English

The Kelmans-Seymour conjecture II: 2-vertices in $K_4^-$

Combinatorics 2016-02-25 v1

Abstract

We use K4K_4^- to denote the graph obtained from K4K_4 by removing an edge, and use TK5TK_5 to denote a subdivision of K5K_5. Let GG be a 5-connected nonplanar graph and {x1,x2,y1,y2}V(G)\{x_1,x_2,y_1,y_2\}\subseteq V(G) such that G[{x1,x2,G[\{x_1,x_2, y1,y2}]K4y_1,y_2\}]\cong K_4^- with y1y2E(G)y_1y_2\notin E(G). Let w1,w2,w3N(y2){x1,x2}w_1,w_2,w_3\in N(y_2)-\{x_1,x_2\} be distinct. We show that GG contains a TK5TK_5 in which y2y_2 is not a branch vertex, or Gy2G-y_2 contains K4K_4^-, or GG has a special 5-separation, or G{y2v:v{w1,w2,w3,x1,x2}}G-\{y_2v:v\notin \{w_1,w_2,w_3,x_1,x_2\}\} contains TK5TK_5.

Keywords

Cite

@article{arxiv.1602.07557,
  title  = {The Kelmans-Seymour conjecture II: 2-vertices in $K_4^-$},
  author = {Dawei He and Yan Wang and Xingxing Yu},
  journal= {arXiv preprint arXiv:1602.07557},
  year   = {2016}
}