Planck-PR4 anisotropy spectra show (better) consistency with General Relativity

TL;DR

The Planck-PR4 anisotropy spectra analysis demonstrates improved consistency with General Relativity, reducing previous anomalies in modified gravity parameters and aligning better with the standard cosmological model.

Contribution

This study updates constraints on modified gravity parameters using Planck-PR4 data, showing enhanced agreement with General Relativity compared to previous Planck-PR3 results.

Findings

Constraints on $\Sigma_0$ and $\gamma_0$ are within 1.5-2$\sigma$ of GR.

The lensing anomaly's impact on modified gravity parameters is reduced.

Planck-PR4 data aligns more closely with $\Lambda$CDM$ predictions.

Abstract

We present the results from a series of analyses on two parametric tests of gravity that modify the growth of linear, sub-horizon matter perturbations in the $\Lambda$CDM model. The first test, known as the $(\mu,\Sigma)$ framework, modifies the Poisson and lensing equations from General Relativity (GR). The second test introduces the growth index $\gamma$, which directly affects the time evolution of matter density perturbations. Our study is motivated by results from the analysis of the Planck-PR3 2018 spectra, which indicate a preference for $\Sigma_0 \neq 0$ and $\gamma_0 > 0.55$, both of which deviate from the $\Lambda$CDM predictions at a significance level of $\sim 2.5\sigma$. To clarify the nature of these anomalous results and understand how the lensing anomaly fits into the picture, we analyze the most recent Planck-PR4 spectra extracted from the updated \texttt{NPIPE} maps. Overall, the Planck-PR4 data show better consistency with GR. The updated likelihood \texttt{Camspec} provides constraints on $\Sigma_0$ and $\gamma_0$ that are consistent with GR within $1.5\sigma$ and $2\sigma$, respectively. The updated likelihoods \texttt{HiLLiPoP} and \texttt{LoLLiPoP} show even closer agreement, with all parameter values consistent with a $\Lambda$CDM cosmology within $1\sigma$. This enhanced consistency is closely correlated with the lensing anomaly. Across the different likelihoods, the tendency of $\Sigma_0$ and $\gamma_0$ to drift towards non-standard values matches the observed preference for $A_L > 1$, both of which are significantly reduced or disappear within the Planck-PR4 data.