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Can gravitational lensing reveal the ghostly axions hiding in dark matter?
Alex Laguë, Keir K. Rogers, Mathew S. Madhavacheril, J. Richard Bond, Erminia Calabrese, Mark J. Devlin, Jo Dunkley, Vera Gluscevic, Renée Hložek, Hidde T. Jense, Thibaut Louis, Frank J. Qu, Bernardita Ried Guachalla, Neelima Sehgal, Blake D. Sherwin, Suzanne T. Staggs, Alexander van Engelen
June 4, 2026
Ultralight axions are exotic dark matter candidates that bend light differently than ordinary matter. Using gravitational lensing maps from Planck, ACT, and SPT-3G, researchers placed the tightest limits on axions between 10⁻²⁶ and 10⁻²⁴.⁵ eV, ruling out axions as more than ~2–9% of dark matter depending on mass. One mass range hints at a possible signal, though it may be a statistical fluke.
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