Quantum extreme black holes at finite temperature and exactly solvable models of 2d dilaton gravity

It is argued that in certain 2d dilaton gravity theories there exist self-consistent solutions of field equations with quantum terms which describe extreme black holes at nonzero temperature. The curvature remains finite on the horizon due to cancellation of thermal divergences in the stress-energy tensor against divergences in the classical part of field equations. The extreme black hole solutions under discussion are due to quantum effects only and do not have classical counterparts. (C) 2000 Elsevier Science B.V. All rights reserved.