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arXiv 2209.02015math.CO
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超图自举渗流的长运行时间问题

Long running times for hypergraph bootstrap percolation

Alberto Espuny Díaz, Barnabás Janzer, Gal Kronenberg, Joanna Lada

摘要:

考虑超图自举渗流过程,其中给定固定的$r$ -均匀超图$H$,并从给定的超图$G_0$开始,在每一步中,我们将创建$H$的新副本的所有边添加到$G_0$。我们感兴趣的是最大限度地增加这一过程在稳定之前所需的步骤数量。对于其中$H=K_{r+1}^{(r)}$与$r\geq3$的情况,我们提供了一个新的$G_0$结构,表明该过程的步骤数可以是$Θ(n^r)$阶。这回答了诺埃尔和兰加纳森最近提出的一个问题。为了证明不同的运行时间可以发生,我们还证明,如果$H$是$K_4^{(3)}$减去一个边缘,那么最大可能的运行时间是$2n-\lfloor \log_2(n-2)\rfloor-6$。然而,如果$H$是$K_5^{(3)}$减去边缘,则该过程可以运行$Θ(n^3)$步骤。

英文摘要:

Consider the hypergraph bootstrap percolation process in which, given a fixed $r$-uniform hypergraph $H$ and starting with a given hypergraph $G_0$, at each step we add to $G_0$ all edges that create a new copy of $H$. We are interested in maximising the number of steps that this process takes before it stabilises. For the case where $H=K_{r+1}^{(r)}$ with $r\geq3$, we provide a new construction for $G_0$ that shows that the number of steps of this process can be of order $Θ(n^r)$. This answers a recent question of Noel and Ranganathan. To demonstrate that different running times can occur, we also prove that, if $H$ is $K_4^{(3)}$ minus an edge, then the maximum possible running time is $2n-\lfloor \log_2(n-2)\rfloor-6$. However, if $H$ is $K_5^{(3)}$ minus an edge, then the process can run for $Θ(n^3)$ steps.

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