Light Through the Geometric Memory of Spacetime: Optical Signatures in Gravitational Lensing

This work proposes an alternative way to think about gravitational lensing. Instead of assuming that weak-field spacetime geometry responds instantly to baryonic matter, it proposes that geometry needs a finite time to relax to its new configuration. From this perspective, part of the lensing signal may come from light traveling through a residual geometric “memory”: spacetime curvature that has not yet fully relaxed to the current baryonic distribution. The manuscript develops this idea and tests it with weak lensing, strong lensing, and colliding galaxy clusters.