Title Korelacije u zračenju iz provala gama-zraka
Title (english) Correlations in radiation from gamma-ray bursts
Author Angelo Zec
Mentor Tomislav Terzić (mentor)
Committee member Tomislav Terzić (član povjerenstva)
Committee member Darko Mekterović (predsjednik povjerenstva)
Committee member Mateo Paulišić (član povjerenstva)
Granter University of Rijeka (Faculty of Physics) Rijeka
Defense date and country 2023-09-28, Croatia
Scientific / art field, discipline and subdiscipline NATURAL SCIENCES Physics
Abstract U nekim modelima kvantne gravitacije javlja se mogućnost narušenja Lorentzove invarijantnosti (eng. Lorentz invariance violation, LIV). Jedan od načina modeliranja LIV-a je modificiranjem fotonske disperzijske relacije, odnosno, uvođenjem ovisnosti brzine fotona o njegovoj energiji. Takva ovisnost može se eksperimentalno ispitati analiziranjem signala iz izvora na kozmološkim udaljenostima. U ovom radu je Monte Carlo simulacijom ispitana metoda analize zračenja iz provale gama-zraka temeljena na metodi maksimalne oštrine. U ispitanoj metodi analize koristi se pretpostavka da se vrijednost sharpness-a raspodjeljuje prema normalnoj raspodjeli. Monte Carlo simulacija provedena je tako da je 250 puta generiran testni uzorak te je na njemu provedena analiza. Četiri testna uzorka dala su rezultat signifikantnosti 3 sigma. Intervali pouzdanosti određeni su primjenom pretpostavke o raspodjeli rezultata prema normalnoj raspodjeli. Kod normalne raspodjele signifikantnost od 3 sigma odgovara razini pouzdanosti od 99,73%, odnosno, očekivana učestalost vrijednosti koja se nalazi izvan 3 sigma je približno jednom u 370 puta. Iz Monte Carlo simulacije dobivena je učestalost vrijednosti koja se nalazi izvan 3 sigma od četiri u 250 puta, odnosno, jednom u 62,5 puta, što je 5,9 puta veća učestalost od očekivane. Pokazano je da se rasipanje vrijednosti sharpness-a ne može opisati normalnom raspodjelom. To znači da metoda određivanja intervala pouzdanosti prema normalnoj raspodjeli nije primjerena za funkciju sharpness. Predloženo je određivanje intervala pouzdanosti promatranjem pokrivanja. Uzimajući u obzir neprimjerenu metodu određivanja intervala pouzdanosti, te činjenicu da forma analize sadrži veliki broj a posteriori odluka, zaključeno je da ispitana metoda analize ne daje vjerodostojne rezultate.
Abstract (english) 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.
Keywords
kvantna gravitacija
astročestična fizika
opća teorija relativnosti
narušenje Lorentzove invarijantnosti
modificirana fotonska disperzijska relacija
provale gama-zraka
Monte Carlo simulacija
metoda maksimalne oštrine
Keywords (english)
Quantum Gravity
astroparticle physics
general theory of relativity
Lorentz invariance violation
modified photon dispersion relation
gamma-ray bursts
Monte Carlo simulation
sharpness maximization method
Language croatian
URN:NBN urn:nbn:hr:194:854172
Study programme Title: physics Study programme type: university Study level: graduate Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
Type of resource Text
File origin Born digital
Access conditions Access restricted to students and staff of home institution
Terms of use
Created on 2023-10-05 18:58:12