Positive-characteristic sparse, sporadic, lacunary, and generic architecture for quotient maps

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Let p>0p>0, let p∤dp\nmid d, and let hdh_d be the reduced separable quotient associated with HdrawH_d^{\rm raw} in characteristic pp. Assume the characteristic-zero case is settled and exclude the small overlaps d=1,2,3d=1,2,3. For a≥1a\geq1, the relevant sparse branches occur when d=pa−1d=p^a-1 or d=pa+1d=p^a+1; the possible sporadic case is (p,d)=(19,6)(p,d)=(19,6); and the first nonsparse Frobenius–lacunary tower occurs when p≠2,3p\ne2,3 and d=2pa+1d=2p^a+1. Writing n=deg⁡hdn=\deg h_d for the degree of the separable quotient, let GhdG_{h_d} denote its monodromy group. Positive-characteristic sparse/sporadic/lacunary/generic architecture. Apart from those stated sparse and sporadic alternatives, every remaining positive-characteristic case with deg⁡hd=n>1\deg h_d=n>1 should satisfy

An≤Ghd≤Sn.A_n\le G_{h_d}\le S_n.

More explicitly, the alternatives are: hd=τ2h_d=\tau^2 when d=pa−1d=p^a-1; the Kummer or Artin–Schreier Frobenius-sparse branch when d=pa+1d=p^a+1; the Klein-four sporadic quotient when (p,d)=(19,6)(p,d)=(19,6) under the certificate-execution hypothesis; and the first nonsparse Frobenius–lacunary tower when p≠2,3p\ne2,3 and d=2pa+1d=2p^a+1. The paper proves primitivity of this tower for every aa and the displayed monodromy bounds for a=1a=1, while the case a>1a>1 is expected to follow from control of the explicit wild inertia representation. The parser reports that the sporadic alternative is forced by a computer-assisted theorem and that, without the certificate-execution hypothesis, the conjecture is false.

References

Primary source

Henry Shin, “Hilbert-90 quotient maps, torsion defects, and symmetric monodromy”, arXiv:2605.25291 (2026).

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