Finite Coverings by Translates of Centrally Symmetric Convex Domains.
We derive new upper bounds for the densities of measurable sets in which avoid a finite set of prescribed distances. The new bounds come from the solution of a linear programming problem. We apply this method to obtain new upper bounds for measurable sets which avoid the unit distance in dimensions . This gives new lower bounds for the measurable chromatic number in dimensions . We apply it to get a short proof of a variant of a recent result of Bukh which in turn generalizes theorems of Furstenberg,...
We prove that the upper Minkowski dimension of a compact set Λ is equal to the convergence exponent of any packing of the complement of Λ with polyhedra of size not smaller than a constant multiple of their distance from Λ.
G.F. Voronoi (1868–1908) wrote two memoirs in which he describes two reduction theories for lattices, well-suited for sphere packing and covering problems. In his first memoir a characterization of locally most economic packings is given, but a corresponding result for coverings has been missing. In this paper we bridge the two classical memoirs.By looking at the covering problem from a different perspective, we discover the missing analogue. Instead of trying to find lattices giving economical...
Angloamerický matematik John Horton Conway byl všestrannou a charismatickou postavou, která významně ovlivnila teorie čísel, grup, her, uzlů, dynamických systémů i rekreační matematiku. Proslul svéráznou povahou i nekonvenčním přístupem k řešení problémů. Tento článek shrnuje stručně jeho neobvyklou životní cestu a představuje čtyři vybrané oblasti z jeho bohaté tvorby: nadreálná čísla, teorii kombinatorických her, hru života a klasifikaci sporadických grup.