Common Origin of Warm Dark Matter and Dark Radiation

TL;DR

This paper proposes a cosmological model where dark radiation and warm dark matter originate from the decay of a late-decaying particle, predicting observable correlations in future cosmological data.

Contribution

It introduces the COWaRD framework linking dark radiation and warm dark matter from a common decay origin, with testable predictions for future observations.

Findings

COWaRD predicts a correlation between dark radiation and large-scale structure suppression.

The model is realized in supersymmetric axion scenarios.

Future CMB, LSS, and 21-cm surveys can test the model's predictions.

Abstract

We consider a cosmological scenario where a relativistic particle and a stable massive particle are simultaneously produced from the decay of a late-decaying particle after Big-Bang Nucleosynthesis but before matter-radiation equality. The relativistic and massive particles behave as dark radiation and warm dark matter, respectively. Due to a common origin, the warmness and abundances are closely related. We refer to the models that lead to such a scenario as Common Origin of Warm and Relativistic Decay Products (COWaRD). We show that COWaRD predicts a correlation between the amount of dark radiation and suppression of the large scale structure, which can be tested in future precision cosmology observations. We demonstrate that COWaRD is realized, as an example, in a class of supersymmetric axion models and that future observations by the next generation Cosmic Microwave Background, Large Scale Structure, and 21-cm surveys can reveal the structure of the theory.