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A pair of letters $x$ and $y$ are said to alternate in a word $w$ if, after removing all letters except for the copies of $x$ and $y$ from $w$, the resulting word is of the form $xyxy\ldots$ (of even or odd length) or $yxyx\ldots$ (of even…

Combinatorics · Mathematics 2025-07-14 Suchanda Roy , Ramesh Hariharasubramanian

Word-representable graphs are a class of graphs that can be represented by words, where edges and non-edges are determined by the alternation of letters in those words. Several papers in the literature have explored the…

Combinatorics · Mathematics 2025-08-22 Herman Z. Q. Chen , Humaira Hameed , Sergey Kitaev

A graph $G = (V, E)$ is word-representable, if there exists a word w over the alphabet V such that for letters ${x, y} \in V$ , $x$ and $y$ alternate in $w$ if and only if $xy \in E$. In this paper, we prove that any non-empty…

Combinatorics · Mathematics 2026-01-29 Biswajit Das , Ramesh Hariharasubramanian

A graph is word-representable if it can be represented in a certain way using alternation of letters in words. Word-representable graphs generalise several important and well-studied classes of graphs, and they can be characterised by…

Combinatorics · Mathematics 2023-06-19 Sergey Kitaev , Haoran Sun

Given a finite word $w$ over a finite alphabet $V$, consider the graph with vertex set $V$ and with an edge between two elements of $V$ if and only if the two elements alternate in the word $w$. Such a graph is said to be word-representable…

Combinatorics · Mathematics 2021-01-15 Marisa Gaetz , Caleb Ji

A word-representable graph is a simple graph $G$ which can be represented by a word $w$ over the vertices of $G$ such that any two vertices are adjacent in $G$ if and only if they alternate in $w$. It is known that the class of…

Discrete Mathematics · Computer Science 2021-09-09 Khyodeno Mozhui , K. V. Krishna

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 2018-09-06 Gi-Sang Cheon , Jinha Kim , Minki Kim , Sergey Kitaev , Artem Pyatkin

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

A graph G=(V,E) is 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) is in E for each x not equal to y. The motivation to study representable graphs came from algebra,…

Combinatorics · Mathematics 2011-08-09 Sergey Kitaev , Pavel Salimov , Christopher Severs , Henning Ulfarsson

A graph $G = (V, E)$ is word-representable, if there exists a word $w$ over the alphabet $V$ such that for letters $\{x,y\}\in V$, $x$ and $y$ alternate in $w$ if and only if $xy \in E$. A graph is co-bipartite if its complement is a…

Combinatorics · Mathematics 2025-01-20 Biswajit Das , 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

Word-representable graphs are a subset of graphs that may be represented by a word $w$ over an alphabet composed of the vertices in the graph. In such graphs, an edge exists if and only if the occurrences of the corresponding vertices…

Data Structures and Algorithms · Computer Science 2025-02-12 Duncan Adamson

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

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 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 literature on word-representable graphs is quite rich, and a number of variations of the original definition have been proposed over the years. We are initiating a systematic study of such variations based on formal languages. In our…

Discrete Mathematics · Computer Science 2024-11-06 Zhidan Feng , Henning Fernau , Pamela Fleischmann , Kevin Mann , Silas Cato Sacher

A graph $G = (\{1, 2, \ldots, n\}, E)$ is $12$-representable if there is a word $w$ over $\{1, 2, \ldots, n\}$ such that two vertices $i$ and $j$ with $i < j$ are adjacent if and only if every $j$ occurs before every $i$ in $w$. These…

Combinatorics · Mathematics 2023-08-31 Asahi Takaoka

Word-representable graphs, which are the same as semi-transitively orientable graphs, generalize several fundamental classes of graphs. In this paper we propose a novel approach to study word-representability of graphs using a technique of…

Combinatorics · Mathematics 2023-12-19 Sumin Huang , Sergey Kitaev , Artem Pyatkin

There is a long line of research in the literature dedicated to word-representable graphs, which generalize several important classes of graphs. However, not much is known about word-representability of split graphs, another important class…

Combinatorics · Mathematics 2019-09-23 Herman Z. Q. Chen , Sergey Kitaev , Akira Saito

A graph is said to be word-representable if there exists a word over its vertex set such that any two vertices are adjacent if and only if they alternate in the word. If no such word exists, the graph is non-word-representable. In the…

Combinatorics · Mathematics 2025-09-04 Khyodeno Mozhui , Tithi Dwary , K. V. Krishna