Reconciling Planck with the local value of $H_0$ in extended parameter space

TL;DR

This paper investigates the discrepancy between Planck CMB data and local Hubble constant measurements by analyzing an extended cosmological parameter space, finding that a phantom dark energy component can reconcile the differences.

Contribution

It introduces a combined analysis of Planck and local H0 data in a 12-parameter space, revealing that phantom dark energy can resolve the tension.

Findings

A phantom-like dark energy component with w ≈ -1.29 can reconcile Planck and local H0 measurements.

Neutrino effective number remains consistent with standard expectations.

Including BAO and supernova data reduces but does not eliminate the tension.

Abstract

The recent determination of the local value of the Hubble constant by Riess et al, 2016 (hereafter R16) is now 3.3 sigma higher than the value derived from the most recent CMB anisotropy data provided by the Planck satellite in a LCDM model. Here we perform a combined analysis of the Planck and R16 results in an extended parameter space, varying simultaneously 12 cosmological parameters instead of the usual 6. We find that a phantom-like dark energy component, with effective equation of state $w=-1.29_{-0.12}^{+0.15}$ at 68 % c.l. can solve the current tension between the Planck dataset and the R16 prior in an extended $\Lambda$CDM scenario. On the other hand, the neutrino effective number is fully compatible with standard expectations. This result is confirmed when including cosmic shear data from the CFHTLenS survey and CMB lensing constraints from Planck. However, when BAO measurements are included we find that some of the tension with R16 remains, as also is the case when we include the supernova type Ia luminosity distances from the JLA catalog.