# Envelopes And Sharp Embeddings Of Function Spaces by Dorothee D. Haroske

By Dorothee D. Haroske

Formerly, no ebook has systematically offered the lately constructed inspiration of envelopes in functionality areas. Envelopes are fairly uncomplicated instruments for the learn of classical and extra complex areas, corresponding to Besov and Triebel-Lizorkin forms, in proscribing occasions. This thought originates from the classical results of the Sobolev embedding theorem, ubiquitous in all components of practical research.

Self-contained and obtainable, Envelopes and Sharp Embeddings of functionality Spaces presents the 1st distinct account of the recent conception of progress and continuity envelopes in functionality areas. The ebook is easily established into elements, first offering a accomplished advent after which studying extra complex issues. the various classical functionality areas mentioned within the first half contain Lebesgue, Lorentz, Lipschitz, and Sobolev. the writer defines progress and continuity envelopes and examines their houses. partly II, the booklet explores the consequences for functionality areas of Besov and Triebel-Lizorkin forms. the writer then offers a number of purposes of the consequences, together with Hardy-type inequalities, asymptotic estimates for entropy, and approximation numbers of compact embeddings.

As one of many key researchers during this progressing box, the writer deals a coherent presentation of the hot advancements in functionality areas, supplying beneficial details for graduate scholars and researchers in useful analysis.

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Additional info for Envelopes And Sharp Embeddings Of Function Spaces

Example text

42). 14) can be reformulated as 1 1 (1,− p1 ) = 1. 28 we restrict ourselves to an example merely, since the main idea of envelopes just relies on those cases where we do not have the corresponding embeddings. We explain this in detail in the next chapters. However, this immediately proves the sharpness of the above assertions, too (and is also known already). 38), we present a family of functions hν that belong to Wn1 , but not to L∞ , as long as 0 < ν < 1 − n1 . For x ∈ Rn , consider the radial functions   hν (x) =  logν 1 + 1 |x| − logν 2, 0 < |x| < 1 0 , otherwise hν (x)    , x ∈ Rn .

N p Rn Step 4. 38). 53) 32 Envelopes and sharp embeddings of function spaces and for p ≤ r < ∞, r u|Lr |u(x)|p |u(x)|r−p dx ≤ = u|C r−p u|Lp p Rn ≤ c u|Wpk r−p u|Wpk p = c u|Wpk r . In view of the above argument it is sufficient to deal with the case of u ∈ C0∞ ∩Wpk such that supp u ⊂ Ω with |Ω| < ∞, and to check the dependence of the constants upon Ω. For simplicity we may even assume from the beginning that Ω is the above cube with edges parallel to the axes of coordinates, and side-length b ≥ 1.

28 we restrict ourselves to an example merely, since the main idea of envelopes just relies on those cases where we do not have the corresponding embeddings. We explain this in detail in the next chapters. However, this immediately proves the sharpness of the above assertions, too (and is also known already). 38), we present a family of functions hν that belong to Wn1 , but not to L∞ , as long as 0 < ν < 1 − n1 . For x ∈ Rn , consider the radial functions   hν (x) =  logν 1 + 1 |x| − logν 2, 0 < |x| < 1 0 , otherwise hν (x)    , x ∈ Rn .