English

Improvement of generalization of Larman-Rogers-Seidel's theorem

Combinatorics 2021-06-18 v1 Metric Geometry

Abstract

A finite set XX in the dd-dimensional Euclidean space is called an ss-distance set if the set of distances between any two distinct points of XX has size ss. In 1977, Larman-Rogers-Seidel proved that if the cardinality of an two-distance set is large enough, then there exists an integer kk such that the two distances α\alpha, β\beta (α<β)(\alpha < \beta) having the integer condition, namely, α2β2=k1k\frac{\alpha^2}{\beta^2}=\frac{k-1}{k}. In 2011, Nozaki generalized Larman-Rogers-Seidel's theorem to the case of ss-distance sets, i.e. if the cardinality of an ss-distance set X2N|X|\geqslant 2N with distances α1,α2,,αs\alpha_1,\alpha_2,\cdots,\alpha_s, where N=(d+s1s1)+(d+s2s2)N=\binom{d+s-1}{s-1}+\binom{d+s-2}{s-2}, then the numbers ki=j=1,2,,s, jiαj2αj2αi2k_i=\prod_{j=1,2,\cdots,s,\text{ }j\neq i}\frac{\alpha_{j}^{2}}{\alpha_{j}^{2}-\alpha_{i}^{2}} are integers. In this note, we reduce the lower bound of the requirement of integer condition of ss-distance sets in Rd\mathbb{R}^d. Furthermore, we can show that there are only finitely many ss-distance sets XX in Rd\mathbb{R}^d with X2(d+s1s1).|X|\geqslant 2\binom{d+s-1}{s-1}.

Keywords

Cite

@article{arxiv.2106.09582,
  title  = {Improvement of generalization of Larman-Rogers-Seidel's theorem},
  author = {Cheng-Jui Yeh and Wei-Hsuan Yu},
  journal= {arXiv preprint arXiv:2106.09582},
  year   = {2021}
}

Comments

6 pages, no figure