EXTENDED IRREVERSIBLE THERMODYNAMICS - AN UNFINISHED TASK

Linear irreversible thermodynamics (LIT) has been a very successful theory in describing irreversible phenomena occurring in systems whose states do not deviate appreciably from the equilibrium state, and is well founded both in kinetic theory and in statistical mechanics. The regime where these phenomena occur corresponds to very small wavenumbers and small frequencies, usually referred to as the hydrodynamic regime. The scope and the limitations of LIT are therefore well established. In the past two decades an enormous effort has been made to extend the scope of LIT to incorporate into a logically consistent theory the finite-(k; w) region. Some of these efforts are presently embodied into what is referred to as extended irreversible thermodynamics (EIT). Nevertheless, these theories are far from being well accepted and convincing. The purpose of this paper is to give a very critical discussion of the main ideas behind the best known theories comprising EIT, to point out clearly their accomplishments and to emphasize those issues which are still unsettled. ?he outcome of this discussion will indicate that the desired extension of LIT is not yet accomplished.