  The Kawasaki nonlinear response relation, the transient fluctuation theorem,
and the Jarzynski nonequilibrium work relation are all expressions that
describe the behavior of a system that has been driven from equilibrium by an
external perturbation. In contrast to linear response theory, these expressions
are exact no matter the strength of the perturbation, or how far the system has
been driven away from equilibrium. In this paper I show that these three
relations (and several other closely related results) can all be considered
special cases of a single theorem. This expression is explicitly derived for
discrete time and space Markovian dynamics, with the additional assumptions
that the single time step dynamics preserve the appropriate equilibrium
ensemble, and that the energy of the system remains finite.
