Instability of wormholes with a nonminimally coupled scalar field
  Static, spherically symmetric, traversable wormholes, induced by massless, nonminimally coupled scalar fields in general relativity, are shown to be unstable under spherically symmetric perturbations. The instability is related to blowing-up of the effective gravitational constant on a certain sphere. 
K.A. Bronnikov and S. Grinyok (PFUR, Moscow)