期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 389, 期 4, 页码 1675-1682出版社
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2008.13731.x
关键词
methods : N-body simulations; cosmology : theory; large-scale structure of Universe
资金
- Mitsubishi Foundation
- Japan Society for Promotion of Science (JSPS)
- Grant-in-Aids for Scientific Research [18740132, 18540277, 18654047]
- Grants-in-Aid for Japan Society for the Promotion of Science Fellows
- Grants-in-Aid for Scientific Research [18654047, 18740132, 18540277] Funding Source: KAKEN
We critically examine how well the evolution of large-scale density perturbations is followed in cosmological N-body simulations. We first run a large volume simulation and perform a mode-by-mode analysis in three-dimensional Fourier space. We show that the growth of large-scale fluctuations significantly deviates from linear-theory predictions. The deviations are caused by non-linear coupling with a small number of modes at largest scales owing to finiteness of the simulation volume. We then develop an analytic model based on second-order perturbation theory to quantify the effect. Our model accurately reproduces the simulation results. For a single realization, the second-order effect appears typically as 'zig-zag' patterns around the linear-theory prediction, which imprints artificial 'oscillations' that lie on the real baryon acoustic oscillations. Although an ensemble average of a number of realizations approaches the linear-theory prediction, the dispersions of the realizations remain large even for a large simulation volume of several hundred megaparsecs on a side. For the standard Lambda cold dark matter (Lambda CDM) model, the deviations from linear growth rate are as large as 10 per cent for a simulation volume with L = 500 h(-1) Mpc and for a bin width in wavenumber of Delta k = 0.005 h Mpc(-1), which are comparable to the intrinsic variance of Gaussian random realizations. We find that the dispersions scales as proportional to L-3/2 Delta k(-1/2) and the mean dispersion amplitude can be made smaller than a per cent only if we use a very large volume of L > 2 h(-1) Gpc. The finite box size effect needs to be appropriately taken into account when interpreting results from large-scale structure simulations for future dark energy surveys using baryon acoustic oscillations.
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