A strengthening of Brooks' Theorem for line graphs
The electronic journal of combinatorics, Tome 18 (2011) no. 1
We prove that if $G$ is the line graph of a multigraph, then the chromatic number $\chi(G)$ of $G$ is at most $\max\left\{\omega(G), \frac{7\Delta(G) + 10}{8}\right\}$ where $\omega(G)$ and $\Delta(G)$ are the clique number and the maximum degree of $G$, respectively. Thus Brooks' Theorem holds for line graphs of multigraphs in much stronger form. Using similar methods we then prove that if $G$ is the line graph of a multigraph with $\chi(G) \geq \Delta(G) \geq 9$, then $G$ contains a clique on $\Delta(G)$ vertices. Thus the Borodin-Kostochka Conjecture holds for line graphs of multigraphs.
@article{10_37236_632,
author = {Landon Rabern},
title = {A strengthening of {Brooks'} {Theorem} for line graphs},
journal = {The electronic journal of combinatorics},
year = {2011},
volume = {18},
number = {1},
doi = {10.37236/632},
zbl = {1225.05101},
url = {http://geodesic.mathdoc.fr/articles/10.37236/632/}
}
Landon Rabern. A strengthening of Brooks' Theorem for line graphs. The electronic journal of combinatorics, Tome 18 (2011) no. 1. doi: 10.37236/632
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