetric gravitational equilibria of self-interacting scalar fields $\ensuremath{\varphi}$ with interaction potential $V(\ensuremath{\varphi})=\frac{1}{4}\ensuremath{\lambda}{|\ensuremath{\varphi}|}^{4}$ are determined. Surprisingly, the resulting configuration may differ markedly from the noninteracting case even when $\ensuremath{\lambda}\ensuremath{\ll}1$. Contrary to generally accepted astrophysical folklore, it is found that the maximum masses of such boson stars may be comparable to the Chandrasekhar mass for fermions of mass ${m}_{\mathrm{fermion}}\ensuremath{\sim}{\ensuremath{\lambda}}^{\ensuremath{-}\frac{1}{4}}{m}_{\mathrm{boson}}$.