The concept of entropy. Relation

The Boltzmann expression for entropy represents the traditional link be-tween thermodynamics and statistical mechanics. New theoretical devel-opments like the Unruh effect or the black hole theory suggest a new def-inition of entropy. In this paper we consider the thermodynamics of black holes as seriously founded and we try to see what we can learn from it in the case of ordinary systems for which a pre-relativistic description is suf-ficient. We introduce a space-time model and a new definition of entropy considering the thermal equilibrium from a dynamic point of view. Then we show that for black hole and ordinary systems we have the same relation relating a change of entropy to a change of action. Key words: thermodynamics, entrop