ISSN:
1420-8989
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mathematics
Notes:
Abstract Let U be an invertible operator on a Banach space Y. U is said to betrigonometrically well-bounded provided the sequence {Un} n ∞ =−∞ is the Fourier-Stieltjes transform of a suitable projection-valued function E(·): [0, 2π]→ℬ(Y). This class of operators is known to apply naturally to a variety of classical phenomena which exclude the presence of spectral measures. In the case Y reflexive we use the Cesáro means σn(U, t) of the trigonometric series ∑k≠0 k−eiktUk, whichformally transfers the discrete Hilbert transform to Y, in order to give three separate necessary and sufficient conditions for U to be trigonometrically well-bounded. One of these conditions is sup {∥σn(U,t)∥: n ≥ 1, t ∈ [0,2π]} 〈 ∞
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01202516