The Functional Calculus for Sectorial Operators

The present monograph deals with the functional calculus for unbounded operators in general and for sectorial operators in particular. Sectorial operators abound in the theory of evolution equations, especially those of parabolic type. They satisfy a certain resolvent condition that leads to a holomorphic functional calculus based on Cauchy-type integrals. Via an abstract extension procedure, this elementary functional calculus is then extended to a large class of (even meromorphic) functions.

With this functional calculus at hand, the book elegantly covers holomorphic semigroups, fractional powers, and logarithms. Special attention is given to perturbation results and the connection with the theory of interpolation spaces. A chapter is devoted to the exciting interplay between numerical range conditions, similarity problems and functional calculus on Hilbert spaces. Two chapters describe applications, for example to elliptic operators, to numerical approximations of parabolic equations, and to the maximal regularity problem.

This book is the first systematic account of a subject matter which lies in the intersection of operator theory, evolution equations, and harmonic analysis. It is an original and comprehensive exposition of the theory as a whole. Written in a clear style and optimally organised, it will prove useful for the advanced graduate as well as for the experienced researcher.

First systematic account of functional calculus for sectorial (and other types of unbounded) operators Emphasizes the calculus aspect of the matter, thus paving the way for making functional calculus a working tool A chapter on fractional powers combines elegance with comprehensibility, even in the most general setting The Hilbert space results, duly arranged and comprehensibly presented, appear in book form for the first time Includes supplementary material: sn.pub/extras

Résumé

This book contains a systematic and partly axiomatic treatment of the holomorphic functional calculus for unbounded sectorial operators. The account is generic so that it can be used to construct and interrelate holomorphic functional calculi for other types of unbounded operators. Particularly, an elegant unified approach to holomorphic semigroups is obtained. The last chapter describes applications to PDE, evolution equations and approximation theory as well as the connection with harmonic analysis.

Contenu
Axiomatics for Functional Calculi.- The Functional Calculus for Sectorial Operators.- Fractional Powers and Semigroups.- Strip-type Operators and the Logarithm.- The Boundedness of the H?-Calculus.- Interpolation Spaces.- The Functional Calculus on Hilbert Spaces.- Differential Operators.- Mixed Topics.