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We present an extension to the short-characteristic ray-tracing and non-equilibrium photon-ionization code C2Ray. The new version includes the effects of helium and improved multi-frequency heating. The motivation for this work is to be…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Martina M. Friedrich , Garrelt Mellema , Ilian T. Iliev , Paul R. Shapiro

Three non-equilibrium photoionisation algorithms for hydrodynamical grid-based simulation codes are compared in terms of accuracy, timestepping criteria, and parallel scaling. Explicit methods with first-order time accuracy for photon…

Astrophysics of Galaxies · Physics 2012-03-09 Jonathan Mackey

We present a new numerical method for calculating the transfer of ionizing radiation, called C^2-Ray=Conservative, Causal Ray-tracing method. The method is explicitly photon-conserving, so the depletion of ionizing photons by bound-free…

Astrophysics · Physics 2009-11-11 Garrelt Mellema , Ilian T. Iliev , Marcelo A. Alvarez , Paul R. Shapiro

A technique is presented for producing synthetic images from numerical simulations whereby the image resolution is adapted around prominent features. In so doing, adaptive image ray-tracing (AIR) improves the efficiency of a calculation by…

Instrumentation and Methods for Astrophysics · Physics 2015-05-20 E. R. Parkin

Numerical methods for radiative transfer play a key role in modern-day astrophysics and cosmology, including study of the inhomogeneous reionization process. In this context, ray tracing methods are well-regarded for accuracy but notorious…

Instrumentation and Methods for Astrophysics · Physics 2025-12-16 Nathan X. Marshak , Kathlynn Simotas , Zarija Lukić , Hyunbae Park , James Ahrens , Chris R. Johnson

Crank-Nicolson (C-N) Method combined with $ B $-spline basis set can be used in both time-dependent and time-independent calculations of the photoionization cross sections of atoms and molecules. For time-independent systems, it is found…

Atomic Physics · Physics 2014-09-15 Xue-Bin Bian

We present the methodology of a photon-conserving, spatially-adaptive, ray-tracing radiative transfer algorithm, designed to run on multiple parallel Graphic Processing Units (GPUs). Each GPU has thousands computing cores, making them…

Cosmology and Nongalactic Astrophysics · Physics 2018-10-17 Blake Hartley , Massimo Ricotti

The computation time required by standard finite difference methods with fixed timesteps for solving fractional diffusion equations is usually very large because the number of operations required to find the solution scales as the square of…

Numerical Analysis · Mathematics 2024-06-28 Santos B. Yuste , Joaquin Quintana-Murillo

In this paper, we develop a method for obtaining the approximate solution for the evolution of single-step transformations under non-isothermal conditions. We have applied it to many reaction models and obtained very simple analytical…

Materials Science · Physics 2008-11-11 Jordi Farjas , Pere Roura

Recently, a new framework to compute the photoionization rate in streamer discharges accurately and efficiently using the integral form and the fast multipole method (FMM) was presented. This paper further improves the efficiency of this…

Plasma Physics · Physics 2021-12-21 Bo Lin , Chijie Zhuang

We present a fast adaptive method for the evaluation of heat potentials, which plays a key role in the integral equation approach for the solution of the heat equation, especially in a non-stationary domain. The algorithm utilizes a…

Numerical Analysis · Mathematics 2024-12-06 Chengyue Song , Jun Wang

Particle-in-cell codes are now standard tools for studying ultra-intense laser-plasma interactions. Motivated by direct laser acceleration of electrons in sub-critical plasmas, we examine temporal resolution requirements that must be…

We introduce the correlation-efficient time-evolution (CETE) algorithm for simulating quantum many-body dynamics. CETE recasts each step of time evolution as a time-independent correlation problem: the ansatz begins from a mean-field single…

Quantum Physics · Physics 2025-11-19 Michael Rose , David A. Mazziotti

This work aims to improve the efficiency of text-to-image diffusion models. While diffusion models use computationally expensive UNet-based denoising operations in every generation step, we identify that not all operations are equally…

Computer Vision and Pattern Recognition · Computer Science 2024-02-21 Amirhossein Habibian , Amir Ghodrati , Noor Fathima , Guillaume Sautiere , Risheek Garrepalli , Fatih Porikli , Jens Petersen

One of the most important steps of document image processing is binarization. The computational requirements of locally adaptive binarization techniques make them unsuitable for devices with limited computing facilities. In this paper, we…

Computer Vision and Pattern Recognition · Computer Science 2012-10-12 Ayatullah Faruk Mollah , Subhadip Basu , Mita Nasipuri

We construct a new formulation that allows efficient exploration of steady-state accretion processes onto compact objects. Accretion onto compact objects is a common scenario in astronomy. These systems serve as laboratories to probe the…

High Energy Astrophysical Phenomena · Physics 2023-09-06 Kaho Tse , Alexander Heger , Ryosuke Hirai , Duncan K. Galloway

We review several parallel tempering schemes and examine their main ingredients for accuracy and efficiency. The present study covers two selection methods of temperatures and several choices for the exchange of replicas, including a recent…

Statistical Mechanics · Physics 2015-06-16 A. Malakis , T. Papakonstantinou

A program to compute photo-ionization functions and fitting parameters for an efficient photo-ionization model is presented. The code integrates the product of spectrum emission intensity, the photo-ionization yield and the absorption…

Plasma Physics · Physics 2020-05-21 Yifei Zhu , Yun Wu , Jianzhong Li

We compare numerical methods for solving the radiative transfer equation in the context of the photoionization of intergalactic gaseous hydrogen and helium by a central radiating source. Direct integration of the radiative transfer equation…

Instrumentation and Methods for Astrophysics · Physics 2023-01-18 Ka-Hou Leong , Avery Meiksin , Althea Lai , K. H. To

Precise temperature measurements on systems of few ultracold atoms is of paramount importance in quantum technologies, but can be very resource-intensive. Here, we put forward an adaptive Bayesian framework that substantially boosts the…

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