Displaying 21 – 40 of 69

Showing per page

Coarea integration in metric spaces

Malý, Jan (2003)

Nonlinear Analysis, Function Spaces and Applications

Let X be a metric space with a doubling measure, Y be a boundedly compact metric space and u : X Y be a Lebesgue precise mapping whose upper gradient g belongs to the Lorentz space L m , 1 , m 1 . Let E X be a set of measure zero. Then ^ m ( E u - 1 ( y ) ) = 0 for m -a.e. y Y , where m is the m -dimensional Hausdorff measure and ^ m is the m -codimensional Hausdorff measure. This property is closely related to the coarea formula and implies a version of the Eilenberg inequality. The result relies on estimates of Hausdorff content of level sets...

Compact embedding theorems for generalized Sobolev spaces

Maria Manfredini (1993)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

In this Note we give some compact embedding theorems for Sobolev spaces, related to m -tuples of vectors fields of C 1 class on R N .

Compact embeddings of Besov spaces involving only slowly varying smoothness

António Caetano, Amiran Gogatishvili, Bohumír Opic (2011)

Czechoslovak Mathematical Journal

We characterize compact embeddings of Besov spaces B p , r 0 , b ( n ) involving the zero classical smoothness and a slowly varying smoothness b into Lorentz-Karamata spaces L p , q ; b ¯ ( Ω ) , where Ω is a bounded domain in n and b ¯ is another slowly varying function.

Compact embeddings of Brézis-Wainger type.

Fernando Cobos, Thomas Kühn, Tomas Schonbek (2006)

Revista Matemática Iberoamericana

Let Ω be a bounded domain in Rn and denote by idΩ the restriction operator from the Besov space Bpq1+n/p(Rn) into the generalized Lipschitz space Lip(1,-α)(Ω). We study the sequence of entropy numbers of this operator and prove that, up to logarithmic factors, it behaves asymptotically like ek(idΩ) ~ k-1/p if α > max (1 + 2/p + 1/q, 1/p). Our estimates improve previous results by Edmunds and Haroske.

Compact operators and approximation spaces

Fernando Cobos, Oscar Domínguez, Antón Martínez (2014)

Colloquium Mathematicae

We investigate compact operators between approximation spaces, paying special attention to the limit case. Applications are given to embeddings between Besov spaces.

Compactly supported frames for spaces of distributions associated with nonnegative self-adjoint operators

S. Dekel, G. Kerkyacharian, G. Kyriazis, P. Petrushev (2014)

Studia Mathematica

A small perturbation method is developed and employed to construct frames with compactly supported elements of small shrinking support for Besov and Triebel-Lizorkin spaces in the general setting of a doubling metric measure space in the presence of a nonnegative self-adjoint operator whose heat kernel has Gaussian localization and the Markov property. This allows one, in particular, to construct compactly supported frames for Besov and Triebel-Lizorkin spaces on the sphere, on the interval with...

Compactness criteria in function spaces

Monika Dörfler, Hans G. Feichtinger, Karlheinz Gröchenig (2002)

Colloquium Mathematicae

The classical criterion for compactness in Banach spaces of functions can be reformulated into a simple tightness condition in the time-frequency domain. This description preserves more explicitly the symmetry between time and frequency than the classical conditions. The result is first stated and proved for L ² ( d ) , and then generalized to coorbit spaces. As special cases, we obtain new characterizations of compactness in Besov-Triebel-Lizorkin, modulation and Bargmann-Fock spaces.

Currently displaying 21 – 40 of 69