DMGT

ISSN 1234-3099 (print version)

ISSN 2083-5892 (electronic version)

https://doi.org/10.7151/dmgt

Discussiones Mathematicae Graph Theory

Journal Impact Factor (JIF 2022): 0.7

5-year Journal Impact Factor (2022): 0.7

CiteScore (2022): 1.9

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Discussiones Mathematicae Graph Theory

Article in volume


Authors:

S. Eoh

Soogang Eoh

Seoul National University

email: oops_creep@hanmail.net

M. Choi

Myungho Choi

Seoul National University

email: nums8080@naver.com

S-R. Kim

Suh-Ryung Kim

Seoul National University

email: srkim@snu.ac.kr

Title:

The niche graphs of multipartite tournaments

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Source:

Discussiones Mathematicae Graph Theory 43(4) (2023) 1123-1146

Received: 2020-11-23 , Revised: 2021-06-29 , Accepted: 2021-07-01 , Available online: 2021-07-21 , https://doi.org/10.7151/dmgt.2424

Abstract:

The niche graph of a digraph $D$ has $V(D)$ as the vertex set and an edge $uv$ if and only if $(u,w) \in A(D)$ and $(v,w) \in A(D)$, or $(w,u) \in A(D)$ and $(w,v) \in A(D)$ for some $w \in V(D)$. The notion of niche graphs was introduced by Cable et al. [Niche graphs, Discrete Appl. Math. 23 (1989), 231–241] as a variant of competition graphs. If a graph is the niche graph of a digraph $D$, it is said to be niche-realizable through $D$. If a graph $G$ is niche-realizable through a $k$-partite tournament for an integer $k \ge 2$, then we say that the pair $(G, k)$ is niche-realizable. Bowser et al. [Niche graphs and mixed pair graphs of tournaments, J. Graph Theory 31 (1999) 319–332] studied the graphs that are niche-realizable through a tournament and Eoh et al. [The niche graphs of bipartite tournaments, Discrete Appl. Math. 282 (2020) 86–95] recently studied niche-realizable pairs $(G, k)$ for $k=2$. In this paper, we extend their work for $k \ge 3$. We show that the niche graph of a $k$-partite tournament has at most three components if $k \ge 3$ and is connected if $k \ge 4$. Then we find all the niche-realizable pairs $(G, k)$ in each case: $G$ is disconnected; $G$ is a complete graph; $G$ is connected and triangle-free.

Keywords:

niche graph, multipartite tournament, niche-realizable pair, true twins, triangle-free graph

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