Holomorphic H\"ormander-Type Functional Calculus on Sectors and Strips

TL;DR

This paper extends and refines multiplier theorems for sectorial and strip-type operators using a new class of holomorphic H"ormander-type functions with finer smoothness, improving existing results for symmetric contraction semigroups.

Contribution

It introduces a new scale of holomorphic H"ormander-type functions on sectors and strips, and combines these with recent results to enhance multiplier theorems for broader classes of operators.

Findings

Refined multiplier theorems for sectorial and strip-type operators.

Introduction of a finer smoothness scale for holomorphic H"ormander functions.

Improved smoothness conditions in multiplier theorems for symmetric contraction semigroups.

Abstract

In this paper, recent abstract multiplier theorems for $0$-sectorial and $0$-strip type operators by Kriegler and Weis (2018) are refined and generalized to arbitrary sectorial and strip-type operators. To this end, holomorphic H\"ormander-type functions on sectors and strips are introduced with a scale of smoothness being finer than the classical polynomial one. Moreover, we establish alternative descriptions of these spaces involving Schwartz and "holomorphic Schwartz" functions. Finally, the abstract results are combined with a recent result by Carbonaro and Dragi\v{c}evi\'c (2017) to obtain an improvement -- with respect to the smoothness condition -- of the known H\"ormander-type multiplier theorem for general symmetric contraction semigroups.