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A new model to describe the dynamics of particles undergoing diffusion in general relativity is proposed. The evolution of the particle system is described by a Fokker-Planck equation without friction on the tangent bundle of spacetime. It…

General Relativity and Quantum Cosmology · Physics 2015-05-28 Simone Calogero

We present the energy density and flux distribution of a heavy quark moving through high temperature QCD plasmas and compare them with those in the strongly coupled N = 4 SYM plasma. The Boltzmann equation is reformulated as a Fokker-Planck…

Nuclear Theory · Physics 2011-10-05 Juhee Hong

The development of radiation hydrodynamical methods that are able to follow gas dynamics and radiative transfer self-consistently is key to the solution of many problems in numerical astrophysics. Such fluid flows are highly complex, rarely…

Diffusive shock acceleration is a prominent mechanism for producing energetic particles in space and in astrophysical systems. Such energetic particles have long been predicted to affect the hydrodynamic structure of the shock, in turn…

High Energy Astrophysical Phenomena · Physics 2020-12-16 Damiano Caprioli , Colby C. Haggerty , Pasquale Blasi

A possible way to calculate particle spectra as a function of position in pulsar wind nebulae is to solve a Fokker-Planck transport equation. This paper presents numerical solutions to the transport equation with the processes of…

High Energy Astrophysical Phenomena · Physics 2013-09-24 M. J. Vorster , H. Moraal

The nuclei fraction in cosmic rays (CR) far exceeds the fraction of other CR species, such as antiprotons, electrons, and positrons. Thus the majority of information obtained from CR studies is based on interpretation of isotopic abundances…

Astrophysics · Physics 2009-11-10 I. V. Moskalenko , A. W. Strong , S. G. Mashnik

This work investigates the evolution of the distribution of charged particles due to the mechanism of stochastic turbulent acceleration (STA) in presence of small-scale turbulence with a mean magnetic field. STA is usually modelled as a…

High Energy Astrophysical Phenomena · Physics 2023-07-19 Sayan Kundu , Nishant Singh , Bhargav Vaidya

Computational fluid dynamics is a crucial tool to theoretically explore the cosmos. In the last decade, we have seen a substantial methodological diversification with a number of cross-fertilizations between originally different methods.…

Instrumentation and Methods for Astrophysics · Physics 2023-01-25 Stephan Rosswog

Resolving the most fundamental questions in cosmology requires simulations that match the scale, fidelity, and physical complexity demanded by next-generation sky surveys. To achieve the realism needed for this critical scientific…

We develop a spectrally accurate numerical method to compute solutions of a model partial differential equation used in plasma physics to describe diffusion in velocity space due to Fokker-Planck collisions. The solution is represented as a…

Classical Analysis and ODEs · Mathematics 2015-03-18 Jon Wilkening , Antoine Cerfon

Atmospheric escape is crucial to understand the evolution of planets in and out of the Solar system and to interpret atmospheric observations. While hydrodynamic escape simulations have been actively developed incorporating detailed…

Earth and Planetary Astrophysics · Physics 2024-02-27 Yuichi Ito , Tatsuya Yoshida , Akifumi Nakayama

Recent precise measurements of cosmic ray (CR) spectra show that the energy distribution of protons is softer than those of heavier nuclei, and there are spectral hardenings for all nuclear compositions above $\sim$200 GV. Models proposed…

High Energy Astrophysical Phenomena · Physics 2017-08-02 Yiran Zhang , Siming Liu , Qiang Yuan

Resonant scattering of energetic protons off magnetic irregularities is the main process in cosmic ray diffusion. The typical theoretical description uses Alfven waves in the low frequency limit. We demonstrate that the usage of…

Solar and Stellar Astrophysics · Physics 2014-05-09 Cedric Schreiner , Felix Spanier

The gyro-resonant cosmic-ray (CR) streaming instability is believed to play a crucial role in CR transport, leading to growth of Alfv\'en waves at small scales that scatter CRs, and impacts the interaction of CRs with the ISM on large…

High Energy Astrophysical Phenomena · Physics 2019-05-15 Xue-Ning Bai , Eve C. Ostriker , Illya Plotnikov , James M. Stone

We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV-TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-MHD galaxy simulations with star formation and…

High Energy Astrophysical Phenomena · Physics 2023-08-29 Philip F. Hopkins , Iryna S. Butsky , Georgia V. Panopoulou , Suoqing Ji , Eliot Quataert , Claude-Andre Faucher-Giguere , Dusan Keres

Numerical modeling of galactic cosmic rays (GCRs) penetration through the heliosphere to the vicinity of the Sun is considered. Galactic cosmic rays are charged particles with energies exceeding 10 MeV/nucl., originating from far beyond the…

High Energy Astrophysical Phenomena · Physics 2025-09-04 D. A. Shestakov , V. V. Izmodenov

The diffusion forecasting is a nonparametric approach that provably solves the Fokker-Planck PDE corresponding to It\^o diffusion without knowing the underlying equation. The key idea of this method is to approximate the solution of the…

Numerical Analysis · Mathematics 2018-01-17 John Harlim , Haizhao Yang

An analytic solution for a Fokker-Planck equation that describes propagation of energetic particles through a scattering medium is obtained. The solution is found in terms of an infinite series of mixed moments of particle distribution. The…

High Energy Astrophysical Phenomena · Physics 2017-02-01 M. A. Malkov

More and more observations have indicated the existence of slow diffusion phenomena in astrophysical environments, such as around the supernova remnants and pulsar $\gamma$-ray halos, where the diffusion coefficient of cosmic rays (CRs)…

High Energy Astrophysical Phenomena · Physics 2025-06-24 Yawen Xiao , Jianfu Zhang , Siyao Xu

Cosmic rays (CRs) are an important source of feedback in a variety of astrophysical contexts. Magneto-hydrodynamical (MHD) simulations treating CRs as a fluid have shown that how their feedback operates is strongly dependent on their…

Astrophysics of Galaxies · Physics 2025-09-25 Joki Rosdahl , Yohan Dubois , Benoit Commercon , Nimatou Diallo , Nai Chieh Lin , Alexandre Marcowith