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A logarithmic approximation of linearly-ordered colourings
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).ORCID iD: 0000-0002-5379-345X
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Algebra, Combinatorics and Topology.ORCID iD: 0009-0006-4903-1328
Department of Computer Science, University of Oxford, UK.
Department of Computer Science, University of Oxford, UK.
2024 (English)In: Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques, APPROX/RANDOM 2024, Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing , 2024, article id 7Conference paper, Published paper (Refereed)
Abstract [en]

A linearly ordered (LO) k-colouring of a hypergraph assigns to each vertex a colour from the set {0, 1, . . ., k − 1} in such a way that each hyperedge has a unique maximum element. Barto, Batistelli, and Berg conjectured that it is NP-hard to find an LO k-colouring of an LO 2-colourable 3-uniform hypergraph for any constant k ≥ 2 [STACS’21] but even the case k = 3 is still open. Nakajima and Živný gave polynomial-time algorithms for finding, given an LO 2-colourable 3-uniform hypergraph, an LO colouring with O*(√n) colours [ICALP’22] and an LO colouring with O*(√3 n) colours [ACM ToCT’23]. Very recently, Louis, Newman, and Ray gave an SDP-based algorithm with O*(√5 n) colours. We present two simple polynomial-time algorithms that find an LO colouring with O(log2(n)) colours, which is an exponential improvement.

Place, publisher, year, edition, pages
Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing , 2024. article id 7
Keywords [en]
Approximation, Hypergraph, Linear ordered colouring, Promise Constraint Satisfaction Problems
National Category
Computer Sciences Discrete Mathematics
Identifiers
URN: urn:nbn:se:kth:diva-354305DOI: 10.4230/LIPIcs.APPROX/RANDOM.2024.7ISI: 001545634500007Scopus ID: 2-s2.0-85204434826OAI: oai:DiVA.org:kth-354305DiVA, id: diva2:1902964
Conference
27th International Conference on Approximation Algorithms for Combinatorial Optimization Problems, APPROX 2024 and the 28th International Conference on Randomization and Computation, RANDOM 2024, August 28-30, 2024, London, United Kingdom of Great Britain and Northern Ireland
Note

Part of ISBN: 9783959773485

QC 20241003

Available from: 2024-10-02 Created: 2024-10-02 Last updated: 2025-12-08Bibliographically approved

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Håstad, JohanMartinsson, Björn

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