English

Strong chordality in tournaments and multipartite tournaments with possible loops

Combinatorics 2025-09-24 v1

Abstract

Strongly chordal digraphs are included in the class of chordal digraphs and generalize strongly chordal graphs and chordal bipartite graphs. They are the digraphs that admit a linear ordering of its vertex set for which their adjacency matrix does not contain the Γ\Gamma matrix as a submatrix. In general, it is not clear if these digraphs can be recognized in polynomial time. We focus on multipartite tournaments with possible loops. We give a polynomial-time recognition algorithm and a forbidden induced subgraph characterization of the strong chordality for each of the following cases: tournaments with possible loops, reflexive multipartite tournaments, irreflexive bipartite tournaments, irreflexive tournaments minus one arc, and balanced digraphs. In addition, we prove that in a strongly chordal digraph the minimum size of a total dominating set equals the maximum number of disjoint in-neighborhoods, and this number can be calculated in linear time given a Γ\Gamma-free ordering of the input graph.

Keywords

Cite

@article{arxiv.2509.18541,
  title  = {Strong chordality in tournaments and multipartite tournaments with possible loops},
  author = {Pavol Hell and César Hernández-Cruz and Jing Huang},
  journal= {arXiv preprint arXiv:2509.18541},
  year   = {2025}
}

Comments

33 pages, 10 figures