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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Discrete & computational geometry 20 (1998), S. 143-153 
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Consider the d -dimensional euclidean space E d . Two main results are presented: First, for any N∈ N, the number of types of periodic equivariant tilings $({\cal T},\Gamma)$ that have precisely N orbits of (2,4,6, . . . ) -flags with respect to the symmetry group Γ , is finite. Second, for any N∈ N, the number of types of convex, periodic equivariant tilings $({\cal T},\Gamma)$ that have precisely N orbits of tiles with respect to the symmetry group Γ , is finite. The former result (and some generalizations) is proved combinatorially, using Delaney symbols, whereas the proof of the latter result is based on both geometric arguments and Delaney symbols. 〈lsiheader〉 〈onlinepub〉7 August, 1998 〈editor〉Editors-in-Chief: &lsilt;a href=../edboard.html#chiefs&lsigt;Jacob E. Goodman, Richard Pollack&lsilt;/a&lsigt; 〈pdfname〉20n2p143.pdf 〈pdfexist〉yes 〈htmlexist〉no 〈htmlfexist〉no 〈texexist〉no 〈sectionname〉 〈/lsiheader〉
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Discrete & computational geometry 20 (1998), S. 477-498 
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. This paper gives several conditions in geometric crystallography which force a structure X in R n to be an ideal crystal. An ideal crystal in R n is a finite union of translates of a full-dimensional lattice. An (r,R) -set is a discrete set X in R n such that each open ball of radius r contains at most one point of X and each closed ball of radius R contains at least one point of X . A multiregular point system X is an (r,R) -set whose points are partitioned into finitely many orbits under the symmetry group Sym(X) of isometries of R n that leave X invariant. Every multiregular point system is an ideal crystal and vice versa. We present two different types of geometric conditions on a set X that imply that it is a multiregular point system. The first is that if X ``looks the same'' when viewed from n+2 points { y i : 1 \leq i \leq n + 2 } , such that one of these points is in the interior of the convex hull of all the others, then X is a multiregular point system. The second is a ``local rules'' condition, which asserts that if X is an (r,R) -set and all neighborhoods of X within distance ρ of each x∈X are isometric to one of k given point configurations, and ρ exceeds CRk for C = 2(n 2 +1) log 2 (2R/r+2) , then X is a multiregular point system that has at most k orbits under the action of Sym(X) on R n . In particular, ideal crystals have perfect local rules under isometries.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Mathematik 106 (1988), S. 107-114 
    ISSN: 1436-5081
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new stability property of the densest circle packing in the plane is proved. This property is related to a conjecture ofL. Fejes Tóth.
    Type of Medium: Electronic Resource
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