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ЖУРНАЛЫ // Сибирские электронные математические известия // Архив

Сиб. электрон. матем. изв., 2020, том 17, страницы 338–363 (Mi semr1216)

Эта публикация цитируется в 3 статьях

Дискретная математика и математическая кибернетика

О максимальных графических разбиениях, ближайших к заданному графическому разбиению

В. А. Баранский, Т. А. Сеньчонок

Ural Federal University, 51, Lenina ave., Ekaterinburg, 620083, Russia

Аннотация: A graphical partition is called maximal if it is maximal under domination among graphical partitions of a given weight. Let $\lambda$ and $\mu$ be partitions such that $\mu\leq\lambda$. The height of $\lambda$ over $\mu$ is the number of transformations in some shortest sequence of elementary transformations which transforms $\lambda$ to $\mu$, denoted by $\mathrm{height}(\lambda,\mu)$. For a given graphical partition $\mu$, a maximal graphical partition $\lambda$ such that $\mu\leq\lambda$ and $\mathrm{sum}(\mu)= \mathrm{sum}(\lambda)$ is called the $h$-nearest to $\mu$ if it has the minimal height over $\mu$ among all maximal graphical partitions $\lambda'$ such that $\mu\leq\lambda'$ and $\mathrm{sum}(\mu)= \mathrm{sum}(\lambda')$. The aim is to prove the following result:
Let $\mu$ be a graphical partition and $\lambda$ be an $h$-nearest maximal graphical partition to $\mu$. Then where $r=r(\mu)$ is the rank, $\mathrm{hd}(\mu))$ is the head and $\mathrm{tl}(\mu))$ is the tail of the partition $\mu$, $l(\mathrm{tl}(\mu))$ is the length of $\mathrm{tl}(\mu)$.
We provide an algorithm that generates some $h$-nearest to $\mu$ maximal graphical partition $\lambda$ such that $r(\lambda)=r(\mu)$. For the case $l(\mathrm{tl}(\mu))<r(\mu)$, we also provide an algorithm that generates some $h$-nearest to $\mu$ maximal graphical partition $\lambda$ such that $r(\lambda)=r(\mu)-1$.
In addition we present a new proof of the Kohnert's criterion for a partition to be graphical not using other criteria.

Ключевые слова: threshold graphs, lattice of integer partitions, graphical partition, maximal graphical partition, Ferrer's diagram.

УДК: 519.165

MSC: 05A17

Поступила 9 ноября 2019 г., опубликована 10 марта 2020 г.

DOI: 10.33048/semi.2020.17.022



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