A Maschke type theorem for Doi-Hopf modules and applications

[摘要] We prove a Maschke type theorem for Doi-Hopf modules. A sufficient condition in order to have a Maschke type property is that there exists a normalized integral map for the Doi-Hopf datum in question. The results are applied to graded modules and to Yetter-Drinfel'd modules. As another application, a characterization of cosemisimple coalgebras over a field is given. (C) 1997 Academic Press.

[发布日期] 1997-01-15