Given a finite point set $P$ in the plane, a subset $S \subseteq P$ is called an island in $P$ if $conv(S) \cap P = S$. We say that $S\subset P$ is a visible island if the points in $S$ are pairwise visible and $S$ is an island in $P$. The famous Big-line Big-clique Conjecture states that for any $k \geq 3$ and $\ell \geq 4$, there is an integer $n = n(k,\ell)$, such that every finite set of at least $n$ points in the plane contains $\ell$ collinear points or $k$ pairwise visible points. In this paper, we show that this conjecture is false for visible islands, by constructing arbitrarily large finite point sets in the plane with no 4 collinear members and no visible island of size $2^{42}$.
翻译:鉴于飞机上设定的限定点为美元,如果美元Conv(S)\cap P=S美元,则子数S\subseteq P$称为美元,如果美元Conv(S)\cap P=S美元,我们说美元S\sucset P$是可见的岛屿,如果美元是双向可见的,美元Socset P$是按P美元计算的岛屿。著名的大线大队预测称,对于任何一美元Geq 3美元和美元Geq 4美元来说,有一个整数$n=n(k,\ell)美元,因此每套至少一美元的定点都含有美元/ell$collinear点或一美元双向可见点。在本文中,我们表明,这种对可见岛屿来说,通过在飞机上建造没有4个Collinearimar成员和没有明显大小的可见度岛屿(242美元)的任意的大型定点,对可见的定点对可见的岛屿来说是虚假的。