Thermodynamical behaviour of composite stringy black holes

We study the thermodynamical and geometrical behaviour of the black holes that arise as solutions of the heterotic string action. We discuss the near-horizon scaling behaviour of the solutions that are described by two-dimensional Anti-de Sitter space (AdS(2)). We find that finite-energy excitations of AdS(2) are suppressed only for scaling limits characterized by a dilaton constant near the horizon, whereas this suppression does not occur when the dilaton is nan-constant. (C) 2000 Elsevier Science B.V. All rights reserved.