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Clique minors in double‐critical graphs
Abstract:A connected t‐chromatic graph G is double‐critical if urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0001 is urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0002‐colorable for each edge urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0003. A long‐standing conjecture of Erdős and Lovász that the complete graphs are the only double‐critical t‐chromatic graphs remains open for all urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0004. Given the difficulty in settling Erdős and Lovász's conjecture and motivated by the well‐known Hadwiger's conjecture, Kawarabayashi, Pedersen, and Toft proposed a weaker conjecture that every double‐critical t‐chromatic graph contains a urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0005 minor and verified their conjecture for urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0006. Albar and Gonçalves recently proved that every double‐critical 8‐chromatic graph contains a K8 minor, and their proof is computer assisted. In this article, we prove that every double‐critical t‐chromatic graph contains a urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0007 minor for all urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0008. Our proof for urn:x-wiley:03649024:media:jgt22216:jgt22216-math-0009 is shorter and computer free.
Keywords:clique minor  double‐critical graph  separating set
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