English

An \'etale realization which does not exist

Algebraic Topology 2018-04-03 v3 Algebraic Geometry

Abstract

For a global field, local field, or finite field kk with infinite Galois group, we show that there can not exist a functor from the Morel--Voevodsky A1\mathbb{A}^1-homotopy category of schemes over kk to a genuine Galois equivariant homotopy category satisfying a list of hypotheses one might expect from a genuine equivariant category and an \'etale realization functor. For example, these hypotheses are satisfied by genuine Z/2\mathbb{Z}/2-spaces and the R\mathbb{R}-realization functor constructed by Morel--Voevodsky. This result does not contradict the existence of \'etale realization functors to (pro-)spaces, (pro-)spectra or complexes of modules with actions of the absolute Galois group when the endomorphisms of the unit is not enriched in a certain sense. It does restrict enrichments to representation rings of Galois groups.

Keywords

Cite

@article{arxiv.1709.09999,
  title  = {An \'etale realization which does not exist},
  author = {Jesse Leo Kass and Kirsten Wickelgren},
  journal= {arXiv preprint arXiv:1709.09999},
  year   = {2018}
}

Comments

18 pages. To appear in the New Directions in Homotopy Theory volume of Contemporary Mathematics. V2 has a slightly generalized main theorem, and stable realization functors are explicitly assumed to be additive, which is necessary. V3 minor modifications

R2 v1 2026-06-22T21:57:54.141Z