THE QUANTUM MECHANICS OF ISOLATED SYSTEMS

John P. Lowe

John P. Lowe

John P. Lowe

Jason S. Alexander, T.J. Gin

K. Zalewski

The Schrodinger equation with a time-dependent hamiltonian is sometimes applied to the study of non-isolated systems. It is shown that this is correct (with a proper choice of the hamiltonian) if and only if the state of the system is initially pure and remains so with increasing time. Further the problem of describing a non-isolated system by the density matrix of a pure state is discussed. (auth)