Displaying 21 – 40 of 88

Showing per page

Hölder functions in Bergman type spaces

Yingwei Chen, Guangbin Ren (2012)

Studia Mathematica

It seems impossible to extend the boundary value theory of Hardy spaces to Bergman spaces since there is no boundary value for a function in a Bergman space in general. In this article we provide a new idea to show what is the correct version of Bergman spaces by demonstrating the extension to Bergman spaces of a result of Hardy-Littlewood in Hardy spaces, which characterizes the Hölder class of boundary values for a function from Hardy spaces in the unit disc in terms of the growth of its derivative....

Idempotents in quotients and restrictions of Banach algebras of functions

Thomas Vils Pedersen (1996)

Annales de l'institut Fourier

Let 𝒜 β be the Beurling algebra with weight ( 1 + | n | ) β on the unit circle 𝕋 and, for a closed set E 𝕋 , let J 𝒜 β ( E ) = { f 𝒜 β : f = 0 on a neighbourhood of E } . We prove that, for β > 1 2 , there exists a closed set E 𝕋 of measure zero such that the quotient algebra 𝒜 β / J 𝒜 β ( E ) is not generated by its idempotents, thus contrasting a result of Zouakia. Furthermore, for the Lipschitz algebras λ γ and the algebra 𝒜 𝒞 of absolutely continuous functions on 𝕋 , we characterize the closed sets E 𝕋 for which the restriction algebras λ γ ( E ) and 𝒜 𝒞 ( E ) are generated by their idempotents.

Instability of the eikonal equation and shape from shading

Ian Barnes, Kewei Zhang (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

In the shape from shading problem of computer vision one attempts to recover the three-dimensional shape of an object or landscape from the shading on a single image. Under the assumptions that the surface is dusty, distant, and illuminated only from above, the problem reduces to that of solving the eikonal equation |Du|=f on a domain in 2 . Despite various existence and uniqueness theorems for smooth solutions, we show that this problem is unstable, which is catastrophic for general numerical algorithms. ...

Lipschitz extensions of convex-valued maps

Alberto Bressan, Agostino Cortesi (1986)

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

Si dimostra che ogni funzione multivoca lipschitziana con costante di Lipschitz M , definita su un sottoinsieme di uno spazio di Hilbert H a valori compatti e convessi in n , può essere estesa su tutto H ad una funzione multivoca lipschitziana con costante minore di 7 nM. In generale, non esistono invece estensioni aventi la stessa costante di Lipschitz M .

Currently displaying 21 – 40 of 88