Decoherent Histories for Space–Time Domains

J. J. Halliwell

Juan Pablo Paz, Wojciech Hubert Zurek

We prove that for an open system, in the Markovian regime, it is always possible to construct an infinite number of nontrivial sets of histories that exactly satisfy the probability sum rules. In spite of being perfectly consistent, these sets manifest a very nonclassical behavior: they are quite unstable under the addition of an extra instant to the list of times defining the history. To eliminate this feature---the implications of which we discuss---and to achieve the stability that characterizes the quasiclassical domain, it is necessary to separate the instants which define the history by time intervals significantly larger than the typical decoherence time. In this case environment induced superselection is very effective. The quasiclassical domain is defined by predictably evolving perferred states, ``pointer projectors,'' which give rise to consistent preferred sets of histories.

Ed Seidewitz

A. J. Short

Murray Gell‐Mann, James B. Hartle

We sketch a quantum mechanical framework for the universe as a whole. Within that framework we propose a program for describing the ultimate origin in quantum cosmology of the quasiclassical domain of familiar experience and for characterizing the process of measurement. Predictions in quantum mechanics are made from probabilities for sets of alternative histories. Probabilities can be assigned only to sets of histories that approximately decohere. Decoherence is defined and the mechanism of decoherence is reviewed. Decoherence requires a sufficiently coarse-grained description of alternative histories of the universe. A quasiclassical domain consists of a branching set of alternative decohering histories, described by a coarse graining that is maximally refined consistent with decoherence, with individual branches that exhibit a high level of classical correlation in time. A quasiclassical domain is emergent in the universe as a consequence of the initial condition and the action function of the elementary particles. It is an important question whether all the quasiclassical domains are roughly equivalent or whether there are various essentially inequivalent ones. A measurement is a correlation with variables in a quasiclassical domain. An observer (or information gathering and utilizing system) is a complex adaptive system that has evolved to exploit the relative predictability of a quasiclassical domain. We suggest that resolution of many of the problems of interpretation presented by quantum mechanics is to be accomplished, not by further scrutiny of the subject as it applies to reproducible laboratory situations, but rather by an examination of alternative histories of the universe, stemming from its initial condition, and a study of the problem of quasiclassical domains.

Joe Zhou

DGFT Trilogy is an ambitious three-volume work by Joe X. Zhou that proposes a new ontological framework for reality: Decoherence-Generated Foliation Theory (DGFT). Bridging quantum mechanics, relativity, cosmology, and philosophy, the trilogy argues that reality emerges through the irreversible transition from coherent possibility (S-domain) to historical record (N-domain) via a universal Posting Functional. Book I establishes the philosophical and logical foundations; Book II develops the cosmological and physical architecture of emergent spacetime, matter, and history; Book III provides the formal mathematical reconciliation between Hilbert structure, Lorentzian geometry, and the no-signaling universe. Bold, interdisciplinary, and provocative, DGFT challenges conventional assumptions about time, space, causality, and existence itself.