Inductive Giannelli–McKay condition for quasisimple groups

From papers

Let SS be a quasisimple group with cyclic center, let pp be a prime, let PSylp(S)P\in\operatorname{Syl}_p(S), and set A=Aut(S)PA=\operatorname{Aut}(S)_P. For χIrrp(S)\chi\in\operatorname{Irr}_{p'}(S), write AχA_\chi for its stabilizer in AA, and let c\geq_c denote the central-isomorphism relation on character triples. Inductive Giannelli–McKay condition. There should exist an AA-stable subgroup NS(P)M<SN_S(P)\leq M<S and an AA-equivariant bijection

Ψ:Irrp(S)Irrp(M)\Psi:\operatorname{Irr}_{p'}(S)\longrightarrow\operatorname{Irr}_{p'}(M)

with Ψ(χ)(1)χ(1)\Psi(\chi)(1)\leq\chi(1) and

(SAχ,S,χ)c(MAχ,M,Ψ(χ))(S\rtimes A_\chi,S,\chi)\geq_c(M\rtimes A_\chi,M,\Psi(\chi))

for every χIrrp(S)\chi\in\operatorname{Irr}_{p'}(S). This is a reduction condition intended to imply the global Giannelli–McKay conjecture from suitable verification on covering groups of simple groups. The paper presents it as a condition to be imposed in the reduction, and later verifies related cases, but no general resolution is stated.

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Primary source

Nguyen N. Hung, J. Miquel Martínez and Gabriel Navarro, “Sum of the squares of the p'-character degrees”, arXiv:2505.21267 (2026).

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