Counting proper colourings in 4-regular graphs via the Potts model
The electronic journal of combinatorics, Tome 25 (2018) no. 4
We give tight upper and lower bounds on the internal energy per particle in the antiferromagnetic $q$-state Potts model on $4$-regular graphs, for $q\ge 5$. This proves the first case of a conjecture of the author, Perkins, Jenssen and Roberts, and implies tight bounds on the antiferromagnetic Potts partition function. The zero-temperature limit gives upper and lower bounds on the number of proper $q$-colourings of $4$-regular graphs, which almost proves the case $d=4$ of a conjecture of Galvin and Tetali. For any $q \ge 5$ we prove that the number of proper $q$-colourings of a $4$-regular graph is maximised by a union of $K_{4,4}$'s.
DOI :
10.37236/7743
Classification :
05C15, 82B20, 90C35
Mots-clés : graph colouring, Potts model, graph homomorphisms
Mots-clés : graph colouring, Potts model, graph homomorphisms
Affiliations des auteurs :
Ewan Davies  1
@article{10_37236_7743,
author = {Ewan Davies},
title = {Counting proper colourings in 4-regular graphs via the {Potts} model},
journal = {The electronic journal of combinatorics},
year = {2018},
volume = {25},
number = {4},
doi = {10.37236/7743},
zbl = {1398.05082},
url = {http://geodesic.mathdoc.fr/articles/10.37236/7743/}
}
Ewan Davies. Counting proper colourings in 4-regular graphs via the Potts model. The electronic journal of combinatorics, Tome 25 (2018) no. 4. doi: 10.37236/7743
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