Generalized coorbit space theory and inhomogeneous function spaces of Besov-Lizorkin-Triebel type

TL;DR

This paper extends coorbit space theory to include inhomogeneous Besov-Lizorkin-Triebel spaces using abstract continuous frames, providing new atomic decompositions, wavelet characterizations, and applications to various weighted and mixed smoothness spaces.

Contribution

It significantly generalizes coorbit space theory to cover inhomogeneous spaces via abstract frames, enabling broader atomic decompositions and wavelet characterizations.

Findings

Unified atomic decomposition framework for coorbit spaces.

New wavelet characterizations with smoothness and decay conditions.

Applicability to weighted, 2-microlocal, and mixed smoothness spaces.

Abstract

Coorbit space theory is an abstract approach to function spaces and their atomic decompositions. The original theory developed by Feichtinger and Gr{\"o}chenig in the late 1980ies heavily uses integrable representations of locally compact groups. Their theory covers, in particular, homogeneous Besov-Lizorkin-Triebel spaces, modulation spaces, Bergman spaces, and the recent shearlet spaces. However, inhomogeneous Besov-Lizorkin-Triebel spaces cannot be covered by their group theoretical approach. Later it was recognized by Fornasier and the first named author that one may replace coherent states related to the group representation by more general abstract continuous frames. In the first part of the present paper we significantly extend this abstract generalized coorbit space theory to treat a wider variety of coorbit spaces. A unified approach towards atomic decompositions and Banach frames with new results for general coorbit spaces is presented. In the second part we apply the abstract setting to a specific framework and study coorbits of what we call Peetre spaces. They allow to recover inhomogeneous Besov-Lizorkin-Triebel spaces of various types of interest as coorbits. We obtain several old and new wavelet characterizations based on precise smoothness, decay, and vanishing moment assumptions of the respective wavelet. As main examples we obtain results for weighted spaces (Muckenhoupt, doubling), general 2-microlocal spaces, Besov-Lizorkin-Triebel-Morrey spaces, spaces of dominating mixed smoothness, and even mixtures of the mentioned ones. Due to the generality of our approach, there are many more examples of interest where the abstract coorbit space theory is applicable.