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We study nonuniform sampling in shift-invariant spaces and the construction of Gabor frames with respect to the class of totally positive functions whose Fourier transform factors as $ \hat g(\xi)= \prod_{j=1}^n (1+2\pi i\delta_j\xi)^{-1}…

Functional Analysis · Mathematics 2018-04-11 Karlheinz Gröchenig , José Luis Romero , Joachim Stöckler

We develop a representation of reverse-time migration in terms of Fourier integral operators the canonical relations of which are graphs. Through the dyadic parabolic decomposition of phase space, we obtain the solution of the wave equation…

Numerical Analysis · Mathematics 2015-09-24 Fredrik Andersson , Maarten V. de Hoop , Herwig Wendt

There is a growing attention given to utilizing Lagrangian and Hamiltonian mechanics with network training in order to incorporate physics into the network. Most commonly, conservative systems are modeled, in which there are no frictional…

Machine Learning · Computer Science 2024-05-28 Veera Sundararaghavan , Megna N. Shah , Jeff P. Simmons

We obtain estimates for the $L^{p}$-norm of the short-time Fourier transform (STFT) for functions in modulation spaces, providing information about the concentration on a given subset of $\mathbb{R}^{2}$, leading to deterministic guarantees…

Functional Analysis · Mathematics 2018-08-08 Luis Daniel Abreu , Michael Speckbacher

We study the approach to the adiabatic limit in periodically driven systems. Specifically focusing on a spin-1/2 in a magnetic field we find that, when the parameters of the Hamiltonian lead to a quasi-degeneracy in the Floquet spectrum,…

Quantum Physics · Physics 2017-10-18 Angelo Russomanno , Giuseppe E. Santoro

This is the final part of a series of papers where we study perturbations of divergence form second order elliptic operators $-\operatorname{div} A \nabla$ by first and zero order terms, whose complex coefficients lie in critical spaces,…

Analysis of PDEs · Mathematics 2023-02-07 Simon Bortz , Steve Hofmann , José Luis Luna Garcia , Svitlana Mayboroda , Bruno Poggi

The concept of R-duals of a frame was introduced by Casazza, Kutyniok and Lammers in 2004, with the motivation to obtain a general version of the duality principle in Gabor analysis. For tight Gabor frames and Gabor Riesz bases the three…

Functional Analysis · Mathematics 2015-10-19 Diana T. Stoeva , Ole Christensen

To investigate neural network parameters, it is easier to study the distribution of parameters than to study the parameters in each neuron. The ridgelet transform is a pseudo-inverse operator that maps a given function $f$ to the parameter…

Machine Learning · Computer Science 2024-04-22 Sho Sonoda , Isao Ishikawa , Masahiro Ikeda

We study the connection between STFT multipliers $A^{g_1,g_2}_{1\otimes m}$ having windows $g_1,g_2$, symbols $a(x,\omega)=(1\otimes m)(x,\omega)=m(\omega)$, $(x,\omega)\in\mathbb{R}^{2d}$, and the Fourier multipliers $T_{m_2}$ with symbol…

Functional Analysis · Mathematics 2024-07-09 Peter Balazs , Federico Bastianoni , Elena Cordero , Hans G. Feichtinger , Nina Schweighofer

In this article, we develop comprehensive frequency domain methods for estimating and inferring the second-order structure of spatial point processes. The main element here is on utilizing the discrete Fourier transform (DFT) of the point…

Methodology · Statistics 2025-01-24 Junho Yang , Yongtao Guan

The $\alpha$-modulation transform is a time-frequency transform generated by square-integrable representations of the affine Weyl-Heisenberg group modulo suitable subgroups. In this paper we prove new conditions that guarantee the…

Functional Analysis · Mathematics 2016-03-02 Michael Speckbacher , Dominik Bayer , Stephan Dahlke , Peter Balazs

Recent work of the operator algebraists P. Muhly and B. Solel, primarily motivated by the theory of operator algebras and mathematical physics, delineates a general abstract framework where system theory ideas appear in disguised form.…

Functional Analysis · Mathematics 2009-06-08 J. A. Ball , S. ter Horst

This paper is devoted to wavelet analysis on adele ring $\bA$ and the theory of pseudo-differential operators. We develop the technique which gives the possibility to generalize finite-dimensional results of wavelet analysis to the case of…

Functional Analysis · Mathematics 2011-07-11 A. Yu. Khrennikov , A. V. Kosyak , V. M. Shelkovich

Employing a phase space which includes the (Riemann-Liouville) fractional derivative of curves evolving on real space, we develop a restricted variational principle for Lagrangian systems yielding the so-called restricted fractional…

Mathematical Physics · Physics 2018-03-01 Fernando Jiménez , Sina Ober-Blöbaum

In this paper, $\mathcal{G}(g,L,M,N)$ denotes a $L-$window Gabor system on a periodic set $\mathbb{S}$, where $L,M,M\in \mathbb{N}$ and $g=\{g_l\}_{l\in \mathbb{N}_L}\subset \ell^2(\mathbb{S})$. We characterize which $g$ generates a…

Functional Analysis · Mathematics 2025-05-06 Najib Khachiaa

Theta series for lattices with indefinite signature $(n_+,n_-)$ arise in many areas of mathematics including representation theory and enumerative algebraic geometry. Their modular properties are well understood in the Lorentzian case…

Number Theory · Mathematics 2020-11-20 Sergei Alexandrov , Sibasish Banerjee , Jan Manschot , Boris Pioline

In this paper, we present an equivalent form of the $\Delta_2 $-condition which allow us to redefine the topological vector space structure of a modular spaces using the filter base. We show also the characterization of closed subsets (in…

Functional Analysis · Mathematics 2007-05-23 A. Hajji

This article is based on lecture notes prepared for the August 2006 Cologne Summer School. The first part contains background material and references for beginners. The second (and main) part is a survey of the current status in the theory…

Algebraic Geometry · Mathematics 2010-01-18 Mihnea Popa

Stability of linear systems with uncertain bounded time-varying delays is studied under assumption that the nominal delay values are not equal to zero. An input-output approach to stability of such systems is known to be based on the bound…

Optimization and Control · Mathematics 2007-05-23 Eugenii Shustin , Emilia Fridman

A central question in the LLM debate is whether transformers can infer rules absent from training, or whether apparent generalisation reduces to similarity-based interpolation over observed examples. We test a strong interpolation-only…

Machine Learning · Computer Science 2026-03-19 Andy Gray