# Fourier imaging of non-linear structure formation

## TL;DR

This paper introduces a Fourier space decomposition technique to analyze non-linear structure formation in cosmology, revealing mode coupling, power transfer, and vorticity effects from N-body simulations, aiding model calibration.

## Contribution

It presents a novel Fourier decomposition method to study non-linear mode coupling and power transfer in cosmological structure formation from N-body simulations.

## Key findings

- Identifies power transfer from large to small scales.
- Detects the stable clustering regime.
- Highlights the importance of vorticity at certain scales.

## Abstract

We perform a Fourier space decomposition of the dynamics of non-linear cosmological structure formation in LCDM models. From N-body simulations involving only cold dark matter we calculate 3-dimensional non-linear density, velocity divergence and vorticity Fourier realizations, and use these to calculate the fully non-linear mode coupling integrals in the corresponding fluid equations. Our approach allows for a reconstruction of the amount of mode coupling between any two wavenumbers as a function of redshift. With our Fourier decomposition method we identify the transfer of power from larger to smaller scales, the stable clustering regime, the scale where vorticity becomes important, and the suppression of the non-linear divergence power spectrum as compared to linear theory. Our results can be used to improve and calibrate semi-analytical structure formation models.