English

Ribbon complexes for the 0-Hecke algebra

Combinatorics 2026-01-21 v1 Rings and Algebras Representation Theory

Abstract

We construct explicit tableau-level maps between indecomposable projective modules for the type A 0-Hecke algebra that assemble into canonical split short exact sequences lifting the basic ribbon product rule in NSym via concatenation and near-concatenation. Iterating these maps yields cochain complexes indexed by generalized ribbons; we prove these complexes are acyclic in positive degrees and that their zeroth cohomology is the projective module indexed by full concatenation. We apply these complexes, together with VandeBogert's ribbon Schur module criterion, to prove Koszulness for a naturally defined internally graded algebra object built from the 0-Hecke tower. Finally, we define skew projective modules whose noncommutative Frobenius characteristics realize skewing by fundamental quasisymmetric functions on NSym.

Keywords

Cite

@article{arxiv.2601.13324,
  title  = {Ribbon complexes for the 0-Hecke algebra},
  author = {Ayah Almousa and Bryan Lu},
  journal= {arXiv preprint arXiv:2601.13324},
  year   = {2026}
}

Comments

24 pages

R2 v1 2026-07-01T09:11:18.124Z