Questions tagged [graph-minors]

A minor of a graph $\Gamma$ is a graph, obtained form a subgraph of $\Gamma$ by edge contractions. Robertson-Seymour theorem states that any family of graphs closed under finite minors can be defined by a finite set of forbidden minors (graphs that can not be minors of graphs from that family). A minor is called topological iff it is obtained form a subgraph by collapsing paths of degree-two vertices to single edges. To be used with [graph-theory] tag.