English

Schubert curves in the orthogonal Grassmannian

Combinatorics 2019-03-06 v1 Algebraic Geometry

Abstract

We develop a combinatorial rule to compute the real geometry of type B Schubert curves S(λ)S(\lambda_\bullet) in the orthogonal Grassmannian OGn\mathrm{OG}_n, which are one-dimensional Schubert problems defined with respect to orthogonal flags osculating the rational normal curve. Our results are natural analogs of results previously known only in type A. First, using the type B Wronski map, we show that the real locus of the Schubert curve has a natural covering map to RP1\mathbb{RP}^1, with monodromy operator ω\omega defined as the commutator of jeu de taquin rectification and promotion on skew shifted semistandard tableaux. We then introduce two different algorithms to compute ω\omega without rectifying the skew tableau. The first uses recently-developed shifted tableau crystal operators, while the second uses local switches much like jeu de taquin. The switching algorithm further computes the K-theory coefficient of the Schubert curve: its nonadjacent switches precisely enumerate Pechenik and Yong's shifted genomic tableaux. The connection to K-theory also gives rise to a partial understanding of the complex geometry of these curves.

Keywords

Cite

@article{arxiv.1903.01673,
  title  = {Schubert curves in the orthogonal Grassmannian},
  author = {Maria Gillespie and Jake Levinson and Kevin Purbhoo},
  journal= {arXiv preprint arXiv:1903.01673},
  year   = {2019}
}

Comments

43 pages

R2 v1 2026-06-23T07:58:22.813Z