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We model the thermodynamics of local structures within the hard sphere liquid at arbitrary volume fractions through the \textit{morphometric} calculation of $n$-body correlations. We calculate absolute free energies of local geometric…

Statistical Mechanics · Physics 2019-02-20 Joshua F. Robinson , Francesco Turci , Roland Roth , C. Patrick Royall

The spherical collapse scenario has great importance in cosmology since it captures several crucial aspects of structure formation. The presence of self-similar solutions in the Einstein-de Sitter (EdS) model greatly simplifies its…

Cosmology and Nongalactic Astrophysics · Physics 2022-08-03 Han Zhang , Tobias Weinzierl , Holger Schulz , Baojiu Li

In this paper we present preliminary results from cosmological simulations of modified gravity in the dark matter sector. Our results show improvements over standard cold dark matter cosmology. The abundance of low-mass haloes in the…

Astrophysics · Physics 2008-07-08 Wojciech A. Hellwing

If the accelerated expansion of the Universe at the present epoch is driven by a dark energy scalar field, there may well be a non-trivial coupling between the dark energy and the cold dark matter (CDM) fluid. Such interactions give rise to…

Astrophysics · Physics 2014-11-18 Marco Baldi , Valeria Pettorino , Georg Robbers , Volker Springel

Hydrodynamic cosmological simulations at present usually employ either the Lagrangian SPH technique, or Eulerian hydrodynamics on a Cartesian mesh with adaptive mesh refinement. Both of these methods have disadvantages that negatively…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 Volker Springel

The main features of a three dimensional, high-resolution special relativistic hydro code based on relativistic Riemann solvers are described. The capabilities and performance of the code are discussed. In particular, we present the results…

Astrophysics · Physics 2009-10-31 M. A. Aloy , J. M. Ibanez , J. M. Marti , E. Muller

We outline the content and theoretical support for the proposal of "hydrodynamics on (mini)superspace" (or a non-linear extension of quantum cosmology) as an effective framework for quantum gravity in a cosmological context. The basis for…

General Relativity and Quantum Cosmology · Physics 2024-03-19 Daniele Oriti

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

We present a novel method for efficient direct integration of gravitational N-body systems with a large variation in characteristic time scales. The method is based on a recursive and adaptive partitioning of the system based on the…

Instrumentation and Methods for Astrophysics · Physics 2014-10-08 Jürgen Jänes , Federico I. Pelupessy , Simon F. Portegies Zwart

We have developed a method of solving for multi-species chemical reaction flows in non--equilibrium and self--consistently with the hydrodynamic equations in an expanding FLRW universe. The method is based on a backward differencing scheme…

Astrophysics · Physics 2009-10-28 Peter Anninos , Yu Zhang , Tom Abel , Michael L. Norman

Modifications to gravity can provide attractive alternatives to the dark components of the standard model of cosmology. These modifications to general relativity (GR) must be hidden at small scales where theory is well tested, and so one…

Cosmology and Nongalactic Astrophysics · Physics 2018-02-06 Benjamin Bose

We present a new general relativistic hydrodynamics code specifically designed to study magneto-rotational, relativistic, stellar core collapse. The code is an extension of an existing (and thoroughly tested) hydrodynamics code, which has…

Astrophysics · Physics 2008-11-26 P. Cerdá-Durán , J. A. Font

A new code and methodology are introduced for solving the general relativistic magnetohydrodynamic (GRMHD) equations in fixed background spacetimes using time-explicit, finite-volume discretization. The code has options for solving the…

Astrophysics · Physics 2009-11-13 Peter Anninos , P. Chris Fragile , Jay D. Salmonson

We present a new magnetohydrodynamic-particle-in-cell (MHD-PIC) code integrated into the Athena++ framework. It treats energetic particles as in conventional PIC codes while the rest of thermal plasmas are treated as background fluid…

High Energy Astrophysical Phenomena · Physics 2023-05-31 Xiaochen Sun , Xue-Ning Bai

A combined N--body/SPH code is presented which benefits from the high speed of the special purpose hardware GRAPE (GRAvity PipE). Besides gravitational forces, GRAPE also returns the list of neighbours and can, therefore, be used to speed…

Astrophysics · Physics 2015-06-24 Matthias Steinmetz

We present a new code designed to solve the equations of classical ideal magneto-hydrodynamics (MHD) in three dimensions, submitted to a constant gravitational field. The purpose of the code centers on the analysis of solar phenomena within…

Solar and Stellar Astrophysics · Physics 2015-10-22 J. J. Gonzalez-Aviles , A. Cruz-Osorio , F. D. Lora-Clavijo , F. S. Guzman

We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations of galaxies and the large-scale structure. In particular, we combine, implement, modify and test a vast majority of SPH improvement…

Cosmology and Nongalactic Astrophysics · Physics 2015-10-21 A. M. Beck , G. Murante , A. Arth , R. -S. Remus , A. F. Teklu , J. M. F. Donnert , S. Planelles , M. C. Beck , P. Foerster , M. Imgrund , K. Dolag , S. Borgani

I begin with a brief history of N-body simulation and visualization and then go on to describe various methods for creating images and animations of modern simulations in cosmology and galactic dynamics. These techniques are incorporated…

Astrophysics · Physics 2008-12-18 John Dubinski

We examine how three fundamentally different numerical hydrodynamics codes follow the evolution of an isothermal galactic disc with an external spiral potential. We compare an adaptive mesh refinement code (RAMSES), a smoothed particle…

Astrophysics of Galaxies · Physics 2016-08-08 C. G. Few , C. Dobbs , A. Pettitt , L. Konstandin

We describe the development of a flux-limited gray radiation solver for the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of…

Instrumentation and Methods for Astrophysics · Physics 2015-05-28 W. Zhang , L. Howell , A. Almgren , A. Burrows , J. Bell