On 27th of June 2025, Jelena Strišković successfully defended her doctoral thesis entitled “Study of active galactic nuclei variability and Lorentz invariance violation with MAGIC and LST-1 telescopes” at the Faculty of Physics (FIZRI) of the University of Rijeka. The thesis was supervised by Tomislav Terzić (FIZRI) and co-supervised by Dijana Dominis Prester (FIZRI) and Daniel Kerszberg (Laboratoire de physique nucléaire et des hautes énergies, Paris). The defence committee, composed of Michele Doro (University of Padova), José Manuel Carmona (University of Zaragoza), and Marina Manganaro (FIZRI), issued a unanimous decision that the thesis had been defended.

The thesis addresses searches for Lorentz invariance violation (LIV) through time-of-flight measurements of gamma-ray flares from active galactic nuclei (AGN), using observational data from the MAGIC and LST-1 telescopes. Quantum gravity models suggest that the speed of photons may depend on their energy, an effect that could become detectable over cosmological distances. Among the key contributions, the thesis presents the development and testing of the novel BASiL method for improving signal estimation in gamma-ray experiments (published in Phys. Rev. D 103, 123001, 2021), an analysis of a bright flare of the blazar BL Lacertae observed with MAGIC in September 2020 (including variability and multiwavelength spectral modelling), and LIV searches based on a bright flare of the blazar Markarian 421 observed by MAGIC in April 2014 (published in the Journal of Cosmology and Astroparticle Physics 044, 2024) — where for the first time in LIV studies a binned-likelihood approach was applied.

The committee’s evaluation praised the thesis as well-structured and remarkably clear, noting that original contributions are clearly identified, the English language is excellent, and the overall quality is outstanding. The full thesis text is available in the FIZRI repository.