English

Roots of unity in $K(n)$-local rings

Algebraic Topology 2019-12-05 v3

Abstract

The goal of this paper is to address the following question: if AA is an Ek\mathbf{E}_{k}-ring for some k1k\geq 1 and f ⁣:π0ABf\colon\pi_0 A \to B is a map of commutative rings, when can we find an Ek\mathbf{E}_{k}-ring RR with an Ek\mathbf{E}_{k}-ring map g ⁣:ARg\colon A \to R such that π0g=f\pi_0 g = f? A classical result in the theory of realizing E\mathbf{E}_\infty-rings, due to Goerss--Hopkins, gives an affirmative answer to this question if ff is etale. The goal of this paper is to provide answers to this question when ff is ramified. We prove a non-realizability result in the K(n)K(n)-local setting for every n1n\geq 1 for HH_\infty-rings containing primitive ppth roots of unity. As an application, we give a proof of the folk result that the Lubin--Tate tower from arithmetic geometry does not lift to a tower of HH_\infty-rings over Morava EE-theory.

Keywords

Cite

@article{arxiv.1707.09957,
  title  = {Roots of unity in $K(n)$-local rings},
  author = {Sanath K. Devalapurkar},
  journal= {arXiv preprint arXiv:1707.09957},
  year   = {2019}
}

Comments

7 pages; improved introduction; version accepted by Proc. Amer. Math. Soc