English

Wildly ramified unitary local models for special parahorics. The odd dimensional case

Number Theory 2025-08-15 v2 Algebraic Geometry

Abstract

We construct local models for wildly ramified unitary similitude groups of odd dimension n3n\geq 3 with special parahoric level structure and signature (n1,1)(n-1,1). We first give a lattice-theoretic description for parahoric subgroups using Bruhat-Tits theory in residue characteristic two, and apply them to define local models following the lead of Rapoport-Zink and Pappas-Rapoport. In our case, there are two conjugacy classes of special parahoric subgroups. We show that the local models are smooth for the one class and normal, Cohen-Macaulay for the other class. We also prove that they represent the v-sheaf local models of Scholze-Weinstein. Under some additional assumptions, we obtain an explicit moduli interpretation of the local models.

Keywords

Cite

@article{arxiv.2406.16774,
  title  = {Wildly ramified unitary local models for special parahorics. The odd dimensional case},
  author = {Jie Yang},
  journal= {arXiv preprint arXiv:2406.16774},
  year   = {2025}
}

Comments

Final version, to appear in Algebra & Number Theory