Rational Thermodynamics

In Chaps. 7 and 8, it was assumed that the instantaneous local state of the system out of equilibrium was characterized by the union of classical variables and a number of additional variables (fluxes in EIT, internal variables in IVT). Only their instantaneous value at the present time was taken into account and their evolution was described by a set of ordinary differential equations. An alternative attitude, followed in the early developments of rational thermodynamics (RT), is to select a smaller number of variables than necessary for an exhaustive description. The price to be paid is that the state of the material body will be characterized not only by the instantaneous value of the variables, but also by their values taken in the past, namely by their history.