Abstract. A classical theorem of John Thompson on character degrees asserts that if the degree of every ordinary irreducible character of a finite group G is 1 or divisible by a prime p, then G has a normal p-complement. We obtain a significant improvement of this result by considering the average of p ′ -degrees of irreducible characters. We also consider fields of character values and prove several improvements of earlier related results.
Abstract. A classical theorem of John Thompson on character degrees asserts that if the degree of every ordinary irreducible character of a finite group G is 1 or divisible by a prime p, then G has a normal p-complement. We obtain a significant improvement of this result by considering the average of p ′ -degrees of irreducible characters. We also consider fields of character values and prove several improvements of earlier related results.
“…In joint work with M. Isaacs and M. Loukaki [3], we proved that if the average character degree of a finite group is ≤ 3 then G is solvable. The main result of this note provides a similar result for the average Sylow number.…”
“…For a finite group G, let Irr(G) denote the set of all irreducible (complex) characters of G and acd(G) := 1 |Irr(G)| χ∈Irr (G) χ (1) denote the average character degree of G. Answering affirmatively a question of Berkovich and Zhmud' [3], Magaard and Tong-Viet [12] proved that if acd(G) < 2, then G is solvable. This was improved by Isaacs, Loukaki and Moretó [8] where the hypothesis was weakened to acd(G) < 3. In [8], the authors also obtained the connection between the average character degree and other important characteristics of finite groups such as nilpotency and supersolvability.…”
Section: Introductionmentioning
confidence: 99%
“…This was improved by Isaacs, Loukaki and Moretó [8] where the hypothesis was weakened to acd(G) < 3. In [8], the authors also obtained the connection between the average character degree and other important characteristics of finite groups such as nilpotency and supersolvability. These results demonstrate that the structure of a finite group is somehow controlled by its average character degree.…”
We prove that if the average of the degrees of the irreducible characters of a finite group G is less than 16 5 , then G is solvable. This solves a conjecture of I. M. Isaacs, M. Loukaki and the first author. We discuss related questions.
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