English

Noncommutative relative de Rham--Witt complex via the norm

Algebraic Geometry 2024-10-10 v1 Algebraic Topology K-Theory and Homology

Abstract

In [Ill79], Illusie constructed de Rham-Witt complex of smooth Fp\mathbb F_p-algebras R, which computes the crystalline cohomology of R, a Zp\mathbb Z_p-lift of the de Rham cohomology of R. There are two different extensions of de Rham-Witt complex: a relative version discovered by Langer-Zink, and a noncommutative version, called Hochschild-Witt homology, constructed by Kaledin. The key to Kaledin's construction is his polynomial Witt vectors. In this article, we introduce a common extension of both: relative Hochschild-Witt homology. It is simply defined to be topological Hochschild homology relative to the Tambara functor W(Fp)W(\mathbb F_p). Adopting Hesselholt's proof of his HKR theorem, we deduce an HKR theorem for relative Hochschild-Witt homology, which relates its homology groups to relative de Rham-Witt complex. We also identify Kaledin's polynomial Witt vectors as the relative Hill-Hopkins-Ravenel norm, which allows us to identify our Hochschild-Witt homology relative to Fp\mathbb F_p with Kaledin's Hochschild-Witt homology. As a consequence, we deduce a comparison between Hochschild-Witt homology and topological restriction homology, fulfilling a missing part of [Kal19].

Keywords

Cite

@article{arxiv.2410.05998,
  title  = {Noncommutative relative de Rham--Witt complex via the norm},
  author = {Zhouhang Mao},
  journal= {arXiv preprint arXiv:2410.05998},
  year   = {2024}
}

Comments

24 pages, preliminary

R2 v1 2026-06-28T19:12:56.273Z