Flowing with Time: a New Approach to Nonlinear Cosmological Perturbations

Abstract

Nonlinear effects are crucial in order to compute the cosmological matter power spectrum to the accuracy required by future generation surveys. Here, a new approach is presented, in which the power spectrum, the bispectrum and higher order correlations, are obtained -- at any redshift and for any momentum scale -- by integrating a system of differential equations. The method is similar to the familiar BBGKY hierarchy. Truncating at the level of the trispectrum, the solution of the equations corresponds to the summation of an infinite class of perturbative corrections. Compared to other resummation frameworks, the scheme discussed here is particularly suited to cosmologies other than LambdaCDM, such as those based on modifications of gravity and those containing massive neutrinos. As a first application, we compute the Baryonic Acoustic Oscillation feature of the power spectrum, and compare the results with perturbation theory, the halo model, and N-body simulations. The density-velocity and velocity-velocity power spectra are also computed, showing that they are much less contaminated by nonlinearities than the density-density one. The approach can be seen as a particular formulation of the renormalization group, in which time is the flow parameter.

20 pages, 7 figures. Matches version published on JCAP

References in corpus (6)

• Resumming Cosmological Perturbations via the Lagrangian Picture: One-loop Results in Real Space and in Redshift Space
• Nonlinear Evolution of Baryon Acoustic Oscillations
• The detectability of baryonic acoustic oscillations in future galaxy surveys
• Impact of massive neutrinos on nonlinear matter power spectrum
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• Generation of Vorticity and Velocity Dispersion by Orbit Crossing
• Simulations of Baryon Acoustic Oscillations II: Covariance matrix of the matter power spectrum
• Nonlinear power spectrum in the presence of massive neutrinos: perturbation theory approach, galaxy bias and parameter forecasts
• Chasing the non-linear evolution of matter power spectrum with numerical resummation method: solution of closure equations
• Large-Scale Structure in Brane-Induced Gravity I. Perturbation Theory