English

Reciprocity laws and $K$-theory

K-Theory and Homology 2016-11-23 v3 Algebraic Geometry

Abstract

We associate to a full flag F\mathcal{F} in an nn-dimensional variety XX over a field kk, a "symbol map" μF:K(FX)ΣnK(k)\mu_{\mathcal{F}}:K(F_X) \to \Sigma^n K(k). Here, FXF_X is the field of rational functions on XX, and K()K(\cdot) is the KK-theory spectrum. We prove a "reciprocity law" for these symbols: Given a partial flag, the sum of all symbols of full flags refining it is 00. Examining this result on the level of KK-groups, we re-obtain various "reciprocity laws". Namely, when XX is a smooth complete curve, we obtain degree of a principal divisor is zero, Weil reciprocity, Residue theorem, Contou-Carr\`{e}re reciprocity. When XX is higher-dimensional, we obtain Parshin reciprocity.

Keywords

Cite

@article{arxiv.1410.5391,
  title  = {Reciprocity laws and $K$-theory},
  author = {Evgeny Musicantov and Alexander Yom Din},
  journal= {arXiv preprint arXiv:1410.5391},
  year   = {2016}
}
R2 v1 2026-06-22T06:29:59.897Z