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A capacity approach to the Poincaré inequality and Sobolev imbeddings in variable exponent Sobolev spaces.

Petteri Harjulehto, Peter Hästö (2004)

Revista Matemática Complutense

We study the Poincaré inequality in Sobolev spaces with variable exponent. Under a rather mild and sharp condition on the exponent p we show that the inequality holds. This condition is satisfied e.g. if the exponent p is continuous in the closure of a convex domain. We also give an essentially sharp condition for the exponent p as to when there exists an imbedding from the Sobolev space to the space of bounded functions.

A characterization of Sobolev spaces via local derivatives

David Swanson (2010)

Colloquium Mathematicae

Let 1 ≤ p < ∞, k ≥ 1, and let Ω ⊂ ℝⁿ be an arbitrary open set. We prove a converse of the Calderón-Zygmund theorem that a function f W k , p ( Ω ) possesses an L p derivative of order k at almost every point x ∈ Ω and obtain a characterization of the space W k , p ( Ω ) . Our method is based on distributional arguments and a pointwise inequality due to Bojarski and Hajłasz.

A chart preserving the normal vector and extensions of normal derivatives in weighted function spaces

Katrin Schumacher (2009)

Czechoslovak Mathematical Journal

Given a domain Ω of class C k , 1 , k , we construct a chart that maps normals to the boundary of the half space to normals to the boundary of Ω in the sense that ( - x n ) α ( x ' , 0 ) = - N ( x ' ) and that still is of class C k , 1 . As an application we prove the existence of a continuous extension operator for all normal derivatives of order 0 to k on domains of class C k , 1 . The construction of this operator is performed in weighted function spaces where the weight function is taken from the class of Muckenhoupt weights.

A commutator theorem with applications.

Mario Milman (1993)

Collectanea Mathematica

We give an extension of the commutator theorems of Jawerth, Rochberg and Weiss [9] for the real method of interpolation. The results are motivated by recent work by Iwaniek and Sbordone [6] on generalized Hodge decompositions. The main estimates of these authors are based on a commutator theorem for a specific operator acting on Lp spaces and through the use of the complex method of interpolation. In this note we give an extension of the Iwaniek-Sbordone theorem to general real interpolation scales....

A finite element analysis for elastoplastic bodies obeying Hencky's law

Ivan Hlaváček (1981)

Aplikace matematiky

Using the Haar-Kármán principle, approximate solutions of the basic boundary value problems are proposed and studied, which consist of piecewise linear stress fields on composite triangles. The torsion problem is solved in an analogous manner. Some convergence results are proven.

A Fourier analytical characterization of the Hausdorff dimension of a closed set and of related Lebesgue spaces

Hans Triebel, Heike Winkelvoss (1996)

Studia Mathematica

Let Γ be a closed set in n with Lebesgue measure |Γ| = 0. The first aim of the paper is to give a Fourier analytical characterization of Hausdorff dimension of Γ. Let 0 < d < n. If there exist a Borel measure µ with supp µ ⊂ Γ and constants c 1 > 0 and c 2 > 0 such that c 1 r d µ ( B ( x , r ) ) c 2 r d for all 0 < r < 1 and all x ∈ Γ, where B(x,r) is a ball with centre x and radius r, then Γ is called a d-set. The second aim of the paper is to provide a link between the related Lebesgue spaces L p ( Γ ) , 0 < p ≤ ∞, with respect to...

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