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Distinct letters $x$ and $y$ alternate in a word $w$ if after deleting in $w$ all letters but the copies of $x$ and $y$ we either obtain a word of the form $xyxy\cdots$ (of even or odd length) or a word of the form $yxyx\cdots$ (of even or…

Combinatorics · Mathematics 2019-07-23 Gi-Sang Cheon , Jinha Kim , Minki Kim , Sergey Kitaev

This paper investigates the new notion of $2$-word-$\pi$-repre\-sentable graphs: the nodes of the graph correspond to the letters of the two words and there exists an edge between two nodes if the projections of any two letters of both…

Combinatorics · Mathematics 2026-05-27 Duncan Adamson , Amanita Dietz , Pamela Fleischmann , Annika Huch , Silas Cato Sacher

A graph $G = (V, E)$ is said to be word-representable if a word $w$ can be formed using the letters of the alphabet $V$ such that for every pair of vertices $x$ and $y$, $xy \in E$ if and only if $x$ and $y$ alternate in $w$. A…

Combinatorics · Mathematics 2026-01-29 Eshwar Srinivasan , Ramesh Hariharasubramanian

For an arbitrary word $w$ on an alphabet, we can define the alternating symbol graph, $G(w)$, as the graph in which the edge $(a, b)$ is in $E$ iff the letters $a$ and $b$ alternate in the word $w$. A graph $G = (V, E)$ is said to be…

Combinatorics · Mathematics 2018-06-14 Ameya Daigavane , Mrityunjay Singh , Benny K. George

A graph $G = (V, E)$ is said to be word-representable if a word $w$ can be formed using the letters of the alphabet $V$ such that for every pair of vertices $x$ and $y$, $xy \in E$ if and only if $x$ and $y$ alternate in $w$. Gaetz and Ji…

Combinatorics · Mathematics 2025-12-25 Eshwar Srinivasan , Ramesh Hariharasubramanian

A graph $G=(V,E)$ is word-representable if there exists a word $w$ over the alphabet $V$ such that letters $x$ and $y$ alternate in $w$ if and only if $(x,y)\in E$. A triangular grid graph is a subgraph of a tiling of the plane with…

Combinatorics · Mathematics 2015-03-30 Zongqing Chen , Sergey Kitaev , Brian Y. Sun

A graph $G=(V,E)$ is said to be word-representable if there exists a word $w$ over the alphabet $V$ such that two distinct letters $x,y\in V$ alternate in $w$ if and only if $xy \in E$. Word-representable graphs form a well-studied graph…

Combinatorics · Mathematics 2026-05-26 Suchanda Roy , Ramesh Hariharasubramanian

A graph G(V, E) is word-representable if there exists a word w over V such that distinct letters x and y alternate in w iff $xy \in E$. We introduce p-complete squares and p-complete square-free word-representable graphs. A word is…

Discrete Mathematics · Computer Science 2025-12-25 Biswajit Das , Ramesh Hariharasubramanian

The notion of $12$-representable graphs was introduced as a variant of a well-known class of word-representable graphs. Recently, these graphs were shown to be equivalent to the complements of simple-triangle graphs. This indicates that a…

Discrete Mathematics · Computer Science 2023-04-18 Asahi Takaoka

The notion of word-representable graphs is a generalization of comparability graphs, in which graphs are represented by words. The complexity of word-representation of a word-representable graph is captured through the representation…

Combinatorics · Mathematics 2026-02-17 Khyodeno Mozhui , K. V. Krishna

A graph $G=(V,E)$ is word-representable if there exists a word $w$ over the alphabet $V$ such that letters $x$ and $y$, $x\neq y$, alternate in $w$ if and only if $(x,y)\in E$. Halld\'{o}rsson et al.\ have shown that a graph is…

Combinatorics · Mathematics 2015-08-03 Thomas Z. Q. Chen , Sergey Kitaev , Brian Y. Sun

In this work, we characterize the class of word-representable graphs with respect to the modular decomposition. Consequently, we determine the representation number of a word-representable graph in terms of the permutation-representation…

Combinatorics · Mathematics 2024-12-24 Tithi Dwary , K. V. Krishna

Let $G$ be a graph with vertex set $V(G)$. Let $n$ and $k$ be non-negative integers such that $n + 2k \leq |V(G)| - 2$ and $|V(G)| - n$ is even. If when deleting any $n$ vertices of $G$ the remaining subgraph contains a matching of $k$…

Combinatorics · Mathematics 2007-05-23 Guizhen Liu , Qinglin Yu

The $k$-representation number of a graph $G$ is the minimum cardinality of the system of vertex subsets with the property that every edge of $G$ is covered at least $k$ times while every non-edge is covered at most $(k-1)$ times. In…

Combinatorics · Mathematics 2024-03-05 Ayush Basu , Vojtěch Rödl , Marcelo Sales

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…

Combinatorics · Mathematics 2021-08-06 M M Akbar , P D Akrobotu , C P Brewer

In this work, we show that the class of word-representable graphs is closed under split recomposition and determine the representation number of the graph obtained by recomposing two word-representable graphs. Accordingly, we show that the…

Discrete Mathematics · Computer Science 2024-01-05 Tithi Dwary , K. V. Krishna

A graph $G = (V,E)$ is word-representable if there is a word $w$ over the alphabet $V$ such that $x$ and $y$ alternate in $w$ if and only if the edge $(x, y)$ is in $G$. It is known [6] that all $3$-colourable graphs are word-representable,…

Combinatorics · Mathematics 2018-10-01 Marc Elliot Glen

These notes concern aspects of various graphs whose vertex set is a group $G$ and whose edges reflect group structure in some way (so that they are invariant under the action of the automorphism group of $G$). The graphs I will discuss are…

Group Theory · Mathematics 2021-03-29 Peter J. Cameron

While the problem of determining the representation number of an arbitrary word-representable graph is NP-hard, this problem is open even for bipartite graphs. The representation numbers are known for certain bipartite graphs including all…

Combinatorics · Mathematics 2025-06-03 Khyodeno Mozhui , K. V. Krishna

The class of word-representable graphs, introduced in connection with the study of the Perkins semigroup by Kitaev and Seif, has attracted significant attention in combinatorics and theoretical computer science due to its deep connections…

Combinatorics · Mathematics 2025-12-16 Eshwar Srinivasan , Ramesh Hariharasubramanian