Nonclassicality of axionlike dark matter through gravitational self-interactions

Michael Kopp, Vasileios Fragkos, Igor Pikovski

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Axionlike particles (ALPs) are promising dark matter candidates. They are typically described by a classical field, motivated by large phase space occupation numbers. Here we show that such a description is accompanied by a quantum effect: squeezing due to gravitational self-interactions. For a typical QCD axion today, the onset of squeezing is reached on μs scales and grows over millennia. Thus within the usual models based on the classical Schrödinger-Poisson equation, a type of Gross-Pitaevskii equation, any viable ALP is nonclassical. We also show that squeezing may be relevant on the scales of other self-gravitating systems such as galactic haloes, or solitonic cores. Conversely, our results highlight the incompleteness and limitations of the classical single field description of ALPs.

Original languageEnglish
Article number043517
JournalPhysical Review D
Volume106
Issue number4
DOIs
StatePublished - 15 Aug 2022

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