Multi-Messenger Time Delays from Lensed Gravitational Waves
  We investigate the potential of high-energy astrophysical events, from which
both massless and massive signals are detected, to probe fundamental physics.
In particular, we consider how strong gravitational lensing can induce time
delays in multi-messenger signals originating from the same source. Obvious
messenger examples are massless photons and gravitational waves, and massive
neutrinos, although more exotic applications can also be imagined, such as to
massive gravitons or axions. The different propagation times of the massive and
massless particles can, in principle, place bounds on the total neutrino mass
and probe cosmological parameters. Whilst measuring such an effect may pose a
significant experimental challenge, we believe that the `massive time delay'
represents an unexplored fundamental physics phenomenon.
