2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/140203We study differential forms invariant under a finite reflection group over a field of arbitrary characteristic. In particular, we prove an analogue of Saito's freeness criterion for invariant differential 1-forms. We also discuss how twisted wedging endows the invariant forms with the structure of a free exterior algebra in certain cases. Some of the results are extended to the case of relative invariants with respect to a linear character.16 pagesRepresentation TheoryCommutative Algebra13A50, 20C, 52C35text