Recognizing Axionic Dark Matter by Compton and de Broglie Scale Modulation of Pulsar Timing
Ivan De Martino, Tom Broadhurst, S.-H. Henry Tye, Tzihong Chiueh, Hsi-Yu Schive, Ruth Lazkoz · 2017 · 83 citationsRead the paper
Light axionic dark matter, motivated by string theory, is increasingly favored for the ``no weakly interacting massive particle era''. Galaxy formation is suppressed below a Jeans scale of $\ensuremath{\simeq}{10}^{8}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ by setting the axion mass to ${m}_{B}\ensuremath{\sim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$, and the large dark cores of dwarf galaxies are explained as solitons on the de Broglie scale. This is persuasive, but detection of the inherent scalar field oscillation at the Compton frequency ${\ensuremath{\omega}}_{B}=(2.5\text{ }\text{ }\text{months}{)}^{\ensuremath{-}1}({m}_{B}/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV})$ would be definitive. By evolving the coupled Schr\"odinger-Poisson equation for a Bose-Einstein condensate, we predict the dark matter is fully modulated by de Broglie interference, with a dense soliton core of size $\ensuremath{\simeq}150\text{ }\text{ }\mathrm{pc}$, at the Galactic center. The oscillating field pressure induces general relativistic time dilation in proportion to the local dark matter density and pulsars within this dense core have detectably large timing residuals of $\ensuremath{\simeq}400\text{ }\text{ }\mathrm{nsec}/({m}_{B}/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV})$. This is encouraging as many new pulsars should be discovered near the Galactic center with planned radio surveys. More generally, over the whole Galaxy, differences in dark matter density between pairs of pulsars imprints a pairwise Galactocentric signature that can be distinguished from an isotropic gravitational wave background.
What the full text shows
Theory or simulation- Pulsars within the Galactic center's dense soliton core exhibit timing residuals due to oscillating field pressure. — ~400 nsec / (mB / 10^-22 eV) (Axion mass mB ~ 10^-22 eV)
- The dark matter density distribution is fully modulated on the de-Broglie scale, forming a central soliton core. — ~150 pc radius (Milky Way Galactic center)
- Pulsar timing residuals in the central soliton are significantly higher than those of local pulsars. — 2-3 orders of magnitude higher (Within the central Kiloparsec of the Galaxy)
- Relative timing residuals for pulsar pairs can be enhanced if they are located near density maxima and are out of phase. — 100% enhancement (Pairwise measurements across the Galaxy)
- Timing residuals for pulsars in local dwarf spheroidal galaxies are lower than those at the Galactic center. — ~10^-3 smaller (Solitonic cores of dwarf spheroidal galaxies)
- Setup
- Simulations of a massive halo (10^11 M_sun) using the ψDM approach; assumed Hubble constant H0 = 70 km/sec/Mpc and axion mass mB ~ 10^-22 eV.
- How
- The authors evolved the coupled Schrödinger-Poisson equation for a Bose-Einstein condensate to simulate dark matter halo structure. They calculated the resulting general relativistic time dilation (frequency shift) induced by oscillating scalar field pressure on pulsar timing residuals.
- Limitations
- Detection within the inner 100 pc is compromised by high plasma density and ISM irregularities causing pulse smearing. · Blind searches at high frequencies (<10 GHz) are currently impractical with single dishes. · Single pulsar pairs are insufficient for detection; an ensemble is required to average over modulations.
Summarized by Gemma 4 from the open-access full text · 3 Oct 2026. Read it