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Echo of interactions in the dark sector

Suresh Kumar, Rafael C. Nunes

TL;DR

This work probes late-time interactions between dark matter and dark energy by parameterizing a coupling $\delta$ in an interacting vacuum energy model, studied under two neutrino scenarios: $\nu$IVCDM and $\nu_s$IVCDM. By combining Planck CMB data with BAO, JLA, and galaxy-cluster measurements, the authors show that including GC data drives $\delta$ to negative values at 99% CL, suggesting DM decays into vacuum energy and potentially addressing the $H_0$ and $\sigma_8$ tensions, especially in the sterile-neutrino case where $m_{\nu_s} = 0.37^{+0.11}_{-0.11}$ eV and $N_{\rm eff}$ remains consistent with the 4-parameter extension. The analysis reveals strong correlations: $\delta$ with $H_0$ and $\sigma_8$, and $N_{\rm eff}$ with $H_0$, indicating that extra relativistic degrees of freedom can lift the Hubble constant while the dark-sector coupling suppresses clustering. The results bolster the case for a non-minimal dark sector and show that combining CMB, large-scale structure, and neutrino properties can yield meaningful constraints on dark-energy–dark-matter interactions, with sterile-neutrino scenarios offering notable tension-reduction potential. Future data from large-scale structure and neutrino experiments will be crucial to further test these interacting models.

Abstract

We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from CMB temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination CMB + BAO + JLA suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99\% confidence level. We deduce that the current tensions on the parameters $H_0$ and $σ_8$ can be alleviated within the framework of the interacting as well as non-interacting vacuum energy models with sterile neutrinos.

Echo of interactions in the dark sector

TL;DR

This work probes late-time interactions between dark matter and dark energy by parameterizing a coupling in an interacting vacuum energy model, studied under two neutrino scenarios: IVCDM and IVCDM. By combining Planck CMB data with BAO, JLA, and galaxy-cluster measurements, the authors show that including GC data drives to negative values at 99% CL, suggesting DM decays into vacuum energy and potentially addressing the and tensions, especially in the sterile-neutrino case where eV and remains consistent with the 4-parameter extension. The analysis reveals strong correlations: with and , and with , indicating that extra relativistic degrees of freedom can lift the Hubble constant while the dark-sector coupling suppresses clustering. The results bolster the case for a non-minimal dark sector and show that combining CMB, large-scale structure, and neutrino properties can yield meaningful constraints on dark-energy–dark-matter interactions, with sterile-neutrino scenarios offering notable tension-reduction potential. Future data from large-scale structure and neutrino experiments will be crucial to further test these interacting models.

Abstract

We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from CMB temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination CMB + BAO + JLA suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99\% confidence level. We deduce that the current tensions on the parameters and can be alleviated within the framework of the interacting as well as non-interacting vacuum energy models with sterile neutrinos.

Paper Structure

This paper contains 8 sections, 3 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Interaction in the dark sector
  3. The models
  4. Observational Constraints
  5. Analysis of constraints on $\nu$IVCDM model
  6. Analysis of constraints on $\nu_s$IVCDM model
  7. Analysis of the tensions on $H_0$ and $\sigma_8$
  8. Conclusions

Figures (4)

  • Figure 1: One-dimensional marginalized distribution, and 68% and 95% CL regions for some selected parameters of the $\nu$IVCDM model.
  • Figure 2: One-dimensional marginalized distribution, and 68% and 95% CL regions for some selected parameters of the $\nu_s$IVCDM model.
  • Figure 3: Constraints on $\sigma_8 - \delta$ parametric space coloured by $H_0$ values for the $\nu$IVCDM (left panel) and $\nu_s$IVCDM (right panel) models from CMB + BAO + JLA + CFHTLenS + SZ data.
  • Figure 4: 1D marginalized probability distributions of $H_0$ and $\sigma_8$ for $\nu$IVCDM (upper panel) and $\nu_s$IVCDM (lower panel) models. The vertical gray band in left panels corresponds to $H_0 = 73.24 \pm 1.74$ km s${}^{-1}$Mpc Riess while in right panels it corresponds to $\sigma_8 = 0.75 \pm 0.03$S8_planck. CBJ stands for CMB + BAO + JLA.