Boson stars in general scalar-tensor gravitation: equilibrium configurations

Abstract

We study equilibrium configurations of boson stars in the framework of general scalar-tensor theories of gravitation. We analyze several possible couplings, with acceptable weak field limits and, when known, nucleosynthesis bounds, in order to work in the cosmologically more realistic cases of these kinds of theories. We find that for general scalar-tensor gravitation the range of masses boson stars might have is comparable with the general relativistic case. We also analyze the possible formation of boson stars along different eras of cosmic evolution, allowing for the effective gravitational constant far out from the star to deviate from its current value. In these cases, we find that the boson star masses are sensitive to these kinds of variations, within a typical few percent. We also study cases in which the coupling is implicitly defined, through the dependence on the radial coordinate, allowing it to have significant variation in the radius of the structure.