Fadeev-popov Ghosts and 1 + 1

Recently Callan, Giddings, Harvey and the author derived a set of one-loop semiclassical equations describing black hole formation/evaporation in two-dimensional dilaton gravity conformally coupled to N scalar fields. These equations were subsequently used to show that an incoming matter wave develops a black hole type singularity at a critical value φ cr of the dilaton field. In this paper a modification to these equations arising from the Fadeev-Popov determinant is considered and shown to have dramatic effects for N < 24, in which case φ cr becomes complex. The N < 24 equations are solved along the leading edge of an incoming matter shock wave and found to be non-singular. The shock wave arrives at future null infinity in a zero energy state, gravitationally cloaked by negative energy Hawking radiation. Static black hole solutions supported by a radiation bath are also studied. The interior of the event horizon is found to be non-singular and asymptotic to deSitter space for N < 24, at least for sufficiently small mass. It is noted that the one-loop approximation is not justified by a small parameter for small N. However an alternate theory (with different matter content) is found for which the same equations arise to leading order in an adjustable small parameter.