Conjectural invariant six-dimensional subvariety of the special fiber

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,pL+)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,pL+)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

G0,12rG1,r13G2,r22,G_{0,1}^{2r}\oplus G_{1,r-1}^3\oplus G_{2,r-2}^2, G0,1rG1,2r1G1,r1G3,2r3G2,r2,G_{0,1}^r\oplus G_{1,2r-1}\oplus G_{1,r-1}\oplus G_{3,2r-3}\oplus G_{2,r-2}, G1,2r1G1,r13G3,2r3,G_{1,2r-1}\oplus G_{1,r-1}^3\oplus G_{3,2r-3},

and

G1,r17.G_{1,r-1}^7.

These give locally closed subvarieties of dimensions 66, 55, 44 and 33, respectively. Moreover, G(A,pL+)G(\mathbb A^{\infty,p}\otimes L^+) acts trivially on the set of irreducible components of M×FprFp\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.

Sources & referencesView supporting material

Primary source

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

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