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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 solution sets of information inequalities

Nihat Ay, Walter Wenzel (2012)

Kybernetika

We investigate solution sets of a special kind of linear inequality systems. In particular, we derive characterizations of these sets in terms of minimal solution sets. The studied inequalities emerge as information inequalities in the context of Bayesian networks. This allows to deduce structural properties of Bayesian networks, which is important within causal inference.

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...

On stabbing triangles by lines in 3-space

Boris Aronov, Jiří Matoušek (1995)

Commentationes Mathematicae Universitatis Carolinae

We give an example of a set P of 3 n points in 3 such that, for any partition of P into triples, there exists a line stabbing Ω ( n ) of the triangles determined by the triples.

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