On the representation number of a crown graph

Glen, Marc and Kitaev, Sergey and Pyatkin, Artem (2018) On the representation number of a crown graph. Discrete Applied Mathematics, 244. pp. 89-93. ISSN 0166-218X

[thumbnail of Glen-etal-DAM-2018-On-the-representation-number-of-a-crown]
Preview
 Text (Glen-etal-DAM-2018-On-the-representation-number-of-a-crown)
Glen_etal_DAM_2018_On_the_representation_number_of_a_crown.pdf
Accepted Author Manuscript
License: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 logo
Download (221kB)| Preview

    Abstract

    A graph G = (V,E) is word-representable if there exists a word ω over the alphabet V such that letters x and y alternate in ω if and only if xy is an edge in E . It is known (Kitaev and Pyatkin, 2008) that any word-representable graph G is k-word-representable for some k, that is, there exists a word ω representing G such that each letter occurs exactly k times in ω. The minimum such k is called G’s representation number. A crown graph (also known as a cocktail party graph) Hn,n is a graph obtained from the complete bipartite graph Kn,n by removing a perfect matching. In this paper, we show that for n≥ 5,Hn,n ’s representation number is [n / 2]. This result not only provides a complete solution to the open Problem 7.4.2 in Kitaev and Lozin (2015), but also gives a negative answer to the question raised in Problem 7.2.7 in Kitaev and Lozin (2015) on 3-word-representability of bipartite graphs. As a byproduct, we obtain a new example of a graph class with a high representation number.

    ORCID iDs

    Glen, Marc, Kitaev, Sergey ORCID logoORCID: https://orcid.org/0000-0003-3324-1647 and Pyatkin, Artem;
    CORE (COnnecting REpositories)