Cepstrum analysis of interfering delayed signals as a tool for detecting gravitational lenses

Gravitational lenses might be discoverable by measuring the time differential for propagation of radiation from source to observer along different paths, even if the ray trajectories cannot be resolved in angle. To this end, cepstrum analysis may be performed on the intensity variations of individual variable emission sources (such as quasars) at optical and radio wavelengths simultaneously. The method suggested could greatly augment the class of sources serving as candidates for detection of gravitational lenses