Gravitational perturbation around a Schwarzschild black-hole pierced by a cosmic string

Leysens, Gwenaël
(2026)

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Details

Supervisors
Ringeval, Christophe
Faculty
Faculté des sciences
Degree label
Master [120] en sciences physiques, à finalité approfondie
Abstract
enThis master's thesis investigates the gravitational perturbations and quasi-normal mode (QNM) spectrum of a Schwarzschild black hole pierced by a cosmic string, described by the Aryal-Ford-Vilenkin (AFV) metric. The Regge-Wheeler formalism is adapted to this conical background, where the angular eigenvalue ℓ(ℓ+1) is replaced by λ(λ+1), with λ = k + |m|/α encoding the deficit angle α induced by the string. The α-independence of the radial perturbation equations is established through an explicit computation of the perturbed Ricci tensor, and the QNM spectrum is then computed using the WKB approximation, revealing how the deficit angle shifts the ringdown frequencies relative to the Schwarzschild case. These results open the possibility of probing the existence of cosmic strings through the gravitational-wave signature they would imprint on a black hole's ringdown.