Joachim Toft

activity

20242026

collaborators

5 papers

math.FA2026

Compactness for pseudo-differential and Toeplitz operators on modulation spaces

Elmira Nabizadeh-Morsalfard, Christine Pfeuffer, Nenad Teofanov +1

We deduce various norm equivalences, and convolution estimates for the modulation space $M_{(I ¨ )}^{♯, q}$ consisting of all $f \in M_{(I ¨ )}^{\infty, q}$ such that $|V_Ïf \cdot…

math.FA2025

Quantitative uncertainty principles for time-frequency Gaussian decay

Lenny Neyt, Joachim Toft, Jasson Vindas

For real symmetric positive definite matrices $A$ and $B$ , we characterize when a function $f \in L^{2} (R^{d})$ satisfies \[ |f(x)| \lesssim e^{-(\frac12 - Î») \langle Ax, x\r…

math.FA2025

Non-isometric translation and modulation invariant Hilbert spaces

P. K. Ratnakumar, Joachim Toft, Jasson Vindas

Let $H$ be a Hilbert space of distributions on $R^{d}$ which contains at least one non-zero element in $D^{'} (R^{d})$ . If there is a constant $C_{0} > 0$ su…

math.FA2025

Norm estimates for a broad class of modulation spaces, and continuity of Fourier type operators

Joachim Toft, Christine Pfeuffer, Nenad Teofanov

Let $B$ be a normal quasi-Banach function space with respect to $r_{0} \in (0, 1]$ and $v_{0}$ , $I ¨ $ be $v$ -moderate, and let $r \in [r_{0}, \infty]$ . Then we prove that $f$ belon…

math.FA2024

Hermite expansions for spaces of functions with nearly optimal time-frequency decay

Lenny Neyt, Joachim Toft, Jasson Vindas

We establish Hermite expansion characterizations for several subspaces of the FrÃ©chet space of functions on the real line satisfying \begin{equation*} |f(x)| \lesssim e^{-(\frac{1…