skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The CLASSgal code for relativistic cosmological large scale structure

Abstract

We present accurate and efficient computations of large scale structure observables, obtained with a modified version of the CLASS code which is made publicly available. This code includes all relativistic corrections and computes both the power spectrum C{sub ℓ}(z{sub 1},z{sub 2}) and the corresponding correlation function ξ(θ,z{sub 1},z{sub 2}) of the matter density and the galaxy number fluctuations in linear perturbation theory. For Gaussian initial perturbations, these quantities contain the full information encoded in the large scale matter distribution at the level of linear perturbation theory. We illustrate the usefulness of our code for cosmological parameter estimation through a few simple examples.

Authors:
; ;  [1];  [2]
  1. Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24 quai Ernest Ansermet, Genève 4, 1211 (Switzerland)
  2. Institut de Théorie des Phénomènes Physiques, École Polytechnique Fédérale de Lausanne, CH-1015, Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
22369910
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2013; Journal Issue: 11; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRECTIONS; CORRELATION FUNCTIONS; DENSITY; DISTRIBUTION; FLUCTUATIONS; GALAXIES; INFORMATION; MATTER; PERTURBATION THEORY; RELATIVISTIC RANGE; SPECTRA

Citation Formats

Dio, Enea Di, Montanari, Francesco, Durrer, Ruth, and Lesgourgues, Julien, E-mail: Enea.DiDio@unige.ch, E-mail: Francesco.Montanari@unige.ch, E-mail: Julien.Lesgourgues@cern.ch, E-mail: Ruth.Durrer@unige.ch. The CLASSgal code for relativistic cosmological large scale structure. United States: N. p., 2013. Web. doi:10.1088/1475-7516/2013/11/044.
Dio, Enea Di, Montanari, Francesco, Durrer, Ruth, & Lesgourgues, Julien, E-mail: Enea.DiDio@unige.ch, E-mail: Francesco.Montanari@unige.ch, E-mail: Julien.Lesgourgues@cern.ch, E-mail: Ruth.Durrer@unige.ch. The CLASSgal code for relativistic cosmological large scale structure. United States. doi:10.1088/1475-7516/2013/11/044.
Dio, Enea Di, Montanari, Francesco, Durrer, Ruth, and Lesgourgues, Julien, E-mail: Enea.DiDio@unige.ch, E-mail: Francesco.Montanari@unige.ch, E-mail: Julien.Lesgourgues@cern.ch, E-mail: Ruth.Durrer@unige.ch. 2013. "The CLASSgal code for relativistic cosmological large scale structure". United States. doi:10.1088/1475-7516/2013/11/044.
@article{osti_22369910,
title = {The CLASSgal code for relativistic cosmological large scale structure},
author = {Dio, Enea Di and Montanari, Francesco and Durrer, Ruth and Lesgourgues, Julien, E-mail: Enea.DiDio@unige.ch, E-mail: Francesco.Montanari@unige.ch, E-mail: Julien.Lesgourgues@cern.ch, E-mail: Ruth.Durrer@unige.ch},
abstractNote = {We present accurate and efficient computations of large scale structure observables, obtained with a modified version of the CLASS code which is made publicly available. This code includes all relativistic corrections and computes both the power spectrum C{sub ℓ}(z{sub 1},z{sub 2}) and the corresponding correlation function ξ(θ,z{sub 1},z{sub 2}) of the matter density and the galaxy number fluctuations in linear perturbation theory. For Gaussian initial perturbations, these quantities contain the full information encoded in the large scale matter distribution at the level of linear perturbation theory. We illustrate the usefulness of our code for cosmological parameter estimation through a few simple examples.},
doi = {10.1088/1475-7516/2013/11/044},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 11,
volume = 2013,
place = {United States},
year = 2013,
month =
}
  • An improved three-dimensional hierarchical particle-mesh (HPM) N-body code for the gravitational evolution of structure in the universe has been developed and tested. The basis of the code is a standard particle-mesh (PM) code where Poisson's equation is solved on a critical grid with fast Fourier transform techniques and periodic boundary conditions. Several subgrids and father grids can fit into a cube. The fields from the father grid, and its father grid, and so on, are treated as external fields. There is no back-reaction to father grids, and particles can enter and exit subgrids. In a four grid code the dynamicmore » range can be extended to 6000 in length and 11 orders of magnitude in mass. The initial conditions are generated with a random phase realization of the power spectrum of the growing mode using the Zel'dovich approximation (1970). The HPM code is much faster than tree codes and particle-particle-mesh codes, and has a much larger dynamic range. 28 refs.« less
  • A phenomenological model based on the liquid crystal blue phase is proposed as a model for a late-time cosmological phase transition. Topological defects, in particular thick strings and/or domain walls, are presented as seeds for structure formation. It is shown that the observed large-scale structure, including quasi-periodic wall structure, can be well fitted in the model without violating the microwave background isotropy bound or the limits from induced gravitational waves and the millisecond pulsar timing. Furthermore, such late-time transitions can produce objects such as quasars at high redshifts. The model appears to work with either cold or hot dark matter.more » 32 refs.« less
  • We discuss the nonlinear multiplicative stochastic behavior of chaotic inflation with an emphasis on the relevance of the scaling'' effect for large-scale structure formation. We derive a simple criterion for the appearance of scaling behavior in the {lambda}{phi}{sup 4} inflaton model in an asymptotic limit which remains valid throughout the inflationary epoch. We show explicitly that in this limit the onset of the scaling regime does not require any special initial conditions and that it is independent of the self-coupling constant {lambda}. A decrease in the dispersion of field fluctuations at late times is seen in the course of stochasticmore » evolution, and shown to follow from the squeezing'' of probability distributions due to the nonlinear stochastic effect. Non-Gaussian statistics in adiabatic fluctuations are important only for superhorizon scales and the scaling regime does not lead to any significant statistical properties on currently observable scales. However, the scaling effect gives some cosmological consequences very different from what we expect in the naive diffusion approximation for quantum fluctuations. We show that the classical treatment (deterministic) of the inflaton field (essentially a quantum-mechanical object) becomes valid towards the end of inflation because of nonlinear effects.« less
  • Knowledge of N-point correlation functions for all N allows one to invert and obtain the probability distribution of mass fluctuations in a fixed volume. I apply this to the hierarchical sequence of higher order correlations with dimensionless amplitudes suggested by the BBGKY equations. The resulting distribution is significantly non-Gaussian, even for quite small mean square fluctuations. The qualitative and to some degree quantitative results are to a large degree independent of the exact sequence of amplitudes. An ensemble of such models compared with N-body simulations fails in detail to account for the low-density frequency distribution. Subject headings: cosmology-galaxies: clustering-numerical methods
  • We study the evolution of global monopoles by means of numerical simulations, and find that the monopoles obey a scaling solution in which there are a fixed number of monopoles in every horizon volume. Monopoles which form at the grand unification scale can serve as seeds for galaxy and large-scale structure formation.