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Scalar wave scattering by many small particles of arbitrary shapes with impedance boundary condition is studied. The problem is solved asymptotically and numerically under the assumptions a << d << lambda, where k = 2pi/lambda is the wave…

Numerical Analysis · Mathematics 2016-02-16 Alexander Ramm , Nhan Tran

In several recent works \cite{Causley2013a}, \cite{Causley2013}, we developed a new second order, A-stable approach to wave propagation problems based on the method of lines transpose (MOL$^T$) formulation combined with alternating…

Numerical Analysis · Mathematics 2013-08-15 Matthew F. Causley , Andrew J. Christlieb

We present a unified treatment of the Fourier spectra of spherically symmetric nonlocal diffusion operators. We develop numerical and analytical results for the class of kernels with weak algebraic singularity as the distance between source…

Numerical Analysis · Mathematics 2019-09-04 Yu Li , Richard Mikael Slevinsky

We present 2D Monte Carlo radiative transfer simulations of prestellar cores. We consider two types of asymmetry: disk-like asymmetry, in which the core is denser towards the equatorial plane than towards the poles; and axial asymmetry, in…

Astrophysics · Physics 2009-11-10 D. Stamatellos , A. P. Whitworth , P. Andre , D. Ward-Thompson

We use 2n streams, where n is an integer, of axially symmetric radiation to solve the equation of transfer for a layered medium. This is a generalization of Schuster's classic 2 stream model. As is well known, using only the first 2n…

Atmospheric and Oceanic Physics · Physics 2022-06-03 W. A. van Wijngaarden , W. Happer

We consider the two dimensional quantitative imaging problem of recovering a radiative source inside an absorbing and scattering medium from knowledge of the outgoing radiation measured at the boundary. The medium has an anisotropic…

Numerical Analysis · Mathematics 2021-01-21 Hiroshi Fujiwara , Kamran Sadiq , Alexandru Tamasan

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The…

Plasma Physics · Physics 2009-09-25 N. A. Zabotin , A. G. Bronin

Radiation transport plays a crucial role in star formation models, as certain questions within this field cannot be accurately addressed without taking it into account. Given the high complexity of the interstellar medium from which stars…

Instrumentation and Methods for Astrophysics · Physics 2024-03-11 Richard Wünsch

We discuss work toward developing a 2.5D non-LTE radiative transfer code. Our code uses the short characteristic method with modifications to handle realistic 3D wind velocities. We also designed this code for parallel computing facilities…

Astrophysics · Physics 2007-05-23 J. Zsargo , D. J. Hillier , L. N. Georgiev

The radiative transport of photons through arbitrary three-dimensional (3D) structures of dust is a challenging problem due to the anisotropic scattering of dust grains and strong coupling between different spatial regions. The radiative…

Astrophysics of Galaxies · Physics 2017-07-19 K. D. Gordon , M. Baes , S. Bianchi , P. Camps , M. Juvela , R. Kuiper , T. Lunttila , K. A. Misselt , G. Natale , T. Robitaille , J. Steinacker

Many astrophysical phenomena exhibit relativistic radiative flows. While velocities in excess of $v \sim 0.1c$ can occur in these systems, it has been common practice to approximate radiative transfer to $\cO(v/c)$. In the case of neutrino…

Astrophysics · Physics 2007-05-23 Christian Y. Cardall , Eric J. Lentz , Anthony Mezzacappa

We introduce the radiative transfer code Sweep for the cosmological simulation suite Arepo. Sweep is a discrete ordinates method in which the radiative transfer equation is solved under the infinite speed of light, steady state assumption…

Instrumentation and Methods for Astrophysics · Physics 2023-01-25 Toni Peter , Ralf S. Klessen , Guido Kanschat , Simon C. O. Glover , Peter Bastian

Since the mass of the electron is very small relative to atomic masses, Thomson scattering of low-energy photons ($h\nu \ll m_ec^2$) produces thermal Doppler frequency shifts that are much larger than atomic Doppler widths. A method is…

Astrophysics · Physics 2011-05-23 G. B. Rybicki , D. G. Hummer

Motivated by observational and theoretical work which both suggest very small scale ($\lesssim 1\,$pc) structure in the circum-galactic medium of galaxies and in other environments, we study Lyman-$\alpha$ (Ly$\alpha$) radiative transfer in…

Astrophysics of Galaxies · Physics 2017-11-22 Max Gronke , Mark Dijkstra , Michael McCourt , S. Peng Oh

Two-frequency radiative transfer (2f-RT) theory is developed for classical waves in random media. Depending on the ratio of the wavelength to the scale of medium fluctuation 2f-RT equation is either a Boltzmann-like integral equation with a…

Optics · Physics 2009-11-13 Albert C. Fannjiang

This paper presents a neural network approach for solving two-dimensional optical tomography (OT) problems based on the radiative transfer equation. The mathematical problem of OT is to recover the optical properties of an object based on…

Computational Physics · Physics 2019-10-14 Yuwei Fan , Lexing Ying

We present benchmark problems and solutions for the continuum radiative transfer (RT) in a 2D disk configuration. The reliability of three Monte-Carlo and two grid-based codes is tested by comparing their results for a set of well-defined…

Astrophysics · Physics 2009-11-10 I. Pascucci , S. Wolf , J. Steinacker , C. P. Dullemond , Th. Henning , G. Niccolini , P. Woitke , B. Lopez

Thermal radiative transfer models physical phenomena ranging from supernovas in astrophysics to radiation from a hohlraum striking a fusion target in plasma physics. Transport and absorption of particles in radiative transfer at different…

Numerical Analysis · Mathematics 2026-02-20 Chinmay Patwardhan , Jonas Kusch

We consider the numerical approximation of boundary conditions in radiative transfer problems by a perfectly matched layer approach. The main idea is to extend the computational domain by an absorbing layer and to use an appropriate…

Numerical Analysis · Mathematics 2018-02-26 Herbert Egger , Matthias Schlottbom

In the present paper we describe a simple black box algorithm for efficiently and accurately solving scattering problems related to the scattering of time-harmonic waves from radially-symmetric potentials in two dimensions. The method uses…

Numerical Analysis · Mathematics 2020-08-03 Jeremy Hoskins , Vladimir Rokhlin