The traditional formalism of quantum mechanics is mainly used to describe ensembles of identical systems (with a density-operator formalism) or single isolated systems, but is not capable of describing single open quantum objects with many degrees of freedom showing pure-state stochastic dynamical behaviour. In particular, stochastic 'line-migration' as in single-molecule spectroscopy of defect molecules in a molecular matrix is not adequately described. Starting with the Bohr scenario of stochastic quantum jumps (between strict energy eigenstates), we try to incorporate more general (...) pure-state stochastic dynamical behaviour into the quantum mechanical formalism.Probability distributions of (approximately) pure states, arising through the stochastic pure-state dynamics for long times, give rise to appropriate decompositions of thermal density operators. These decompositions of density operators into pure states mediate between quantum mechanics for ensembles of molecules and quantum theory for single molecules (or single dressed quantum objects). We suggest that such decompositions should be consistent with infinite limits (e.g. the Born-Oppenheimer limit for infinite nuclear masses) in the sense that quantum fluctuations (around classical behaviour in the infinite limit) die out asymptotically. (shrink)

In June 1998 Hans Primas turned 70 y ears old. Although he himself is not fond of jubilees and although he lik es to play the decimal system of numb ers do wn as contingent, this is nev ertheless a suitable o ccasion to re ect on the professional work of one of the rare distinguished contemp orary scientists who attach equal imp ortance to exp erimen tal and theoretical and conceptual lines of researc h. Hans Primas' in terests ha (...) ve covered an enormous range: metho ds and instruments for n uclear magnetic resonance, theoretical c hemistry , C - and W -algebraic formulations of quantum mechanics, the measurement problem and its various implications, holism and realism in quantum theory , theory reduction, the w ork and p ersonality of Wolfgang Pauli, as well as Jungian psychology . In man y of these elds he provided imp ortan t and original fo o d for though t, in some cases going far b eyond the ev eryda y business in the scientic world. As is the case with other scien tists who are conceptually innov ativ e, Hans Primas is read more than he is quoted. His in uence is due to his writings. Even with the current ood of publications, he still p erforms the miracle of ha ving scientists eagerly a waiting his next publication. His external life, by wa y of contrast, is not very sp ectacular. With the exception of a brief p erio d as a guest professor at Washington Univ ersity at St. Louis, he has never b een a wa y from Zuric h for an y length of time. He has nev er b een a warded an y prizes, nev er organized a congress, nev er done any organizational work in a scientic so ciety . He delib erately distanced himself from the hustle and bustle of national and in ternational scien tic business. (shrink)

This NATO Advanced Study Institute centered on large-scale molecular systems: Quantum mechanics, although providing a general framework for the description of matter, is not easily applicable to many concrete systems of interest; classical statistical methods, on the other hand, allow only a partial picture of the behaviour of large systems. The aim of the ASI was to present both aspects of the subject matter and to foster interaction between the scientists working in these important areas of theoretical physics and theoretical (...) chemistry. The quantum-mechanical part was mostly based on the operator-algebraic formulation of quantum mechanics and comprised quantum statistics of infinite systems with special em phasis on macroscopic observables, equilibrium conditions, irreversibility on the one hand, symmetry breaking for molecules in the radiation field and macroscopic quantum phenomena in the theory of superconductivity (BCS-theory) on the other hand. In addition, phase-space methods for many-body systems were also presented. Statistical physics was the main topic in the other lectures of the School; much emphasis was put on the statistical features of macros copic ("large") systems, the lectures dealt with mass and energy transport im polymers, in gels and in microemulsions, with aggregation and growth phenomena, with relaxation in complex, correlated systems, with conduction and optical properties of polymers, and with the means of describing disordered systems, above all fractals and related hierarchical models. (shrink)

Quantum systems have a holistic structure, which implies that they cannot be divided into parts. In order tocreate (sub)objects like individual substances, molecules, nuclei, etc., in a universal whole, the Einstein-Podolsky-Rosen correlations between all the subentities, e.g. all the molecules in a substance, must be suppressed by perceptual and mental processes.Here the particular problems ofGestalt (shape)perception are compared with the attempts toattribute a shape to a quantum mechanical system like a molecule. Gestalt perception and quantum mechanics turn out (on an (...) informal level) to show similar features and problems: holistic aspects, creation of objects, dressing procedures, influence of the observer, classical quantities and structures. The attribute classical of a property or structure means thatholistic correlations to any other quantity do not exist or that these correlations are considered as irrelevant and therefore eliminated (either deliberately and by declaration or in a mental process that is not under rational control). An example of animposed classical structure is the nuclear frame of a molecule. Candidates for classical properties that arenot imposed by the observer could be the charge of a particle or the handedness of a molecule. It is argued here that at least part of a molecule's shape can begenerated automatically by the environment. A molecular shape of this sort arises in addition to Lamb shift-type energy corrections. (shrink)