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2-Colorings of Hypergraphs with Large Girth
Mathematical Notes ( IF 0.6 ) Pub Date : 2020-07-01 , DOI: 10.1134/s0001434620070202
Yu. A. Demidovich

A hypergraph $$H=(V,E)$$ has property $$B_k$$ if there exists a 2-coloring of the set $$V$$ such that each edge contains at least $$k$$ vertices of each color. We let $$m_{k,g}(n)$$ and $$m_{k,b}(n)$$ , respectively, denote the least number of edges of an $$n$$ -homogeneous hypergraph without property $$B_k$$ which contains either no cycles of length at least $$g$$ or no two edges intersecting in more than $$b$$ vertices. In the paper, upper bounds for these quantities are given. As a consequence, we obtain results for $$m^{*}_k(n)$$ , i.e., for the least number of edges of an $$n$$ -homogeneous simple hypergraph without property $$B_k$$ . Let $$\Delta(H)$$ be the maximal degree of vertices of a hypergraph $$H$$ . By $$\Delta_k(n,g)$$ we denote the minimal degree $$\Delta$$ such that there exists an $$n$$ -homogeneous hypergraph $$H$$ with maximal degree $$\Delta$$ and girth at least $$g$$ but without property $$B_k$$ . In the paper, an upper bound for $$\Delta_k(n,g)$$ is obtained.

中文翻译:

2-大周长超图的着色

超图 $$H=(V,E)$$ 具有属性 $$B_k$$,如果存在集合 $$V$$ 的 2-着色使得每条边至少包含每个边的 $$k$$ 个顶点颜色。我们让 $$m_{k,g}(n)$$ 和 $$m_{k,b}(n)$$ 分别表示 $$n$$ -同构超图的最少边数$$B_k$$ 不包含长度至少为 $$g$$ 的循环,或者不包含在超过 $$b$$ 个顶点相交的两条边。在论文中,给出了这些数量的上限。因此,我们获得了 $$m^{*}_k(n)$$ 的结果,即,对于没有 $$B_k$$ 属性的 $$n$$ -齐次简单超图的边数最少。令 $$\Delta(H)$$ 是超图 $$H$$ 的最大顶点度数。通过 $$\Delta_k(n, g)$$ 我们表示最小度数 $$\Delta$$ 使得存在一个 $$n$$ -同质超图 $$H$$,最大度数 $$\Delta$$ 和周长至少 $$g$ $ 但没有财产 $$B_k$$ 。在论文中,得到了$$\Delta_k(n,g)$$的上界。
更新日期:2020-07-01
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