Cosmological Nbody simulations with suppressed variance
Abstract
We present and test a method that dramatically reduces variance arising from the sparse sampling of wavemodes in cosmological simulations. The method uses two simulations which are fixed (the initial Fourier mode amplitudes are fixed to the ensemble average power spectrum) and paired (with initial modes exactly out of phase). We measure the power spectrum, monopole and quadrupole redshiftspace correlation functions, halo mass function and reduced bispectrum at z = 1. By these measures, predictions from a fixed pair can be as precise on nonlinear scales as an average over 50 traditional simulations. The fixing procedure introduces a nonGaussian correction to the initial conditions; we give an analytic argument showing why the simulations are still able to predict the mean properties of the Gaussian ensemble. We anticipate that the method will drive down the computational time requirements for accurate largescale explorations of galaxy bias and clustering statistics, and facilitating the use of numerical simulations in cosmological data interpretation.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 October 2016
 DOI:
 10.1093/mnrasl/slw098
 arXiv:
 arXiv:1603.05253
 Bibcode:
 2016MNRAS.462L...1A
 Keywords:

 methods: numerical;
 cosmology: theory;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 6 pages, 5 figures. Version accepted for publication in MNRAS