Linear response theory for quantum open systems
  Basing on the theory of Feynman's influence functional and its hierarchical equations of motion, we develop a linear response theory for quantum open systems. Our theory provides an effective way to calculate dynamical observables of a quantum open system at its steady-state, which can be applied to various fields of non-equilibrium condensed matter physics. 
J. H. Wei and YiJing Yan
cond-mat.mes-hall cond-mat.str-el