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

Eleonora Di Valentino, Alessandro Melchiorri, Joseph Silk

TL;DR

The paper investigates the Planck-R16 H0 tension by expanding the ΛCDM parameter space to 12 parameters, allowing w, N_eff, Σmν, r, dn_s/dln k, A_lens, and curvature to vary. Using CosmoMC with Planck 2015 and an H0 prior from R16, it finds a phantom-like w (≈ -1.29) and H0 ≈ 73.5 km/s/Mpc that align Planck with the local measurement, with N_eff near the standard value. Inclusion of BAO or JLA reduces the w<-1 preference and reintroduces tension with R16, while weak lensing and CMB lensing continue to favor w<-1. Varying curvature in an 11-parameter space does not fully solve the tension unless BAO or lensing data are included. The results suggest possible new physics in dark energy or systematic effects, highlighting the need for future data to resolve the discrepancy.

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 $Λ$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.

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

TL;DR

The paper investigates the Planck-R16 H0 tension by expanding the ΛCDM parameter space to 12 parameters, allowing w, N_eff, Σmν, r, dn_s/dln k, A_lens, and curvature to vary. Using CosmoMC with Planck 2015 and an H0 prior from R16, it finds a phantom-like w (≈ -1.29) and H0 ≈ 73.5 km/s/Mpc that align Planck with the local measurement, with N_eff near the standard value. Inclusion of BAO or JLA reduces the w<-1 preference and reintroduces tension with R16, while weak lensing and CMB lensing continue to favor w<-1. Varying curvature in an 11-parameter space does not fully solve the tension unless BAO or lensing data are included. The results suggest possible new physics in dark energy or systematic effects, highlighting the need for future data to resolve the discrepancy.

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 at 68 % c.l. can solve the current tension between the Planck dataset and the R16 prior in an extended 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.

Paper Structure

This paper contains 4 sections, 1 figure, 2 tables.

Table of Contents

  1. Introduction
  2. Method
  3. Results
  4. Conclusions

Figures (1)

  • Figure 1: Constraints at $68 \%$ and $95 \%$ c.l. on the $N_{eff}$ vs $w$ plane assuming the Planck data set with and without the R16 prior on $H_0$. As one can see, when the R16 prior is included, a preference for $w<-1$ is clearly present, while $N_{eff}$ is consistent with the standard expectations. An extended $\Lambda$CDM theoretical framework of $12$ parameters is assumed in the analysis.