A shorter proof of the path-width theorem

Abstract

A graph has {\em path-width} at most $w$ if it can be built from a sequence of graphs each with at most $w+1$ vertices, by overlapping consecutive terms. Every graph with path-width at least $w-1$ contains every $w$-vertex forest as a minor: this was originally proved by Bienstock, Robertson, Thomas and the author, and was given a short proof by Diestel. Here we give a proof even shorter and simpler than that of Diestel.