On 23 December 2011 SCL's Ivana Vidanovic defended her PhD thesis entitled "Numerical study of quantum gases at low temperatures" done under the supervision of Antun Balaz. This is the first PhD thesis defended as a part of a national research project ON171017.

The research presented in the thesis investigates the phenomenon of Bose-Einstein condensation using various numerical and analytical approaches, including the effective action approach, developed earlier at SCL. Ivana has helped in generalizing this method to many-body systems and later initiated its application to calculation of spectra and eigenfunctions of low-dimensional systems using the exact diagonalization of the evolution operator. This approach was then successfully applied to fast-rotating BECs in anharmonic traps, where it allowed study of global properties of a BEC with high precision, as well as its dynamics after the trapping potential is switched off (time evolution of density profiles and calculation of time of flight absorption graphs). Afterwards, as a main research topic of her thesis, Ivana has studied collective oscillation modes and parametric resonance effects in BEC due to the harmonic modulation of the atomic scattering length via Feshbach resonances. She has performed extensive numerical simulations and developed Poincare-Lindstedt perturbative theory for analytic calculation of frequency shifts in collective modes.

The above results, presented in detail in the thesis, are obtained in part through a collaboration with Dr. Axel Pelster, within PI-BEC and NAD-BEC bilateral projects. The members of the thesis committee (Antun Balaz and Aleksandar Bogojevic from the Institute of Physics Belgrade; Suncica Elezovic-Hadzic and Milan Knezevic from the Faculty of Physics, University of Belgrade) were impressed with Ivana's results and her presentation of the thesis.

• PhD thesis in English
• Presentation in Serbian