The size of edge-critical uniquely 3-colorable planar graphs
The electronic journal of combinatorics, Tome 20 (2013) no. 3
A graph $G$ is uniquely $k$-colorable if the chromatic number of $G$ is $k$ and $G$ has only one $k$-coloring up to permutation of the colors. A uniquely $k$-colorable graph $G$ is edge-critical if $G-e$ is not a uniquely $k$-colorable graph for any edge $e\in E(G)$. In this paper, we prove that if $G$ is an edge-critical uniquely $3$-colorable planar graph, then $|E(G)|\leq \frac{8}{3}|V(G)|-\frac{17}{3}$. On the other hand, there exists an infinite family of edge-critical uniquely 3-colorable planar graphs with $n$ vertices and $\frac{9}{4}n-6$ edges. Our result gives a first non-trivial upper bound for $|E(G)|$.
DOI :
10.37236/3228
Classification :
05C10, 05C15, 05C35
Mots-clés : graph theory, planar graphs, unique coloring
Mots-clés : graph theory, planar graphs, unique coloring
Affiliations des auteurs :
Naoki Matsumoto  1
@article{10_37236_3228,
author = {Naoki Matsumoto},
title = {The size of edge-critical uniquely 3-colorable planar graphs},
journal = {The electronic journal of combinatorics},
year = {2013},
volume = {20},
number = {3},
doi = {10.37236/3228},
zbl = {1295.05090},
url = {http://geodesic.mathdoc.fr/articles/10.37236/3228/}
}
Naoki Matsumoto. The size of edge-critical uniquely 3-colorable planar graphs. The electronic journal of combinatorics, Tome 20 (2013) no. 3. doi: 10.37236/3228
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