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Sibirskie Èlektronnye Matematicheskie Izvestiya [Siberian Electronic Mathematical Reports], 2024, Volume 21, Issue 1, Pages 495–500
DOI: https://doi.org/doi.org/10.33048/semi.2024.21.035
(Mi semr1698)
 

Discrete mathematics and mathematical cybernetics

Describing edges in normal plane maps having no adjacent $3$-faces

O. V. Borodina, A. O. Ivanovab

a Sobolev Institute of Mathematics, pr. Koptyuga, 4, 630090, Novosibirsk, Russia
b Ammosov North-Eastern Federal University, st. Kulakovskogo, 48, 677013, Yakutsk, Russia
Abstract: The weight $w(e)$ of an edge $e$ in a normal plane map (NPM) is the degree-sum of its end-vertices. An edge $e=uv$ is an $(i,j)$-edge if $d(u)\le i$ and $d(v)\le j$. In 1940, Lebesgue proved that every NPM has a $(3,11)$-edge, or $(4,7)$-edge, or $(5,6)$-edge, where 7 and 6 are best possible. In 1955, Kotzig proved that every $3$-polytope has an edge $e$ with $w(e)\le13$, which bound is sharp. Borodin (1987), answering Erdős' question, proved that every NPM has such an edge. Moreover, Borodin (1991) refined this by proving that there is either a $(3,10)$-edge, or $(4,7)$-edge, or $(5,6)$-edge.
Given an NPM, we observe some upper bounds on the minimum weight of all its edges, denoted by $w$, of those incident with a $3$-face, $w^*$, and those incident with two $3$-faces, $w^{**}$. In particular, Borodin (1996) proved that if $w^{**}=\infty$, that is if an NPM has no edges incident with two $3$-faces, then either $w^*\le9$ or $w\le8$, where both bounds are sharp. The purpose of our note is to refine this result by proving that in fact $w^{**}=\infty$ implies either a $(3,6)$- or $(4,4)$-edge incident with a $3$-face, or a $(3,5)$-edge, which description is tight.
Keywords: planar graph, plane map, structure properties, $3$-polytope, weight.
Funding agency Grant number
Ministry of Science and Higher Education of the Russian Federation FWNF-2022-0017
FSRG-2023-0025
The first author' work was supported by the Ministry of Science and Higher Education of the Russian Federation (project no. FWNF-2022-0017). The second author's work was supported by the Ministry of Science and Higher Education of the Russian Federation (Grant No. FSRG-2023-0025).
Received November 14, 2023, published June 23, 2024
Document Type: Article
UDC: 519.172.2
MSC: 05C75
Language: English
Citation: O. V. Borodin, A. O. Ivanova, “Describing edges in normal plane maps having no adjacent $3$-faces”, Sib. Èlektron. Mat. Izv., 21:1 (2024), 495–500
Citation in format AMSBIB
\Bibitem{BorIva24}
\by O.~V.~Borodin, A.~O.~Ivanova
\paper Describing edges in normal plane maps having no adjacent $3$-faces
\jour Sib. \`Elektron. Mat. Izv.
\yr 2024
\vol 21
\issue 1
\pages 495--500
\mathnet{http://mi.mathnet.ru/semr1698}
\crossref{https://doi.org/doi.org/10.33048/semi.2024.21.035}
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