Minimal index of a -crossed product by a finite group

Authors:
Ja A Jeong and Gie Hyun Park

Journal:
Proc. Amer. Math. Soc. **129** (2001), 2031-2038

MSC (2000):
Primary 46L05, 46L55

DOI:
https://doi.org/10.1090/S0002-9939-00-05810-X

Published electronically:
December 4, 2000

MathSciNet review:
1825914

Full-text PDF

Abstract | References | Similar Articles | Additional Information

Abstract: Let be the -crossed product of a simple unital -algebra by a finite group . In this paper we show that the canonical conditional expectation from to has the minimal index if is simple. It is also proved that if is an outer action, then the canonical one is the unique conditional expectation of index-finite type from to , while there are infinitely many conditional expectations when a nontrivial subgroup of acts innerly on .

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Additional Information

**Ja A Jeong**

Affiliation:
Division of Liberal Arts, Myongji University, Yongin, 449–728, Korea

Address at time of publication:
BK21 Mathematical Sciences Division, Seoul National University, Seoul, 151-742 Korea

Email:
jajeong@math.snu.ac.kr

**Gie Hyun Park**

Affiliation:
Department of Mathematics, Hanshin University, Osan, 447–791, Korea

Email:
ghpark@hucc.hanshin.ac.kr

DOI:
https://doi.org/10.1090/S0002-9939-00-05810-X

Received by editor(s):
May 3, 1999

Received by editor(s) in revised form:
November 10, 1999

Published electronically:
December 4, 2000

Additional Notes:
The first author was partially supported by GARC-KOSEF and BSRI

Communicated by:
David R. Larson

Article copyright:
© Copyright 2000
American Mathematical Society