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MLAPM: Simulating Structure Formation from Collisionless Matter
Alexander Knebe,
Andrew Green, James Binney
Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP
Abstract:
We present a computer code written in C that is designed to
simulate structure formation from collisionless matter.
The code is purely grid-based and uses a recursively refined
Cartesian grid to solve Poisson's equation for the potential,
rather than obtaining the potential from a Green's function.
Refinements can have arbitrary shapes and in practice closely
follow the complex morphology of the density field that evolves.
The timestep shortens by a factor two with each successive
refinement. It is argued that an appropriate choice of softening
length is of great importance and that the softening should be
at all points an appropriate multiple of the local inter-particle
separation. Unlike tree and P3M codes, multigrid codes
automatically satisfy this requirement. We show that at early
times and low densities in cosmological simulations, the
softening needs to be significantly smaller relative to the
inter-particle separation than in virialized regions. Tests
of the ability of the code's Poisson solver to recover the
gravitational fields of both virialized halos and Zel'dovich
waves are presented, as are tests of the code's ability to
reproduce analytic solutions for plane-wave evolution. The
times required to conduct a LCDM cosmological simulation for
various configurations are compared with the times required to
complete the same simulation with the ART, AP3M and GADGET codes.
The power spectra, halo mass functions and halo-halo correlation
functions of simulations conducted with different codes are compared.
Subject headings: cosmology: large-scale structure of universe, dark
matter, galaxies: formation, galaxies: halos
Latest Version: 1.0; 2001 March 30
Archived: 2001 April 3
Paper: MNRAS in press, preprint:
astro-ph/0103503
Language: C
External Explanatory Pages:
http://www-thphys.physics.ox.ac.uk/users/MLAPM/
Source Code:
mlapm-v1.0.tgz