On the Projectivity of module coalgebras

Author:
Siu-Hung Ng

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

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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 is a finite dimensional subHopf algebra of a Hopf algebra , then is normal in if and only if . This improves a result by S. Montgomery (1993).

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Additional 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

Email:
shng@math.ucsc.edu

DOI:
https://doi.org/10.1090/S0002-9939-98-04599-7

Received by editor(s):
September 27, 1996

Received by editor(s) in revised form:
April 3, 1997

Communicated by:
Ken Goodearl

Article copyright:
© Copyright 1998
American Mathematical Society