,
Will Perkins
,
Xavier Povill
Creative Commons Attribution 4.0 International license
In 1970, Hajnal and Szemerédi proved a conjecture of Erdős stating that any graph with maximum degree Δ admits an equitable (Δ+1)-coloring, that is, a coloring where color class sizes differ by at most 1. In 2007 Kierstead and Kostochka reproved their result and provided a polynomial-time algorithm which produces such a coloring. In this paper we study the problem of approximately sampling uniformly random equitable colorings. A series of works gives polynomial-time sampling algorithms for colorings without the color class constraint, the latest improvement being by Carlson and Vigoda for q ≥ 1.809 Δ. In this paper we give a polynomial-time sampling algorithm for equitable colorings when q > 2Δ. Moreover, our results extend to colorings with small deviations from equitable (and as a corollary, establishing their existence). The proof uses the framework of the geometry of polynomials for multivariate polynomials, and as a consequence establishes a multivariate local Central Limit Theorem for color class sizes of uniform random colorings.
@InProceedings{kuchukova_et_al:LIPIcs.ICALP.2026.134,
author = {Kuchukova, Aiya and Perkins, Will and Povill, Xavier},
title = {{Sampling Colorings with Fixed Color Class Sizes}},
booktitle = {53rd International Colloquium on Automata, Languages, and Programming (ICALP 2026)},
pages = {134:1--134:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-428-4},
ISSN = {1868-8969},
year = {2026},
volume = {374},
editor = {Bhattacharya, Sayan and Nanongkai, Danupon and Benedikt, Michael and Puppis, Gabriele},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2026.134},
URN = {urn:nbn:de:0030-drops-265231},
doi = {10.4230/LIPIcs.ICALP.2026.134},
annote = {Keywords: sampling, approximate counting, graph coloring, zero-freeness, Potts model, LCLT}
}