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The Koopman-von Neumann equation describes the evolution of wavefunctions associated with autonomous ordinary differential equations and can be regarded as a quantum physics-inspired formulation of classical mechanics. The main advantage…

Dynamical Systems · Mathematics 2026-04-10 Stefan Klus , Feliks Nüske , Patrick Gelß

The study of resonances of the Schr\"{o}dinger operator has a long-standing tradition in mathematical physics. Extensive theoretical investigations have explored the proximity of resonances to the real axis, their distribution, and bounds…

Numerical Analysis · Mathematics 2025-04-17 Bo Gong , Takumi Sato , Jiguang Sun , Xinming Wu

The space of $(2,0)$ models is of particular interest among all heterotic-string models because it includes the models with the minimal $SO(10)$ unification structure, which is well motivated by the Standard Model of particle physics data.…

High Energy Physics - Theory · Physics 2014-07-09 P. Athanasopoulos , A. E. Faraggi , D. Gepner

We compute, in topological terms, the spectral flow of an arbitrary family of self-adjoint Dirac type operators with classical (local) boundary conditions on a compact Riemannian manifold with boundary under the assumption that the initial…

Analysis of PDEs · Mathematics 2012-10-08 M. I. Katsnelson , V. E. Nazaikinskii

The spectral flow is a well-known quantity in spectral theory that measures the variation of spectra about $0$ along paths of selfadjoint Fredholm operators. The aim of this work is twofold. Firstly, we consider homotopy invariance…

Functional Analysis · Mathematics 2019-10-14 Maciej Starostka , Nils Waterstraat

We offer a spectral analysis for a class of transfer operators. These transfer operators arise for a wide range of stochastic processes, ranging from random walks on infinite graphs to the processes that govern signals and recursive wavelet…

Mathematical Physics · Physics 2018-02-14 Palle E. T. Jorgensen , Myung-Sin Song

In this work we develop a nonlinear decomposition, associated with nonlinear eigenfunctions of the p-Laplacian for p \in (1, 2). With this decomposition we can process signals of different degrees of smoothness. We first analyze solutions…

Analysis of PDEs · Mathematics 2019-09-18 Ido Cohen , Guy Gilboa

Let $A(t)$ be a continuous path of Fredhom operators, we first prove that the spectral flow $sf(A(t))$ is cogredient invariant. Based on this property, we give a decomposition formula of spectral flow if the path is invariant under a…

Functional Analysis · Mathematics 2018-08-14 Xijun Hu , Li Wu

We establish a semiclassical trace formula in a general framework of microhyperbolic hermitian systems of $h$-pseudodifferential operators, and apply it to the study of the spectral shift function associated to a pair of selfadjoint…

Mathematical Physics · Physics 2017-02-28 Marouane Assal , Mouez Dimassi , Setsuro Fujiié

By applying new functional analysis tools in the framework of Fourier interpolation formulas, such as sc-Fredholm operators and Schauder frames, we are able to improve and refine several properties of these aforementioned formulas on the…

Classical Analysis and ODEs · Mathematics 2025-03-21 Gabriele Cassese , João P. G. Ramos

The paper pursues three objectives. Firstly, we provide an expanded version of spectral analysis of self-adjoint Toeplitz operators, initially built by M. Rosenblum in the 1960's. We offer some improvements to Rosenblum's approach: for…

Spectral Theory · Mathematics 2022-01-27 Alexander V. Sobolev , Dmitri Yafaev

The isospectral renormalization group is a powerful method to analyze the spectrum of operators in quantum field theory. It was introduced in 1995 [see \cite{BachFrohlichSigal1995}, \cite{BachFrohlichSigal1998}] and since then it has been…

Mathematical Physics · Physics 2013-08-06 Volker Bach , Miguel Ballesteros , Jürg Fröhlich

We study the phase-space concentration of the so-called generalized metaplectic operators whose main examples are Schr\"odinger equations with bounded perturbations. To reach this goal, we perform a so-called $\mathcal{A}$-Wigner analysis…

Analysis of PDEs · Mathematics 2022-09-15 Elena Cordero , Gianluca Giacchi , Luigi Rodino

A method for approximate solution of initial value and spectral problems for one dimensional Dirac equation based on an analytic approximation of the transmutation operator is presented. In fact the problem of numerical approximation of…

Classical Analysis and ODEs · Mathematics 2021-01-29 Nelson Gutiérrez Jiménez , Sergii M. Torba

Active Flux is an extension of the Finite Volume method and additionally incorporates point values located at cell boundaries. This gives rise to a globally continuous approximation of the solution. Originally, the Active Flux method…

Numerical Analysis · Mathematics 2024-11-26 Rémi Abgrall , Wasilij Barsukow , Christian Klingenberg

This paper is devoted to the Neumann-Kirchhoff Laplacian on a finite metric graph. We prove an index theorem relating the nodal deficiency of an eigenfunction with (1) the Morse index of the Dirichlet-to-Neumann map, (2) its positive index…

Spectral Theory · Mathematics 2025-05-20 Ram Band , Marina Prokhorova , Gilad Sofer

The inverse spectral theory for a self-adjoint one-dimensional Dirac operator associated periodic potentials is formulated via a Riemann-Hilbert problem approach. The resulting formalism is also used to solve the initial value problem for…

Analysis of PDEs · Mathematics 2026-01-12 Gino Biondini , Zechuan Zhang

Dense flow visualization is a popular visualization paradigm. Traditionally, the various models and methods in this area use a continuous formulation, resting upon the solid foundation of functional analysis. In this work, we examine a…

Graphics · Computer Science 2020-07-06 Daniel Preuß , Tino Weinkauf , Jens Krüger

This note is about the topology of the path space of linear Fredholm operators on a real Hilbert space. Fitzpatrick and Pejsachowicz introduced the parity of such a path, based on the Leray-Schauder degree of a path of parametrices. Here an…

Mathematical Physics · Physics 2020-01-22 Nora Doll , Hermann Schulz-Baldes , Nils Waterstraat

To treat the spectral statistics of quantum maps and flows that are fully chaotic classically, we use the rigorous Riemann-Siegel lookalike available for the spectral determinant of unitary time evolution operators $F$. Concentrating on…

Chaotic Dynamics · Physics 2015-06-05 P. Braun , F. Haake