English

Perfect matching index vs. circular flow number of a cubic graph

Combinatorics 2020-08-12 v1

Abstract

The perfect matching index of a cubic graph GG, denoted by π(G)\pi(G), is the smallest number of perfect matchings that cover all the edges of GG. According to the Berge-Fulkerson conjecture, π(G)5\pi(G)\le5 for every bridgeless cubic graph~GG. The class of graphs with π5\pi\ge 5 is of particular interest as many conjectures and open problems, including the famous cycle double cover conjecture, can be reduced to it. Although nontrivial examples of such graphs are very difficult to find, a few infinite families are known, all with circular flow number Φc(G)=5\Phi_c(G)=5. It has been therefore suggested [Electron. J. Combin. 23 (2016), #\#P3.54] that π(G)5\pi(G)\ge 5 might imply Φc(G)5\Phi_c(G)\ge 5. In this article we dispel these hopes and present a family of cyclically 44-edge-connected cubic graphs of girth at least 55 (snarks) with π5\pi\ge 5 and Φc4+23\Phi_c\le 4+\frac23.

Keywords

Cite

@article{arxiv.2008.04775,
  title  = {Perfect matching index vs. circular flow number of a cubic graph},
  author = {Edita Máčajová and Martin Škoviera},
  journal= {arXiv preprint arXiv:2008.04775},
  year   = {2020}
}

Comments

arXiv admin note: text overlap with arXiv:2008.01398