2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53712There are several ways to establish and study thermal properties of black holes. I review here method of Fulling and Ruijsenaars, based on the analytic structure of Green functions on the complex plane. This method provides a clear distinction between zero and finite temperature field theories, and allows for quick evaluation of black hole temperature. (Lectures presented at the Danube Workshop '93, June 1993, Belgrade, Yugoslavia.)14 pages, Plain TexHigh Energy Physics - Theorytext