No-scalar-hair theorem for spherically symmetric reflecting stars
  It is proved that spherically symmetric compact reflecting objects cannot support static bound-state configurations made of scalar fields whose self-interaction potential $V(\psi^2)$ is a monotonically increasing function of its argument. Our theorem rules out, in particular, the existence of massive scalar hair outside the surface of a spherically symmetric compact reflecting star. 
Shahar Hod
gr-qc astro-ph.HE hep-th