Pulsar Timing Array signature from oscillating metric perturbations due to ultra-light axion

Jai Chan Hwang, Donghui Jeong, Hyerim Noh, Clemente Smarra

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

A coherently oscillating ultra-light axion can behave as dark matter. In particular, its coherently oscillating pressure perturbations can source an oscillating scalar metric perturbation, with a characteristic oscillation frequency which is twice the axion Compton frequency. A candidate in the mass range 10(-24,-21) eV can provide a signal in the frequency range tested by current and future Pulsar Timing Array (PTA) programs. Involving the pressure perturbations in a highly nonlinear environment, such an analysis demands a relativistic and nonlinear treatment. Here, we provide a rigorous derivation of the effect assuming weak-gravity and slow-motion limit of Einstein's gravity in zero-shear gauge and show that dark matter's velocity potential determines the oscillation phase and frequency change. A monochromatic PTA signal correlated with the velocity field would confirm the prediction, for example, by cross-correlating the PTA results with the future local velocity flow measurements.

Original languageEnglish (US)
Article number014
JournalJournal of Cosmology and Astroparticle Physics
Volume2024
Issue number2
DOIs
StatePublished - Feb 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics

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