New wave-wave interaction conditions
New conditions for wave-wave interaction are considered. It is shown that using these conditions allows us to discover and describe new features of wave-wave interaction. Specifically, it is shown that an electromagnetic wave in a stationary periodic medium can excite a wave with a different frequency. It is shown that waves with different frequencies can effectively interact in such a medium. It is shown that these conditions can reveal new features of three-wave interaction in nonlinear media. The use of new conditions in quantum mechanics has revealed a number of new features in the dynamics of particles and their interactions with each other. In particular, new energy levels have been discovered that can exist even in stationary periodic potentials. An assessment is given of the level of additive and multiplicative noise that can suppress the interaction process