Volume 87, Number 5, 385-389, DOI: 10.1007/s00013-006-1756-0

A construction of two distinct canonical sets of lifts of Brauer characters of a p-solvable group

James P. Cossey

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Abstract

In [5], Navarro defines the set Irr(G|Q,d)\subseteqq Irr(G)\hbox{Irr}(G|Q,\delta)\subseteqq \hbox{Irr}(G) , where Q is a p-subgroup of a p-solvable group G, and shows that if δ is the trivial character of Q, then Irr(G|Q, δ) provides a set of canonical lifts of IBrp(G), the irreducible Brauer characters with vertex Q. Previously, in [2], Isaacs defined a canonical set of lifts Bπ(G) of Iπ(G). Both of these results extend the Fong-Swan Theorem to π-separable groups, and both construct canonical sets of lifts of the generalized Brauer characters. It is known that in the case that 2∈π, or if |G| is odd, we have Bπ(G) = Irr(G|Q, 1Q). In this note we give a counterexample to show that this is not the case when 2 Ï p2\notin \pi . It is known that if N\triangleleft GN\triangleleft G and χ∈Bπ(G), then the constituents of χN are in Bπ (N). However, we use the same counterexample to show that if N\triangleleft GN\triangleleft G , and χ∈Irr(G|Q, 1Q) is such that θ ∈Irr(N) and [θ, χ N]  ≠  0, then it is not necessarily the case that θ ∈Irr(N) inherits this property.

Mathematics Subject Classification (2000).  Primary 20C20

Received: 17 October 2005

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