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X-ray reflection spectroscopy is currently one of the leading techniques for studying the inner part of accretion disks around black holes, measuring black hole spins, and even testing fundamental physics in strong gravitational fields.…

High Energy Astrophysical Phenomena · Physics 2022-10-14 Swarnim Shashank , Shafqat Riaz , Askar B. Abdikamalov , Cosimo Bambi

We present a new evolution system for Einstein's field equations which is based on tetrad fields and conformally compactified hyperboloidal spatial hypersurfaces which reach future null infinity. The boost freedom in the choice of the…

General Relativity and Quantum Cosmology · Physics 2011-06-07 James M. Bardeen , Olivier Sarbach , Luisa T. Buchman

Recent years have seen a significant progress in the development of general relativistic codes for the numerical solution of the equations of magnetohydrodynamics in spacetimes with high and dynamical curvature. These codes are valuable…

High Energy Astrophysical Phenomena · Physics 2024-04-23 Yosuke Mizuno , Luciano Rezzolla

We present an adaptive multiresolution method for the numerical simulation of ideal magnetohydrodynamics in two space dimensions. The discretization uses a finite volume scheme based on a Cartesian mesh and an explicit compact Rung-Kutta…

We prove that spacetime is locally inertial at points of shock wave collision in General Relativity. The result applies for collisions between shock waves coming from different characteristic families, in spherically symmetric spacetimes.…

General Relativity and Quantum Cosmology · Physics 2017-02-08 Moritz Reintjes

We examine the teleparallel formulation of non-minimally coupled scalar Einstein-Gauss-Bonnet gravity. In the teleparallel formulation, gravity is described by torsion instead of curvature, causing the usual Gauss-Bonnet invariant expressed…

General Relativity and Quantum Cosmology · Physics 2023-09-26 Sebastian Bahamonde , Daniela D. Doneva , Ludovic Ducobu , Christian Pfeifer , Stoytcho S. Yazadjiev

We have developed a new computer code, RELDAFNA, to solve the conservative equations of special relativistic hydrodynamics (SRHD) using adaptive mesh refinement (AMR) on parallel computers. We have implemented a characteristic-wise, finite…

High Energy Astrophysical Phenomena · Physics 2023-10-05 Ygal Y. Klein

We present a new adaptive method for electronic structure calculations based on novel fast algorithms for reduction of multivariate mixtures. In our calculations, spatial orbitals are maintained as Gaussian mixtures whose terms are selected…

Numerical Analysis · Mathematics 2019-06-19 Gregory Beylkin , Lucas Monzon , Xinshuo Yang

We present an adaptive-order positivity-preserving conservative finite-difference scheme that allows a high-order solution away from shocks and discontinuities while guaranteeing positivity and robustness at discontinuities. This is…

We develop a new relativistic radiation hydrodynamics code based on the Monte-Carlo algorithm. In this code, we implement a new scheme to achieve the second-order accuracy in time in the limit of a large packet number for solving the…

High Energy Astrophysical Phenomena · Physics 2023-02-15 Kyohei Kawaguchi , Sho Fujibayashi , Masaru Shibata

We present a new framework for statistical inference on Riemannian manifolds that achieves high-order accuracy, addressing the challenges posed by non-Euclidean parameter spaces frequently encountered in modern data science. Our approach…

Statistics Theory · Mathematics 2026-02-03 Chengzhu Huang , Anru R. Zhang

We present a finite-volume, genuinely 4th-order accurate numerical method for solving the equations of resistive relativistic magnetohydrodynamics (Res-RMHD) in Cartesian coordinates. In our formulation, the magnetic field is evolved in…

High Energy Astrophysical Phenomena · Physics 2024-07-12 Andrea Mignone , Vittoria Berta , Marco Rossazza , Matteo Bugli , Giancarlo Mattia , Luca Del Zanna , Lorenzo Pareschi

We describe the special relativistic extension of the CRONOS code, which has been used for studies of gamma-ray binaries in recent years. The code was designed to be easily adaptable, allowing the user to easily change existing…

High Energy Astrophysical Phenomena · Physics 2021-09-29 David Huber , Ralf Kissmann

We investigate the suitability and properties of a quasi-Kinnersley tetrad and a geometrically motivated coordinate system as tools for quantifying both strong-field and wave-zone effects in numerical relativity (NR) simulations. We fix the…

General Relativity and Quantum Cosmology · Physics 2012-12-18 Fan Zhang , Jeandrew Brink , Béla Szilágyi , Geoffrey Lovelace

In computational relativity, critical behaviour near the black hole threshold has been studied numerically for several models in the last decade. In this paper we present a spatial Galerkin method, suitable for finding numerical solutions…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Benedikt Zeller , Ralf Hiptmair

Many problems at the forefront of theoretical astrophysics require the treatment of magnetized fluids in dynamical, strongly curved spacetimes. Such problems include the origin of gamma-ray bursts, magnetic braking of differential rotation…

Astrophysics · Physics 2009-11-10 Matthew D. Duez , Yuk Tung Liu , Stuart L. Shapiro , Branson C. Stephens

Finding constrained saddle points on Riemannian manifolds is significant for analyzing energy landscapes arising in physics and chemistry. Existing works have been limited to special manifolds that admit global regular level-set…

Numerical Analysis · Mathematics 2026-01-16 Yukuan Hu , Laura Grazioli

With the advance of supercomputers we can now afford simulations with very large ranges of scales. In astrophysical applications, e.g. simulating Solar, stellar and planetary atmospheres, interstellar medium, etc; physical quantities, like…

Instrumentation and Methods for Astrophysics · Physics 2025-06-04 Andrius Popovas

We investigate relativistic low angular momentum accretion of inviscid perfect fluid onto a Schwarzschild black hole. The simulations are performed with a general-relativistic, high-resolution (second-order), shock-capturing, hydrodynamical…

General Relativity and Quantum Cosmology · Physics 2018-03-13 Patryk Mach , Michał Piróg , José A. Font

Projected gradient descent and its Riemannian variant belong to a typical class of methods for low-rank matrix estimation. This paper proposes a new Nesterov's Accelerated Riemannian Gradient algorithm by efficient orthographic retraction…

Optimization and Control · Mathematics 2023-06-05 Hongyi Li , Zhen Peng , Chengwei Pan , Di Zhao