Critical collapse of a scalar field in semiclassical loop quantum gravity

Abstract

We study the collapse in spherical symmetry of a massless scalar field minimally coupled to gravity using the semiclassical equations that are expected from loop quantum gravity. We find the critical behavior of the mass as a function of the parameters of the initial data similar to that found by Choptuik in classical general relativity for a large set of initial data and values of the polymerization parameter. Contrary to wide expectations for quantum gravity, our semiclassical field equations have an exact scale invariance, as do the classical field equations. As one would then expect, we numerically find that the phase transition is second order: again, as in the classical case.