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We develop two algorithms, based on maximum likelihood (ML) inference, for estimating the parameters of polarized radio sources which emit at a single rotation measure (RM), e.g., pulsars. These algorithms incorporate the flux density…

Instrumentation and Methods for Astrophysics · Physics 2017-10-25 D. H. F. M. Schnitzeler , K. J. Lee

We propose a general algorithm for approximating nonstandard Bayesian posterior distributions. The algorithm minimizes the Kullback-Leibler divergence of an approximating distribution to the intractable posterior distribution. Our method…

Computation · Statistics 2014-07-29 Tim Salimans , David A. Knowles

We present a theoretical framework to model the electric response of cell aggregates. We establish a coarse representation for each cell as a combination of membrane and cytoplasm dipole moments. Then we compute the effective conductivity…

Computational Engineering, Finance, and Science · Computer Science 2020-08-28 Pouria A. Mistani , Samira Pakravan , Frederic G. Gibou

This study reexamines diffusive representations for fractional integrals with the goal of pioneering new variants of such representations. These variants aim to offer highly efficient numerical algorithms for the approximate computation of…

Numerical Analysis · Mathematics 2025-07-08 Renu Chaudhary , Kai Diethelm

This paper is devoted to the error analysis of a time-spectral algorithm for fractional diffusion problems of order $\alpha$ ($0 < \alpha < 1$). The solution regularity in the Sobolev space is revisited, and new regularity results in the…

Numerical Analysis · Mathematics 2021-06-08 Hao Luo , Xiaoping Xie

Equilibrium measures are special invariant measures of chaotic dynamical systems and iterated function systems, commonly studied as salient examples of fractal measures. While useful analytic expressions are rare, computational exploration…

Dynamical Systems · Mathematics 2023-12-19 Caroline L. Wormell

Radio polarimetry is a three-dimensional statistical problem. The three-dimensional aspect of the problem arises from the Stokes parameters Q, U, and V, which completely describe the polarization of electromagnetic radiation and…

Astrophysics of Galaxies · Physics 2015-05-20 M. M. McKinnon

Fourier series multiscale method, a concise and efficient analytical approach for multiscale computation, will be developed out of this series of papers. In the sixth paper, exact analysis of the wave propagation in a beam with rectangular…

Numerical Analysis · Mathematics 2022-08-30 Weiming Sun , Zimao Zhang

An approach for measuring linear X-ray polarization over a broad-band using conventional spectroscopic optics is described. A set of multilayer-coated flats reflect the dispersed X-rays to the instrument detectors. The intensity variation…

Astrophysics · Physics 2009-11-13 Herman L. Marshall

We give a new fast method for evaluating sprectral approximations of nonlinear polynomial functionals. We prove that the new algorithm is convergent if the functions considered are smooth enough, under a general assumption on the spectral…

Numerical Analysis · Mathematics 2012-07-17 Erwan Faou , Fabio Nobile , Christophe Vuillot

Kernel methods represent some of the most popular machine learning tools for data analysis. Since exact kernel methods can be prohibitively expensive for large problems, reliable low-rank matrix approximations and high-performance…

Numerical Analysis · Mathematics 2018-04-17 Jianwei Xiao , Ming Gu

Partial frequency redistribution (PRD), describing the formation of the line profile, has negligible observational effects for optical depths smaller than ~10^3, at the resolving power of most current instruments. However, when the spectral…

Earth and Planetary Astrophysics · Physics 2015-05-27 Roxana E. Lupu , Paul D. Feldman , Stephan R. McCandliss , Darrell F. Strobel

This paper presents new quadrature rules for functions in a reproducing kernel Hilbert space using nodes drawn by a sampling algorithm known as randomly pivoted Cholesky. The resulting computational procedure compares favorably to previous…

Numerical Analysis · Mathematics 2023-12-08 Ethan N. Epperly , Elvira Moreno

The point spread function (PSF) of a translation invariant imaging system is its impulse response, which cannot always be measured directly. This is the case in high energy X-ray radiography, and it must be estimated from images of…

Numerical Analysis · Mathematics 2017-09-27 Kevin T. Joyce , Johnathan M. Bardsley , Aaron Luttman

A novel approach towards the spectral analysis of stationary random bivariate signals is proposed. Using the Quaternion Fourier Transform, we introduce a quaternion-valued spectral representation of random bivariate signals seen as…

Methodology · Statistics 2017-11-22 Julien Flamant , Nicolas Le Bihan , Pierre Chainais

For a variant of the algorithm in [Pit19] (arXiv:1903.10816) to compute the approximate density or distribution function of a linear mixture of independent random variables known by a finite sample, it is presented a proof of the functional…

Statistics Theory · Mathematics 2019-06-19 Thomas Pitschel

The polarization of an X-ray beam that produces electrons with velocity components perpendicular to the beam generates an azimuthal distribution of the ejected electrons. We present methods for simulating and for analyzing the angular…

Instrumentation and Methods for Astrophysics · Physics 2015-03-10 C. G. Montgomery , J. H. Swank

In many practical applications, spatial data are often collected at areal levels (i.e., block data) and the inferences and predictions about the variable at points or blocks different from those at which it has been observed typically…

Computation · Statistics 2020-01-10 Peter Simonson , Douglas Nychka , Soutir Bandyopadhyay

We investigate the oblique incidence of transverse waves on a randomly layered medium in the limit of strong disorder. An approximate method for calculating the inverse localization length based on the assumptions of zero energy flux and…

Disordered Systems and Neural Networks · Physics 2007-05-23 K. Yu. Bliokh , V. D. Freilikher

We study the transmission and reflection of a plane electromagnetic wave through a two dimensional array of rf-SQUIDs. The basic equations describing the amplitudes of the magnetic field and current in the split-ring resonators are…

Optics · Physics 2015-06-23 J. -G. Caputo , I. Gabitov , A. I. Maimistov