6 papers
A Circular Disformal Kerr Black Hole
Jibril Ben Achour, Adolfo Cisterna, Hugo Roussille
The Kerr solution is the cornerstone of General Relativity (GR) for modelling astrophysical rotating black holes and for testing GR through gravitational-wave observations and blac…
Algebraically special perturbations of the Kerr black hole: a metric formulation
Jibril Ben Achour, Clara Montagnon, Hugo Roussille
Perturbations of the Kerr black hole are notoriously difficult to describe in the metric formalism and are usually studied in terms of perturbations of the Weyl scalars. In this wo…
Black hole photon ring beyond General Relativity: an integrable parametrization
Jibril Ben Achour, Eric Gourgoulhon, Hugo Roussille
In recent years, the shape of the photon ring in black holes images has been argued to provide a sharp test of the Kerr hypothesis for future black hole imaging missions. In this w…
Disformal gravitational waves
Jibril Ben Achour, Mohammad Ali Gorji, Hugo Roussille
Contrary to conformal transformations, disformal transformations can change the principal null directions of a spacetime geometry. Thus, depending on the frame a gravitational wave…
Magnetic levitation in the field of a rotating dipole
Grégoire Le Lay, Sarah Layani, Adrian Daerr +5
It is well known that two permanent magnets of fixed orientation will either always repel or attract one another regardless of the distance between them. However, if one magnet is…
Quadratic perturbations of the Schwarzschild black hole: The algebraically special sector
Jibril Ben Achour, Hugo Roussille
We investigate quadratic algebraically special perturbations (ASPs) of the Schwarzschild black hole. Their dynamics are derived from the expansion up to second order in perturbatio…