English

The Merino--Welsh conjecture is false for matroids

Combinatorics 2024-02-26 v2

Abstract

The matroidal version of the Merino--Welsh conjecture states that the Tutte polynomial TM(x,y)T_M(x,y) of any matroid MM without loops and coloops satisfies that max(TM(2,0),TM(0,2))TM(1,1).\max(T_M(2,0),T_M(0,2))\geq T_M(1,1). Equivalently, if the Merino--Welsh conjecture is true for all matroids without loops and coloops, then the following inequalities are also satisfied for all matroids without loops and coloops: TM(2,0)+TM(0,2)2TM(1,1),T_M(2,0)+T_M(0,2)\geq 2T_M(1,1), and TM(2,0)TM(0,2)TM(1,1)2.T_M(2,0)T_M(0,2)\geq T_M(1,1)^2. We show a counter-example for these inequalities.

Cite

@article{arxiv.2311.01932,
  title  = {The Merino--Welsh conjecture is false for matroids},
  author = {Csongor Beke and Gergely Kál Csáji and Péter Csikvári and Sára Pituk},
  journal= {arXiv preprint arXiv:2311.01932},
  year   = {2024}
}

Comments

6 pages

R2 v1 2026-06-28T13:10:42.795Z