A duality theorem for Hopf comodule coalgebras
Let \(H\) be a finite dimensional Hopf algebra, \(C\) a left \(H\)-comodule coalgebra. Then, under a technical hypothesis that a certain right \(H^*\) coaction is strongly co-inner, the author shows that \((C\times H) \times H^* \cong C \otimes (H \times H^*)\). This is the analogue of a duality theorem for Hopf module algebras due to \textit{R. Blattner} and \textit{S. Montgomery} [J. Algebra 95, 153-172 (1985; Zbl 0589.16010)].
scientific article; zbMATH DE number 682121