Universally extendible characters

Abstract

Let theta be an ordinary character or a Brauer character of a finite group N. We show that theta extends to every overgroup $G=G_{\theta }⊵N$ if and only if Z(N) <= Ker(theta) and the deflated character of Inn(N) extends to Aut(N)_theta. This equivalence is compatible with fields of values. A similar investigation for extensions from subnormal subgroups leads to a new characteristic subgroup of N.

14 pages