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We study the non-equilibrium dynamics of a pseudoscalar axion-like particle (ALP) weakly coupled to degrees of freedom in thermal equilibrium by obtaining its reduced density matrix. Its time evolution is determined by the in-in effective action which we obtain to leading order in the (ALP) coupling but to \emph{all orders} in the couplings of the bath to other fields within or beyond the standard model.
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Nonequilibrium dynamics of axionlike particles: The quantum master equation
We study the nonequilibrium dynamics of axionlike particles (ALP) coupled to Standard Model degrees of freedom in thermal equilibrium. The quantum master equation (QME) for the ALP reduced density matrix is derived to leading order in the coupling of the ALP to the thermal bath, but to all orders of the bath couplings to degrees of freedom within or beyond the Standard Model other than the ALP. The QME describes the damped oscillation dynamics of an initial misaligned ALP condensate, thermalization with the bath, decoherence, and entropy production within a unifying framework. The ALP energy density features two components: a “cold” component from the misaligned condensate and a “hot” component from thermalization with the bath.
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- Award ID(s):
- 2111743
- PAR ID:
- 10624938
- Publisher / Repository:
- physical review D
- Date Published:
- Journal Name:
- Physical Review D
- Volume:
- 107
- Issue:
- 6
- ISSN:
- 2470-0010
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1103/PhysRevD.107.063518
