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We show that for an arbitrary totally positive function $g\in L^1(\mathbb{R} )$ and $\alpha \beta$ rational, the Gabor family $\{e^{2\pi i \beta l t} g(t-\alpha k): k,l \in \mathbb{Z} \}$ is a frame for $L^2(\mathbb{R})$, if and only if…

Functional Analysis · Mathematics 2024-05-21 Karlheinz Gröchenig

A frame is a system of vectors $S$ in Hilbert space $\mathscr{H}$ with properties which allow one to write algorithms for the two operations, analysis and synthesis, relative to $S$, for all vectors in $\mathscr{H}$; expressed in…

Functional Analysis · Mathematics 2015-01-29 Palle Jorgensen , Feng Tian

Let $X$ be a compact Riemann surface of genus $g\geq 2$ equipped with flat conical metric $|\Omega|$, where $\Omega$ be a holomorphic quadratic differential on $X$ with $4g-4$ simple zeroes. Let $K$ be the canonical line bundle on $X$.…

Differential Geometry · Mathematics 2020-01-22 Alexey Kokotov

The duality principle for Gabor frames is one of the pillars of Gabor analysis. We establish a far-reaching generalization to Morita equivalent $C^*$-algebras where the equivalence bimodule is a finitely generated projective Hilbert…

Operator Algebras · Mathematics 2019-05-07 Are Austad , Mads S. Jakobsen , Franz Luef

Starting from the study of pseudodifferential operators with completely periodic symbols, we obtain results of continuity and invertibility of a class of Gabor operators on time-frequency invariant Banach spaces. As an applications we find…

Functional Analysis · Mathematics 2024-05-03 Gianluca Garello , Alessandro Morando

A Gabor system generated by a window function $g\in L^2(\mathbb{R}^d)$ and a separable set $\Lambda\times \Gamma \subset \mathbb{R}^{2d}$ is the collection of time-frequency shifts of $g$ given by $\mathcal G(g, \Lambda\times \Gamma) =…

Functional Analysis · Mathematics 2022-02-15 Christina Frederick , Azita Mayeli

Here we will consider examples of conformally flat manifolds that are conformally equivalent to open subsets of the n-dimensional sphere. For such manifolds we shall introduce a Cauchy kernel and Cauchy integral formula for sections tasking…

Complex Variables · Mathematics 2007-05-23 John Ryan

The quantum mechanical harmonic oscillator Hamiltonian generates a one-parameter unitary group W(\theta) in L^2(R) which rotates the time-frequency plane. In particular, W(\pi/2) is the Fourier transform. When W(\theta) is applied to any…

Mathematical Physics · Physics 2009-11-07 Gerald Kaiser

We present the theory of Cauchy-Fantappi\'e integral operators, with emphasis on the situation when the domain of integration, $D$, has minimal boundary regularity. Among these operators we focus on those that are more closely related to…

Complex Variables · Mathematics 2013-11-21 Loredana Lanzani , Elias M. Stein

We investigate vector-valued Gabor frames (sometimes called Gabor superframes) based on Hermite functions $H_n$. Let $h= (H_0, H_1, ..., H_n)$ be the vector of the first $n+1$ Hermite functions. We give a complete characterization of all…

Functional Analysis · Mathematics 2010-12-21 Karlheinz Gröchenig , Yurii Lyubarskii

We introduce a localization concept for operator-valued frames, where the quality of localization is measured by the associated operator-valued Gram matrix belonging to some suitable Banach algebra. We prove that intrinsic localization of…

Functional Analysis · Mathematics 2025-05-29 Lukas Köhldorfer , Peter Balazs

Given a total sequence in a Hilbert space, we speak of an upper (resp. lower) semi-frame if only the upper (resp. lower) frame bound is valid. Equivalently, for an upper semi-frame, the frame operator is bounded, but has an unbounded…

Mathematical Physics · Physics 2012-10-12 J-P. Antoine , P. Balazs

In this article, we define the spherical $\pi$-operator over domains in the $(n-1)$-D unit sphere $S^n$ of $R^n$ and develop new and analogous results on the operator it self and its mapping properties. We introduce the spherical Dirac…

Classical Analysis and ODEs · Mathematics 2008-11-21 Dejenie A. Lakew

In this paper, we introduce the generalized Cauchy dual $w(T) = T(T^{*}T)^{\dagger}$ of a closed operator $T$ with the closed range between Hilbert spaces and present intriguing findings that characterize the Cauchy dual of $T$.…

Functional Analysis · Mathematics 2024-12-18 Arup Majumdar , P. Sam Johnson , Ram N. Mohapatra

We identify a class of continuous compactly supported functions for which the known part of the Gabor frame set can be extended. At least for functions with support on an interval of length two, the curve determining the set touches the…

Functional Analysis · Mathematics 2016-02-19 Ole Christensen , Hong Oh Kim , Rae Young Kim

Operator-valued frames (or g-frames) are generalizations of frames and fusion frames and have been used in packets encoding, quantum computing, theory of coherent states and more. In this paper, we give a new formula for operator-valued…

Functional Analysis · Mathematics 2015-04-27 L. Gavruta , P. Gavruta

Frame theory has been rapidly generalized and various generalizations have been developed. In this paper, we present a brief survey of the frames in Hilbert $C^{\ast}$-modules, including frames, $\ast$-frames, g-frames, $\ast$-g-frames,…

Functional Analysis · Mathematics 2022-12-20 M'hamed Ghiati , Mohammed Mouniane , Mohamed Rossafi

We build on our recent results on the Lipschitz dependence of the extreme spectral values of one-parameter families of pseudodifferential operators with symbols in a weighted Sj\"ostrand class. We prove that larger symbol classes lead to…

Functional Analysis · Mathematics 2024-07-26 Karlheinz Gröchenig , José Luis Romero , Michael Speckbacher

We investigate an infinite dimensional analog of the theory of Lagrangian manifolds with complex germs. To such a manifold we assign a canonical operator that depends on creation and annihilation operators. This operator is by definition…

q-alg · Mathematics 2008-02-03 V. P. Maslov , O. Yu. Shvedov

We introduce a new concept of frame operators for Banach spaces we call a Hilbert-Schauder frame operator. This is a hybird between standard frame theory for Hilbert spaces and Schauder frame theory for Banach spaces. Most of our results…

Functional Analysis · Mathematics 2012-06-28 Rui Liu