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arXiv · 2310.08272

From QFT to Boltzmann: Freeze-in in the presence of oscillating condensates

Wen-Yuan Ai·Ankit Beniwal·Angelo Maggi·David J. E. Marsh
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Abstract

Scalar dark matter (DM), and axions in particular, have an irreducible abundance of particles produced by freeze-in due to portal interactions with the Standard Model plasma in the early Universe. In addition, vacuum misalignment and other mechanisms can lead to the presence of a cold, oscillating condensate. Therefore, generically, the evolution of the DM in both forms, condensate and particles, needs to be studied simultaneously. In non-equilibrium quantum field theory, the condensate and particles are described by one- and two-point functions, respectively. The fundamental coupled equations of motion (EoMs) of these objects are non-local. To simplify the EoMs and bring them into a familiar form for relic abundance calculations, we perform a Markovianization process for a quasi-harmonically oscillating homogeneous condensate, leading to local EoMs for the particle distribution function and the envelope function of condensate oscillation. This reduces the dynamics to a pair of coupled Boltzmann equations, and we derive explicitly the form of the collision operators for all particle and condensate interactions.

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Wen-Yuan Ai, Ankit Beniwal, Angelo Maggi, David J. E. Marsh. 2023-10-12. From QFT to Boltzmann: Freeze-in in the presence of oscillating condensates. https://doi.org/10.1007/jhep02(2024)122

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