Bose-Einstein condensation and dark radiation production from bosonic warm dark matter
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→ϕϕ 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 rc, 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, ΔNeff.
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BibTeX
@misc{zhang2026boseeinstein,
title = {{Bose-Einstein condensation and dark radiation production from bosonic warm dark matter}},
author = {Zhijian Zhang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.29947},
eprint = {2608.29947},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29947},
}
RIS
TY - UNPB
TI - Bose-Einstein condensation and dark radiation production from bosonic warm dark matter
AU - Zhijian Zhang
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2608.29947
UR - https://arxiv.org/abs/2608.29947
AB - 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→ϕϕ 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_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_eff.
ER -