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"On the crossing number of the join of the wheel on six vertices with a path"
Author(s) -
Štefan Berežný,
MICHAL STAŠ
Publication year - 2022
Publication title -
carpathian journal of mathematics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.812
H-Index - 25
eISSN - 1843-4401
pISSN - 1584-2851
DOI - 10.37193/cjm.2022.02.06
Subject(s) - combinatorics , conjecture , mathematics , crossing number (knot theory) , join (topology) , graph , path (computing) , computer science , engineering , aerospace engineering , intersection (aeronautics) , programming language
The crossing number $\mathrm{cr}(G)$ of a graph $G$ is the minimum number of edge crossings over all drawings of $G$ in the plane. The main aim of the paper is to give the crossing number of join product $W_5+P_n$ for the wheel $W_5$ on six vertices, where $P_n$ is the path on $n$ vertices. Sta\v s and Valiska conjectured that the crossing number of $W_m+P_n$ is equal to $Z(m+1)Z(n) + (Z(m)-1) \big \lfloor \frac{n}{2} \big \rfloor + n +1$, for all $m\geq 3$, $n\geq 2$, where Zarankiewicz's number is defined as $Z(n)=\big \lfloor \frac{n}{2} \big \rfloor \big \lfloor \frac{n-1}{2} \big \rfloor $ for $n\geq 1$. Recently, this conjecture was proved for $W_3+P_n$ by Kle\v s\v c and Schr\"otter, and for $W_4+P_n$ by Sta\v s and Valiska. We establish the validity of this conjecture for $W_5+P_n$. The conjecture also holds due to some isomorphisms for $W_m+P_2$, $W_m+P_3$ by Kle\v s\v c, and for $W_m+P_4$ by Sta\v s for all $m\geq 3$.

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