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Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"

A special issue of Entropy (ISSN 1099-4300).

Deadline for manuscript submissions: closed (30 April 2018)

Special Issue Editors

Guest Editor
Dr. Jan Walleczek

Phenoscience Laboratories, Novalisstrasse 11, 10115 Berlin, Germany
Website | E-Mail
Interests: quantum ontology; nonlocal information; effective non-signalling; experimenter free will; quantum complexity; non-equilibrium systems
Guest Editor
Dr. Gerhard Grössing

Austrian Institute for Nonlinear Studies, Akademiehof, Friedrichstrasse 10, 1010 Vienna, Austria
Website | E-Mail
Interests: analytic quantum modeling; nonlinear sub-quantum dynamics; computer simulations; non-signalling and special relativity
Guest Editor
Dr. Paavo Pylkkänen

Department of Philosophy, History, Culture and Art Studies, P.O. Box 24 (Unioninkatu 40 A), FI-00014 University of Helsinki, Helsinki, Finland
Website | E-Mail
Interests: Bohmian quantum information; quantum ontology and causality; physics of the conscious agent
Guest Editor
Prof. Dr. Basil Hiley

Emeritus Professor at Birkbeck, London University and Honorary Research Associate in the Department of Physics, University College of London, London, UK
E-Mail
Interests: foundations of quantum theory and general relativity; algebraic approach to quantum phenomena; orthogonal and symplectic Clifford algebras

Special Issue Information

Dear Colleagues,

Emergent quantum mechanics (EmQM) is a research program that explores the possibility of an ontology for quantum mechanics. The resurgence of interest in realist approaches to quantum mechanics, including deterministic and indeterministic ones, challenges the standard textbook view. For example, standard “no-go” theorems against the possibility of realist, i.e., ontologically-grounded, quantum mechanics are increasingly recognized as falling short of their stated aim. Recent work also indicates that traditional assumptions and theorems such as nonlocality, contextuality, free choice, and non-signalling, need not necessarily contradict the existence of certain quantum ontologies.

On the occasion of David Bohm’s 100th birthday, a symposium on emergent quantum mechanics will be held at the University of London, Senate House, on October 26–28, 2017 (www.emqm17.org). This Special Issue features expert views that critically evaluate the prospects and significance—for 21st century physics—of ontological quantum mechanics, an approach which David Bohm helped pioneer. In original de Broglie-Bohm theory, the mathematical formalism refers to hypothetical ontic elements (e.g., John Bell’s “beables”) such as the quantum potential. In the 21st century, realist quantum approaches often distinguish between ψ-epistemic and ψ-ontic ontological quantum theories. Unlike ψ-ontic theories, the ψ-epistemic theories do not view the wave function ψ as a state of reality. Nevertheless, both types of approaches posit—again—the possibility of an ontological foundation for quantum mechanics.

Twenty-five years ago, David Bohm and Basil Hiley pointed out, in the book “The Undivided Universe”, the close resemblance between key properties of deterministic, hidden-variable, pilot-wave theory and emergence theory, i.e., the theory describing the emergent formation of ordered (i.e., negentropic) states in nonlinear, self-organizing systems, such as deterministic chaos. The notion of ‘emergence’, when applied in the context of an EmQM, often entails two meanings: (1) theory emergence, or (2) physical emergence. Theory emergence describes the idea that the results of orthodox quantum theory might be derived from a more general, deeper-level (sub-)quantum theory. More specifically, the notion of ‘physical emergence’ in quantum systems holds that the orthodox quantum view is neither complete nor fundamental but that an as-yet unknown (sub-) quantum ontology might exist. Consequently, essential questions directing the EmQM research agenda are: Is reality intrinsically random or fundamentally interconnected? Is the universe local or nonlocal? Might a radically new conception of reality include a new form of “quantum causality”?  

This Special Issue explores the possibility of an ontology for quantum mechanics. The focus is the search for a "deeper-level"  theory for quantum mechanics that interconnects three fields of knowledge: emergence, the quantum, and information. Contributions will be featured that present current advances in realist approaches to quantum mechanics, including new experiments, work in quantum foundations, and the physics of the quantum observer and the conscious experimenter agent.

