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The Heisenberg-Euler Lagrangian is not only a topic of fundamental interest, but also has a rich variety of diverse applications in astrophysics, nonlinear optics and elementary particle physics etc. We discuss the series representation of…

High Energy Physics - Phenomenology · Physics 2009-11-10 S. R. Valluri , U. D. Jentschura , D. R. Lamm

We deal with the solution of a generic linear inverse problem in the Hilbert space setting. The exact right hand side is unknown and only accessible through discretised measurements corrupted by white noise with unknown arbitrary…

Numerical Analysis · Mathematics 2023-02-14 Bastian Harrach , Tim Jahn , Roland Potthast

We study the existence and uniqueness of solutions of a nonlinear integro-differential problem which we reformulate introducing the notion of the decreasing rearrangement of the solution. A dimensional reduction of the problem is obtained…

Computer Vision and Pattern Recognition · Computer Science 2024-01-29 Gonzalo Galiano , Emanuele Schiavi , Julián Velasco

This computer science master thesis aims at modelling the nonlinearities of a loudspeaker. A piecewise linear approximation is initially explored and then we present a nonlinear Volterra model to simulate the behavior of the system. The…

Sound · Computer Science 2017-03-02 Alessandro Loriga

This letter announces and summarizes results obtained in arXiv:1111.5051 and considers several natural extensions. The aforementioned paper proposes a procedure to reconstruct coefficients in a second-order, scalar, elliptic equation from…

Analysis of PDEs · Mathematics 2012-03-07 Guillaume Bal , Gunther Uhlmann

This note is devoted to inverse spectral problems for canonical Hamiltonian systems on the half-line. An approach to inverse spectral problems based on the use of truncated Toeplitz operators has been especially effective in the case when…

Spectral Theory · Mathematics 2024-08-16 Alexei Poltoratski , Ashley Ran Zhang

In this note we study inverse spectral problems for canonical Hamiltonian systems, which encompass a broad class of second order differential equations on a half-line. Our goal is to extend the classical resultss developed in the work of…

Spectral Theory · Mathematics 2023-05-25 Nikolai Makarov , Alexei Poltoratski

Quantitative image reconstruction in photoacoustic tomography requires the solution of a coupled physics inverse problem involvier light transport and acoustic wave propagation. In this paper we address this issue employing the radiative…

Analysis of PDEs · Mathematics 2017-02-16 Markus Haltmeier , Lukas Neumann , Linh V. Nguyen , Simon Rabanser

Errors in the data and the forward operator of an inverse problem can be handily modelled using partial order in Banach lattices. We present some existing results of the theory of regularisation in this novel framework, where errors are…

Computer Vision and Pattern Recognition · Computer Science 2018-08-15 Artur Gorokh , Yury Korolev , Tuomo Valkonen

The paper studies inverse problems of determining unknown coefficients in various semi-linear and quasi-linear wave equations. We introduce a method to solve inverse problems for non-linear equations using interaction of three waves, that…

Analysis of PDEs · Mathematics 2023-05-10 Ali Feizmohammadi , Matti Lassas , Lauri Oksanen

In this article the correctness of al inear inverse problem with semi-nonlocal boundary conditions for a three-dimensional equation in a parallelepiped is considered. The equation itself is a fourth order mixed type equation of the second…

Analysis of PDEs · Mathematics 2024-07-24 Sirojiddin Dzhamalov , Bakhtiyor Khalkhadzhaev

The Levenberg-Marquardt algorithm is one of the most popular algorithms for finding the solution of nonlinear least squares problems. Across different modified variations of the basic procedure, the algorithm enjoys global convergence, a…

Optimization and Control · Mathematics 2020-04-08 E. Bergou , Y. Diouane , V. Kungurtsev

We develop a numerical method for solving a system of nonlinear integral equations involving two integral terms: at the current time t, one integral is taken from 0 to t, and a different integral is taken from t to infinity. We prove the…

Numerical Analysis · Mathematics 2008-09-15 S. A. Belbas

Diffraction tomography is a noninvasive technique that estimates the refractive indices of unknown objects and involves an inverse-scattering problem governed by the wave equation. Recent works have shown the benefit of nonlinear models of…

Image and Video Processing · Electrical Eng. & Systems 2021-07-09 Tao Hong , Thanh-an Pham , Eran Treister , Michael Unser

Finite linear least squares is one of the core problems of numerical linear algebra, with countless applications across science and engineering. Consequently, there is a rich and ongoing literature on algorithms for solving linear least…

Numerical Analysis · Mathematics 2021-10-27 Paz Fink Shustin , Haim Avron

In this paper, we consider the imaging problem of terahertz (THz) tomography, in particular as it appears in non-destructive testing. We derive a nonlinear mathematical model describing a full THz tomography experiment, and consider linear…

Numerical Analysis · Mathematics 2020-10-29 Simon Hubmer , Alexander Ploier , Ronny Ramlau , Peter Fosodeder , Sandrine van Frank

Our work concerns the study of inverse problems of heat and wave equations involving the fractional Laplacian operator with zeroth order nonlinear perturbations. We recover nonlinear terms in the semilinear equations from the knowledge of…

Analysis of PDEs · Mathematics 2023-08-10 Pu-Zhao Kow , Shiqi Ma , Suman Kumar Sahoo

This paper investigates the structure of fully nonlinear equations and their applications to geometric problems. We solve some fully nonlinear version of the Loewner-Nirenberg and Yamabe problems. Notably, we introduce Morse theory…

Analysis of PDEs · Mathematics 2025-03-25 Rirong Yuan

In tomographic reconstruction, the goal is to reconstruct an unknown object from a collection of line integrals. Given a complete sampling of such line integrals for various angles and directions, explicit inverse formulas exist to…

Numerical Analysis · Mathematics 2018-01-18 Tristan van Leeuwen , Simon Maretzke , K. Joost Batenburg

Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is…