Finiteness conjecture for structurally atypical intersections

Let XX be a complex analytic space with a special structure, and let MXM\subset X be a closed subvariety. A product subvariety Y1×Y2MY_1\times Y_2\subset M is maximal if it is not properly contained in a larger product subvariety with compatible product structures. A subvariety W=W1×W2XW=W_1\times W_2\subset X is a weakly special product subvariety if both W1×{point}W_1\times\{\mathrm{point}\} and {point}×W2\{\mathrm{point}\}\times W_2 are weakly special in XX; an MM-weakly special subvariety is a weakly special subvariety of XX contained in MM. Write Y1×Y2ws\langle Y_1\times Y_2\rangle_{\mathrm{ws}} for its smallest weakly special subvariety.

Finiteness conjecture. There exists a finite set ΣpΣM\Sigma_{\mathrm{p}}\cup\Sigma_M, where Σp\Sigma_{\mathrm{p}} consists of weakly special product subvarieties and ΣM\Sigma_M consists of MM-weakly special subvarieties of XX, such that every maximal product subvariety Y1×Y2MY_1\times Y_2\subset M satisfies either

Y1×Y2ws=W1×W2Σp,\langle Y_1\times Y_2\rangle_{\mathrm{ws}}=W_1\times W_2\in\Sigma_{\mathrm{p}},

or Y1×Y2WMY_1\times Y_2\subset W\subset M for some WΣMW\in\Sigma_M.

This conjecture is already unknown for abelian varieties; the source also explains that the ΣM\Sigma_M alternative is necessary for Shimura varieties.

Sources & referencesView supporting material

Primary source

Ke Chen, Tianzhi Hu, Ruiran Sun and Kang Zuo, “On the distribution of non-rigid families in the moduli spaces”, arXiv:2408.11604 (2026).

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