Talk detail

Participant	Amador de Oliveira, Leandro
Institution	Universidade Federal do Pará - Rua Augusto Corrêa, 01 - Guamá - Belém - Pará - Brazil

Session	AT3	Accepted	Yes	Order	8	Time	16:50 - 17:05	15' + 5'
Talk	Oral abstract	Title	Quasinormal modes of the Draining Bathtub
Co-authors	Sam R. Dolan and Luis C. B. Crispino
Abstract	Under certain conditions, sound waves in a fluid may be governed by a Klein-Gordon equation on an `effective spacetime' determined by the background flow properties. Here we consider the draining bathtub: a circulating, draining flow whose effective spacetime shares key features with the rotating black hole (Kerr) spacetime. We present an investigation of the role of quasinormal (QN) mode of this system. First, we simulate a perturbation in the time domain by applying a finite-difference method, to demonstrate the ubiquity of `QN ringing'. Next, we solve the wave equation in the frequency domain with the continued-fraction method, to compute QN spectra numerically. We then explore the geometric link between (prograde and retrograde) null geodesic orbits on the spacetime, and the properties of the QN spectra. We develop a `geodesic expansion' method which leads to asymptotic expressions (in inverse powers of mode number $m$) for the spectra and the radial functions.