Matter Power Spectra in Viable $f(R)$ Gravity Models with Massive Neutrinos

TL;DR

This study examines matter power spectra in viable $f(R)$ gravity models with massive neutrinos, revealing enhanced spectra and relaxed neutrino mass constraints compared to $\\Lambda$CDM, with implications for cosmological parameter estimation.

Contribution

It provides the first detailed analysis of matter power spectra in $f(R)$ models with massive neutrinos, including updated neutrino mass constraints using modified MGCAMB.

Findings

Matter power spectrum enhancement in $f(R)$ models.

Higher neutrino mass bounds in $f(R)$ models than $\\Lambda$CDM.

Constraints on neutrino parameters vary with model type.

Abstract

We investigate the matter power spectra in the power law and exponential types of viable $f(R)$ theories along with massive neutrinos. The enhancement of the matter power spectrum is found to be a generic feature in these models. In particular, we show that in the former type, such as the Starobinsky model, the spectrum is magnified much larger than the latter one, such as the exponential model. A greater scale of the total neutrino mass, $\Sigma m_{\nu}$, is allowed in the viable $f(R)$ models than that in the $\Lambda$CDM one. We obtain the constraints on the neutrino masses by using the CosmoMC package with the modified MGCAMB. Explicitly, we get $\Sigma m_{\nu} < 0.451 \ (0.214)\ \mathrm{eV}$ at 95% C.L. in the Starobinsky (exponential) model, while the corresponding one for the $\Lambda$CDM model is $\Sigma m_{\nu} < 0.200\ \mathrm{eV}$. Furthermore, by treating the effective number of neutrino species $N_{\mathrm{eff}}$ as a free parameter along with $\Sigma m_{\nu}$, we find that $N_{\mathrm{eff}} = 3.78^{+0.64}_{-0.84} (3.47^{+0.74}_{-0.60})$ and $\Sigma m_{\nu} = 0.533^{+0.254}_{-0.411}$ ($< 0.386) \ \mathrm{eV}$ at 95% C.L. in the Starobinsky (exponential) model.