Abstract:
The concept of a generating functional that allows one to find mean values of any product of
spin operators by differentiation with respect to the functional argument is introduced. The
equation for the time evolution of this functional is found and it replaces the equation of motion
for the density matrix. By formulating suitable “boundary conditions,” one can transform
this equation to an integral equation whose solution enables one to obtain “kinetic equations”
for spin waves.
Citation:
S. V. Peletminskii, A. A. Yatsenko, “Generating functional method for spin variables”, TMF, 16:2 (1973), 260–273; Theoret. and Math. Phys., 16:2 (1973), 820–829