2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55772Using reflection positivity as the main tool, we establish a connection between the existence of a critical point in classical spin models and the triviality of a certain local cohomology class related to the Noether current of the model in the continuum limit. Furthermore we find a relation between the location of the critical point and the momentum space autocorrelation function of the Noether current.13 pages, Talk given at the XIIth Max Born Symposioum, Wroclaw, Poland. Some misprints correctedHigh Energy Physics - TheoryHigh Energy Physics - Latticetext