Black hole catalysis of false vacuum decay: The semiclassical decay rate and importance of greybody factors
It was suggested over thirty years ago that microscopic black holes can exponentially enhance the decay rate of a metastable false vacuum. The interest in this phenomenon has revived recently due to its possible phenomenological relevance for the physics of the early universe. Upon reviewing the motivation, I will discuss challenges raised by the attempts to describe black hole catalysis of vacuum decay using standard semiclassical methods. I will then present a generalized method applicable to the case of a realistic black hole which is not in equilibrium with its environment. The method will be illustrated on an example of a two-dimensional toy model, with emphasis on the role played by the black hole greybody factors. The proposed formalism is not limited to black holes and applies to tunneling in out-of-equilibrium systems in general.