On 8th of November, the Faculty of Physics of the University of Rijeka celebrated its anniversary. On that occasion, the faculty dean, Rajka Jurdana-Šepić presented awards, appreciation certificates, and acknowledgements. Angelo Zec received an award for the best master thesis defended at the Faculty of Physics in 2023.

From the award justification: Angelo Zec defended a master thesis entitled “Correlations in radiation from gamma-ray bursts” (available at: urn:nbn:hr:194:854172). The aim of the work was to examine the analysis method and results in the research article Xu, H.; Oh, B.-Q. “Regularity of high energy photon events from gamma rays bursts” (JCAP, 2018, 1801, 050), which claims that the observed correlation between gamma-ray detection energies and times from gamma-ray bursts (GRBs) is caused by Lorentz symmetry breaking. To this end, Angelo developed a computer code which generated Monte Carlo simulations of gamma-ray bursts and analyzed the simulated data. The results and conclusions of Xu & Ma (2018) are based on the assumption that the values ​​obtained in their analysis are distributed according to the normal distribution. Angelo showed that this assumption is wrong, that the distribution of the results is not symmetrical, and that this assumption cannot be used to determine the confidence intervals. Moreover, he proposed the coverage to be determined by counting, and in this way determined that in the work of Xu & Ma (2018) the frequency of values ​​that are outside the 3σ interval is overestimated by as much as 5.9 times. The final conclusion of Angelo’s work is: “Taking into account the inappropriate method of determining the confidence interval, and the fact that the form of analysis contains a large number of a posteriori decisions, it was concluded that the analyzed method of analysis does not give reliable results.”
It is important to note that Angelo showed great independence in research, organisation and writing the thesis. He developed the computer code for simulation and data analysis independently. On his own initiative, he decided to investigate coverage by counting and conducted the necessary analysis. He formulated his conclusions with a high level of independence. The diploma thesis was written legibly and clearly, and the methods, results and conclusions were presented in an understandable and objective way.

Thesis abstract: Some models of quantum gravity allow for violation of Lorentz invariance. This can be modelled by modifying the photon dispersion relation. In other words, photon would have energy dependent speed. This form of dependence can be experimentally tested by analysing signals from cosmological sources. In this work, the method of analysis of gamma-ray light curves based on sharpness maximization method was tested with Monte Carlo simulation. In the tested method of analysis it is assumed that sharpness is distributed according to the normal distribution. In Monte Carlo simulation, test sample was generated and analysed 250 times. Four test samples gave 3 sigma significance. In confidence intervals formation it was assumed that results are distributed according to the normal distribution. In normal distribution, 3 sigma significance relates to confidence level of 99,73%. In other words, expected frequency of results that fall outside 3 sigma region is one in 370. Frequency from Monte Carlo simulation is four in 250, or, one in 62,5. That is 5,9 times more frequent than expected. Additionally, it was demonstrated that distribution of sharpness can not be described with normal distribution. This implies that used method of formation of confidence intervals is not suitable. Formation of confidence intervals from coverage was suggested. Considering usage of non suitable method of confidence interval formation and large number of a posteriori decisions in process of analysis, it was concluded that the tested method of analysis does not produce plausible results.