2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/109954Based on past contributions by Robert Schrader and Michael Karowski I review the problem of existence of interacting quantum field theory and present recent ideas and results on rigorous constructions.26 pagesHigh Energy Physics - TheoryTitle Positivity and Integrability (Mathematical Physics at the FU-Berlin)text