Abstract

AbstractWe study the fields of values of the irreducible characters of a finite group of degree not divisible by a primep. In the case where$p=2$, we fully characterise these fields. In order to accomplish this, we generalise the main result of [ILNT] to higher irrationalities. We do the same for odd primes, except that in this case the analogous results hold modulo a simple-to-state conjecture on the character values of quasi-simple groups.

Highlights

  • It is of great interest to study the values of the complex irreducible characters of a finite group

  • If (1) is odd and Q( ) = Q( ) for a square-free integer ≠ −1, ≡ 1. This is a consequence of the recent main result of [ILNT], whose proof uses the classification of finite simple groups: if (1) is odd, either Q( ) is contained in the cyclotomic field Q for some odd integer or ∈ Q( )

  • Before going into the main results of this paper, we prove that given any abelian extension /Q, where ⊆ C, there exist a finite group and ∈ Irr( ) such that = Q( )

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Summary

Introduction

It is of great interest to study the values of the complex irreducible characters of a finite group. If is a character (not necessarily irreducible) of a finite group , the field of values Q( ) of is the smallest field containing ( ) for all ∈. If (1) is odd and Q( ) = Q( ) for a square-free integer ≠ −1, ≡ 1 (mod 4) This is a consequence of the recent main result of [ILNT], whose proof uses the classification of finite simple groups: if (1) is odd, either Q( ) is contained in the cyclotomic field Q for some odd integer or ∈ Q( ). F = Q( )/Q | ∈ Irr ′ ( ), a finite group , where Irr ′ ( ) is the set of complex irreducible characters of of degree not divisible by ?

Gabriel Navarro and Pham Huu Tiep
Proofs of Theorems A2 and B2
Proofs of Theorems A1 and B1
Proof of Theorem A3
Further reductions
Special linear and unitary groups
Completion of the proof of Theorem A3
Evidence in support of Conjecture B3
Results on Conjecture C
Full Text
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