Perturbations of the Hºº-calculus

Autores: Nigel J. Kalton
Localización: Collectanea mathematica, ISSN 0010-0757, Vol. 58, Fasc. 3, 2007, págs. 291-325
Idioma: español
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Resumen
- Suppose A is a sectorial operator on a Banach space X, which admits an H1calculus.
  
  We study conditions on a multiplicative perturbation B of A which ensure that B also has an H1calculus.
  
  We identify a class of bounded operators T : X ! X, which we call strongly triangular, such that if B = (1+T)Ais sectorial then it also has anH1calculus.
  
  In the caseX is a Hilbert space an operator is strongly triangular if and only ifPsn(T)/n < 1where (sn(T))1n=1 are the singular values of T.