Impact on the power spectrum of Screening in Modified Gravity Scenarios

TL;DR

This paper investigates how screened modified gravity models like $f(R)$, dilaton, and symmetron affect the matter power spectrum across different regimes using semi-analytical methods, extending understanding beyond linear theory.

Contribution

It combines exact perturbation theory and halo modeling to accurately predict the matter power spectrum in screened modified gravity scenarios, matching simulations up to certain scales.

Findings

Perturbation theory extends analysis up to $k\lesssim 0.15\,h\mathrm{Mpc}^{-1}$.

Halo model achieves agreement with simulations up to $k\lesssim 3\,h\mathrm{Mpc}^{-1}$ for $f(R)$ models.

Different behaviors observed in perturbative expansions and spherical collapse for each gravity model.

Abstract

We study the effects of screened modified gravity of the $f(R)$, dilaton and symmetron types on structure formation, from the quasi-linear to the non-linear regime, using semi-analytical methods. For such models, where the range of the new scalar field is typically within the Mpc range and below in the cosmological context, non-linear techniques are required to understand the deviations of the power spectrum of the matter density contrast compared to the $\Lambda$-CDM template. This is nowadays commonly tackled using extensive N-body simulations. Here we present new results combining exact perturbation theory at the one loop level (and a partial resummation of the perturbative series) with a halo model. The former allows one to extend the linear perturbative analysis up to $k\lesssim 0.15{\rm h Mpc}^{-1}$ at the perturbative level while the latter leads to a reasonable, up to a few percent, agreement with numerical simulations for $k\lesssim 3{\rm h Mpc}^{-1}$ for large curvature $f(R)$ models, and $k\lesssim 1{\rm h Mpc}^{-1}$ for dilatons and symmetrons, at $z=0$. We also discuss how the behaviors of the perturbative expansions and of the spherical collapse differ for $f(R)$, dilaton, and symmetron models.