  Quantum evaporation of Callan-Giddings-Harvey-Strominger (CGHS) black holes
is analyzed in the mean field approximation. This semi-classical theory
incorporates back reaction. Detailed analytical and numerical calculations show
that, while some of the assumptions underlying the standard evaporation
paradigm are borne out, several are not. Furthermore, if the black hole is
initially macroscopic, the evaporation process exhibits remarkable universal
properties (which are distinct from the features observed in the simplified,
exactly soluble models). Although the literature on CGHS black holes is quite
rich, these features had escaped previous analyses, in part because of lack of
required numerical precision, and in part because certain properties and
symmetries of the model were not fully recognized. Finally, our results provide
support for the full quantum gravity scenario recently developed by Ashtekar,
Taveras and Varadarajan.
