English

Bowen--Franks groups and minus class groups of cyclotomic number fields with prime conductor

Number Theory 2026-05-05 v1 Combinatorics

Abstract

Let pp be an odd rational prime and consider the cyclotomic number field K=Q(ζp)K = \mathbb{Q}(\zeta_{p}) of conductor pp. We construct a directed graph YY on p1p-1 vertices for which the torsion part of the corresponding Bowen--Franks group is closely related to the minus part of the class group of KK. In particular, both groups have the same cardinality up to an explicit power of pp. Furthermore, they are both Gal(K/Q)\mathrm{Gal}(K/\mathbb{Q})-modules, and we prove the equality of the cardinalities of their isotypic components after tensoring them with the valuation ring of an appropriate \ell-adic field for p1\ell \nmid p-1.

Keywords

Cite

@article{arxiv.2605.01398,
  title  = {Bowen--Franks groups and minus class groups of cyclotomic number fields with prime conductor},
  author = {Antonio Lei and Katharina Müller and Daniel Vallières},
  journal= {arXiv preprint arXiv:2605.01398},
  year   = {2026}
}