Hopf algebraic homogeneous spaces interpreted rationally: the Abe-Kanno theorem

We present a Hopf algebraic generalization of the Abe-Kanno theorem on a correspondence between subgroups of an algebraic group and invariant subfields of the field of rational functions.

It applies to residually finite-dimensional Hopf algebras admitting an artinian classical quotient ring and is used in the paper to derive some general properties of such Hopf algebras.