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The generalized maximum entropy method (GMEM) is a special modification of the standard maximum entropy method (MEM) which seeks solutions in the space of complex functions. In this work a reduced version of the GMEM intended for…

Astrophysics · Physics 2015-06-24 Anisa T. Bajkova

We have developed a new software tool, Lensview, for modelling resolved gravitational lens images. Based on the LensMEM algorithm, the software finds the best fitting lens mass model and source brightness distribution using a maximum…

Astrophysics · Physics 2009-11-11 Randall B. Wayth , Rachel L. Webster

Radio polarisation images of the jets of Active Galactic Nuclei (AGN) can provide a deep insight into the launching and collimation mechanisms of relativistic jets. However, even at VLBI scales, resolution is often a limiting factor in the…

Astrophysics of Galaxies · Physics 2016-09-07 Colm P. Coughlan , Denise C. Gabuzda

We have developed a C++ implementation of the Maximum Entropy Method (MEM) suitable for deconvolving VLBI polarisation data. The first results of this implementation are presented and compared with CLEAN-based deconvolutions of the same…

Astrophysics of Galaxies · Physics 2013-07-26 Colm P. Coughlan , Denise C. Gabzuda

The Maximum Entropy Method (MEM) for the deconvolution of radio interferometry images is mathematically well based and presents a number of advantages over the usual CLEAN deconvolution, such as appreciably higher resolution. The…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Colm Coughlan , Denise Gabuzda

The maximum entropy method (MEM) is a well known deconvolution technique in radio-interferometry. This method solves a non-linear optimization problem with an entropy regularization term. Other heuristics such as CLEAN are faster but highly…

Instrumentation and Methods for Astrophysics · Physics 2022-10-27 M. Cárcamo , P. Román , S. Casassus , V. Moral , F. R. Rannou

The challenge in weak gravitational lensing caused by galaxies and clusters is to infer the projected mass density distribution from gravitational lensing measurements, known as the inversion problem. We introduce a novel theoretical…

Instrumentation and Methods for Astrophysics · Physics 2025-10-06 Jan Jakob , Björn Malte Schäfer

The finite-size effect in gravitational microlensing provides a possibility to measure the limb darkening of distant stars. We use the Finite Element Method (FEM) as an inversion tool for discretization and inversion of the…

Solar and Stellar Astrophysics · Physics 2020-03-25 L. Golchin , S. Rahvar

We discuss the LensClean algorithm which for a given gravitational lens model fits a source brightness distribution to interferometric radio data in a similar way as standard Clean does in the unlensed case. The lens model parameters can…

Astrophysics · Physics 2016-08-30 O. Wucknitz

Over the past decade, the gravitational lensing of the Cosmic Microwave Background (CMB) has become a powerful tool for probing the matter distribution in the Universe. The standard technique used to reconstruct the CMB lensing signal…

Cosmology and Nongalactic Astrophysics · Physics 2020-06-02 Boryana Hadzhiyska , Blake D. Sherwin , Mathew Madhavacheril , Simone Ferraro

An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to…

Medical Physics · Physics 2009-11-11 A Jannetta , J C Jackson , C J Kotre , I P Birch , K J Robson , R Padgett

Mapping the relativistic jets emanating from AGN requires the use of a deconvolution algorithm to account for the effects of missing baseline spacings. The CLEAN algorithm is the most commonly used algorithm in VLBI imaging today and is…

Instrumentation and Methods for Astrophysics · Physics 2015-06-17 Colm P. Coughlan , Denise C. Gabuzda

Imaging interferometric data in radio astronomy requires the use of non-linear algorithms that rely on different assumptions on the source structure and may produce non-unique results. This is especially true for Very Long Baseline…

Instrumentation and Methods for Astrophysics · Physics 2024-01-19 A. Mus , I. Martí-Vidal

We demonstrate that the maximum-entropy method for gravitational lens reconstruction presented in Bridle et al. (1998) may be applied even when only shear \emph{or} magnification information is present. We also demonstrate that the method…

Astrophysics · Physics 2007-05-23 S. L. Bridle , M. P. Hobson , Richard Saunders , A. N. Lasenby

Gravitational lenses offer the possibility of accurately determining the Hubble parameter (H_0) over cosmological distances, and B0218+357 is one of the most promising systems for an application of this technique. In particular this system…

Astrophysics · Physics 2007-05-23 A. D. Biggs , I. W. A. Browne , T. W. B. Muxlow , P. N. Wilkinson

Unwanted nonlinear gamma distortion frequently occurs in a great diversity of images during the procedures of image acquisition, processing, and/or display. And the gamma distortion often varies with capture setup change and luminance…

Image and Video Processing · Electrical Eng. & Systems 2021-12-08 Yong Lee , Shaohua Zhang , Miao Li , Xiaoyu He

The wavelet Maximum Entropy on the Mean (wMEM) approach to the MEG inverse problem is revisited and extended to infer brain activity from full space-time data. The resulting dimensionality increase is tackled using a collection of…

Machine Learning · Statistics 2018-07-25 Marie-Christine Roubaud , Jean-Marc Lina , Julie Carrier , B Torrésani

The paper addresses the problem to estimate the power spectral density of an ARMA zero mean Gaussian process. We propose a kernel based maximum entropy spectral estimator. The latter searches the optimal spectrum over a class of high order…

Optimization and Control · Mathematics 2020-04-30 Mattia Zorzi

We have developed a new technique called Direct Shear Mapping (DSM) to measure gravitational lensing shear directly from observations of a single background source. The technique assumes the velocity map of an un-lensed, stably-rotating…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-26 Catherine O. de Burgh-Day , Edward N. Taylor , Rachel L. Webster , Andrew M. Hopkins

We propose a new, two-stage algorithm for inverting strong gravitational lenses. The key to the algorithm is decoupling the effects of lens magnification and intrinsic structure in the background source in the appearance of lensed arcs.…

Astrophysics · Physics 2007-05-23 P. Newbury , G. G. Fahlman
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