Cosmological constraints in extended parameter space from the Planck 2018 Legacy release

Abstract: We present new constraints on extended cosmological scenarios using the recent data from the Planck 2018 Legacy release. In addition to the six parameters of the standard LCDM model, we also simultaneously vary the dark energy equation of state, the neutrino mass, the neutrino effective number, the running of the spectral index and the lensing amplitude $A_L$. We confirm that a resolution of the Hubble tension is given by a dark energy equation of state with w<-1, ruling out quintessence models at high statistical significance. This solution is, however, not supported by BAO and Pantheon data. We find no evidence for evolving dark energy, i.e. $w_a \neq 0$. The neutrino effective number is always in agreement with the expectations of the standard model based on three active neutrinos. The running of the spectral index also is always consistent with zero. Despite the increase in the number of parameters, the $A_L$ lensing anomaly is still present at more than two standard deviations. The $A_L$ anomaly significantly affects the bounds on the neutrino mass that can be larger by a factor four with respect to those derived under standard $\Lambda$CDM. While the lensing data reduces the evidence for $A_L>1$, the inclusion of BAO and Pantheon increase its statistical significance.