Skew Calabi-Yau property of faithfully flat Hopf Galois extensions

Abstract

This paper shows that if $H$ is a Hopf algebra and $A \subseteq B$ is a faithfully flat $H$-Galois extension, then $B$ is skew Calabi-Yau provided $A$ and $H$ are. Specifically, for cleft extensions $A \subseteq B$, the Nakayama automorphism of $B$ can be derived from those of $A$ and $H$, along with the homological determinant of the $H$-action on $A$. This finding is based on the study of the Hopf bimodule structure on $\mathrm{Ext}^i_{A^e}(A, B^e)$.