Speaker
Description
Understanding the nature of dark matter remains a central challenge in physics. Flux-ratio anomalies in strongly lensed quasars provide one of the few observational probes of dark matter structure down to ∼ 10⁶ M⊙. Here we present the first population-level statistical analysis of cusp-configuration flux-ratio anomalies using the latest set of microlensing-free measurements from 17 quadruply imaged quasars, including new JWST observations. We introduce a macromodel-independent framework that maps lens configurations into a unified cusp-parameter–opening-angle $R_{\rm cusp}-\phi$ parameter space, enabling direct comparison across dark matter scenarios. We identify a specific geometric class of cusp lenses in which flux-ratio anomalies are intrinsically sensitive to dark matter microphysics and cannot be absorbed by macromodel complexity. Bayesian model comparison reveals decisive evidence (Bayes factor > 100) favouring fuzzy dark matter over both cold and self-interacting dark matter, which represents the strongest gravitational-lensing evidence for wave-like dark matter and makes falsifiable predictions for forthcoming surveys.