Integral Theory for Hopf Algebroids

Author: Böhm Gabriella  

Publisher: Springer Publishing Company

ISSN: 1386-923X

Source: Algebras and Representation Theory, Vol.8, Iss.4, 2005-10, pp. : 563-599

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Abstract

The theory of integrals is used to analyze the structure of Hopf algebroids. We prove that the total algebra of a Hopf algebroid is a separable extension of the base algebra if and only if it is a semi-simple extension and if and only if the Hopf algebroid possesses a normalized integral. It is a Frobenius extension if and only if the Hopf algebroid possesses a nondegenerate integral. We give also a sufficient and necessary condition in terms of integrals, under which it is a quasi-Frobenius extension, and illustrate by an example that this condition does not hold true in general. Our results are generalizations of classical results on Hopf algebras.