English

Interval hypergraphic lattices

Combinatorics 2025-12-08 v2

Abstract

For a hypergraph H\mathbb{H} on [n][n], the hypergraphic poset PHP_\mathbb{H} is the transitive closure of the oriented skeleton of the hypergraphic polytope H\triangle_\mathbb{H} (the Minkowski sum of the standard simplices H\triangle_H for all HHH \in \mathbb{H}). Hypergraphic posets include the weak order for the permutahedron (when H\mathbb{H} is the complete graph on [n][n]) and the Tamari lattice for the associahedron (when H\mathbb{H} is the set of all intervals of [n][n]), which motivates the study of lattice properties of hypergraphic posets. In this paper, we focus on interval hypergraphs, where all hyperedges are intervals of [n][n]. We characterize the interval hypergraphs I\mathbb{I} for which PIP_\mathbb{I} is a lattice, a distributive lattice, a semidistributive lattice, and a lattice quotient of the weak order.

Keywords

Cite

@article{arxiv.2411.09832,
  title  = {Interval hypergraphic lattices},
  author = {Nantel Bergeron and Vincent Pilaud},
  journal= {arXiv preprint arXiv:2411.09832},
  year   = {2025}
}

Comments

31 pages, 8 figures; Version 2: minor corrections from referee suggestions

R2 v1 2026-06-28T20:00:34.764Z