English

On groups with square-free gcd of character degree and codegree

Group Theory 2025-07-16 v2

Abstract

Let GG be a finite group and χ\chi be an irreducible character of GG. The codegree of χ\chi is defined as χc(1)=G:kerχχ(1)\chi^c(1) =\frac{|G: \ker\chi|}{\chi(1)}. In a paper by Gao, Wang, and Chen, it was shown that GG cannot satisfy the condition that gcd(χ(1),χc(1))\gcd(\chi(1),\chi^c(1)) is prime for all χIrr(G)#\chi\in\text{Irr}(G)^\#. We generalize this theorem by solving one of Guohua Qian's unsolved problems on character codegrees. Qian inquires about the structure of non-solvable finite groups with square-free gcd\gcd instead. We prove that if GG is such that gcd(χ(1),χc(1))\gcd(\chi(1),\chi^c(1)) is square-free for every irreducible character χ\chi, then G/Sol(G)G/\text{Sol}(G) is isomorphic to one among a particular list of almost simple groups.

Keywords

Cite

@article{arxiv.2507.03100,
  title  = {On groups with square-free gcd of character degree and codegree},
  author = {Karam Aldahleh and Alan Kappler and Neil Makur and Yong Yang},
  journal= {arXiv preprint arXiv:2507.03100},
  year   = {2025}
}

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10 pages