Conjectural invariant six-dimensional subvariety of the special fiber

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Let R\mathcal R be sufficiently small, and let MR,Ω\mathfrak M_{\mathcal R,\Omega} be the special moduli space over Fpr\mathbb F_{p^r} equipped with its Z(A∞,p)×G(A∞,p⊗L+)Z(\mathbb A^{\infty,p})\times G(\mathbb A^{\infty,p}\otimes L^+)-action. Let Y(1)[q∞]Y^{(1)}[\mathfrak q^\infty] denote the relevant formal q\mathfrak q-divisible group.

Invariant-subvariety conjecture. The special fiber of MR,Ω\mathfrak M_{\mathcal R,\Omega} contains a nonempty Z(A∞,p)×G(A∞,p⊗L+)Z(\mathbb A^{\infty,p})\times G(\mathbb A^{\infty,p}\otimes L^+)-invariant subvariety M‾\overline{\mathfrak M} of dimension 66 over Fpr\mathbb F_{p^r} such that the formal isogeny types of Y(1)[q∞]Y^{(1)}[\mathfrak q^\infty] at its points with values in a perfect field are among

G0,12r⊕G1,r−13⊕G2,r−22,G_{0,1}^{2r}\oplus G_{1,r-1}^3\oplus G_{2,r-2}^2, G0,1r⊕G1,2r−1⊕G1,r−1⊕G3,2r−3⊕G2,r−2,G_{0,1}^r\oplus G_{1,2r-1}\oplus G_{1,r-1}\oplus G_{3,2r-3}\oplus G_{2,r-2}, G1,2r−1⊕G1,r−13⊕G3,2r−3,G_{1,2r-1}\oplus G_{1,r-1}^3\oplus G_{3,2r-3},

and

G1,r−17.G_{1,r-1}^7.

These give locally closed subvarieties of dimensions 66, 55, 44 and 33, respectively. Moreover, G(A∞,p⊗L+)G(\mathbb A^{\infty,p}\otimes L^+) acts trivially on the set of irreducible components of M‾×FprF‾p\overline{\mathfrak M}\times_{\mathbb F_{p^r}}\overline{\mathbb F}_p.

The conjecture seeks a smaller and more canonical variety inside the special fiber, with controlled formal isogeny strata and trivial action on irreducible components. The supplied text gives no resolution status.

References

Primary source

Oliver Bültel, “Further Counterexamples to Zarhin's conjecture about micro weights”, arXiv:2207.08706 (2025).

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