On the projectivity of module coalgebras
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- by Siu-Hung Ng
- Proc. Amer. Math. Soc. 126 (1998), 3191-3198
- DOI: https://doi.org/10.1090/S0002-9939-98-04599-7
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Abstract:
In this paper, we derive some criteria for the projectivity of a module coalgebra over a finite dimensional Hopf algebra. In particular, we show that any Hopf algebra over a field of characteristic zero is faithfully flat over its group-like subHopf algebra. Finally, we prove that if $B$ is a finite dimensional subHopf algebra of a Hopf algebra $A$, then $B$ is normal in $A$ if and only if $AB^+ = B^+A$. This improves a result by S. Montgomery (1993).References
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Bibliographic Information
- Siu-Hung Ng
- Affiliation: Department of Mathematics, Rutgers University, New Brunswick, New Jersey 08903
- Address at time of publication: Department of Mathematics, University of California at Santa Cruz, Santa Cruz, California 95064
- MR Author ID: 343929
- Email: shng@math.ucsc.edu
- Received by editor(s): September 27, 1996
- Received by editor(s) in revised form: April 3, 1997
- Communicated by: Ken Goodearl
- © Copyright 1998 American Mathematical Society
- Journal: Proc. Amer. Math. Soc. 126 (1998), 3191-3198
- MSC (1991): Primary 16W30
- DOI: https://doi.org/10.1090/S0002-9939-98-04599-7
- MathSciNet review: 1469428