Motivated by Wallace's thesis that pilot wave beables should be decoherence-preferred to recover quantum predictions, we consider the relation between pilot wave beables and decoherence. We prove that without any connection between beables and decoherence the overlap between macrcopic states becomes negligible. This is sufficient to recover quantum predictions, so that Wallace's thesis has to be rejected. A natural connection between decoherence and beables appears if the decomposition into systems used by decoherence is based on the beables. While our first result becomes inapplicable in this case, we present evidence that the overlap becomes negligible too.
Motivated by Wallace's thesis that pilot wave beables should be decoherence-preferred to recover quantum predictions, we consider the relation between pilot wave beables and decoherence. We prove that without any connection between beables and decoherence the overlap between macrcopic states becomes negligible. This is sufficient to recover quantum predictions, so that Wallace's thesis has to be rejected. A natural connection between decoherence and beables appears if the decomposition into systems used by decoherence is based on the beables. While our first result becomes inapplicable in this case, we present evidence that the overlap becomes negligible too.
It has been experimentally demonstrated that quantum coherence can persist in macroscopic phenomena [J.R. Friedman et al.,Nature, 406 (2000) 43]. To face the challenge of this new fact, in this article QM in its standard form is assumed to be extended by one beable (hidden variable), i. e., a quantum observable with always definite values in nature (but usually only statistically given in the quantum state). Localization is taken as the most plausible beable. The paradoxical aspects of conventional QM take now a different form. Suitably defining the notion of "subject" fully within the QM formalism, proving the quantum conditional subsystem-state theorem, and choosing the relative-decoherence interpretation of QM, the paradoxes formally disappear, leaving one with decoherence relative to the definite values of the beable; thus being only appearance, not absolute reality in QM. Relative to a different subject one has perseverance of coherence. Hence, in this approach it is claimed that decoherence and coherence, both exist in reality, but are not "seen" by the same subject, and "subject" is, in this interpretation, indispensable. The two mentioned, apparently contradictory phenomena, are in this way decoupled from each other, contradiction is avoided, and any one of the two can be treated in the way that is usual in QM.
John Bell once argued that one ought to select, out of the 'observables' of quantum theory, some subset of 'beables' that can be consistently ascribed determinate values. Moreover, this subset should be selected so as to guarantee (among other things) that we can dispense with the orthodox interpretation's loose talk about 'measurement values': "...the probability of a beable being a particular value would be calculated just as was formerly calculated the probability of observing that value". Working in the framework of C*-algebras (in particular, Segal algebras), I propose an algebraic characterization of those subsets of bounded observables of a quantum system that can have beable status with respect to any (fixed) state of the system. It turns out that observables with beable status in a state need not all commute (a possibility Bell himself does not consider), but they must at least form a certain kind of 'quasicommutative' subalgebra determined by the state. A virtue of the analysis is that it applies to beables with continuous spectra, usually neglected in discussions of the no-hidden-variables theorems. In the (very) special case where the algebra of observables for a system is representable on a finite-dimensional Hilbert space, I give a complete characterization of the maximal beable subalgebras determined by any state of the system; the infinite-dimensional case remains open. These results are discussed in relation to previous results of a similar nature, to 'no-collapse' interpretations of quantum mechanics, and to algebraic relativistic quantum field theory.
Pilot-wave theories provide possible solutions to the measurement problem. In such theories, quantum systems are not only described by the state vector but also by some additional variables. These additional variables, also called beables, can be particle positions, field configurations, strings, etc. In this paper we focus our attention on pilot-wave theories in which the additional variables are field configurations. The first such theory was proposed by Bohm for the free electromagnetic field. Since Bohm, similar pilot-wave theories have been proposed for other quantum fields. The purpose of this paper is to present an overview and further development of these proposals. We discuss various bosonic quantum field theories such as the Schrödinger field, the free electromagnetic field, scalar quantum electrodynamics and the Abelian Higgs model. In particular, we compare the pilot-wave theories proposed by Bohm and by Valentini for the electromagnetic field, finding that they are equivalent. We further discuss the proposals for fermionic fields by Holland and Valentini. In the case of Holland's model we indicate that further work is required in order to show that the model is capable of reproducing the standard quantum predictions. We also consider a similar model, which does not seem to reproduce the standard quantum predictions. In the case of Valentini's model we point out a problem that seems hard to overcome.
Abstract Present quantum mechanics has been a source of puzzlement since its inception in 1927. The theory has been undoubtedly successful predicting results in a large number of experimental situations. However, its heavy epistemological legacy, coming from the initial ideas of Niels Bohr about complementarity and about the possibility for physical description, has turned quantum mechanics in a kind of ontological black box. This work is an attempt to overcome such epistemological opacity, proposing an interpretation that will present Bohrian quantum mechanics formalism and the pilot-wave framework as two complementary and mutually non-exclusive theoretical descriptions of quantum phenomena. The two theories will, hopefully, become the foundations of a new and more complete approach to quantum reality. One that will, simultaneously, serve as a highly efficient predictive formalism and also as an intelligible description about quantum phenomena in four-dimensional spacetime. I will start from the pilot-wave framework, proposing that quantum waves are memory carrying structures that encode probabilistic distributions of the fundamental behaviors of corpuscles. This nomological information, as I will call it, will have a necessitarian weight upon all corpuscles behaviors, in the sense that the only behaviors allowed in Nature are the ones that can be encoded or have been encoded in the quantum wave carriers. Such a picture of quantum physics will imply that corpuscles exchange nomological information with the carrier waves, by means of the guidage or pilot-wave effect. Secondly, I will suggest that the actual Bohrian quantum mechanics formalism, the one used in the Copenhagen School interpretation, describes not the actual states and properties of quantum corpuscular entities, but the nomological information about those states and properties. As such Bohrian quantum mechanics is a description about not the actual physical observable dynamics, but about the dynamics of the nomological information encoded in the carrier quantum waves. The adoption and consistent interplay of both theoretical descriptions, pilot-wave mode and Bohrian mode, will serve epistemological completeness in the study of quantum phenomena.
The alternative pilot-wave theory of quantum phenomena—associated especially with Louis de Broglie, David Bohm, and John Bell—reproduces the statistical predictions of ordinary quantum mechanics but without recourse to special ad hoc axioms pertaining to measurement. That (and how) it does so is relatively straightforward to understand in the case of position measurements and, more generally, measurements, whose outcome is ultimately registered by the position of a pointer. Despite a widespread belief to the contrary among physicists, the theory can also account successfully for phenomena involving spin. The main goal of this paper is to explain how the pilot-wave theory's account of spin works. Along the way, we provide illuminating comparisons between the orthodox and pilot-wave accounts of spin and address some puzzles about how the pilot-wave theory relates to the important theorems of Kochen and Specker and Bell.