A cosmic degeneracy story: structure formation with warm dark matter and scale-dependent primordial non-Gaussianities

TL;DR

This paper investigates how scale-dependent primordial non-Gaussianities and Warm Dark Matter influence cosmic structure formation, revealing their similarities and differences, and proposing a mixed dark matter model that matches standard cosmology's power spectrum.

Contribution

It demonstrates the near-linear superposition of WDM and sPNG effects on structure formation and introduces a mixed dark matter model that aligns with ΛCDM power spectra while differing in halo statistics.

Findings

WDM and sPNG produce similar matter power spectra but differ in halo and void statistics.

The combined effects of WDM and sPNG are approximately additive at low redshift.

A mixed hot and cold dark matter model with sPNG can replicate ΛCDM power spectra at z ≤ 3.

Abstract

It has been recently shown that cosmological models with scale-dependent primordial non-Gaussianities (sPNG) could provide a possible path to solve current cosmic tensions. Moreover, it has been pointed out that some of these models might mimic the effects of Warm Dark Matter (WDM) for several observables at low redshift. Here, we confirm the qualitative similarity of the matter power spectrum for sPNG and WDM models, but also point out differences in the halo mass function and void size function. We then jointly simulate WDM and sPNG together. Such simulations allow us to demonstrate that the joint impact of WDM and sPNG is close to the linear superposition of their respective effects at low redshift, at the percent level. We finally propose a model with mixed hot and cold dark matter together with sPNG, that reproduces the $\Lambda$CDM power spectrum at redshifts $z \leq 3$ but is still distinct in terms of halo statistics.