论文标题
Kronecker序列的五距离定理
A five distance theorem for Kronecker sequences
论文作者
论文摘要
三个距离定理(也称为三个差距定理或Steinhaus问题)指出,对于任何给定的实际数字$α$和整数$ n $,Kronecker连续元素之间的距离最多有三个值,而Kronecker序列$α,2α,2α,2α,\ ldots,nα$ mode则较高的距离。 $ \vecα,2 \vecα,\ ldots,n \vecα$ modulo an Integer晶格。我们证明,在$ \vecα$和$ n $的所有选择中,在两个维度上,最多可以作为最近邻居之间的距离出现的五个值。此外,对于几乎每$ \vecα$,对于无限的$ n $来说,确实出现了五个不同的距离,因此五个是最好的一般上限。在较高的维度中,我们具有相似的显式,但更精确的上限。例如,在三个维度中,我们的界限是13,尽管我们认为真相为9。这可能被视为一个维度在一个维度中的间隙长度的概括。对于大锥角度,我们使用几何参数来产生与三个距离定理直接类似的明确边界。对于小圆锥角,我们在单模型晶格的空间中使用奇异的均相流理论,以表明(a)几乎所有$ \vecα$无限的数量是(a)不受限制的,并且(b)以$ \ \vecα$界定满足某些二苯胺条件。
The three distance theorem (also known as the three gap theorem or Steinhaus problem) states that, for any given real number $α$ and integer $N$, there are at most three values for the distances between consecutive elements of the Kronecker sequence $α, 2α,\ldots, Nα$ mod 1. In this paper we consider a natural generalisation of the three distance theorem to the higher dimensional Kronecker sequence $\vecα, 2\vecα,\ldots, N\vecα$ modulo an integer lattice. We prove that in two dimensions there are at most five values that can arise as a distance between nearest neighbors, for all choices of $\vecα$ and $N$. Furthermore, for almost every $\vecα$, five distinct distances indeed appear for infinitely many $N$ and hence five is the best possible general upper bound. In higher dimensions we have similar explicit, but less precise, upper bounds. For instance in three dimensions our bound is 13, though we conjecture the truth to be 9. We furthermore study the number of possible distances from a point to its nearest neighbor in a restricted cone of directions. This may be viewed as a generalisation of the gap length in one dimension. For large cone angles we use geometric arguments to produce explicit bounds directly analogous to the three distance theorem. For small cone angles we use ergodic theory of homogeneous flows in the space of unimodular lattices to show that the number of distinct lengths is (a) unbounded for almost all $\vecα$ and (b) bounded for $\vecα$ that satisfy certain Diophantine conditions.