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Transactions of the American Mathematical Society
ISSN 1088-6850(e) ISSN 0002-9947(p)
     

Frobenius-Schur indicators for subgroups and the Drinfel'd double of Weyl groups

Author(s): Robert Guralnick; Susan Montgomery
Journal: Trans. Amer. Math. Soc. 361 (2009), 3611-3632.
MSC (2000): Primary 16W30, 20C15, 20G42
Posted: February 4, 2009
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Abstract: If $ G$ is any finite group and $ k$ is a field, there is a natural construction of a Hopf algebra over $ k$ associated to $ G$, the Drinfel'd double $ D(G)$. We prove that if $ G$ is any finite real reflection group, with Drinfel'd double $ D(G)$ over an algebraically closed field $ k$ of characteristic not $ 2$, then every simple $ D(G)$-module has Frobenius-Schur indicator +1. This generalizes the classical results for modules over the group itself. We also prove some new results about Weyl groups. In particular, we prove that any abelian subgroup is inverted by some involution. Also, if $ E$ is any elementary abelian $ 2$-subgroup of the Weyl group $ W$, then all representations of $ C_W(E)$ are defined over $ \mathbb{Q}$.


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Additional Information:

Robert Guralnick
Affiliation: Department of Mathematics, University of Southern California, Los Angeles, California 90089-2532
Email: guralnic@usc.edu

Susan Montgomery
Affiliation: Department of Mathematics, University of Southern California, Los Angeles, California 90089-2532
Email: smontgom@usc.edu

DOI: 10.1090/S0002-9947-09-04659-5
PII: S 0002-9947(09)04659-5
Keywords: Drinfel'd double, Schur indicator, Weyl groups, reflection groups, rationality of representations
Received by editor(s): March 26, 2007
Posted: February 4, 2009
Additional Notes: The authors were supported by NSF grants DMS 0140578 and DMS 0401399.
Copyright of article: Copyright 2009, American Mathematical Society
The copyright for this article reverts to public domain after 28 years from publication.


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