Stationary Phase and the Theory of Measurement 1/N Expansion

The measuring process is studied, where a macroscopic number N of particles in the detector interact with the object. When N →∞ , the fluctuation of the object between different eigenstates of the operator O to be measured is suppressed, frozen to one and the same state while the detector is on. During this period, the stationary phase accompanying the macrovariable is established to have a one to one correspondence with the eigenvalue of O. A model is studied which produces the ideal result when N →∞ and the correction terms are calculated in powers of 1/N . It is identical to the expansion including the fluctuation of the object successively. Subject Index: 060, 062