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arXiv 1808.04060math.CO
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超图的刚性染色与邻接性

Rigid colourings of hypergraphs and contiguity

Peter Ayre, Catherine Greenhill

摘要:

研究了$k$ -均匀随机超图的$q$ -着色问题,其中$q,k \geq 3$,并确定了其刚性阈值.对于刚性阈值以上的边缘密度,我们表明,几乎所有的解决方案都有一个线性数量的顶点是线性冻结,这意味着它们不能被相邻的一系列的着色,每个改变颜色的一个次线性数量的顶点。当边缘密度低于阈值时,我们证明了所有的顶点,但消失的比例可以通过一个序列的着色包围,包围只有一个顶点的时间。这种变化的几何形状的解决方案空间已被假设为是由天真的着色算法所面临的算法障碍的原因。我们的计算验证了统计物理学家使用非严格腔方法的预测。这类问题的传统模型是随机着色模型,其中选择一个随机超图,然后选择该超图的随机着色。然而,种植模型通常更容易工作,首先选择随机着色,然后随机选择尊重着色的边缘。作为我们的分析的一部分,我们表明,凝聚相变,随机着色模型是连续的种植模型。这个结果是独立的利益。

英文摘要:

We consider the problem of $q$-colouring a $k$-uniform random hypergraph, where $q,k \geq 3$, and determine the rigidity threshold. For edge densities above the rigidity threshold, we show that almost all solutions have a linear number of vertices that are linearly frozen, meaning that they cannot be recoloured by a sequence of colourings that each change the colour of a sublinear number of vertices. When the edge density is below the threshold, we prove that all but a vanishing proportion of the vertices can be recoloured by a sequence of colourings that recolour only one vertex at a time. This change in the geometry of the solution space has been hypothesised to be the cause of the algorithmic barrier faced by naive colouring algorithms. Our calculations verify predictions made by statistical physicists using the non-rigorous cavity method. The traditional model for problems of this type is the random colouring model, where a random hypergraph is chosen and then a random colouring of that hypergraph is selected. However, it is often easier to work with the planted model, where a random colouring is selected first, and then edges are randomly chosen which respect the colouring. As part of our analysis, we show that up to the condensation phase transition, the random colouring model is contiguous with respect to the planted model. This result is of independent interest.

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