Эта публикация цитируется в
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Дискретная математика и математическая кибернетика
All tight descriptions of $3$-paths in plane graphs with girth at least $9$
V. A. Aksenova,
O. V. Borodinb,
A. O. Ivanovac a Novosibirsk National Research University,
str. Pirogova, 1,
630090, Novosibirsk, Russia
b Sobolev Institute of Mathematics,
pr. Koptyuga, 4,
630090, Novosibirsk, Russia
c Ammosov North-Eastern Federal University,
str. Kulakovskogo, 48,
677000, Yakutsk, Russia
Аннотация:
Lebesgue (1940) proved that every plane graph with minimum degree
$\delta$ at least
$3$ and girth
$g$ at least
$5$ has a path on three vertices (
$3$-path) of degree
$3$ each. A description is tight if no its parameter can be strengthened, and no triplet dropped.
Borodin et al. (2013) gave a tight description of
$3$-paths in plane graphs with
$\delta\ge3$ and
$g\ge3$, and another tight description was given by Borodin, Ivanova and Kostochka in 2017.
Borodin and Ivanova (2015) gave seven tight descriptions of
$3$-paths when
$\delta\ge3$ and
$g\ge4$. Furthermore, they proved that this set of tight descriptions is complete, which was a result of a new type in the structural theory of plane graphs. Also, they characterized (2018) all one-term tight descriptions if
$\delta\ge3$ and
$g\ge3$. The problem of producing all tight descriptions for
$g\ge3$ remains widely open even for
$\delta\ge3$.
Recently, several tight descriptions of
$3$-paths were obtained for plane graphs with
$\delta=2$ and
$g\ge4$ by Jendrol', Maceková, Montassier, and Soták, four of which descriptions are for
$g\ge9$.
In this paper, we prove ten new tight descriptions of
$3$-paths for
$\delta=2$ and
$g\ge9$ and show that no other tight descriptions exist.
Ключевые слова:
plane graph, structure properties, tight description, $3$-path, minimum degree, girth.
УДК:
519.172.2
MSC: 05C75 Поступила 5 сентября 2018 г., опубликована
16 октября 2018 г.
Язык публикации: английский
DOI:
10.17377/semi.2018.15.095