2 research outputs found
Immersion and clustered coloring
Hadwiger and Haj\'{o}s conjectured that for every positive integer ,
-minor free graphs and -topological minor free graphs are
properly -colorable, respectively. Clustered coloring version of these two
conjectures which only require monochromatic components to have bounded size
has been extensively studied. In this paper we consider the clustered coloring
version of the immersion-variant of Hadwiger's and Haj\'{o}s' conjecture
proposed by Lescure and Meyniel and independently by Abu-Khzam and Langston. We
determine the minimum number of required colors for -immersion free graphs,
for any fixed graph , up to a small additive absolute constant. Our result
is tight for infinitely many graphs .
A key machinery developed in this paper is a lemma that reduces a clustering
coloring problem on graphs to the one on the torsos of their tree-cut
decomposition or tree-decomposition. A byproduct of this machinery is a unified
proof of a result of Alon, Ding, Oporowski and Vertigan and a result of the
author and Oum about clustered coloring graphs of bounded maximum degree in
minor-closed families