Joachim Toft

activity

20242026

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

2 citations · 2 across the 5 of their papers we have counts for

collaborators

6 papers

math.FA2026

Fractional symplectic Fourier transforms and their actions on function and distribution spaces

Lenny Neyt, Joachim Toft

We consider symplectic analogues of the fractional Fourier transforms and obtain convenient representations in terms of Bargmann transforms and Wigner distributions. We show that t…

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 $M_{(ω)}^{♯, q}$ consisting of all $f \in M_{(ω)}^{\infty, q}$ such that $|V_ϕf \cdot ω|…

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 - λ) \langle Ax, x\ra…

math.FA2024

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 $v_{0}$ , $ω$ be $v$ -moderate, and let $r \in [r_{0}, \infty]$ . Then we prove that $f$ belong…

math.FA2024

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.FA2024★ 2 cited

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 Fréchet space of functions on the real line satisfying \begin{equation*} |f(x)| \lesssim e^{-(\frac{1}…