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Symmetric forms, idempotents and involutary antiisomorphisms
Published online by Cambridge University Press: 22 January 2016
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Let G be a finite group, F a field and M an irreducible F[G]-module. By ^ we denote the F-linear involutary antiautomorphism of F[G], induced by inversion on group elements. Suppose that char (F) ≠. 2. We then show that M carries a non-singular G-invariant symmetric bilinear form with values in F if and only if there exists a ^-invariant idempotent e ∈ F [G] which generates the projective cover of M. This extends earlier results of W. Willems [Wi]. The assertion is not true if char(F) = 2.
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- Copyright © Editorial Board of Nagoya Mathematical Journal 1992
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