We introduce the kinematic lensing ratio (KiLeR), a geometric dark-energy probe from weak lensing. Combining shear ratios with intrinsic galaxy shapes inferred from kinematics, KiLeR naturally mitigates most first-order lensing systematics, including redshift errors, intrinsic alignments, and baryonic effects. The forecast on Roman shows a 192% improvement in the state-of-the-art dark energy constraints from adding KiLeR, providing independent tests of the evolving dark energy hint in the DESI DR2 BAO+CMB+SN analysis. We quantify the science requirements on systematic and statistical error control and discuss the pathways towards KiLeR observation.
@article{arxiv.2604.26015,
title = {Kinematic Lensing Ratio: Reviving Weak Lensing Cosmography as a Geometric Dark Energy Probe},
author = {Qinxun Li},
journal= {arXiv preprint arXiv:2604.26015},
year = {2026}
}
Comments
5 pages, 3 figures, 1 table (main text). Resubmitted after addressing the referee's comments. Comments are welcome! See also my talk at Dark Energy from Home: https://www.youtube.com/watch?v=6NWnWb92vcE&t=4s