English

Sorting orders, subword complexes, Bruhat order and total positivity

Combinatorics 2010-11-05 v2 Algebraic Geometry

Abstract

In this note we construct a poset map from a Boolean algebra to the Bruhat order which unveils an interesting connection between subword complexes, sorting orders, and certain totally nonnegative spaces. This relationship gives a new proof of Bj\"orner and Wachs' result \cite{BW} that the proper part of Bruhat order is homotopy equivalent to the proper part of a Boolean algebra --- that is, to a sphere. We also obtain a geometric interpretation for sorting orders. We conclude with two new results: that the intersection of all sorting orders is the weak order, and the union of sorting orders is the Bruhat order.

Keywords

Cite

@article{arxiv.0909.2828,
  title  = {Sorting orders, subword complexes, Bruhat order and total positivity},
  author = {Drew Armstrong and Patricia Hersh},
  journal= {arXiv preprint arXiv:0909.2828},
  year   = {2010}
}

Comments

10 pages, 1 figure. This is the official version. It is more official than the version that appears in Advances in Applied Mathematics

R2 v1 2026-06-21T13:46:43.920Z