2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59170We show a rigid connection between two classical objects: the R.Thompson group F and the Dunce hat. A diagram group of a directed 2-complex contains a copy of F if and only if the complex contains a copy of the Dunce hat.11 pagesGroup TheoryAlgebraic Topology20text