The thermal properties of black holes in the presence of quantum fields can
be revealed through solutions of the semi-classical Einstein equation. We
present a brief but self-contained review of the main features of the
semi-classical back reaction problem for a black hole in the microcanonical
ensemble. The solutions, obtained for conformal scalars, massless spinors and
U(1) gauge bosons, are used to calculate the O(ℏ) corrections to the
temperature and thermodynamical entropy of a Schwarzschild black hole. In each
spin case considered, the entropy corrections ΔS(r), are positive
definite and monotone increasing with increasing distance r from the hole,
and are of the same order as the naive flat space radiation entropy.Comment: 10 pages in plain LaTex. Based on a talk presented at the Third
Workshop on Quantum Field Theory under the Influence of External Conditions,
Leipzig, Germany, 18-22 September, 199