Particle production by white holes

A white hole is the time reverse of a spacetime in which gravitational collapse has occurred to form a black hole. We find that in quantum field theory in a white-hole background, for any initial state of the field which is a product of a state on the horizon with a state at past null infinity, an infinite particle and energy flux occurs at future null infinity when the white-hole horizon is seen to terminate. This may be interpreted as a quantum version of the classical white-hole instability discussed by Eardley. Consequently, there appear to be considerable difficulties in incorporating white holes into a consistent picture of a thermodynamic self-gravitating quantum system. This provides evidence that the laws of quantum gravity may not be time-reversal invariant.