Constraints from High-Precision Measurements of the Cosmic Microwave Background: The Case of Disintegrating Dark Matter with ${\Lambda}$ or Dynamical Dark Energy

Understand

In recent years discrepancies have emerged in measurements of the present-day rate of expansion of the universe $H_0$ and in estimates of the clustering of matter $S_8$.

• Using the most recent cosmological observations we reexamine a novel model proposed to address these tensions, in which cold dark matter disintegrates into dark radiation.
• The disintegration process is controlled by its rate $Q = \alpha \mathcal{H} \rho_{\rm ddm}$, where $\alpha$ is a (constant) dimensionless parameter quantifying the strength of the disintegration mechanism and $\mathcal{H}$ is the conformal Hubble rate in the spatially flat Friedmann-Lema\^{i}tre-Robertson-Walker universe and $\rho_{\rm ddm}$ is the energy density of the disintegrating cold dark matter.
• We constrain this model with the latest 2018 Planck temperature and polarization data, showing that there is no evidence for $\alpha \neq 0$ and that it cannot solve the $H_0$ tension below $3\sigma$, clashing with the result obtained by analyzing the Planck 2015 temperature data.