Microscopic entropy

We have obtained a microscopic expression for entropy in terms of ℋ function based on nonunitary A transformation that leads from the time evolution as a unitary group to a Markovian dynamics and unifies the reversible and irreversible aspects of quantum mechanics. This requires a new representation outside the Hilbert space. In terms of ℋ, we show the entropy production and the entropy flow during the emission and absorption of radiation by an atom. Analyzing the time inversion experiment we emphasize the importance of precollisional and postcollisional correlations, which break the symmetry between incoming and outgoing waves. We consider the influence of spatial configuration of the system on the initial correlations in terms of the ℋ function in a three-dimensional situation. In a subsequent paper we discuss a model including virtual transitions. © 2003 Wiley Periodicals, Inc.FLWINTexte issu de :Complexity :microscopic and macroscopic aspects :workshop in honour of Ilya Prigogine on the occasion of his 85th birthday :Fondation des Treilles, France, July 8-14, 2002SCOPUS: cp.j