Quantum Fluctuations of Effective Fields and the Correspondence Principle

The question of Bohr correspondence in quantum field theory is considered from a dynamical point of view. It is shown that the classical description of particle interactions is inapplicable even in the limit of large particles' masses because of finite quantum fluctuations of the fields produced. In particular, it is found that the relative value of the root mean square fluctuation of the Coulomb and Newton potentials of a massive particle is equal to 1/sqrt{2}. It is shown also that in the case of a macroscopic body, the quantum fluctuations are suppressed by a factor 1/sqrt{N}, where N is the number of particles in the body. An adequate macroscopic interpretation of the correspondence principle is given.