Year: 2026
Type: preprint
Abstract: We investigate the quantum statistical effects of bosonic warm dark matter (BWDM) in a microscopic model in which dark radiation (DR) is produced through the annihilation process $χχ\rightarrowϕϕ$ mediated by a Yukawa interaction. By decomposing the BWDM phase-space distribution into thermal and Bose--Einstein condensed components, we derive the thermally averaged annihilation cross sections for the thermal--thermal, thermal--condensate, and condensate--condensate channels, including the Sommerfeld enhancement. We find that, for the relatively small scalar DR masses considered here, the thermal--condensate channel remains subdominant. The transition between the thermal--thermal dominated and condensate--condensate dominated regimes is characterized by a critical condensate fraction $r_{\rm c}$, which depends mainly on the BWDM mass and the scalar DR mass. For condensate fractions above this critical value, the condensate--condensate channel can dominate the present-day annihilation rate. We further constrain the BWDM parameter space using the observational upper bound on the additional effective number of relativistic species, $ΔN_{\mathrm{eff}}$.
Source: arXiv (Cornell University)
Author: Zhang, Zhijian
Institution: Beijing Normal University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204956363