Leart Sabani and Lucía Vélez Tartajo Successfully Defend their Theses

The master thesis defense season at the CoG kicked off with a bang, as two of our students, Leart Sabani and Lucía Vélez Tartajo, successfully defended their projects on the 20th and 22nd of May respectively. Both defenses were a perfect mix of high-level conceptual presentation of abstract physical ideas and technical analysis of the problems at hand.

Leart’s thesis, Listening to Oscillatons: Gravitational Wave Scattering and Resonant Energy Transfer, explores oscillatons, structures formed by ultra-light scalar fields that have been proposed as dark matter candidates. Using numerical methods, Leart solved the background equations to obtain different oscillaton configurations. He then applied perturbation theory to investigate the dynamics of gravitational perturbations and their interactions with oscillatons. His work demonstrates that, under specific conditions, parametric resonances can arise, enabling energy transfer between the background field and the perturbation. These results suggest that such resonances could potentially reveal the existence of dark matter through observable signatures in gravitational waves.

Lucía’s thesis, Understanding Black Hole Spectroscopy, focused on black hole ringdown, the final stage of a black hole merger, during which the remnant black hole settles into equilibrium while emitting gravitational waves, characterized by quasinormal modes (QNMs). In her thesis, Lucía showed that the relative excitation of these QNMs depends strongly on how the black hole is perturbed, while also further establishing the connection between black hole ringing and the photon sphere. Her research provides valuable insight into how QNM excitation may be inferred from earlier stages of the merger, such as the inspiral phase, paving the way for the development of even more accurate waveform models.

Both Leart and Lucía will be deeply missed at the CoG, where they have been highly active and valued members of the community, contributing enthusiastically to both its academic and social environment. We are confident that they both have bright futures ahead and wish them the very best in their next chapters.

May 29, 2026, 6:25 a.m.