On the flatness and the projectivity over Hopf subalgebras of Hopf algebras over discrete valuation rings

Nguyen Dai Duong, Phung Ho Hai, Nguyen Huy Hung

We study the flatness and the projectivity of Hopf algebras, defined over a Dedekind ring, over their Hopf subalgebras. We give a criterion for the faithful flatness and use it to…