English

Evaluating the tame Brauer group of open varieties over local fields

Algebraic Geometry 2025-11-27 v1 Number Theory

Abstract

In this document we let UU be a smooth variety of pure dimension dd over a local field kvk_v with unit ball Ov\mathcal{O}_v and residue field F\mathbb{F} of characteristic p>0p>0 and we set nn to be a positive integer such that pnp\nmid n. For various uU(kv)u\in U(k_v) we study the evaluation map u:H2(U,μn)H2(kv,μn)u^*:\mathrm{H}^2(U,\mu_n)\to \mathrm{H}^2(k_v,\mu_n). We suppose that UU embeds as an open subscheme in a regular scheme X\mathcal{X} that is of finite type over Ov\mathcal{O}_v. We assume that Z:=XUZ:=\mathcal{X}\setminus U is a divisor and we endow it with its reduced scheme structure. We show that for u1,u2U(kv)u_1,u_2\in U(k_v) that lift to x1,x2X(Ov)x_1,x_2\in \mathcal{X}(\mathcal{O}_v) we obtain the same evaluation map u1=u2u_1^*=u_2^* under the two conditions that first, there is an equality of reductions x1=x2\overline{x_1}=\overline{x_2} in X(F)\mathcal{X}(\mathbb{F}) and second, that cl(x1Z)=cl(x2Z)\mathrm{cl}(x_1\cap Z)=\mathrm{cl}(x_2\cap Z) holds in Hx2d(Z,μnd)\mathrm{H}^{2d}_{|\overline{x}|}(Z,\mu_n^{\otimes d}).

Keywords

Cite

@article{arxiv.2511.21457,
  title  = {Evaluating the tame Brauer group of open varieties over local fields},
  author = {Victor de Vries},
  journal= {arXiv preprint arXiv:2511.21457},
  year   = {2025}
}

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