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arXiv 0801.3706math.MGmath.CO
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球面双距离集

Spherical two-distance sets

Oleg R. Musin

摘要:

n维欧几里得空间中的单位向量集S称为球面二距离集,如果有两个数a和b,且S的不同向量的内积为a或b.球面二距离集的最大基数g(n)不超过n(n+3)/2。已知该上界对于n= 2,6,22是紧的。正则单形的边的中点集给出了g(n)的下界L(n)=n(n+1)/2。本文用多项式方法证明了对非负a+b,S的最大基数不大于L(n).对于a+b<0的情形,我们提出了基于Delsarte方法的|S|的上界.利用这一点,我们证明了g(n)=L(n),其中6<n<22,23<n<40,g(23)=276或277。

英文摘要:

A set S of unit vectors in n-dimensional Euclidean space is called spherical two-distance set, if there are two numbers a and b, and inner products of distinct vectors of S are either a or b. The largest cardinality g(n) of spherical two-distance sets is not exceed n(n+3)/2. This upper bound is known to be tight for n=2,6,22. The set of mid-points of the edges of a regular simplex gives the lower bound L(n)=n(n+1)/2 for g(n. In this paper using the so-called polynomial method it is proved that for nonnegative a+b the largest cardinality of S is not greater than L(n). For the case a+b<0 we propose upper bounds on |S| which are based on Delsarte's method. Using this we show that g(n)=L(n) for 6<n<22, 23<n<40, and g(23)=276 or 277.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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