Dynamics of transitions between symmetric states of quantum systems

The probabilities of particle transitions between two equivalent positions for the system in dynamical equilibrium are exactly calculated. The results are obtained in the form of correlation functions, which makes it possible to analyze corresponding problems for the gas phase as well as for the condensed one. The method of calculating probabilities is developed which is based on the locality of the interaction inducing the transition and does not require this interaction to be small. The results obtained are illustrated by simple examples.