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Decaying warm dark matter revisited

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Decaying dark matter models provide a physically motivated way of channeling energy between the matter and radiation sectors. In principle, this could affect the predicted value of the Hubble constant in such a way as to accommodate the discrepancies between CMB inferences and local measurements of the same. Here, we revisit the model of warm dark matter decaying non-relativistically to invisible radiation. In particular, we rederive the background and perturbation equations starting from a decaying neutrino model and describe a new, computationally efficient method of computing the decay product perturbations up to large multipoles. We conduct MCMC analyses to constrain all three model parameters, for the first time including the mass of the decaying species, and assess the ability of the model to alleviate the Hubble and σ8 tensions, the latter being the discrepancy between the CMB and weak gravitational lensing constraints on the amplitude of matter fluctuations on an 8 h−1 Mpc−1 scale. We find that the model reduces the H0 tension from ∼ 4σ to ∼ 3σ and neither alleviates nor worsens the S8 ≡ σ8m/0.3)0.5 tension, ultimately showing only mild improvements with respect to ΛCDM. However, the values of the model-specific parameters favoured by data is found to be well within the regime of relativistic decays where inverse processes are important, rendering a conclusive evaluation of the decaying warm dark matter model open to future work.

TidsskriftJournal of Cosmology and Astroparticle Physics
StatusUdgivet - aug. 2022

Bibliografisk note

Funding Information:
The authors are very grateful to Nikita Blinov for useful discussions and interpretations of our results. The numerical computations presented in this work were conducted at the Centre for Scientific Computing, Aarhus https://phys.au.dk/forskning/faciliteter/cscaa. E.B.H. and T.T. are supported by a research grant (29337) from the VILLUM FONDEN.

Publisher Copyright:
© 2022 IOP Publishing Ltd and Sissa Medialab.

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