Ringing the initial Universe: the response of overdensity and transformed-density power spectra to initial spikes

Understand

We present an experiment in which we 'ring' a set of cosmological N-body-simulation initial conditions, placing spikes in the initial power spectrum at different wavenumber bins.

• We then measure where these spikes end up in the final conditions.
• In the usual overdensity power spectrum, most sensitive to contracting and collapsing dense regions, initial power on slightly non-linear scales (k ~ 0.3 h/Mpc) smears to smaller scales, coming to dominate the initial power once there.
• Log-density and Gaussianized-density power spectra, sensitive to low-density (expanding) and high-density regions, respond differently: initial spikes spread symmetrically in scale, both upward and downward.