Projectivity and flatness over the graded ring of semi-coinvariants

Let \(k\) be a field, \(C\) a bialgebra with bijective antipode, \(A\) a right \(C\)-comodule algebra, \(G\) any subgroup of the monoid of grouplike elements of \(C\). We give necessary and sufficient conditions for the projectivity and flatness over the graded ring of semi-coinvariants of \(A\). Wh...

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Bibliographic Details
Date:2018
Main Author: Guedenon, T.
Format: Article
Language:English
Published: Lugansk National Taras Shevchenko University 2018
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Online Access:https://admjournal.luguniv.edu.ua/index.php/adm/article/view/640
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Journal Title:Algebra and Discrete Mathematics

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Algebra and Discrete Mathematics
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Summary:Let \(k\) be a field, \(C\) a bialgebra with bijective antipode, \(A\) a right \(C\)-comodule algebra, \(G\) any subgroup of the monoid of grouplike elements of \(C\). We give necessary and sufficient conditions for the projectivity and flatness over the graded ring of semi-coinvariants of \(A\). When \(A\) and \(C\) are commutative and \(G\) is any subgroup of the monoid of grouplike elements of the coring \(A \otimes C\), we prove similar results for the graded ring of conormalizing elements of \(A\).