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Monotone Valuations on the Space of Convex Functions

L. Cavallina, A. Colesanti (2015)

Analysis and Geometry in Metric Spaces

We consider the space Cn of convex functions u defined in Rn with values in R ∪ {∞}, which are lower semi-continuous and such that lim|x| } ∞ u(x) = ∞. We study the valuations defined on Cn which are invariant under the composition with rigid motions, monotone and verify a certain type of continuity. We prove integral representations formulas for such valuations which are, in addition, simple or homogeneous.

Monotonic rearrangements of functions with small mean oscillation

Dmitriy M. Stolyarov, Vasily I. Vasyunin, Pavel B. Zatitskiy (2015)

Studia Mathematica

We obtain sharp bounds for the monotonic rearrangement operator from "dyadic-type" classes to "continuous" ones; in particular, for the BMO space and Muckenhoupt classes. The idea is to connect the problem with a simple geometric construction named α-extension.

Monotonicity of the maximum of inner product norms

Boris Lavrič (2004)

Commentationes Mathematicae Universitatis Carolinae

Let 𝕂 be the field of real or complex numbers. In this note we characterize all inner product norms p 1 , ... , p m on 𝕂 n for which the norm x max { p 1 ( x ) , ... , p m ( x ) } on 𝕂 n is monotonic.

More on exposed points and extremal points of convex sets in n and Hilbert space

Stoyu T. Barov (2023)

Commentationes Mathematicae Universitatis Carolinae

Let 𝕍 be a separable real Hilbert space, k with k < dim 𝕍 , and let B be convex and closed in 𝕍 . Let 𝒫 be a collection of linear k -subspaces of 𝕍 . A point w B is called exposed by 𝒫 if there is a P 𝒫 so that ( w + P ) B = { w } . We show that, under some natural conditions, B can be reconstituted as the convex hull of the closure of all its exposed by 𝒫 points whenever 𝒫 is dense and G δ . In addition, we discuss the question when the set of exposed by some 𝒫 points forms a G δ -set.

Multiplication of convex sets in C(K) spaces

José Pedro Moreno, Rolf Schneider (2016)

Studia Mathematica

Let C(K) denote the Banach algebra of continuous real functions, with the supremum norm, on a compact Hausdorff space K. For two subsets of C(K), one can define their product by pointwise multiplication, just as the Minkowski sum of the sets is defined by pointwise addition. Our main interest is in correlations between properties of the product of closed order intervals in C(K) and properties of the underlying space K. When K is finite, the product of two intervals in C(K) is always an interval....

n-ary transit functions in graphs

Manoj Changat, Joseph Mathews, Iztok Peterin, Prasanth G. Narasimha-Shenoi (2010)

Discussiones Mathematicae Graph Theory

n-ary transit functions are introduced as a generalization of binary (2-ary) transit functions. We show that they can be associated with convexities in natural way and discuss the Steiner convexity as a natural n-ary generalization of geodesicaly convexity. Furthermore, we generalize the betweenness axioms to n-ary transit functions and discuss the connectivity conditions for underlying hypergraph. Also n-ary all paths transit function is considered.

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