Siciak’s extremal function of convex sets in
Mirosław Baran (1988)
Annales Polonici Mathematici
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Mirosław Baran (1988)
Annales Polonici Mathematici
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Józef Siciak (1981)
Annales Polonici Mathematici
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M. Obradović, S. Owa (1986)
Matematički Vesnik
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Alexander Koldobsky, Marisa Zymonopoulou (2003)
Studia Mathematica
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We study the extremal volume of central hyperplane sections of complex n-dimensional -balls with 0 < p ≤ 2. We show that the minimum corresponds to hyperplanes orthogonal to vectors ξ = (ξ¹,...,ξⁿ) ∈ ℂⁿ with |ξ¹| = ... = |ξⁿ|, and the maximum corresponds to hyperplanes orthogonal to vectors with only one non-zero coordinate.
Stefan Müller, Vladimír Šverák (1999)
Journal of the European Mathematical Society
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We study solutions of first order partial differential relations , where is a Lipschitz map and is a bounded set in matrices, and extend Gromov’s theory of convex integration in two ways. First, we allow for additional constraints on the minors of and second we replace Gromov’s −convex hull by the (functional) rank-one convex hull. The latter can be much larger than the former and this has important consequences for the existence of ‘wild’ solutions to elliptic systems. Our...
S. Kołodziej (1988)
Annales Polonici Mathematici
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Philippe Laurençot (2002)
Colloquium Mathematicae
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If φ: [0,∞) → [0,∞) is a convex function with φ(0) = 0 and conjugate function φ*, the inequality is shown to hold true for every ε ∈ (0,∞) if and only if φ* satisfies the Δ₂-condition.
B. Platynowicz (1980)
Matematički Vesnik
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Grzegorz Lewicki, Michael Prophet (2007)
Studia Mathematica
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We say that a function from is k-convex (for k ≤ L) if its kth derivative is nonnegative. Let P denote a projection from X onto V = Πₙ ⊂ X, where Πₙ denotes the space of algebraic polynomials of degree less than or equal to n. If we want P to leave invariant the cone of k-convex functions (k ≤ n), we find that such a demand is impossible to fulfill for nearly every k. Indeed, only for k = n-1 and k = n does such a projection exist. So let us consider instead a more general “shape”...
Prakash G. Umarani (1983)
Annales Polonici Mathematici
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Katsuro Sakai, Zhongqiang Yang (2007)
Bulletin of the Polish Academy of Sciences. Mathematics
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Let be the space of all non-empty closed convex sets in Euclidean space ℝ ⁿ endowed with the Fell topology. We prove that for every n > 1 whereas .
Bo’az Klartag (2013)
Annales de la faculté des sciences de Toulouse Mathématiques
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We discuss a method for obtaining Poincaré-type inequalities on arbitrary convex bodies in . Our technique involves a dual version of Bochner’s formula and a certain moment map, and it also applies to some non-convex sets. In particular, we generalize the central limit theorem for convex bodies to a class of non-convex domains, including the unit balls of -spaces in for .
Mirosław Baran, Leokadia Bialas-Ciez (2012)
Annales Polonici Mathematici
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The paper deals with logarithmic capacities, an important tool in pluripotential theory. We show that a class of capacities, which contains the L-capacity, has the following product property: , where and are respectively a compact set and a norm in (j = 1,2), and ν is a norm in , ν = ν₁⊕ₚ ν₂ with some 1 ≤ p ≤ ∞. For a convex subset E of , denote by C(E) the standard L-capacity and by the minimal width of E, that is, the minimal Euclidean distance between two supporting hyperplanes...
G. Paouris (2005)
Studia Mathematica
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The slicing problem can be reduced to the study of isotropic convex bodies K with , where is the isotropic constant. We study the ψ₂-behaviour of linear functionals on this class of bodies. It is proved that for all θ in a subset U of with measure σ(U) ≥ 1 - exp(-c√n). However, there exist isotropic convex bodies K with uniformly bounded geometric distance from the Euclidean ball, such that . In a different direction, we show that good average ψ₂-behaviour of linear functionals...
Leokadia Bialas-Ciez (2012)
Annales Polonici Mathematici
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The paper is concerned with the best constants in the Bernstein and Markov inequalities on a compact set . We give some basic properties of these constants and we prove that two extremal-like functions defined in terms of the Bernstein constants are plurisubharmonic and very close to the Siciak extremal function . Moreover, we show that one of these extremal-like functions is equal to if E is a nonpluripolar set with where , the supremum is taken over all polynomials P of N variables...
Gerd Herzog, Peer Chr. Kunstmann (2015)
Commentationes Mathematicae Universitatis Carolinae
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We prove the existence of functions , the Fourier series of which being universally divergent on countable subsets of . The proof is based on a uniform estimate of the Taylor polynomials of Landau’s extremal functions on .
S. Owa, C. Y. Shen (1988)
Matematički Vesnik
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