By the functional path-integral approach, the functional form of the wave function of the macroscopic system is elucidated. In the macroscopic limit, the Hilbert space is shown to break up according to the c-number value of the macrovariable. The functional form is shown to be preserved under the time evolution and the macroscopic difference of two states can be interpreted as the macroscopic action required to connect them. The measurement theory based on the macrovariables is then given using these properties. The volume is kept finite throughout the discussion.
By the functional path-integral approach, the functional form of the wave function of the macroscopic system is elucidated. In the macroscopic limit, the Hilbert space is shown to break up according to the c-number value of the macrovariable. The functional form is shown to be preserved under the time evolution and the macroscopic difference of two states can be interpreted as the macroscopic action required to connect them. The measurement theory based on the macrovariables is then given using these properties. The volume is kept finite throughout the discussion.