Ogus' principle for Hodge-type Shimura varieties

Consider a Hodge-type Shimura variety SKS_K over a field of characteristic pp with universal family of abelian schemes Y/SKY/S_K, and let HdRg(Y/SK)=gHdR1(Y/SK)H^g_{{\rm dR}}(Y/S_K)=\wedge^gH^1_{{\rm dR}}(Y/S_K) be its Calabi–Yau-type FF-Zip. Let kk be an algebraically closed field containing the residue field, let μ\mu be the associated cocharacter, and write ordx\operatorname{ord}_x for the vanishing order at xx and clpx\mathsf{clp}_x for the corresponding co-length of the Hodge filtration.

Ogus' principle. Assume that the conjugacy class of μ\mu is defined over Fp\mathbf{F}_p. For every xSK(k)x\in S_K(k),

ordxHa(HdRg(Y/SK))=clpxHdRg(Y/SK).\operatorname{ord}_x \mathrm{Ha}(H^g_{{\rm dR}}(Y/S_K))=\mathsf{clp}_x H^g_{{\rm dR}}(Y/S_K).

This proposes that the vanishing order of the classical Hasse invariant at every point equals the co-length of the Hodge filtration. It extends the expected relationship between Hasse invariants and Frobenius–Hodge-filtration geometry to Hodge-type Shimura varieties; the supplied context does not state whether the principle has been proved or remains open.

Sources & referencesView supporting material

Primary source

Wushi Goldring and Stefan Reppen, “An Ogus Principle for Zip period maps: The Hasse invariant's vanishing order via `Frobenius and the Hodge filtration'”, arXiv:2404.05707 (2024).

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