2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54515The BRS symmetry determines physical states, Lagrange densities and candidate anomalies. It renders gauge fixing unobservable in physical states and is required if negative norm states are to decouple also in interacting models. The relevant mathematical structures and the elementary cohomological investigations are presented.Lecture Notes Saalburg 1995, 62 pages, LaTeXHigh Energy Physics - Theorytext