On the physics of rate-distortion theory

We revisit and extend the physical interpretation recently given to a certain identity between large-deviations rate-functions, as well as applications of this identity to rate-distortion theory, as an instance of thermal equilibrium between several physical systems that are brought into contact. Our new interpretation, of mechanical equilibrium between these systems, is shown to have several advantages. This physical point of view also provides a trigger to the development of certain new alternative representations of the rate-distortion function and channel capacity.