SEMINAR 2023

Despite the massless character of their associated particles, electromagnetic and gravitational waves do not travel strictly on the light cone in curved and odd dimensional flat spacetimes. The portion of the wave traveling inside the null cone is dubbed the “tail”, and in the 4-dimensional curved spacetime context, is usually attributed the interaction of the long wavelength modes of the wave’s field with geometric curvature.

I shall describe my efforts to study the causal structure of electromagnetic and gravitational waves – devising methods to cleanly separating the null vs tail signals – primarily in odd dimensional Minkowski and expanding cosmologies. The latter leads to a theoretical observation that gravitational waves in our universe may contain additional polarizations in addition to the usual massless spin-2 tensor ones.