Double-critical graphs and complete minors
The electronic journal of combinatorics, Tome 17 (2010)
A connected $k$-chromatic graph $G$ is double-critical if for all edges $uv$ of $G$ the graph $G - u - v$ is $(k-2)$-colourable. The only known double-critical $k$-chromatic graph is the complete $k$-graph $K_k$. The conjecture that there are no other double-critical graphs is a special case of a conjecture from 1966, due to Erdős and Lovász. The conjecture has been verified for $k$ at most $5$. We prove for $k=6$ and $k=7$ that any non-complete double-critical $k$-chromatic graph is $6$-connected and contains a complete $k$-graph as a minor.
@article{10_37236_359,
author = {Ken-ichi Kawarabayashi and Anders Sune Pedersen and Bjarne Toft},
title = {Double-critical graphs and complete minors},
journal = {The electronic journal of combinatorics},
year = {2010},
volume = {17},
doi = {10.37236/359},
zbl = {1215.05069},
url = {http://geodesic.mathdoc.fr/articles/10.37236/359/}
}
Ken-ichi Kawarabayashi; Anders Sune Pedersen; Bjarne Toft. Double-critical graphs and complete minors. The electronic journal of combinatorics, Tome 17 (2010). doi: 10.37236/359
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