Scale Dilation Dynamics in Flexible Bandwidth Needlet Constructions

TL;DR

This paper investigates how different dilation sequences in flexible bandwidth needlets affect their localization, overlap, and spectral properties, providing insights into their design trade-offs for analyzing functions on the sphere.

Contribution

It characterizes the asymptotic behaviors of dilation sequences and their impact on needlet geometry and spectral coverage, advancing understanding of needlet construction.

Findings

Different asymptotic regimes influence needlet localization and overlap.

Dilation growth rates affect spectral concentration and redundancy.

Insights into needlet coefficient uncorrelation for random fields.

Abstract

Flexible bandwidth needlets offer a versatile multiscale framework for analyzing functions on the sphere. A key element in their construction is the dilation sequence, which controls how the multipole consecutive scales are spaced and overlapped. At any resolution level, this sequence determines the center positions of the needlet weight functions and influences their localization in the spatial domain and spectral concentration properties by means of the relative bandwidth ratio. In this paper, we explore the different asymptotic regimes that arise when the dilation sequence exhibits shrinking, stable (standard), or spreading behavior. Moreover, we assume the dilation sequence grows regularly enough to ensure well-defined asymptotic properties. For each regime, we characterize the impact on the geometry of the center scales and the shape of the multipole windows, with particular attention to their overlap structure and spectral coverage. These insights help to clarify the trade-offs between localization, redundancy, and scalability in the design of needlet-type systems, particularly in relation to the study of the asymptotic uncorrelation of needlet coefficients when applied to random fields.