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

SNIP (2022): 0.902

Discussiones Mathematicae Graph Theory

Article in press


Authors:

J. Tian

Jing Tian

School of Mathematics, Nanjing University of Aeronautics \& Astronautics, Nanjing, Jiangsu 210016, PR China

email: jingtian526@126.com

0000-0002-1578-4798

S. Klavžar

Sandi Klavžar

Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia

email: sandi.klavzar@fmf.uni-lj.si

0000-0002-1556-4744

Title:

Graphs with total mutual-visibility number zero and total mutual-visibility in Cartesian products

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Source:

Discussiones Mathematicae Graph Theory

Received: 2022-12-14 , Revised: 2023-03-22 , Accepted: 2023-03-24 , Available online: 2023-05-01 , https://doi.org/10.7151/dmgt.2496

Abstract:

If $G$ is a graph and $X\subseteq V(G)$, then $X$ is a total mutual-visibility set if every pair of vertices $x$ and $y$ of $G$ admits a shortest $x,y$-path $P$ with $V(P) \cap X \subseteq \{x,y\}$. The cardinality of a largest total mutual-visibility set of $G$ is the total mutual-visibility number $\mu_\textrm{t}(G)$ of $G$. Graphs with $\mu_\textrm{t}(G) = 0$ are characterized as the graphs in which every vertex is the central vertex of a convex $P_3$. The total mutual-visibility number of Cartesian products is bounded and several exact results proved. For instance, $\mu_\textrm{t}(K_n \square K_m) = \max\{n,m\}$ and $\mu_\textrm{t}(T \square H) = \mu_\textrm{t}(T)\mu_\textrm{t}(H)$, where $T$ is a tree and $H$ an arbitrary graph. It is also demonstrated that $\mu_\textrm{t}(G \square H)$ can be arbitrary larger than $\mu_\textrm{t}(G)\mu_\textrm{t}(H)$.

Keywords:

mutual-visibility set, total mutual-visibility set, bypass vertex, Cartesian product of graphs, tree

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