Twistings, crossed coproducts and Hopf-Galois coextensions
arXiv:math/0210460
Abstract
Let be a Hopf algebra. Ju and Cai introduced the notion of twisting of an -module coalgebra. In this note, we study the relationship between twistings, crossed coproducts and Hopf-Galois coextensions. In particular, we show that a twisting of an -Galois coextension remains -Galois if the twisting is invertible.
20 pages