English

Anabelian geometry for Deligne-Mumford curves

Algebraic Geometry 2026-05-05 v1

Abstract

We develop an anabelian framework for general Deligne-Mumford curves, showing that their stack and orbifold structures are encoded in the group-theoretic properties of their \'etale fundamental groups. After establishing the required properties for profinite F-groups, we prove that fundamental geometric features, including hyperbolicity, affineness, and inertia data, can already be detected from low-level solvable quotients of the associated profinite groups, namely at the optimal 3-step level. As a consequence, we obtain some anabelian reconstruction results for Deligne-Mumford curves, their rigidifications, and their coarsification. While the m-step Grothendieck conjecture doesn't hold for Deligne-Mumford curves, we establish a 5-step anabelian theorem for the rigidification of affine Deligne-Mumford curves, namely affine stacky curves. A certain emphasis is given to the role of stack inertia groups.

Keywords

Cite

@article{arxiv.2605.02577,
  title  = {Anabelian geometry for Deligne-Mumford curves},
  author = {Benjamin Collas and Séverin Philip and Naganori Yamaguchi},
  journal= {arXiv preprint arXiv:2605.02577},
  year   = {2026}
}

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36 pages