Excluding Graphs as Immersions in Surface Embedded Graphs
arXiv:1303.6567
Abstract
We prove a structural characterization of graphs that forbid a fixed graph as an immersion and can be embedded in a surface of Euler genus . In particular, we prove that a graph that excludes some connected graph as an immersion and is embedded in a surface of Euler genus has either "small" treewidth (bounded by a function of and ) or "small" edge connectivity (bounded by the maximum degree of ). Using the same techniques we also prove an excluded grid theorem on bounded genus graphs for the immersion relation.