Instantons or monopoles:: Dyons at finite temperature

This article in honor of Yurii Antonovich Simonov's 70th birthday reviews some recent work related to the semiclassical approach to QCD at finite temperature based on classical solutions with nontrivial holonomy. By cooling Monte Carlo generated lattice SU(2) gauge fields, we investigate approximate solutions of the classical field equations as a possible starting point for rethinking the semiclassical approximation of the path integral. We show that old findings of cooling have to be reinterpreted in terms of Kraanvan Baal solutions with generically. nontrivial holonomy instead of Harrington-Shepard caloron solutions with trivial holonomy. The latter represent only a subclass of possible topological configurations and for T < T-c seem to become suppressed due to quantum fluctuations. (c) 2005 Pleiades Publishing, Inc.