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Numerical methods have become a powerful tool for research in astrophysics, but their utility depends critically on the availability of suitable simulation codes. This calls for continuous efforts in code development, which is necessitated…

Instrumentation and Methods for Astrophysics · Physics 2021-08-19 Volker Springel , Rüdiger Pakmor , Oliver Zier , Martin Reinecke

In the macroscopic gravity approach to the averaging problem in cosmology, the Einstein field equations on cosmological scales are modified by appropriate gravitational correlation terms. We present exact cosmological solutions to the…

General Relativity and Quantum Cosmology · Physics 2009-11-11 A. A. Coley , N. Pelavas , R. M. Zalaletdinov

In order to reduce the computational cost of the simulation of electromagnetic responses in geophysical settings that involve highly heterogeneous media, we develop a multiscale finite volume method with oversampling for the quasi-static…

Computational Physics · Physics 2016-10-10 Luz Angelica Caudillo Mata , Eldad Haber , Christoph Schwarzbach

Gaussian random fields have been one of the most popular tools for analyzing spatial data. However, many geophysical and environmental processes often display non-Gaussian characteristics. In this paper, we propose a new class of spatial…

Applications · Statistics 2017-10-03 Minjie Fan , Debashis Paul , Thomas C. M. Lee , Tomoko Matsuo

We propose to study the behavior of complicated numerical solutions to Einstein's equations for generic cosmologies by following the geodesic motion of a swarm of test particles. As an example, we consider a cylinder of test particles…

General Relativity and Quantum Cosmology · Physics 2009-10-22 B. K. Berger , D. Garfinkle , V. Swamy

A new numerical method is presented for solving the rotating shallow water equations on a rotating sphere using quasi-uniform polygonal meshes. The method uses special families of finite element function spaces to mimic key mathematical…

Numerical Analysis · Mathematics 2015-06-23 John Thuburn , Colin J. Cotter

In this article, we present new computational realizations of principal geodesic analysis for the unit sphere $S^2$ and the special orthogonal group $SO(3)$. In particular, we address the construction of long-time smooth lifts across…

Dynamical Systems · Mathematics 2023-04-26 Cristian C. Gebhardt , Jenny Schubert , Marc C. Steinbach

We consider membranes as fluid deformable surface and allow for higher order geometric terms in the bending energy. The evolution equations are derived and numerically solved using surface finite elements. The higher order geometric terms…

Soft Condensed Matter · Physics 2024-12-19 Jan Magnus Sischka , Ingo Nitschke , Axel Voigt

Solutions to the field equations of the Nonsymmetric Gravitational Theory with $g_[i0] = 0$ are obtained for the homogeneous, plane-symmetric, time-dependent case, both in vacuum and in the presence of a perfect fluid. Cosmological…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Pierre Savaria

It has been extensively studied in the literature that solving Maxwell equations is very sensitive to the mesh structure, space conformity and solution regularity. Roughly speaking, for almost all the methods in the literature, optimal…

Numerical Analysis · Mathematics 2023-07-10 Chunyu Chen , Ruchi Guo , Huayi Wei

We present a new $hp$-version space-time discontinuous Galerkin (dG) finite element method for the numerical approximation of parabolic evolution equations on general spatial meshes consisting of polygonal/polyhedral (polytopic) elements,…

Numerical Analysis · Mathematics 2024-11-07 Andrea Cangiani , Zhaonan Dong , Emmanuil H. Georgoulis

We develop a new, efficient, and accurate method to simulate frequency-domain borehole electromagnetic (EM) measurements acquired in the presence of three-dimensional (3D) variations of the anisotropic subsurface conductivity. The method is…

In this paper, we propose a unified algorithmic framework for solving many known variants of \mds. Our algorithm is a simple iterative scheme with guaranteed convergence, and is \emph{modular}; by changing the internals of a single…

Machine Learning · Computer Science 2010-03-31 Arvind Agarwal , Jeff M. Phillips , Suresh Venkatasubramanian

LLM pre-training efficacy increasingly depends on data composition rather than sheer volume. Yet, optimal mixing is hindered by categorization flaws: human taxonomies suffer from ontological misalignment, and Euclidean clustering fails to…

Machine Learning · Computer Science 2026-05-27 Yue Min , Ziyun Qiao , Ruining Chen , Yujun Li

This paper concerns models and convergence principles for dealing with stochasticity in a wide range of algorithms arising in nonlinear analysis and optimization in Hilbert spaces. It proposes a flexible geometric framework within which…

Optimization and Control · Mathematics 2026-02-17 Patrick L. Combettes , Javier I. Madariaga

It has been shown that the Cauchy problem for geodesics in the space of K\"ahler metrics with a fixed cohomology class on a compact complex manifold $M$ can be effectively reduced to the problem of finding the flow of a related hamiltonian…

Symplectic Geometry · Mathematics 2019-09-10 José Mourão , João P. Nunes , Tomás Reis

We investigate the three-dimensional structure of the pulsar magnetosphere through time-dependent numerical simulations of a magnetic dipole that is set in rotation. We developed our own Eulerian finite difference time domain numerical…

Astrophysics · Physics 2009-11-13 Constantinos Kalapotharakos , Ioannis Contopoulos

Astrophysical accretion discs that carry a significant mass compared with their central object are subject to the effect of self-gravity. In the context of circumstellar discs, this can, for instance, cause fragmentation of the disc gas,…

Earth and Planetary Astrophysics · Physics 2024-07-17 Oliver Gressel , Udo Ziegler

The present paper is devoted to investigating the possibility of getting stellar interiors for ultra-dense compact spherical systems portraying an anisotropic matter distribution employing the gravitational decoupling by means of Minimal…

General Relativity and Quantum Cosmology · Physics 2020-03-12 S. K. Maurya , Abdelghani Errehymy , Ksh. Newton Singh , Francisco Tello-Ortiz , Mohammed Daoud

Higher dimensional solutions are obtained for a homogeneous, spatially isotropic cosmological model in Wesson theory of gravitation. Some cosmological parameter are also calculated for this model.

General Relativity and Quantum Cosmology · Physics 2007-05-23 G. S. Khadekar , Shilpa Samdurkar
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