Power spectrum response of largescale structure in 1D and in 3D: tests of prescriptions for postcollapse dynamics
Abstract
The power spectrum response function of the largescale structure of the Universe describes how the evolved power spectrum is modified by a small change in initial power through nonlinear mode coupling of gravitational evolution. It was previously found that the response function for the coupling from small to large scales is strongly suppressed in amplitude, especially at late times, compared to predictions from perturbation theory (PT) based on the singlestream approximation. One obvious explanation for this is that PT fails to describe the dynamics beyond shell crossing. We test this idea by comparing measurements in Nbody simulations to prescriptions based on PT but augmented with adaptive smoothing to account for the formation of nonlinear structures of various sizes in the multistream regime. We first start with onedimensional (1D) cosmology, where the Zel'dovich approximation provides the exact solution in the singlestream regime. Similarly to the threedimensional (3D) case, the response function of the largescale modes exhibits a strong suppression in amplitude at small scales that cannot be explained by the Zel'dovich solution alone. However, by performing adaptive smoothing of initial conditions to identify haloes of different sizes and solving approximately postcollapse dynamics in the threestream regime, agreement between theory and simulations drastically improves. We extend our analyses to the 3D case using the PINOCCHIO algorithm, in which similar adaptive smoothing is implemented on the Lagrangian PT fields to identify haloes and is combined with a spherical halo prescription to account for postcollapse dynamics. Again, a suppression is found in the coupling between small and largescale modes and the agreement with simulations is improved.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2020
 DOI:
 10.1093/mnras/staa2878
 arXiv:
 arXiv:2001.10417
 Bibcode:
 2020MNRAS.499.1769H
 Keywords:

 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 18 pages, 8 figures, accepted by MNRAS