Axions: Bose Einstein Condensate or Classical Field?
arXiv:1405.1139 · doi:10.1016/j.astropartphys.2014.12.007
Abstract
The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligeable.
11 pages, 1 figure, version accepted for publication
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- Correspondence of I- and Q-balls as Non-relativistic Condensates
- Attractive vs. repulsive interactions in the Bose-Einstein condensation dynamics of relativistic field theories
- Dark Matter as a Non-Relativistic Bose-Einstein Condensate with Massive Gravitons
- The Pressure of Misalignment Axions: a Difference from WIMPs in Galaxy Formation?