Far from equilibrium dynamics of Bose-Einstein condensation for Axion Dark Matter

Abstract

Axions and similar very weakly interacting particles are increasingly compelling candidates for the cold dark matter of the universe. Having very low mass and being produced non-thermally in the early Universe, axions feature extremely high occupation numbers. It has been suggested that this leads to the formation of a Bose-Einstein condensate with potentially significant impact on observation and direct detection experiments. In this note we aim to clarify that if Bose-Einstein condensation occurs for light and very weakly interacting dark matter particles, it does not happen in thermal equilibrium but is described by a far-from-equilibrium state. In particular we point out that the dynamics is characterized by two very different timescales, such that condensation occurs on a much shorter timescale than full thermalization.

18 pages, 2 figures. v2 minor clarifications added

References in corpus (8)

• Axion Cosmology
• Bose-Einstein Condensation of Dark Matter Axions
• A High Resolution Search for Dark-Matter Axions
• Nonthermal fixed points and the functional renormalization group
• Basin of attraction for turbulent thermalization and the range of validity of classical-statistical simulations
• Strong versus weak wave-turbulence in relativistic field theory
• Evolution and thermalization of dark matter axions in the condensed regime
• An argument that the dark matter is axions

Cited by in corpus (28)

• Do Dark Matter Axions Form a Condensate with Long-Range Correlation?
• Stochastic fluctuations of bosonic dark matter
• Universal self-similar dynamics of relativistic and nonrelativistic field theories near nonthermal fixed points
• On Longevity of I-ball/Oscillon
• Axions: Bose Einstein Condensate or Classical Field?
• Kinetic theory of non-thermal fixed points in a Bose gas
• Gravitational Waves as a New Probe of Bose-Einstein Condensate Dark Matter
• Quantum and Classical Behavior in Interacting Bosonic Systems
• Non-thermal fixed points: Universal dynamics far from equilibrium
• Off-equilibrium infrared structure of self-interacting scalar fields: Universal scaling, Vortex-antivortex superfluid dynamics and Bose-Einstein condensation
• New astrophysical bounds on ultralight axionlike particles
• Duration of classicality in highly degenerate interacting Bosonic systems
• Correspondence of I- and Q-balls as Non-relativistic Condensates
• Attractive vs. repulsive interactions in the Bose-Einstein condensation dynamics of relativistic field theories
• Universal dynamics and non-thermal fixed points in quantum fluids far from equilibrium
• Gravitational self-interactions of a degenerate quantum scalar field
• From QFT to Boltzmann: Freeze-in in the presence of oscillating condensates
• Scalar field dark matter in hybrid approach
• Kinetic description of Bose-Einstein condensation with test particle simulations
• Squeezing the Axion
• Anomalous scaling at non-thermal fixed points of the sine-Gordon model
• Kinetic theory and classical limit for real scalar quantum field in curved space-time
• Real scalar field, non-relativistic limit, and cosmological expansion
• Fate of homogeneous ${\mathbb{Z}}_2$-symmetric scalar condensates
• Bose-Einstein condensation in relativistic plasma
• Axion Structure Formation II: The Wrath of Collapse
• Supplying Dark Energy from Scalar Field Dark Matter
• Constraints on Axion Dark Matter by Spin-Dependent Macroscopic Force