Discrete characterizations of wave front sets of Fourier-Lebesgue and quasianalytic type

TL;DR

This paper provides a new discrete sampling method to characterize wave front sets of Fourier-Lebesgue and quasianalytic types, enabling microlocal analysis of ultradistributions through lattice sampling of Fourier transforms.

Contribution

It introduces a novel discrete characterization of the analytic wave front set using lattice sampling, advancing the microlocal analysis of ultradistributions.

Findings

Discrete sampling characterizes wave front sets of Fourier-Lebesgue and quasianalytic types.

Microlocal properties are recoverable from Fourier transform samples over a lattice.

The method applies to distributions with specific localizations and growth conditions.

Abstract

We obtain discrete characterizations of wave front sets of Fourier-Lebesgue and quasianalytic type. It is shown that the microlocal properties of an ultradistribution can be obtained by sampling the Fourier transforms of its localizations over a lattice in $\mathbb{R}^{d}$. In particular, we prove the following discrete characterization of the analytic wave front set of a distribution $f\in\mathcal{D}'(\Omega)$. Let $\Lambda$ be a lattice in $\mathbb{R}^{d}$ and let $U$ be an open convex neighborhood of the origin such that $U\cap\Lambda^{*}=\{0\}$. The analytic wave front set $WF_{A}(f)$ coincides with the complement in $\Omega\times(\mathbb{R}^{d}\setminus\{0\})$ of the set of points $(x_0,\xi_0)$ for which there are an open neighborhood $V\subset \Omega\cap (x_0+U)$ of $x_0$, an open conic neighborhood $\Gamma$ of $\xi_0$, and a bounded sequence $(f_p)_{p \in \mathbb{N}}$ in $\mathcal{E}'(\Omega\cap (x_0+U))$ with $f_p= f$ on $V$ such that for some $h > 0$ \[ \sup_{\mu \in \Gamma \cap \Lambda} |\widehat{f_p} (\mu)| |\mu|^p \leq h^{p+1}p!\:, \qquad \forall p \in \mathbb{N}. \]