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Separation of convex polyhedral sets with column parameters

Milan Hladík (2008)

Kybernetika

Separation is a famous principle and separation properties are important for optimization theory and various applications. In practice, input data are rarely known exactly and it is advisable to deal with parameters. In this article, we are concerned with the basic characteristics (existence, description, stability etc.) of separating hyperplanes of two convex polyhedral sets depending on parameters. We study the case, when parameters are situated in one column of the constraint matrix from the...

Separation of ( n + 1 ) -families of sets in general position in 𝐑 n

Mircea Balaj (1997)

Commentationes Mathematicae Universitatis Carolinae

In this paper the main result in [1], concerning ( n + 1 ) -families of sets in general position in 𝐑 n , is generalized. Finally we prove the following theorem: If { A 1 , A 2 , , A n + 1 } is a family of compact convexly connected sets in general position in 𝐑 n , then for each proper subset I of { 1 , 2 , , n + 1 } the set of hyperplanes separating { A i : i I } and { A j : j I ¯ } is homeomorphic to S n + .

Séries de croissance et polynômes d'Ehrhart associés aux réseaux de racines

Roland Bacher, Pierre de La Harpe, Boris Venkov (1999)

Annales de l'institut Fourier

Étant donnés un système de racines R d’une des familles A, B, C, D, F, G et le groupe abélien libre qu’il engendre, on calcule explicitement la série de croissance de ce groupe relativement à R . Les résultats s’interprètent en termes du polynôme d’Ehrhart de l’enveloppe convexe de R .

Sets Expressible as Unions of Staircase n -Convex Polygons

Marilyn Breen (2011)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

Let k and n be fixed, k 1 , n 1 , and let S be a simply connected orthogonal polygon in the plane. For T S , T lies in a staircase n -convex orthogonal polygon P in S if and only if every two points of T see each other via staircase n -paths in S . This leads to a characterization for those sets S expressible as a union of k staircase n -convex polygons P i , 1 i k .

Sets invariant under projections onto one dimensional subspaces

Simon Fitzpatrick, Bruce Calvert (1991)

Commentationes Mathematicae Universitatis Carolinae

The Hahn–Banach theorem implies that if m is a one dimensional subspace of a t.v.s. E , and B is a circled convex body in E , there is a continuous linear projection P onto m with P ( B ) B . We determine the sets B which have the property of being invariant under projections onto lines through 0 subject to a weak boundedness type requirement.

Sets invariant under projections onto two dimensional subspaces

Simon Fitzpatrick, Bruce Calvert (1991)

Commentationes Mathematicae Universitatis Carolinae

The Blaschke–Kakutani result characterizes inner product spaces E , among normed spaces of dimension at least 3, by the property that for every 2 dimensional subspace F there is a norm 1 linear projection onto F . In this paper, we determine which closed neighborhoods B of zero in a real locally convex space E of dimension at least 3 have the property that for every 2 dimensional subspace F there is a continuous linear projection P onto F with P ( B ) B .

Shaking compact sets.

Campi, Stefano, Colesanti, Andrea, Gronchi, Paolo (2001)

Beiträge zur Algebra und Geometrie

Shape tiling.

Keating, Kevin, King, Jonathan L. (1997)

The Electronic Journal of Combinatorics [electronic only]

Shift inequalities of Gaussian type and norms of barycentres

F. Barthe, D. Cordero-Erausquin, M. Fradelizi (2001)

Studia Mathematica

We derive the equivalence of different forms of Gaussian type shift inequalities. This completes previous results by Bobkov. Our argument strongly relies on the Gaussian model for which we give a geometric approach in terms of norms of barycentres. Similar inequalities hold in the discrete setting; they improve the known results on the so-called isodiametral problem for the discrete cube. The study of norms of barycentres for subsets of convex bodies completes the exposition.

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