STEADY-STATE OF PERIODICALLY DRIVEN SYSTEMS IN QUANTUM STATISTICS

A formal theory for the statistical operator of the "steady state" in periodically driven matter is given. For this purpose the periodic fields are changed to have an amplitude increasing with eηt, where η is taken to be zero at the end. This procedure allows for a correct description of energy denominators. The results following from the steady state operator are compared with the long time behaviour obtained from nth order response and are shown to agree. Thus the proposed statistical operator has all properties required. © 1990.