English

Chordal matroids arising from generalized parallel connections II

Combinatorics 2025-01-22 v2

Abstract

In 1961, Dirac showed that chordal graphs are exactly the graphs that can be constructed from complete graphs by a sequence of clique-sums. In an earlier paper, by analogy with Dirac's result, we introduced the class of GF(q)GF(q)-chordal matroids as those matroids that can be constructed from projective geometries over GF(q)GF(q) by a sequence of generalized parallel connections across projective geometries over GF(q)GF(q). Our main result showed that when q=2q=2, such matroids have no induced minor in {M(C4),M(K4)}\{M(C_4),M(K_4)\}. In this paper, we show that the class of GF(2)GF(2)-chordal matroids coincides with the class of binary matroids that have none of M(K4)M(K_4), M(K3,3)M^*(K_{3,3}), or M(Cn)M(C_n) for n4n\geq 4 as a flat. We also show that GF(q)GF(q)-chordal matroids can be characterized by an analogous result to Rose's 1970 characterization of chordal graphs as those that have a perfect elimination ordering of vertices.

Keywords

Cite

@article{arxiv.2405.02099,
  title  = {Chordal matroids arising from generalized parallel connections II},
  author = {James Dylan Douthitt and James Oxley},
  journal= {arXiv preprint arXiv:2405.02099},
  year   = {2025}
}
R2 v1 2026-06-28T16:15:33.818Z