Abstract
A conjecture due to the fourth author states that every d-regular planar multigraph can be d-edge-coloured, provided that for every odd set X of vertices, there are at least d edges between X and its complement. For d=3 this is the four-colour theorem, and the conjecture has been proved for all d≤8, by various authors. In particular, two of us proved it when d=7; and then three of us proved it when d=8. The methods used for the latter give a proof in the d=7 case that is simpler than the original, and we present it here.
Original language | English (US) |
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Pages (from-to) | 276-302 |
Number of pages | 27 |
Journal | Journal of Combinatorial Theory. Series B |
Volume | 115 |
DOIs | |
State | Published - Nov 1 2015 |
All Science Journal Classification (ASJC) codes
- Theoretical Computer Science
- Discrete Mathematics and Combinatorics
- Computational Theory and Mathematics
Keywords
- Discharging
- Edge-colouring
- Four colour theorem
- Planar graph
- Reducible configuration