Light and low 5-stars in normal plane maps with minimum degree 5
- Authors: Borodin O.V.1, Ivanova A.O.2
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Affiliations:
- Sobolev Institute of Mathematics
- Ammosov North-Eastern Federal University
- Issue: Vol 57, No 3 (2016)
- Pages: 470-475
- Section: Article
- URL: https://journals.rcsi.science/0037-4466/article/view/170462
- DOI: https://doi.org/10.1134/S0037446616030071
- ID: 170462
Cite item
Abstract
It is known that there are normal plane maps (NPMs) with minimum degree δ = 5 such that the minimum degree-sum w(S5) of 5-stars at 5-vertices is arbitrarily large. The height of a 5-star is the maximum degree of its vertices. Given an NPM with δ = 5, by h(S5) we denote the minimum height of a 5-stars at 5-vertices in it.
Lebesgue showed in 1940 that if an NPM with δ = 5 has no 4-stars of cyclic type \(\overrightarrow {\left( {5,6,6,5} \right)} \) centered at 5-vertices, then w(S5) ≤ 68 and h(S5) = 41. Recently, Borodin, Ivanova, and Jensen lowered these bounds to 55 and 28, respectively, and gave a construction of a \(\overrightarrow {\left( {5,6,6,5} \right)} \)-free NPM with δ = 5 having w(S5) = 48 and h(S5) = 20.
In this paper, we prove that w(S5) ≤ 51 and h(S5) ≤ 23 for each (\(\overrightarrow {\left( {5,6,6,5} \right)} \)-free NPM with δ = 5.
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About the authors
O. V. Borodin
Sobolev Institute of Mathematics
Author for correspondence.
Email: brdnoleg@math.nsc.ru
Russian Federation, Novosibirsk
A. O. Ivanova
Ammosov North-Eastern Federal University
Email: brdnoleg@math.nsc.ru
Russian Federation, Yakutsk