Linear extension operators for restrictions of function spaces to irregular open sets

• Autorzy: V. S. Rychkov
• Języki publikacji: EN

Abstrakty

EN

Let an open set $Ω ⊂ ℝ^n$ satisfy for some 0≤d≤n and ε > 0 the condition: the $d$-Hausdorff content $H_d(Ω∩B) ≥ ε|B|^{d/n}$ for any ball B centered in Ω of volume |B|≤1. Let $H_p^s$ denote the Bessel potential space on $ℝ^n$ 1 < p < ∞,s > 0, and let $H_p^s[Ω]$ be the linear space of restrictions of elements of $H_p^s$ to Ω endowed with the quotient space norm. We find sufficient conditions for the existence of a linear extension operator for $H_p^s[Ω]$, i.e., a bounded linear operator $H_p^s[Ω]→H_p^s$ such that $ext⨍|_Ω}=⨍$ for all ⨍. The main result is that such an operator exists if (i) d > n-1 and s > (n-d)/min(p,2), or (ii) d≤n-1 and s-[s] > (n-d)/min(p,2). It is an open problem whether these assumptions are sharp.

Słowa kluczowe

EN

Sobolev spaces; Besov-Triebel-Lizorkin spaces; restrictions; extension operators; irregular domains; Hausdorff content; local polynomial approximation; complemented subspaces

Kategorie tematyczne

• 42B25: Maximal functions, Littlewood-Paley theory
• 46E35: Sobolev spaces and other spaces of ``smooth'' functions, embedding theorems, trace theorems

• Wydawca: Institute of Mathematics Polish Academy of Sciences
• Czasopismo: Studia Mathematica
• Rocznik: 2000
• Tom: 140
• Numer: 2
• Strony: 141-162

Daty

wydano

2000

otrzymano

1999-02-08

poprawiono

2000-01-24

Twórcy

autor

V. S. Rychkov

• Mathematisches Institut, Friedrich-Schiller-Universität Jena, Germany
• Mathematics Department, Princeton University, Princeton, NJ 08544, U.S.A.

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