Delone Sets in ℝ3 with 2R-Regularity Conditions

Abstract

A regular system is the orbit of a point with respect to a crystallographic group. The central problem of the local theory of regular systems is to determine the value of the regularity radius, which is the least number such that every Delone set of type (r,R) with identical neighborhoods/clusters of this radius is regular. In this paper, conditions are described under which the regularity of a Delone set in three-dimensional Euclidean space follows from the pairwise congruence of small clusters of radius 2R. Combined with the analysis of one particular case, this result also implies the proof of the “10R-theorem,” which states that if the clusters of radius 10R in a Delone set are congruent, then this set is regular.