2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42779These lectures start with a brief overview of salient features of the critical region of hot QCD. The main emphasis is on the accurate description of static plasma observables by the well-known hierarchy of reduced actions combined with 3D simulations above T\sim 2T_c. A striking pattern emerges, put in perspective by completing the quasi-particle picture57 pages, 13 figures. lectures given at Erice summerschool, September 2002, and Zakopane Summerschool, June 2003High Energy Physics - Phenomenologytext