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We use the classical Fourier analysis to introduce analytic families of weighted differential operators on the unit sphere. These operators are polynomial functions of the usual Beltrami-Laplace operator. New inversion formulas are obtained…

Functional Analysis · Mathematics 2020-05-12 Boris Rubin

Non-self-adjoint second-order ordinary differential operators on a finite interval with complex weights are studied. Properties of spectral characteristics are established and the inverse problem of recovering operators from their spectral…

Spectral Theory · Mathematics 2024-02-09 V. A. Yurko

A new method is proposed to improve the numeri- cal simulation of time dependent problems when the initial and boundary data are not compatible. Unlike earlier methods limited to space dimension one, this method can be used for any space…

Numerical Analysis · Mathematics 2010-11-23 Qingshan Chen , Zhen Qin , Roger Temam

We use the Unified Transform Method (UTM) for the vector case to resolve an interface problem for the Dirac equation on two semi-infinite domains and two finite domains in the massless and massive cases, respectively. The UTM for the vector…

Analysis of PDEs · Mathematics 2026-05-05 C. A. García-Bibiano

Graph signal processing extends spectral analysis to data supported on irregular domains. Existing fractional transforms for two-dimensional graph signals, including the two-dimensional graph fractional Fourier transform (GFRFT), typically…

Signal Processing · Electrical Eng. & Systems 2026-03-03 Mingzhi Wang , Manjun Cui , Feiyue Zhao , Yangfan He , Zhichao Zhang

The classical Fourier analysis of a time signal, in the discrete sense, provides the frequency content of signal under the assumption of periodicity. Although the original signal can be exactly recovered using an inverse transform, the time…

Fluid Dynamics · Physics 2026-01-06 Vilas J. Shinde

Many real-world problems can be naturally described by mathematical formulas. The task of finding formulas from a set of observed inputs and outputs is called symbolic regression. Recently, neural networks have been applied to symbolic…

Machine Learning · Computer Science 2022-10-24 Martin Vastl , Jonáš Kulhánek , Jiří Kubalík , Erik Derner , Robert Babuška

We describe some recent advances in the numerical solution of acoustic scattering problems. A major focus of the paper is the efficient solution of high frequency scattering problems via hybrid numerical-asymptotic boundary element methods.…

Numerical Analysis · Mathematics 2014-10-23 Simon N. Chandler-Wilde , Stephen Langdon

Fourier transforms are ubiquitous mathematical tools in basic and applied sciences. We here report classical and quantum optical realizations of the discrete fractional Fourier transform, a generalization of the Fourier transform. In the…

This paper establishes an extended representation theorem for unit-root VARs. A specific algebraic technique is devised to recover stationarity from the solution of the model in the form of a cointegrating transformation. Closed forms of…

Econometrics · Economics 2021-02-23 Mario Faliva , Maria Grazia Zoia

We introduce a framework for subspace methods which approximate the spectra of self-adjoint, unbounded operators in a local region. Using the projection-valued measure, we derive integrated spectral inequalities that also apply to unbounded…

Numerical Analysis · Mathematics 2026-01-06 Timothy Stroschein

A new approach for solving stiff boundary value problems for systems of ordinary differential equations is presented. Its idea essentially generalizes and extends that from arXiv:1601.04272v8. The approach can be viewed as a methodology…

Numerical Analysis · Mathematics 2021-11-30 Denys Dragunov

This paper presents a novel boundary-optimized fast Fourier extension algorithm for efficient approximation of non-periodic functions. The proposed methodology constructs periodic extensions through strategic utilization of boundary…

Numerical Analysis · Mathematics 2025-08-27 Z. Y. Zhao , Y. F Wang , A. G. Yagola

We consider a boundary value problem for the parabolic Lam\'e type operator being a linearization of the Navier-Stokes' equations for compressible flow of Newtonian fluids. It consists of recovering a vector-function, satisfying the…

Analysis of PDEs · Mathematics 2019-04-16 R. Puzyrev , A. Shlapunov

We demonstrate an application of the spectral method as a numerical approximation for solving Hyperbolic PDEs. In this method a finite basis is used for approximating the solutions. In particular, we demonstrate a set of such solutions for…

Mathematical Physics · Physics 2008-11-26 P. Pedram , M. Mirzaei , S. S. Gousheh

We present a method to solve initial and boundary value problems using artificial neural networks. A trial solution of the differential equation is written as a sum of two parts. The first part satisfies the boundary (or initial) conditions…

Computational Physics · Physics 2016-11-15 I. E. Lagaris , A. Likas , D. I. Fotiadis

In this article, we study the properties of the nonlinear Fourier spectrum in order to gain better control of the temporal support of the signals synthesized using the inverse nonlinear Fourier transform (NFT). In particular, we provide…

Computational Physics · Physics 2018-09-17 Vishal Vaibhav

We study initial-boundary value problems for linear evolution equations of arbitrary spatial order, subject to arbitrary linear boundary conditions and posed on a rectangular 1-space, 1-time domain. We give a new characterisation of the…

Analysis of PDEs · Mathematics 2015-05-28 David A. Smith

We use a novel parameterization of the flowing Hamiltonian to show that the flow equations based on continuous unitary transformations, as proposed by Wegner, can be implemented through a nonlinear partial differential equation involving…

Other Condensed Matter · Physics 2015-06-24 J. N. Kriel , A. Y. Morozov , F. G. Scholtz

An improved scheme for computing coupling parameters of the Kardar-Parisi-Zhang equation from a collection of successive interface profiles, is presented. The approach hinges on a spectral representation of this equation. An appropriate…

Statistical Mechanics · Physics 2009-10-31 Achille Giacometti , Maurice Rossi