Static and nonstatic quantum effects in two-dimensional dilaton gravity

We study back-reaction effects in two-dimensional dilaton gravity. The back -reaction comes from an R-2 term which is a Dart of the one-loop effective action arising from massive scaler field quantization in a certain approxim ation. The peculiarity of this term is that it does not contribute to the H awking radiation of the classical black hole solution of the field equation s. In the static case we examine the horizon and the physical singularity o f the new black hole solutions. Studying the possibility of time dependence we see the generation of a new singularity. The particular solution found still has the structure of a black hole, indicating that nonthermal effects cannot lead, at least in this approximation, to black hole evaporation.