Cosmic Degeneracies II: Structure formation in joint simulations of Warm Dark Matter and $f(R)$ gravity

Understand

We present for the first time the outcomes of a cosmological N-body simulation that simultaneously implements a Warm Dark Matter (WDM) particle candidate and a modified gravitational interaction in the form of $f(R)$ gravity, and compare its results with the individual effects of these two independent extensions of the standard $\Lambda $CDM scenario, and with the reference cosmology itself.

• We consider a rather extreme value of the WDM particle mass ($m_{\rm WDM}=0.4$ keV) and a single realisation of $f(R)$ gravity with $|\bar{f}_{R0}|=10^{-5}$, and we investigate the impact of these models and of their combination on a wide range of cosmological observables with the aim to identify possible observational degeneracies.
• In particular, we focus on the large-scale matter distribution, as well as on the statistical and structural properties of collapsed halos and cosmic voids.
• Differently from the case of combining $f(R)$ gravity with massive neutrinos -- previously investigated in Baldi et al.