Topic: perturbative regime

Taillte May investigates how unstable black-hole quasinormal-mode spectra affect observed gravitational-wave signals. Small changes in a gravitational potential can substantially shift the frequencies normally used to test astrophysical black holes. A simple time-domain model reveals a delay before those shifts appear, tied to the echo travel time between the perturbation and the main potential. In the perturbative regime, the frequency change after one echo agrees with the conventional frequency-domain prediction. Beyond that regime, the intermediate waveform cannot be represented by a single

Small changes in a black-hole potential can strongly shift its quasinormal spectrum, but their effect on a measured waveform is time dependent. This talk uses a simple model to show that frequency changes appear only after an echo-related delay. In a perturbative regime, one echo recovers the usual frequency-domain shift; outside it, intermediate-time behaviour cannot be described by a single constant frequency correction.