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On a generalization of the Selection Theorem of Mahler

Gilbert Muraz, Jean-Louis Verger-Gaugry (2005)

Journal de Théorie des Nombres de Bordeaux

The set 𝒰 𝒟 r of point sets of n , n 1 , having the property that their minimal interpoint distance is greater than a given strictly positive constant r > 0 is shown to be equippable by a metric for which it is a compact topological space and such that the Hausdorff metric on the subset 𝒰 𝒟 r , f 𝒰 𝒟 r of the finite point sets is compatible with the restriction of this topology to 𝒰 𝒟 r , f . We show that its subsets of Delone sets of given constants in n , n 1 , are compact. Three (classes of) metrics, whose one of crystallographic nature,...

On a globalization property

Stefan Rolewicz (1993)

Applicationes Mathematicae

Let (X,τ) be a topological space. Let Φ be a class of real-valued functions defined on X. A function ϕ ∈ Φ is called a local Φ-subgradient of a function f:X → ℝ at a point x 0 if there is a neighbourhood U of x 0 such that f(x) - f( x 0 ) ≥ ϕ(x) - ϕ( x 0 ) for all x ∈ U. A function ϕ ∈ Φ is called a global Φ-subgradient of f at x 0 if the inequality holds for all x ∈ X. The following properties of the class Φ are investigated: (a) when the existence of a local Φ-subgradient of a function f at each point implies...

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