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We present a general method for studying long time asymptotics of nonlinear parabolic partial differential equations. The method does not rely on a priori estimates such as the maximum principle. It applies to systems of coupled equations,…

chao-dyn · Physics 2008-02-03 J. Bricmont , A. Kupiainen , G. Lin

Detection of point sources in images is a fundamental operation in astrophysics, and is crucial for constraining population models of the underlying point sources or characterizing the background emission. Standard techniques fall short in…

Instrumentation and Methods for Astrophysics · Physics 2018-02-28 Tansu Daylan , Stephen K. N. Portillo , Douglas P. Finkbeiner

This paper describes a linear solution method for near-light photometric stereo by exploiting symmetric light source arrangements. Unlike conventional non-convex optimization approaches, by arranging multiple sets of symmetric nearby light…

Computer Vision and Pattern Recognition · Computer Science 2026-03-18 Lilika Makabe , Heng Guo , Hiroaki Santo , Fumio Okura , Yasuyuki Matsushita

The increased sensitivity of future radio telescopes will result in requirements for higher dynamic range within the image as well as better resolution and immunity to interference. In this paper we propose a new matrix formulation of the…

Astrophysics · Physics 2014-11-18 Chen Ben-David , Amir Leshem

Based on luminosity contributions, we develop a spectroscopic modelling method to derive atmospheric parameters of component stars in binary systems. The method is designed for those spectra of binaries which show double-lined features due…

Solar and Stellar Astrophysics · Physics 2023-03-15 Xiang-Lei Chen , A-Li Luo , Jian-Jun Chen , Rui Wang , Xiao-Bin Zhang , Wen Hou , Bo Qiu , Fang Zuo

Determining the equation of state of matter at nuclear density and hence the structure of neutron stars has been a riddle for decades. We show how the imminent detection of gravitational waves from merging neutron star binaries can be used…

General Relativity and Quantum Cosmology · Physics 2014-09-05 Kentaro Takami , Luciano Rezzolla , Luca Baiotti

In this work we address the problem of simultaneous multi-frequency detection of extragalactic point sources in maps of the Cosmic Microwave Background. We apply a new linear filtering technique, the so called `matched matrix filters', that…

Astrophysics · Physics 2009-11-13 D. Herranz , M. Lopez-Caniego , J. L. Sanz , J. Gonzalez-Nuevo

A fundamental assumption adopted in nearly every extragalactic emission-line study is that the attenuation of different emission lines can be described by a single attenuation curve. Here we show this assumption fails in many cases with…

In this paper, a mathematical model is developed to describe the evolution of the concentration of compounds through a gas chromatography column. The model couples mass balances and kinetic equations for all components. Both single and…

Computational Engineering, Finance, and Science · Computer Science 2025-01-03 A. Cabrera-Codony , A. Valverde , K. Born , O. A. I. Noreldin , T. G. Myers

*Context: The optimisation of new multiplex spectrographs (resolution, wavelength range,...), their associated surveys (choice of setup), or their parameterisation pipelines require methods that estimate which wavelengths contain useful…

Instrumentation and Methods for Astrophysics · Physics 2023-06-14 Georges Kordopatis , Vanessa Hill , Karin Lind

We implement a simple, main beam correction in the maximum-likelihood, parametric component separation approach, which allows on accounting for different beamwidths of input maps at different frequencies without any preprocessing. We…

Cosmology and Nongalactic Astrophysics · Physics 2025-05-19 Arianna Rizzieri , Josquin Errard , Radek Stompor

The Neumann--Neumann method is a commonly employed domain decomposition method for linear elliptic equations. However, the method exhibits slow convergence when applied to semilinear equations and does not seem to converge at all for…

Numerical Analysis · Mathematics 2023-12-19 Emil Engström , Eskil Hansen

Ill-posed inverse problems are common in astronomy, and their solutions are unstable with respect to noise in the data. Solutions of such problems are typically found using two classes of methods: parametrization and fitting the data…

Instrumentation and Methods for Astrophysics · Physics 2021-12-17 Damir Gasymov , Ivan Katkov

The observation of a stable doublet pattern in the field-emission electron microscopy of a linear atomic chain requires a stable mechanism breaking the axial symmetry, which is not identified correctly by Mikhailovskij et al. [Phys. Rev. B…

Mesoscale and Nanoscale Physics · Physics 2015-05-18 Nicola Manini , Giovanni Onida

We report an extension of the source imaging method for imaging full three-dimensional sources from three-dimensional like-pair correlations. Our technique consists of expanding the correlation data and the underlying source function in…

Nuclear Theory · Physics 2007-05-23 David A. Brown , Pawel Danielewicz , Mike Heffner , Ron Soltz

Compressed Sensing suggests that the required number of samples for reconstructing a signal can be greatly reduced if it is sparse in a known discrete basis, yet many real-world signals are sparse in a continuous dictionary. One example is…

Information Theory · Computer Science 2015-07-24 Yuanxin Li , Yuejie Chi

All 21-cm signal experiments rely on electronic receivers that affect the data via both multiplicative and additive biases through the receiver's gain and noise temperature. While experiments attempt to remove these biases, the residuals of…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-14 Keith Tauscher , David Rapetti , Bang D. Nhan , Alec Handy , Neil Bassett , Joshua Hibbard , David Bordenave , Richard F. Bradley , Jack O. Burns

We show that nonlinear imaging is possible in periodic waveguide configurations provided that we use two different segments of nonlinear media with opposite signs of the Kerr nonlinearity with, in general, no other restriction about their…

Optics · Physics 2017-03-08 Nikolaos K. Efremidis , Mihalis Mparkas

Differential optical absorption spectroscopy (DOAS) is a powerful tool for detecting and quantifying trace gases in atmospheric chemistry \cite{Platt_Stutz08}. DOAS spectra consist of a linear combination of complex multi-peak multi-scale…

Numerical Analysis · Mathematics 2011-09-30 Y. Sun , L. M. Wingen , B. J. Finlayson-Pitts , J. Xin

The ringdown phase following a binary black hole merger is usually assumed to be well described by a linear superposition of complex exponentials (quasinormal modes). In the strong-field conditions typical of a binary black hole merger,…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Emanuele Berti , Vitor Cardoso , Jose A. Gonzalez , Ulrich Sperhake