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Update on Coupled Dark Energy and the $H_0$ tension

Adrià Gómez-Valent, Valeria Pettorino, Luca Amendola

TL;DR

This work tests a coupled dark energy model with a Peebles-Ratra potential against the Planck 2018 data and an array of late-time probes to reassess constraints on the dark-sector coupling $β$ and potential slope $α$, and to evaluate the impact of SH0ES and H0LICOW on the inferred parameters. The authors implement the model in CLASS, perform Bayesian model comparison with ΛCDM across multiple data combinations, and find data-dependent peaks in $β$ and $α$ that are often diminished by CMB lensing; overall, ΛCDM remains preferred when the full data set is considered. While including SH0ES+H0LICOW modestly shifts the best-fit toward nonzero coupling and a steeper potential, the Bayes factor consistently disfavors the additional CDE parameters, and the inferred Hubble tension is not fully resolved. The results imply that, with current data, the simplest ΛCDM description remains robust, though exploring extended couplings or alternative interaction schemes could still offer marginal improvements for late-time tensions.

Abstract

In this work we provide updated constraints on coupled dark energy (CDE) cosmology with Peebles-Ratra (PR) potential and constant coupling strength $β$. This modified gravity scenario introduces a fifth force between dark matter particles, mediated by a scalar field that plays the role of dark energy. The mass of the dark matter particles does not remain constant, but changes with time as a function of the scalar field. Here we focus on the phenomenological behavior of the model, and assess its ability to describe updated cosmological data sets that include the Planck 2018 cosmic microwave background (CMB) temperature, polarization and lensing, baryon acoustic oscillations, the Pantheon compilation of supernovae of Type Ia, data on $H(z)$ from cosmic chronometers, and redshift-space distortions. We also study which is the impact of the local measurement of $H_0$ from SH0ES and the strong-lensing time delay data from the H0LICOW collaboration on the parameter that controls the strength of the interaction in the dark sector. We find a peak corresponding to a coupling $β> 0$ and to a potential parameter $α> 0$, more or less evident depending on the data set combination. We show separately the impact of each data set and remark that it is especially CMB lensing the one data set that shifts the peak the most towards $Λ$CDM. When a model selection criterion based on the full Bayesian evidence is applied, however, $Λ$CDM is still preferred in all cases, due to the additional parameters introduced in the CDE model.

Update on Coupled Dark Energy and the $H_0$ tension

TL;DR

This work tests a coupled dark energy model with a Peebles-Ratra potential against the Planck 2018 data and an array of late-time probes to reassess constraints on the dark-sector coupling and potential slope , and to evaluate the impact of SH0ES and H0LICOW on the inferred parameters. The authors implement the model in CLASS, perform Bayesian model comparison with ΛCDM across multiple data combinations, and find data-dependent peaks in and that are often diminished by CMB lensing; overall, ΛCDM remains preferred when the full data set is considered. While including SH0ES+H0LICOW modestly shifts the best-fit toward nonzero coupling and a steeper potential, the Bayes factor consistently disfavors the additional CDE parameters, and the inferred Hubble tension is not fully resolved. The results imply that, with current data, the simplest ΛCDM description remains robust, though exploring extended couplings or alternative interaction schemes could still offer marginal improvements for late-time tensions.

Abstract

In this work we provide updated constraints on coupled dark energy (CDE) cosmology with Peebles-Ratra (PR) potential and constant coupling strength . This modified gravity scenario introduces a fifth force between dark matter particles, mediated by a scalar field that plays the role of dark energy. The mass of the dark matter particles does not remain constant, but changes with time as a function of the scalar field. Here we focus on the phenomenological behavior of the model, and assess its ability to describe updated cosmological data sets that include the Planck 2018 cosmic microwave background (CMB) temperature, polarization and lensing, baryon acoustic oscillations, the Pantheon compilation of supernovae of Type Ia, data on from cosmic chronometers, and redshift-space distortions. We also study which is the impact of the local measurement of from SH0ES and the strong-lensing time delay data from the H0LICOW collaboration on the parameter that controls the strength of the interaction in the dark sector. We find a peak corresponding to a coupling and to a potential parameter , more or less evident depending on the data set combination. We show separately the impact of each data set and remark that it is especially CMB lensing the one data set that shifts the peak the most towards CDM. When a model selection criterion based on the full Bayesian evidence is applied, however, CDM is still preferred in all cases, due to the additional parameters introduced in the CDE model.

Paper Structure

This paper contains 15 sections, 16 equations, 4 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Coupled dark energy
  3. Methodology
  4. Data
  5. Description of the individual data sets
  6. Cosmic microwave background
  7. Baryon acoustic oscillations
  8. Supernovae of Type Ia
  9. Cosmic chronometers
  10. Redshift-space distortions
  11. Prior on $H_0$
  12. Strong-lensing time delay distances
  13. Combined data sets
  14. Results
  15. Conclusions

Figures (4)

  • Figure 1: Left plot: Normalized densities $\Omega_{dm}(z)+\Omega_{b}(z)$ and $\Omega_\phi(z)$ for four alternative values of $\beta$ and considering a constant potential. The other parameters (including the current energy densities) have been set to the best-fit $\Lambda$CDM values from the TTTEEE+lowE Planck 2018 analysis Aghanim:2018eyx. Right plot: Here we zoom in the range $z=[2,200]$ of the $\Omega_{dm}+\Omega_b$ curves in order to better visualize their evolution during the matter-dominated epoch, when the system is near the $\phi$MDE fixed point. See the text for details.
  • Figure 2: Theoretical curves of the current matter power spectrum (left plot) and CMB temperature anisotropies (right plot) for the $\Lambda$CDM, two CDE models with $\beta=0.1,\,0.15$ and flat potential, and also for the uncoupled Peebles-Ratra model with $\alpha=0.4$. We set the other parameters as in \ref{['fig:Omegas']}. In the right plot we also include the observational data from Aghanim:2018eyx (in red). These figures show: (i) the enhancement of the growth of matter perturbations caused by $\beta>0$, and the opposite effect produced by $\alpha>0$; and (ii) the shift to larger multipoles and the amplitude suppression of the acoustic peaks induced by increasing values of $\beta$. See the text for further details.
  • Figure 3: $1$ and $2\sigma$ confidence contours obtained using some of the combined data sets described in \ref{['sect:CombiData']} in the $(H_0,\beta)$, $(\sigma_8,\beta)$, and $(\alpha,\beta)$ planes, together with the marginalized one-dimensional posterior distributions for these parameters. See the discussion of these results in \ref{['sect:results']}.
  • Figure 4: $1$ and $2\sigma$ confidence contours obtained with the P18+BSC+RSD and P18lens+BSC+RSD data sets in the most relevant two-dimensional planes of the CDE model parameter space. They allow us to see what is the impact of the CMB lensing on our results. We also show the corresponding marginalized one-dimensional posterior distributions for all the parameters. See the related comments in \ref{['sect:results']}.