Quantum soliton and classical soliton

The interaction between quanta and a static soliton is discussed in the boson theory. As a natural consequence, there appears the quantum coordinate associated with the position of the soliton, which leads to a quantum or classical behavior of the soliton depending on its size and the experimental conditions. It will be shown that the presence of the quantum coordinate (or collective coordinate) is required by the equal‐time canonical commutation relation.