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arXiv 2010.09665math.COmath.AC
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无间隙图正则性的一个新的上界

A new upper bound for the regularity of gap-free graphs

Rimpa Nandi, Ramakrishna Nanduri

摘要:

本文根据无间隙图的最小三角剖分,给出了无间隙图的边理想正则性的一个新的上界。设$H_U=G\cup F_U$是无间隙图$G$的最小三角剖分,对于$G$中的某个极大独立集$U$.令$\mathcal{C}_U$为$H_U$中所有$3$ -路径的$3$ -均匀杂波,其由来自$F_U$的一个边和来自$G$的另一个边组成。然后,我们表明,$\displaystyle \reg(I(G))\leq \reg(I(\C_U))$。作为结果,我们给出了无间隙图的正则性的一个一般上界。此外,如果$\mathcal{H}$是$3$ -均匀杂波,由$G$或$F_U$中的$3$-团和$G$中的$3$ -路径组成,而$G$中的$3$ -路径不是$H_U$中的$3$ -团,则$\reg(I(G))\leq 3$,假设$\mathcal{H}$是弦。这部分回答了Há提出的问题,\cite [Problem $6.3$ ]{h14}和Banerjee、Beyarslan和Há提出的问题,\cite [Problem $7.1$ ]{bbh 19}。

英文摘要:

In this article, we give a new upper bound for the regularity of edge ideals of gap-free graphs, in terms of the their minimal triangulation. Let $H_U=G\cup F_U$ be a minimal triangulation of a gap-free graph $G$, for some maximal independent set $U$ in $G$. Let $\mathcal{C}_U$ be the $3$-uniform clutter of all $3$-paths in $H_U$ which consists of one edge coming from $F_U$ and another edge coming from $G$. Then we show that $\displaystyle \reg(I(G))\leq \reg(I(\C_U))$. As a consequence, we give a general upper bound for the regularity of gap-free graphs. Furthermore, if $\mathcal{H}$ is the $3$-uniform clutter consists of the $3$-cliques in $G$ or in $F_U$, and the $3$-paths in $G$ which are not $3$-cliques in $H_U$, then $\reg(I(G))\leq 3$, provided $\mathcal{H}$ is chordal. This answers partially a question raised by Há, \cite[Problem $6.3$]{h14} and by Banerjee, Beyarslan and Há, \cite[Problem $7.1$]{bbh19}.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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