English

Forest webs and pattern avoidance

Combinatorics 2026-03-19 v1

Abstract

In a recent preprint, Mike Cummings showed that the smooth components of suitably parametrized Springer fibers are in bijection with contracted, fully reduced Pl\"ucker degree-two slr\mathfrak{sl}_r-webs of standard type and that are forests. He showed these are enumerated by sequence A116731 in the OEIS, which is equinumerous with permutations avoiding the patterns {321,2143,3124}. Cummings posed the problem of strengthening this enumerative result by finding a bijection between these webs and a collection of pattern-avoiding permutations. Here we solve this problem, although notably not with the collection of patterns that Cummings had proposed. Rather, we give a bijection between this class of webs and permutations avoiding the patterns {132,4321,3214}.

Keywords

Cite

@article{arxiv.2603.17287,
  title  = {Forest webs and pattern avoidance},
  author = {Jessica Striker and Bridget Eileen Tenner},
  journal= {arXiv preprint arXiv:2603.17287},
  year   = {2026}
}

Comments

9 pages, 5 figures