English

Classifying spaces for \'etale algebras with generators

Rings and Algebras 2023-06-22 v3

Abstract

We construct varieties B(r;An) such that a map X -> B(r;An) corresponds to a degree-n \'etale algebra on X equipped with r generating global sections. We then show that when n = 2, i.e., in the quadratic \'etale case, that the singular cohomology of B(r; An)(R) can be used to reconstruct a famous example of S. Chase and to extend its application to showing that there is a smooth affine r-1-dimensional R-variety on which there are \'etale algebras An of arbitrary degrees n that cannot be generated by fewer than r elements. This shows that in the \'etale algebra case, a bound established by U. First and Z. Reichstein is sharp.

Keywords

Cite

@article{arxiv.1902.07745,
  title  = {Classifying spaces for \'etale algebras with generators},
  author = {Abhishek Kumar Shukla and Ben Williams},
  journal= {arXiv preprint arXiv:1902.07745},
  year   = {2023}
}

Comments

19 pages

R2 v1 2026-06-23T07:46:25.526Z