This paper elucidates the connection between the KS entropy-rate kappa and the time evolution of the physical or statistical entropy S. For a large family of chaotic conservative dynamical systems including the simplest ones, the evolution of S(t) for far-from-equilibrium processes includes a stage during which S is a simple linear function of time whose slope is kappa. The paper presents numerical confirmation of this connection for a number of chaotic symplectic maps, ranging from the simplest 2-dimensional ones to a 4-dimensional and strongly nonlinear map.

Email correspondence to latora@ctp.mit.edu ; 4 pages, 7 eps figures, using REVTeX and BoxedEPS macros