English

On the K-theory of division algebras over local fields

K-Theory and Homology 2019-08-06 v3

Abstract

Let KK be a complete discrete valuation field with finite residue field of characteristic pp, and let DD be a central division algebra over KK of finite index dd. Thirty years ago, Suslin and Yufryakov showed that for all prime numbers \ell different from pp and integers j1j \geq 1 , there exists a "reduced norm" isomorphism of \ell-adic KK-groups NrdD/K ⁣:Kj(D,Z)Kj(K,Z)\operatorname{Nrd}_{D/K} \colon K_j(D,\mathbb{Z}_{\ell}) \to K_j(K,\mathbb{Z}_{\ell}) such that dNrdD/Kd \cdot \operatorname{Nrd}_{D/K} is equal to the norm homomorphism ND/KN_{D/K}. The purpose of this paper is to prove the analogous result for the pp-adic KK-groups. To do so, we employ the cyclotomic trace map to topological cyclic homology and show that there exists a "reduced trace" equivalence TrdA/S ⁣:THH(AD,Zp)THH(SK,Zp)\operatorname{Trd}_{A/S} \colon \operatorname{THH}(A\,|\,D,\mathbb{Z}_p) \to \operatorname{THH}(S\,|\,K,\mathbb{Z}_p) between two pp-complete cyclotomic spectra associated with DD and KK, respectively. Interestingly, we show that if pp divides dd, then it is not possible to choose said equivalence such that, as maps of cyclotomic spectra, dTrdA/Sd \cdot \operatorname{Trd}_{A/S} agrees with the trace TrA/S\operatorname{Tr}_{A/S}, although this is possible as maps of spectra with T\mathbb{T}-action.

Keywords

Cite

@article{arxiv.1807.00104,
  title  = {On the K-theory of division algebras over local fields},
  author = {Lars Hesselholt and Michael Larsen and Ayelet Lindenstrauss},
  journal= {arXiv preprint arXiv:1807.00104},
  year   = {2019}
}