Displaying similar documents to “Extremal sections of complex l p -balls, 0 < p ≤ 2”

Robin functions and extremal functions

T. Bloom, N. Levenberg, S. Ma&#039;u (2003)

Annales Polonici Mathematici

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Given a compact set K N , for each positive integer n, let V ( n ) ( z ) = V K ( n ) ( z ) := sup 1 / ( d e g p ) V p ( K ) ( p ( z ) ) : p holomorphic polynomial, 1 ≤ deg p ≤ n. These “extremal-like” functions V K ( n ) are essentially one-variable in nature and always increase to the “true” several-variable (Siciak) extremal function, V K ( z ) := max[0, sup1/(deg p) log|p(z)|: p holomorphic polynomial, | | p | | K 1 ]. Our main result is that if K is regular, then all of the functions V K ( n ) are continuous; and their associated Robin functions ϱ V K ( n ) ( z ) : = l i m s u p | λ | [ V K ( n ) ( λ z ) - l o g ( | λ | ) ] increase to ϱ K : = ϱ V K for all z outside a pluripolar...

Siciak’s extremal function via Bernstein and Markov constants for compact sets in N

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 E N . 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 Φ E . Moreover, we show that one of these extremal-like functions is equal to Φ E if E is a nonpluripolar set with l i m n M ( E ) 1 / n = 1 where M ( E ) : = s u p | | | g r a d P | | | E / | | P | | E , the supremum is taken over all polynomials P of N variables...

The postage stamp problem and arithmetic in base r

Amitabha Tripathi (2008)

Czechoslovak Mathematical Journal

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Let h , k be fixed positive integers, and let A be any set of positive integers. Let h A : = { a 1 + a 2 + + a r : a i A , r h } denote the set of all integers representable as a sum of no more than h elements of A , and let n ( h , A ) denote the largest integer n such that { 1 , 2 , ... , n } h A . Let n ( h , k ) : = max A : n ( h , A ) , where the maximum is taken over all sets A with k elements. We determine n ( h , A ) when the elements of A are in geometric progression. In particular, this results in the evaluation of n ( h , 2 ) and yields surprisingly sharp lower bounds for n ( h , k ) , particularly for k = 3 .

Sharp estimation of the coefficients of bounded univalent functions close to identity

Lucjan Siewierski

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CONTENTSIntroduction...............................................................................................................................................................................5Definitions and notation.........................................................................................................................................................7The main result........................................................................................................................................................................91....

The gap theorems for some extremal submanifolds in a unit sphere

Xi Guo and Lan Wu (2015)

Communications in Mathematics

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Let M be an n -dimensional submanifold in the unit sphere S n + p , we call M a k -extremal submanifold if it is a critical point of the functional M ρ 2 k d v . In this paper, we can study gap phenomenon for these submanifolds.

Configurations of rank- 40 r extremal even unimodular lattices ( r = 1 , 2 , 3 )

Scott Duke Kominers, Zachary Abel (2008)

Journal de Théorie des Nombres de Bordeaux

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We show that if L is an extremal even unimodular lattice of rank 40 r with r = 1 , 2 , 3 , then L is generated by its vectors of norms 4 r and 4 r + 2 . Our result is an extension of Ozeki’s result for the case r = 1 .

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

Stoyu T. Barov (2023)

Commentationes Mathematicae Universitatis Carolinae

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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.

Product property for capacities in N

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: C ν ( E × E ) = m i n ( C ν ( E ) , C ν ( E ) ) , where E j and ν j are respectively a compact set and a norm in N j (j = 1,2), and ν is a norm in N + N , ν = ν₁⊕ₚ ν₂ with some 1 ≤ p ≤ ∞. For a convex subset E of N , denote by C(E) the standard L-capacity and by ω E the minimal width of E, that is, the minimal Euclidean distance between two supporting hyperplanes...