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A dyadic view of rational convex sets

Gábor Czédli, Miklós Maróti, Anna B. Romanowska (2014)

Commentationes Mathematicae Universitatis Carolinae

Let F be a subfield of the field of real numbers. Equipped with the binary arithmetic mean operation, each convex subset C of F n becomes a commutative binary mode, also called idempotent commutative medial (or entropic) groupoid. Let C and C ' be convex subsets of F n . Assume that they are of the same dimension and at least one of them is bounded, or F is the field of all rational numbers. We prove that the corresponding idempotent commutative medial groupoids are isomorphic iff the affine space F n ...

A second order η -approximation method for constrained optimization problems involving second order invex functions

Tadeusz Antczak (2009)

Applications of Mathematics

A new approach for obtaining the second order sufficient conditions for nonlinear mathematical programming problems which makes use of second order derivative is presented. In the so-called second order η -approximation method, an optimization problem associated with the original nonlinear programming problem is constructed that involves a second order η -approximation of both the objective function and the constraint function constituting the original problem. The equivalence between the nonlinear...

Compactness and countable compactness in weak topologies

W. Kirk (1995)

Studia Mathematica

A bounded closed convex set K in a Banach space X is said to have quasi-normal structure if each bounded closed convex subset H of K for which diam(H) > 0 contains a point u for which ∥u-x∥ < diam(H) for each x ∈ H. It is shown that if the convex sets on the unit sphere in X satisfy this condition (which is much weaker than the assumption that convex sets on the unit sphere are separable), then relative to various weak topologies, the unit ball in X is compact whenever it is countably compact....

Convexity theories 0 fin. Foundations.

Heinrich Kleisli, Helmut Röhrl (1996)

Publicacions Matemàtiques

In this paper we study big convexity theories, that is convexity theories that are not necessarily bounded. As in the bounded case (see [4]) such a convexity theory Γ gives rise to the category ΓC of (left) Γ-convex modules. This is an equationally presentable category, and we prove that it is indeed an algebraic category over Set. We also introduce the category ΓAlg of Γ-convex algebras and show that the category Frm of frames is isomorphic to the category of associative, commutative, idempotent...

Decomposability of Abstract and Path-Induced Convexities in Hypergraphs

Francesco Mario Malvestuto, Marina Moscarini (2015)

Discussiones Mathematicae Graph Theory

An abstract convexity space on a connected hypergraph H with vertex set V (H) is a family C of subsets of V (H) (to be called the convex sets of H) such that: (i) C contains the empty set and V (H), (ii) C is closed under intersection, and (iii) every set in C is connected in H. A convex set X of H is a minimal vertex convex separator of H if there exist two vertices of H that are separated by X and are not separated by any convex set that is a proper subset of X. A nonempty subset X of V (H) is...

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