Can $f(Q)$ gravity challenge $\mathrm{\Lambda }\mathrm{CDM}$?

We study observational constraints on the nonmetricity $f(Q)$-gravity which reproduces an exact $\mathrm{\Lambda }\mathrm{CDM}$ background expansion history while modifying the evolution of linear perturbations. To this purpose we use cosmic microwave background (CMB) radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. We set stringent constraints on the parameter of the model controlling the modifications to the gravitational interaction at linear perturbation level. We find the model to be statistically preferred by data over the $\mathrm{\Lambda }\mathrm{CDM}$ according to the ${\chi }^2$ and deviance information criterion statistics for the combination with CMB, BAO, RSD and SNIa. This is mostly associated to a better fit to the low-$\ell$ tail of CMB temperature anisotropies.

Figure 1

Marginalized constraints at 68% (darker) and 95% (lighter) C.L. on the model parameter $\alpha$ and four cosmological parameters $H_0$, $n_s$, ${\sigma }_8^0$ and ${\mathrm{\Omega }}_m^0$ obtained with the CMB data from Planck 2018 (PLK18, red), its combination with BAO, RSD and SNIa data (PBRS, green) and with DES data (PBRSD, blue).