English

An enriched degree of the Wronski

Algebraic Topology 2022-06-03 v1 Algebraic Geometry

Abstract

Given mpmp different pp-planes in general position in (m+p)(m+p)-dimensional space, a classical problem is to ask how many pp-planes intersect all of them. For example when m=p=2m = p = 2, this is precisely the question of "lines meeting four lines in 3-space" after projectivizing. The Brouwer degree of the Wronski map provides an answer to this general question, first computed by Schubert over the complex numbers and Eremenko and Gabrielov over the reals. We provide an enriched degree of the Wronski for all mm and pp even, valued in the Grothendieck-Witt ring of a field, using machinery from A1\mathbf{A}^1-homotopy theory. We further demonstrate in all parities that the local contribution of an mm-plane is a determinantal relationship between certain Pl\"ucker coordinates of the pp-planes it intersects.

Keywords

Cite

@article{arxiv.2206.01143,
  title  = {An enriched degree of the Wronski},
  author = {Thomas Brazelton},
  journal= {arXiv preprint arXiv:2206.01143},
  year   = {2022}
}

Comments

24 pages, 5 figures. Comments welcome!