Cosmic Degeneracies III: N-body Simulations of Interacting Dark Energy with Non-Gaussian Initial Conditions

TL;DR

This study uses N-body simulations to explore how interacting dark energy and non-Gaussian initial conditions can produce similar large-scale observational signatures, but differ in small-scale structures, highlighting the need for combined probes to distinguish them.

Contribution

First N-body simulations of interacting dark energy with non-Gaussian initial conditions, revealing degeneracies and differences in structure formation.

Findings

Degeneracy in large-scale halo power spectrum with specific parameters

Validation of degeneracy through small-scale matter power spectrum and halo properties

Structural differences in halos and voids can break the degeneracy

Abstract

We perform for the first time N-body simulations of Interacting Dark Energy assuming non-Gaussian initial conditions, with the aim of investigating possible degeneracies of these two theoretically independent phenomena in different observational probes. We focus on the large-scale matter distribution, as well as on the statistical and structural properties of collapsed halos and cosmic voids. On very large scales, we show that it is possible to choose the Interaction and non-Gaussian parameters such that their effects on the halo power spectrum cancel, and the power spectrum is indistinguishable from a $\mathrm{\Lambda CDM}$ model. On small scales, measurements of the non-linear matter power spectrum, halo-matter bias, halo and subhalo mass function and cosmic void number function validate the degeneracy determined on large scales. However, the internal structural properties of halos and cosmic voids, namely halo concentration-mass relation and void density profile, are very different from those measured in the $\mathrm{\Lambda CDM}$ model, thereby breaking the degeneracy. In practice, the values of $\mathrm{f_{NL}}$ required to cancel the effect of interaction are already ruled by observations. Our results show in principle that the combination of large- and small-scale probes is needed to constrain Interacting Dark Energy and Primordial non-Gaussianity separately.