The Master’s thesis of A.V. Ivanov addresses the research on Fréedericksz transitions in cholesteric liquid crystals taking into account thermal fluctuations of a director at finite temperatures.   One of the most important problems in the research of liquid crystals is the analysis of phase transitions in these systems. In the case of the discontinuous transitions, there is a phase transition zone where both phases are in equilibrium and one of the phases is stable, while another is metastable.  In particular, this case exists in cholesteric liquid crystals in external electric or magnetic fields when there is a certain ratio between the system’s parameters. The phase transition here is the Fréedericksz transition which is the re-orientation of the director at fields higher than the threshold fields. This transition is investigated in the refereed thesis. By a direct minimization of a free-energy functional, the author numerically calculated the equilibrium configurations of the system in an external field and studied the stable state range of the distorted and undistorted structures. For the investigation of the transitions between the states, the author analyses the liquid crystal energy surface as a function of the angles which determine the local director orientation in the liquid crystal cell. The minimum energy paths are found using the Geodesic Nudged Elastic Band Method (GNEB). The outline of the method is presented in this thesis. Finding the minimum energy paths allows one to estimate the activation barrier between states and the most probable mechanism of transitions. The author obtained interesting new results about the influence of the thermal fluctuations on the Fréedericksz transition. They have been published in the journal ‘Physical Review E.’ A disadvantage of the work which can be found is the absence of discussion about experimental data as well as the estimation of the nucleation radius value for the Fréedericksz transition which defines the absolute value of energy barrier. This, however, is a separate problem which is beyond the scope of this study. The study presented in this thesis has been conducted at a high scientific level, meets all the requirements for the graduation qualification Master’s thesis, merits an excellent mark and its author, A.V. Ivanov, deserves to be awarded the Master’s degree in Physics.