Smoothness spaces for warped time-frequency representations -- Decomposition spaces and embedding relations

Abstract

In a recent paper, we have shown that warped time-frequency representations provide a rich framework for the construction and study of smoothness spaces matched to very general phase space geometries obtained by diffeomorphic deformations of $\mathbb{R}^d$. Here, we study these spaces, obtained through the application of general coorbit theory, using the framework of decomposition spaces. This allows us to derive embedding relations between coorbit spaces associated to different warping functions, and relate them to established, important smothness spaces. In particular, we show that we obtain $\alpha$-modulation spaces and spaces of dominating mixed smoothness as special cases and, in contrast, that this is only possible for Besov spaces if $d=1$.