  Recent years have witnessed major advances in our understanding of
nonequilibrium processes. The Jarzynski equality, for example, provides a link
between equilibrium free energy differences and finite-time, nonequilibrium
dynamics. We propose a generalization of this relation to non-Hamiltonian
dynamics, relevant for active matter systems, continuous feedback, and computer
simulation. Surprisingly, this relation allows us to calculate the free energy
difference between the desired initial and final equilibrium states using
arbitrary dynamics. As a practical matter, this dissociation between the
dynamics and the initial and final states promises to facilitate a range of
techniques for free energy estimation in a single, universal expression.
