Quasiclassical symmetry properties II

R. E. Prange

Murray Gell‐Mann, James B. Hartle

Three ideas are introduced that when brought together characterize the realistic quasiclassical realms of our quantum universe as particular kinds of sets of alternative coarse-grained histories defined by quasiclassical variables: (i) branch-dependent adaptive coarse grainings that can be close to maximally refined and can simplify calculation, (ii) narrative coarse grainings that describe how features of the universe change over time and allow the construction of an environment, and (iii) a notion of strong decoherence that characterizes realistic mechanisms of decoherence.

Xin Huang

We define the condition of the quasiclassical state of free particles, which is useful in the approximate treatment of quantum systems. Then we introduce classical pure ensembles. Their states are represented using distribution functions on phase space. We compare distribution functions of classical pure ensembles and Wigner distribution functions of quasiclassical states for free particles and draw two conclusions: (i) A wave function does not describe an individual particle but a classical pure ensemble. (ii) Given a quasiclassical wave function, we can tell which classical pure ensemble is described by it.

O. Yu. Shvedov

P. V. Elyutin, D. V. Krivchenkov

Jan Jerzy Sławianowski, Vasyl Kovalchuk, Agnieszka Martens +2 more

In Part I of this series we presented the general ideas of applying group-algebraic methods for describing quantum systems. The treatment was there very "ascetic" in that only the structure of a locally compact topological group was used. Below we explicitly make use of the Lie group structure. Basing on differential geometry enables one to introduce explicitly representation of important physical quantities and formulate the general ideas of quasiclassical representation and classical analogy.