Inductive Giannelli–McKay condition for quasisimple groups

Let SS be a quasisimple group with cyclic center, let pp be a prime, let P∈Syl⁡p(S)P\in\operatorname{Syl}_p(S), and set A=Aut⁡(S)PA=\operatorname{Aut}(S)_P. For χ∈Irr⁡p′(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:Irr⁡p′(S)⟶Irr⁡p′(M)\Psi:\operatorname{Irr}_{p'}(S)\longrightarrow\operatorname{Irr}_{p'}(M)

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

(S⋊Aχ,S,χ)≥c(M⋊Aχ,M,Ψ(χ))(S\rtimes A_\chi,S,\chi)\geq_c(M\rtimes A_\chi,M,\Psi(\chi))

for every χ∈Irr⁡p′(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.

References

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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