Does a boson star rotate?

Abstract
We investigate the possibility of slow rotation for a certain type of boson star. It is shown that a boson star made by a complex scalar field alone cannot rotate at least perturbatively. We have performed an extensive numerical study for the boson star made by a complex scalar field coupled with a U(1) gauge field to obtain negative results. It is argued that vortex lines will be generated for rapid rotation of the boson star.