The concept of energy levels of quantum systems periodically depending on time and having a discrete or a continuous spectrum is justified. A natural concept of adjacent and effective energy levels as well as distances between the levels are introduced. The results of the theory presented are applied to justification of the quantum chaos conjecture for a class of systems including, as a special case, the ''kicked rotator'' model.

quantum chaos, ''kicked rotator'' model

Mathematical modelling in actual problems of science and technics