The extremal functions for triangle-free graphs with excluded minors

Abstract

We prove two results: 1. A graph $G$ on at least seven vertices with a vertex $v$ such that $G-v$ is planar and $t$ triangles satisfies $|E(G)|\le 3|V(G)|-9+t/3$. 2. For $p=2,3,\dots ,9$, a triangle-free graph $G$ on at least $2p-5$ vertices with no $K_p$-minor satisfies $|E(G)|\le (p-2)|V(G)|-(p-2{)}^2$.

arXiv comment12 pages, no figures. Revised according to referees' comments