2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129865We prove a graded version of Alev-Polo's rigidity theorem: the homogenization of the universal enveloping algebra of a semisimple Lie algebra and the Rees ring of the Weyl algebras $A_n(k)$ cannot be isomorphic to their fixed subring under any finite group action. We also show the same result for other classes of graded regular algebras including the Sklyanin algebras.39 pages To be published in Transactions of the American Mathematical SocietyRings and Algebras16A62 (Primary), 16E70, 16W30, 20J50 (Secondary)text