Gravitational lenses hint at earlier cosmic acceleration than expected

Three interacting dark energy models, where dark matter and dark energy exchange energy at a rate tied to the deceleration parameter, were tested against lensing data from early-type galaxies and the cluster Abell 1689. All models prefer negative coupling strengths, implying energy flows from dark energy into dark matter — opposite to common assumptions — and the inferred magnitudes are considerably larger than limits from supernovae, CMB, and BAO. The acceleration transition appears around z ~ 1.8–2.1, roughly a billion years earlier than ΛCDM places it. Gravitational lensing thus acts as an independent probe of dark-sector dynamics sensitive to expansion history in a complementary redshift range.