Triangle Seminars
Wednesday, 9 Dec 2026
TBA
📍 London
Eric Perlmutter
(IPhT, Saclay)
Abstract:
TBA
TBA
Posted by: Kiarash Naderi
TBA
📍 London
Deniz Bozkurt
(DESY)
Abstract:
TBA
TBA
Posted by: Elia de Sabbata
Thursday, 10 Dec 2026
Spatial projection of Kerr quasinormal modes from numerical data
📍 London
Lionel London
(KCL)
Abstract:
When two black holes merge, the newly formed black hole "rings down", like a struck bell, giving off gravitational waves that detectors such as LIGO can measure. The tones of this ringing, called quasinormal modes, are set entirely by the black hole's mass and spin. Measuring them is therefore one of the cleanest tests of Einstein's general relativity. The catch is that these modes are unusual. A guitar string's vibrations can be split into separate harmonics using the same idea as a Fourier series: each harmonic is orthogonal to the others, so you can "project" a vibration onto each one in turn. A ringing black hole loses energy as it rings, and its modes fade away. Ordinary orthogonality fails, so researchers usually resort to fitting curves to simulated signals. That can be unreliable when several modes overlap or the data are noisy. In this talk I will explain, with ideas familiar from linear algebra and Fourier analysis, how a clever change of basis makes black hole modes orthogonal again. This lets us project each mode straight out of computer-simulated data. I will show examples of the method recovering hidden and faint modes, and discuss what noise means for measuring them.
When two black holes merge, the newly formed black hole "rings down", like a struck bell, giving off gravitational waves that detectors such as LIGO can measure. The tones of this ringing, called quasinormal modes, are set entirely by the black hole's mass and spin. Measuring them is therefore one of the cleanest tests of Einstein's general relativity. The catch is that these modes are unusual. A guitar string's vibrations can be split into separate harmonics using the same idea as a Fourier series: each harmonic is orthogonal to the others, so you can "project" a vibration onto each one in turn. A ringing black hole loses energy as it rings, and its modes fade away. Ordinary orthogonality fails, so researchers usually resort to fitting curves to simulated signals. That can be unreliable when several modes overlap or the data are noisy. In this talk I will explain, with ideas familiar from linear algebra and Fourier analysis, how a clever change of basis makes black hole modes orthogonal again. This lets us project each mode straight out of computer-simulated data. I will show examples of the method recovering hidden and faint modes, and discuss what noise means for measuring them.
Posted by: Kymani Armstrong-Williams