Colloquium
Department of Physics, NCU
Theoretical Explorations In Gravitational Wave Physics
Prof. Yi-Zen Chu
Dept. of Physics, NCU
Date 2022.03.08 (Tue)
Place S4-625
Time 14:00-16:00
In curved and odd dimensional flat spacetimes, electromagnetic and gravitational radiation do not travel strictly on the light cone but also inside of it. This latter “tail” radiation will backreact on the emitter of the radiation and thereby exert a self-force on it, altering its dynamics in the future. Such a scenario plays out in the context of Extreme-Mass-Ratio-Inspirals (EMRIs), where a solar mass object orbits and subsequently plunges into the supermassive black holes residing at the core of many — if not most — galaxies. The gravitational waves produced by such systems are the primary targets for future space-based detectors like LISA and TianQin. Hence, understanding this tail induced self-force is of physical importance.
I will describe my research program inspired by the desire to thoroughly understand this tail portion of massless signals and, more generally, the properties of gravitational waves (GWs) — but in the simpler context of the expanding universe we reside in. What features of GWs are distinct to cosmology? This appears to include new memory effects and even potential Cherenkov radiation. I will also describe my recent derivation of the real-time gravitational quadrupole formula — a result first derived by Einstein in 4D, and verified by Hulse and Taylor using binary pulsar systems — but up till last year was only known in frequency space for odd dimensional flat spacetimes.