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Dark sector interaction: a remedy of the tensions between CMB and LSS data

Suresh Kumar, Rafael C. Nunes, Santosh Kumar Yadav

TL;DR

By addressing the $H_0$ and $\sigma_8$ tensions that challenge $\Lambda$CDM, the paper tests a minimal interacting dark sector model (IVCDM) with coupling $Q=\delta H ρ_{de}$ and $w_{de}=-1$ using Planck CMB, KiDS weak lensing, and HST $H_0$ priors. The cosmological evolution is computed with the Boltzmann code CLASS and parameter inference via Monte Python. The analysis finds that the tensions disappear at 68% CL when the dark-sector coupling is allowed, and joint datasets prefer a non-zero negative $\delta$ at 99% CL, indicating energy flow from dark matter to dark energy. Model comparison using the Akaike information criterion favors IVCDM over $\Lambda$CDM for Planck+HST and Planck+HST+KiDS, suggesting the coupling provides a better description of the data. Overall, the results support a dark-sector interaction as a viable resolution to cosmological tensions and motivate further exploration of this framework.

Abstract

The well-known tensions on the cosmological parameters $H_0$ and $σ_8$ within the $Λ$CDM cosmology shown by the Planck-CMB and LSS data are possibly due to the systematics in the data or our ignorance of some new physics beyond the $Λ$CDM model. In this letter, we focus on the second possibility, and investigate a minimal extension of the $Λ$CDM model by allowing a coupling between its dark sector components (dark energy and dark matter). We analyze this scenario with Planck-CMB, KiDS and HST data, and find that the $H_0$ and $σ_8$ tensions disappear at 68\% CL. In the joint analyzes with Planck, HST and KiDS data, we find non-zero coupling in the dark sector up to 99\% CL. Thus, we find a strong statistical support from the observational data for an interaction in the dark sector of the Universe while solving the $H_0$ and $σ_8$ tensions simultaneously.

Dark sector interaction: a remedy of the tensions between CMB and LSS data

TL;DR

By addressing the and tensions that challenge CDM, the paper tests a minimal interacting dark sector model (IVCDM) with coupling and using Planck CMB, KiDS weak lensing, and HST priors. The cosmological evolution is computed with the Boltzmann code CLASS and parameter inference via Monte Python. The analysis finds that the tensions disappear at 68% CL when the dark-sector coupling is allowed, and joint datasets prefer a non-zero negative at 99% CL, indicating energy flow from dark matter to dark energy. Model comparison using the Akaike information criterion favors IVCDM over CDM for Planck+HST and Planck+HST+KiDS, suggesting the coupling provides a better description of the data. Overall, the results support a dark-sector interaction as a viable resolution to cosmological tensions and motivate further exploration of this framework.

Abstract

The well-known tensions on the cosmological parameters and within the CDM cosmology shown by the Planck-CMB and LSS data are possibly due to the systematics in the data or our ignorance of some new physics beyond the CDM model. In this letter, we focus on the second possibility, and investigate a minimal extension of the CDM model by allowing a coupling between its dark sector components (dark energy and dark matter). We analyze this scenario with Planck-CMB, KiDS and HST data, and find that the and tensions disappear at 68\% CL. In the joint analyzes with Planck, HST and KiDS data, we find non-zero coupling in the dark sector up to 99\% CL. Thus, we find a strong statistical support from the observational data for an interaction in the dark sector of the Universe while solving the and tensions simultaneously.

Paper Structure

This paper contains 5 sections, 4 equations, 3 figures, 3 tables.

Table of Contents

  1. INTRODUCTION
  2. Interaction in the dark sector
  3. Data sets and methodology of the analysis
  4. Results and discussion
  5. Final remarks

Figures (3)

  • Figure 1: Parametric space (68% and 95% CL) in the plane $\Omega_{\rm m0}-H_0$ for the $\Lambda$CDM (left panel) and IVCDM model (right panel) from three data sets. In the left panel, it is clear to see that the local measurement of $H_0 =73.24 \pm 1.74$ km s$^{-1}$Mpc$^{-1}$riess (yellow band) is in disagreement with the statistical region of $H_0$ from the three data sets within the $\Lambda$CDM cosmology. In the right panel, we see that there is no tension on $H_0$ within 68% CL in the IVCDM model.
  • Figure 2: Parametric space (at 68% and 95% CL) in the plane $\Omega_{\rm m0}-S_8$ for the $\Lambda$CDM (left panel) and IVCDM model (right panel) from four data sets. In the left panel, we see that the $\Omega_{\rm m0}-S_8$ region given by the Planck data within the $\Lambda$CDM cosmology is clearly in disagreement with the region $S_8 \equiv \sigma_8 \sqrt{\Omega_{\rm m0}/{0.30}} = 0.651 \pm 0.058$, predicted by KiDS data kids01 (red band). In the right panel for the IVCDM model, we observe that there is no tension on $S_8$ within 68% CL.
  • Figure 3: $\delta-H_0$ (left panel) and $\delta-\sigma_8$ (right panel) parametric spaces (68% and 95% CL) for the IVCDM model from three data sets. The yellow band corresponds to local value $H_0 =73.24 \pm 1.74$ km s$^{-1}$Mpc$^{-1}$riess whereas the light red band corresponds to $\sigma_8 = 0.75 \pm 0.03$LSS2.