English

Floor, ceiling, slopes, and $K$-theory

K-Theory and Homology 2023-08-30 v2 Algebraic Topology Number Theory

Abstract

We calculate K(k[x]/xe;Zp)\mathrm K_*(k[x]/x^e;\mathbf Z_p) by evaluating the syntomic cohomology Zp(i)(k[x]/xe)\mathbf Z_p(i)(k[x]/x^e) introduced by Bhatt-Morrow-Scholze and Bhatt-Scholze. This recovers calculations of Hesselholt-Madsen and Speirs, and generalizes an example of Mathew treating the case e=2e=2 and p>2p>2. Our main innovation is systematic use of the floor and ceiling functions, which clarifies matters substantially even for e=2e=2. We furthermore observe a persistent phenomenon of slopes. As an application, we answer some questions of Hesselholt.

Cite

@article{arxiv.2110.04978,
  title  = {Floor, ceiling, slopes, and $K$-theory},
  author = {Yuri J. F. Sulyma},
  journal= {arXiv preprint arXiv:2110.04978},
  year   = {2023}
}

Comments

v2: expanded exposition; added link to interactive figures/source code; fixed wildly incorrect mod-p multiplicative structure. 24 pages, 8 figures

R2 v1 2026-06-24T06:46:48.359Z