Procongruence anabelian conjecture for congruence level structures

Let k\Bbbk be a sub-pp-adic field with absolute Galois group GkG_\Bbbk. Let Mkλ{\mathcal M}^{\lambda}_\Bbbk and Mkμ{\mathcal M}^{\mu}_\Bbbk be moduli stacks of curves with congruence level structures, with geometric base points ξ\overline{\xi} and ξ\overline{\xi}'. Let πˇ1(Mkλ,ξ)\check{\pi}_1({\mathcal M}^{\lambda}_\Bbbk,\overline{\xi}) and πˇ1(Mkμ,ξ)\check{\pi}_1({\mathcal M}^{\mu}_\Bbbk,\overline{\xi}') be their procongruence fundamental groups, equipped with augmentation maps to GkG_\Bbbk, and let IsomGk(,)out\operatorname{Isom}_{G_\Bbbk}(-,-)^\mathrm{out} denote compatible isomorphisms modulo the inner action of the geometric procongruence fundamental group. Procongruence anabelian conjecture for congruence level structures. There is a natural isomorphism of torsors

Isomk(Mkλ,Mkμ)IsomGk(πˇ1(Mkλ,ξ),πˇ1(Mkμ,ξ))out.\operatorname{Isom}_\Bbbk({\mathcal M}^{\lambda}_\Bbbk,{\mathcal M}^{\mu}_\Bbbk)\stackrel{\sim}{\to}\operatorname{Isom}_{G_\Bbbk}(\check{\pi}_1({\mathcal M}^{\lambda}_\Bbbk,\overline{\xi}),\check{\pi}_1({\mathcal M}^{\mu}_\Bbbk,\overline{\xi}'))^\mathrm{out}.

This is the procongruence analogue of the étale anabelian conjecture, replacing the full étale fundamental groups by their congruence completions; the supplied text gives no resolution status.

Sources & referencesView supporting material

Primary source

Marco Boggi and Louis Funar, “Automorphisms of procongruence curve and pants complexes”, arXiv:2004.04135 (2023).

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