Searching for dark matter isocurvature initial conditions with N-body Simulations

TL;DR

This paper investigates the impact of dark matter isocurvature perturbations on structure formation using N-body simulations, finding that halo mass functions are sensitive indicators for small isocurvature fractions.

Contribution

It introduces a simulation-based analysis of dark matter isocurvature effects on structure formation, highlighting the halo mass function as a key observable.

Findings

Matter power spectrum is insensitive to small isocurvature fractions.

Halo mass function shows up to 37% difference at z=3 due to isocurvature.

Future cluster surveys can constrain dark matter isocurvature perturbations.

Abstract

Small fraction of isocurvature perturbations may exist and correlate with adiabatic perturbations in the primordial perturbations. Naively switching off isocurvature perturbations may lead to biased results. We study the effect of dark matter isocurvature on the structure formation through N-body simulations. From the best fit values, we run four sets of simulation with different initial conditions and different box sizes. We find that, if the fraction of dark matter isocurvature is small, we can not detect its signal through matter power spectrum and two point correlation function with large scale survey. However, the halo mass function can give an obvious signal. Compared to 5% difference on matter power spectrum, it can get 37% at $z = 3$ on halo mass function. This indicates that future high precise cluster count experiment can give stringent constraints on dark matter isocurvature perturbations.