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We establish necessary conditions for the appearance of both apparent horizons and singularities in the initial data of spherically symmetric general relativity when spacetime is foliated extrinsically. When the dominant energy condition is…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Jemal Guven , Niall O Murchadha

We present a novel approach to generate higher-order initial conditions (ICs) for cosmological simulations that take into account the distinct evolution of baryons and dark matter. We focus on the numerical implementation and the validation…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-13 Oliver Hahn , Cornelius Rampf , Cora Uhlemann

We describe the first major public data release from cosmological simulations carried out with Argonne's HACC code. This initial release covers a range of datasets from large gravity-only simulations. The data products include halo…

We describe and test a new method for creating initial conditions for cosmological N-body dark matter simulations based on second-order Lagrangian perturbation theory (2lpt). The method can be applied to multi-mass particle distributions…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Adrian Jenkins

Particle-Mesh (PM) codes are still very useful tools for testing predictions of cosmological models in cases when extra high resolution is not very important. We release for public use a cosmological PM N-body code. We provide a complete…

Astrophysics · Physics 2007-05-23 Anatoly Klypin , Jon Holtzman

We describe how to define an extremely large discrete realisation of a Gaussian white noise field that has a hierarchical structure and the property that the value of any part of the field can be computed quickly. Tiny subregions of such a…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Adrian Jenkins

We analyze hierarchical structure formation based on scale-free initial conditions in an Einstein-de Sitter universe, including a baryonic component. We present three independent, smoothed particle hydrodynamics (SPH) simulations, performed…

Astrophysics · Physics 2009-10-30 J. Michael Owen , David H. Weinberg , August E. Evrard , Lars Hernquist , Neal Katz

In this contribution a broad overview of the methodologies of cosmological N-body simulations and a short introduction explaining the general idea behind such simulations is presented. After explaining how to set up the initial conditions…

Astrophysics · Physics 2009-11-10 Alexander Knebe

Galaxy simulations have come a long way from the early days of simple N-body calculations, which considered only gravitational interactions, to the complex, multi-physics models used today. Beginning with initial conditions representative…

Astrophysics of Galaxies · Physics 2025-07-15 Robert Feldmann , Rebekka Bieri

Initial conditions for cosmological N-body simulations are usually calculated by rescaling the present day linear power spectrum obtained from an Einstein-Boltzmann solver to the initial time employing the scale-independent matter growth…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-12 Christian Fidler , Alexander Kleinjohann

The cosmic large-scale structure (LSS) provides a unique testing ground for connecting fundamental physics to astronomical observations. Modeling the LSS requires numerical $N$-body simulations or perturbative techniques that both come with…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-20 Florian List , Oliver Hahn , Cornelius Rampf

Generating pre-initial conditions (or particle loads) is the very first step to set up a cosmological N-body simulation. In this work, we revisit the numerical convergence of pre-initial conditions on dark matter halo properties using a set…

Cosmology and Nongalactic Astrophysics · Physics 2022-02-08 Tianchi Zhang , Shihong Liao , Ming Li , Jiajun Zhang

In astro-ph/0109199, the initial conditions (IC's) of cosmological N-body simulations by the Virgo Consortium are analyzed and it is concluded that the density fluctuations are rather different from the desired ones. We have repeated the…

Astrophysics · Physics 2009-11-10 Alvaro Dominguez , Alexander Knebe

We present a description for setting initial particle displacements and field values for simulations of arbitrary metric theories of gravity, for perfect and imperfect fluids with arbitrary characteristics. We extend the Zel'dovich…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-23 Wessel Valkenburg , Bin Hu

High-resolution (HR) simulations in cosmology, in particular when including baryons, can take millions of CPU hours. On the other hand, low-resolution (LR) dark matter simulations of the same cosmological volume use minimal computing…

Cosmology and Nongalactic Astrophysics · Physics 2024-04-30 Adam Rouhiainen , Michael Gira , Moritz Münchmeyer , Kangwook Lee , Gary Shiu

We address the initial conditions for an expanding cosmology using the holographic principle. For the case of a closed model, the old prescription of Fishler and Susskind, that uses the particle horizon to encode the bulk degrees of…

General Relativity and Quantum Cosmology · Physics 2009-11-11 P. Diaz , M. A. Per , A. Segui

The growth of structure from scale-free initial conditions is one of the most important tests of cosmological simulation methods, providing a realistically complex problem in which numerical results can be compared to rigorous analytic…

Astrophysics · Physics 2007-05-23 J. Michael Owen , David H. Weinberg , Jens V. Villumsen

Current and upcoming cosmological observations allow us to probe structures on smaller and smaller scales, entering highly nonlinear regimes. In order to obtain theoretical predictions in these regimes, large cosmological simulations have…

Graphical simulations are a cornerstone of modern media and films. But existing software packages are designed to run on HPC nodes, and perform poorly in the computing cloud. These simulations have complex data access patterns over complex…

Distributed, Parallel, and Cluster Computing · Computer Science 2016-06-08 Omid Mashayekhi , Chinmayee Shah , Hang Qu , Andrew Lim , Philip Levis

Initial conditions for (Newtonian) cosmological N-body simulations are usually set by re-scaling the present-day power spectrum obtained from linear (relativistic) Boltzmann codes to the desired initial redshift of the simulation. This…

Cosmology and Nongalactic Astrophysics · Physics 2017-06-28 Christian Fidler , Thomas Tram , Cornelius Rampf , Robert Crittenden , Kazuya Koyama , David Wands