The deviation conjectures for finite groups and subgroups

Let GG be a finite group and let H<GH<G. Define the deviation Δ(G,H)\Delta(G,H) as the smallest natural number Δ\Delta such that Δ[H\H]\Delta\cdot[H\backslash H] lies in the image of

ResInd:B(H)B(H).\operatorname{Res}\,\operatorname{Ind}:\mathcal{B}(H)\to\mathcal{B}(H).

Deviation conjectures. With Δ=Δ(G,H)\Delta=\Delta(G,H), one has Δ=1\Delta=1 if and only if H=GH=G, the index [G:H][G:H] divides Δ\Delta, and Δ\Delta divides G|G|. These conjectures propose arithmetic constraints on the deviation, which measures both the failure of normality and the relative size of HH in GG.

Sources & referencesView supporting material

Primary source

Jack S. Calcut, John D. McCarthy and Jeremy J. Walthers, “Topological and algebraic pullback functors”, arXiv:1205.3121 (2012).

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