Rev. Un. Mat. Argentina 51:1 (2010), 79-94
Mathematics Subject Classification (2000): 16T05, 16S40, 16D40, 13B05
Abstract. In previous work, to each Hopf algebra H and each invertible two-cocycle on H, Eli Aljadeff and the first-named author attached a subalgebra B of the free commutative Hopf algebra S generated by the coalgebra underlying H; the algebra B is the subalgebra of coinvariants of a generic Hopf Galois extension. In this paper we give conditions under which S is faithfully flat, or even free, as a B-module. We also show that B is generated as an algebra by certain elements arising from the theory of polynomial identities for comodule algebras developped jointly with Aljadeff.
Downloadable pdf and ps files from arXiv:0911.3719 /Téléchargeable d'arXiv:0911.3719
(17 septembre 2010)