Time-Dependent Invariants for Dirac Equation and Newton-Wigner Position Operator
arXiv:quant-ph/9702035 · doi:10.1088/0031-8949/56/5/001
Abstract
For Dirac equation, operator-invariants containing explicit time-dependence in parallel to known time-dependent invariants of nonrelativistic Schrödinger equation are introduced and discussed. As an example, a free Dirac particle is considered and new invariants are constructed for it. The integral of motion, which is initial Newton-Wigner position operator, is obtained explicitly for a free Dirac particle. For such particle with kick modeled by delta-function of time, the time-depending integral, which has physical meaning of initial momentum, is found.
LATEX,21 pages,submitted to Physica Scripta