Time Delay between Relativistic Images as a probe of Cosmic Censorship
  We study the time delay between successive relativistic images in
gravitational lensing as a possible discriminator between various collapse end
states and hence as a probe of cosmic censorship. Specifically we consider both
black hole and naked singularity spacetimes admitting photon spheres where an
infinite number of relativistic Einstein Rings can be formed at almost the same
radius and naked singularity spacetimes without a photon sphere where multiple
relativistic Einstein Rings can form almost up to the center of the lens. The
metrics we have considered to sample these scenarios are the Schwarzschild
black hole, Janis-Newman-Winicour (naked singularity with photon sphere),
Joshi-Malafarina-Narayan, and Tolman-VI (naked singularities without photon
sphere) which are a fair sample of the theoretical possibilities. We show that
the differential time delay between the relativistic images for naked
singularities without a photon sphere progressively decreases for the models we
study as opposed to that for black holes and naked singularities with a photon
sphere, where it is known to be roughly constant. This characteristic
difference in the time delay between successive images for these two cases can
be potentially exploited for a source with known intrinsic variability to
discriminate between these scenarios even when the images are not spatially
resolved.
