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JOURNALS // Sibirskie Èlektronnye Matematicheskie Izvestiya [Siberian Electronic Mathematical Reports] // Archive

Sib. Èlektron. Mat. Izv., 2016 Volume 13, Pages 584–591 (Mi semr695)

This article is cited in 7 papers

Discrete mathematics and mathematical cybernetics

Light neighborhoods of $5$-vertices in $3$-polytopes with minimum degree $5$

O. V. Borodina, A. O. Ivanovab

a Sobolev Institute of Mathematics, pr. Koptyuga, 4, 630090, Novosibirsk, Russia
b Ammosov North-Eastern Federal University, str. Kulakovskogo, 48, 677000, Yakutsk, Russia

Abstract: In 1940, in attempts to solve the Four Color Problem, Henry Lebesgue gave an approximate description of the neighborhoods of $5$-vertices in the class $\mathbf{P}_5$ of $3$-polytopes with minimum degree $5$.
Given a $3$-polytope $P$, by $w(P)$ ($h(P)$) we denote the minimum degree-sum (minimum of the maximum degrees) of the neighborhoods of $5$-vertices in $P$.
A $5^*$-vertex is a $5$-vertex adjacent to four $5$-vertices. It is known that if a polytope $P$ in $\mathbf{P}_5$ has a $5^*$-vertex, then $h(P)$ can be arbitrarily large.
For each $P$ without vertices of degrees from $6$ to $9$ and $5^*$-vertices in $\mathbf{P}_5$, it follows from Lebesgue's Theorem that $w(P)\le 44$ and $h(P)\le 14$.
In this paper, we prove that every such polytope $P$ satisfies $w(P)\le 42$ and $h(P)\le 12$, where both bounds are tight.

Keywords: planar map, planar graph, $3$-polytope, structural properties, height, weight.

Received May 18, 2016, published June 30, 2016

Language: English

DOI: 10.17377/semi.2016.13.045



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