1998/01/20 by S. Schlieder
Physics and Astronomy · #quant-ph
published as Nuovo Cim. B114 (1999) 1225-1238 · 17 pages
arxiv created 1998/01/20 · arxiv updated 2009/12/01
For quantum mechanical systems an entropy-like quantity Sq is defined. Sq can differ from the usually defined entropy S and Sq may increase with time for an isolated system. The essential condition for the difference between S and Sq is the assumption that the set \bf A of observables which can be represented by a measurement is a proper subset of the set of selfadjoint operators. The underlying idea is made visible in the case of particle systems with non-trivial scattering. The model-character of the reasoning comes from the fact that continuous spectra are replaced by point-spectra. So it seems evident, that no direct connection exists between Sq and the Sinai-Kolmogorov-Entropy at least in this model with pure point-spectra.