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On reduced pairs of bounded closed convex sets.

Jerzy Grzybowski, Ryszard Urbanski (2003)

Revista Matemática Complutense

In this paper certain criteria for reduced pairs of bounded closed convex set are presented. Some examples of reduced and not reduced pairs are enclosed.

On set covariance and three-point test sets

Jan Rataj (2004)

Czechoslovak Mathematical Journal

The information contained in the measure of all shifts of two or three given points contained in an observed compact subset of d is studied. In particular, the connection of the first order directional derivatives of the described characteristic with the oriented and the unoriented normal measure of a set representable as a finite union of sets with positive reach is established. For smooth convex bodies with positive curvatures, the second and the third order directional derivatives of the characteristic...

On smooth points of boundaries of open sets

S. Rolewicz (2009)

Studia Mathematica

The notions of smooth points of the boundary of an open set and α(·) intrinsically paraconvex sets are introduced. It is shown that for an α(·) intrinsically paraconvex open set the set of smooth points is a dense G δ -set of the boundary.

On some vector balancing problems

Apostolos Giannopoulos (1997)

Studia Mathematica

Let V be an origin-symmetric convex body in n , n≥ 2, of Gaussian measure γ n ( V ) 1 / 2 . It is proved that for every choice u 1 , . . . , u n of vectors in the Euclidean unit ball B n , there exist signs ε j - 1 , 1 with ε 1 u 1 + . . . + ε n u n ( c l o g n ) V . The method used can be modified to give simple proofs of several related results of J. Spencer and E. D. Gluskin.

On splitting infinite-fold covers

Márton Elekes, Tamás Mátrai, Lajos Soukup (2011)

Fundamenta Mathematicae

Let X be a set, κ be a cardinal number and let ℋ be a family of subsets of X which covers each x ∈ X at least κ-fold. What assumptions can ensure that ℋ can be decomposed into κ many disjoint subcovers? We examine this problem under various assumptions on the set X and on the cover ℋ: among other situations, we consider covers of topological spaces by closed sets, interval covers of linearly ordered sets and covers of ℝⁿ by polyhedra and by arbitrary convex sets. We focus on...

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