a1 Fachbereich Mathematik Universität Mainz D-6500 Mainz, Federal Republic of Germany
The known characterization of the Mathieu group M12 by the structure of the centralizer of a 2-central involution is based on the application of the theory of exceptional characters and uses in addition a block theoretic result which asserts that a simple group of order |M12| is isomorphic to M12. The details of the proof of the latter result had never been published. We show here that M12 can be handled in a completely elementary and group theoretical way.
(Received July 05 1989)
1980 Mathematics subject classification (Amer. Math. Soc.) (1985 Revision)