CGCA Seminar – Nicolas Yunes

The Sound of Symmetry

Prof. Nicolas Yunes
University of Illinois Urbana-Champaign

What replaces Kerr when Einstein’s equations are modified, how does such a black hole ring, and can gravitational-wave data tell the difference? Connecting these questions requires consistent descriptions of both the stationary geometry and its dynamical response. I will discuss recent progress in constructing rotating black-hole solutions and calculating their gravitational quasinormal modes in effective field theories of gravity. These calculations reveal parity-dependent frequency shifts and raise a deeper question: what symmetry protects the equality of the even- and odd-parity spectra of Kerr? I will describe a framework for understanding this isospectrality. Finally, I will show how theory-specific spectra enter ringdown models and allow current gravitational-wave observations to constrain departures from general relativity, emphasizing the assumptions and regimes of validity needed to connect these calculations to observational tests.