摘要： A finite collection of unit vectors S⊂Rn is called a spherical two-distance set if there are two numbers a and b such that the inner products of distinct vectors from S are either a or b. We prove that if a≠−b, then a two-distance set that forms a tight frame for Rn is a spherical embedding of a strongly regular graph. We also describe all two-distance tight frames obtained from a given graph. Together with an earlier work by S. Waldron (2009) [22] on the equiangular case, this completely characterizes two-distance tight frames. As an intermediate result, we obtain a classification of all two-distance 2-designs. 出版者： Elsevier Inc 出版日期： 2015-06-15 出處： Linear algebra and its applications, 2015-06, Vol.475, p.163-175 資源來源： Elsevier ScienceDirect Journals Complete 版權： 2015 Elsevier Inc. 識別號： ISSN: 0024-3795 識別號： EISSN: 1873-1856 識別號： DOI: 10.1016/j.laa.2015.02.020
