On the Existence of Word-representable Line Graphs of Non-word-representable Graphs

An open question in the theory of word-representable graphs for the past decade has been whether the line graph of a non-word-representable graph is always non-word-representable. By formulating an appropriate optimization problem for the decision problem of 3-semi-transitive graphs, we show that th...

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Bibliographic Details
Main Authors Akbar, M M, Akrobotu, P D, Brewer, C P
Format Journal Article
LanguageEnglish
Published 05.08.2021
Subjects
Mathematics - Combinatorics
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Summary:An open question in the theory of word-representable graphs for the past decade has been whether the line graph of a non-word-representable graph is always non-word-representable. By formulating an appropriate optimization problem for the decision problem of 3-semi-transitive graphs, we show that the line graph of a non-word-representable graph can be word-representable. Using IBM's CPLEX solver, we demonstrate for several known word-representable and non-word-representable graphs that the line graph of a graph is 3-semi-transitive when there is a solution to the optimization problem. This results in an example where the line graph of a non-word-representable graph is both 3-semi-transitive and semi-transitive and thus is word-representable.
DOI:10.48550/arxiv.2108.02363