Boson stars: gravitational equilibria of self-interacting scalar fields

The physics of boson stars - spherically symmetric gravitational equilibria of self-interacting scalar fields in asymptotically flat space-times - is investigated analytically. Numerical results are presented in graphs, and significant differences are found between this case and that of equilibrium configurations of noninteracting boson fields (Ruffini and Bonazzola, 1969), even for values of the dimensionless coupling parameter (lambda) much less than 1. The maximum mass of a boson star is shown to be of the same magnitude as the Chandrasekhar mass for fermions with masses approximately equal to the mass of a boson divided by the fourth root of lambda. The possibility that boson stars of this mass could have arisen during the gravitational condensation of bosonic dark matter in the early Universe is considered. (T.K.)