The aim of this book is to present a formulation of the non-equilibrium
physics in nanoscale systems in terms of many-body states and operators
and, in addition, discuss a diagrammatic approach to Green functions
expressed by many-body states. The intention is not to give an account
of strongly correlated systems as such. Thus, the focus of this book
ensues from the typical questions that arise when addressing nanoscale
systems from a practical point of view, e.g. current-voltage
asymmetries, negative differential conductance, spin-dependent
tunneling. The focus is on nanoscale systems constituted of complexes of
subsystems interacting with one another, under non-equilibrium
conditions, in which the local properties of the subsystems are
preferably being described in terms of its (many-body) eigenstates.