Backreaction of axion coherent oscillations

Mor Rozner, Vincent Desjacques

Research output: Contribution to journalArticlepeer-review

Abstract

We investigate how coherent oscillations backreact on the evolution of the condensate wave function of ultralight axions in the nonrelativistic regime appropriate to cosmic structure formation. The coherent oscillations induce higher harmonics beyond the fundamental mode considered so far when a self-interaction is present, and imprint oscillations in the gravitational potential. We emphasize that the effective self-interaction felt by the slowly-varying envelop of the wave function always differs from the bare Lagrangian interaction potential. We also point out that, in the hydrodynamical formulation of the Gross-Pitaevskii equation, oscillations in the gravitational potential result in an attractive force that counteracts the effect of the quantum pressure arising from the strong delocalization of the particles. Since these effects become significant on physical scales less than the (large) Compton wavelength of the particle, they are presumably not very relevant on the mildly nonlinear scales traced by intergalactic neutral hydrogen for axion masses consistent with the bounds from the Lyman-α forest. However, they might affect the formation of virialized cosmological structures and their stability.

Original languageEnglish
Article number023530
JournalPhysical Review D
Volume98
Issue number2
DOIs
StatePublished - 23 Jul 2018

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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