Topics of the Special Issue:

  • Interpretations of Quantum Mechanics 
  • Nonlocality and Violation of Bell Inequalities
  • Quantum Probabilities and Contextuality
  • Quantum Causality and Ontology
  • Information Measures in Quantum Theory
  • Quantum Observation and the Physics of the Experimenter Agent
  • Nonlinear Methods applied to Quantum Theory
  • Self-organization and Quantum Emergence
  • Hidden Variable Theories and Relativity
  • Emergent Space-time 

Dr. Jan Walleczek
Dr. Gerhard Grössing
Dr. Paavo Pylkkänen
Dr. Basil Hiley
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (10 papers)

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Research

Open AccessArticle Observables and Unobservables in Quantum Mechanics: How the No-Hidden-Variables Theorems Support the Bohmian Particle Ontology
Entropy 2018, 20(5), 381; https://doi.org/10.3390/e20050381
Received: 23 April 2018 / Revised: 5 May 2018 / Accepted: 17 May 2018 / Published: 18 May 2018
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Abstract
The paper argues that far from challenging—or even refuting—Bohm’s quantum theory, the no-hidden-variables theorems in fact support the Bohmian ontology for quantum mechanics. The reason is that (i) all measurements come down to position measurements; and (ii) Bohm’s theory provides a clear and
[...] Read more.
The paper argues that far from challenging—or even refuting—Bohm’s quantum theory, the no-hidden-variables theorems in fact support the Bohmian ontology for quantum mechanics. The reason is that (i) all measurements come down to position measurements; and (ii) Bohm’s theory provides a clear and coherent explanation of the measurement outcome statistics based on an ontology of particle positions, a law for their evolution and a probability measure linked with that law. What the no-hidden-variables theorems teach us is that (i) one cannot infer the properties that the physical systems possess from observables; and that (ii) measurements, being an interaction like other interactions, change the state of the measured system. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle Feynman Paths and Weak Values
Entropy 2018, 20(5), 367; https://doi.org/10.3390/e20050367
Received: 16 April 2018 / Revised: 4 May 2018 / Accepted: 9 May 2018 / Published: 14 May 2018
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Abstract
There has been a recent revival of interest in the notion of a ‘trajectory’ of a quantum particle. In this paper, we detail the relationship between Dirac’s ideas, Feynman paths and the Bohm approach. The key to the relationship is the weak value
[...] Read more.
There has been a recent revival of interest in the notion of a ‘trajectory’ of a quantum particle. In this paper, we detail the relationship between Dirac’s ideas, Feynman paths and the Bohm approach. The key to the relationship is the weak value of the momentum which Feynman calls a transition probability amplitude. With this identification we are able to conclude that a Bohm ‘trajectory’ is the average of an ensemble of actual individual stochastic Feynman paths. This implies that they can be interpreted as the mean momentum flow of a set of individual quantum processes and not the path of an individual particle. This enables us to give a clearer account of the experimental two-slit results of Kocsis et al. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle Experimental Non-Violation of the Bell Inequality
Entropy 2018, 20(5), 356; https://doi.org/10.3390/e20050356
Received: 7 April 2018 / Revised: 24 April 2018 / Accepted: 2 May 2018 / Published: 10 May 2018
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Abstract
A finite non-classical framework for qubit physics is described that challenges the conclusion that the Bell Inequality has been shown to have been violated experimentally, even approximately. This framework postulates the primacy of a fractal-like ‘invariant set’ geometry IU in cosmological state
[...] Read more.
A finite non-classical framework for qubit physics is described that challenges the conclusion that the Bell Inequality has been shown to have been violated experimentally, even approximately. This framework postulates the primacy of a fractal-like ‘invariant set’ geometry I U in cosmological state space, on which the universe evolves deterministically and causally, and from which space-time and the laws of physics in space-time are emergent. Consistent with the assumed primacy of I U , a non-Euclidean (and hence non-classical) metric g p is defined in cosmological state space. Here, p is a large but finite integer (whose inverse may reflect the weakness of gravity). Points that do not lie on I U are necessarily g p -distant from points that do. g p is related to the p-adic metric of number theory. Using number-theoretic properties of spherical triangles, the Clauser-Horne-Shimony-Holt (CHSH) inequality, whose violation would rule out local realism, is shown to be undefined in this framework. Moreover, the CHSH-like inequalities violated experimentally are shown to be g p -distant from the CHSH inequality. This result fails in the singular limit p = , at which g p is Euclidean and the corresponding model classical. Although Invariant Set Theory is deterministic and locally causal, it is not conspiratorial and does not compromise experimenter free will. The relationship between Invariant Set Theory, Bohmian Theory, The Cellular Automaton Interpretation of Quantum Theory and p-adic Quantum Theory is discussed. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle Quantum Trajectories: Real or Surreal?
Entropy 2018, 20(5), 353; https://doi.org/10.3390/e20050353
Received: 8 April 2018 / Revised: 27 April 2018 / Accepted: 2 May 2018 / Published: 8 May 2018
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Abstract
The claim of Kocsis et al. to have experimentally determined “photon trajectories” calls for a re-examination of the meaning of “quantum trajectories”. We will review the arguments that have been assumed to have established that a trajectory has no meaning in the context
[...] Read more.
The claim of Kocsis et al. to have experimentally determined “photon trajectories” calls for a re-examination of the meaning of “quantum trajectories”. We will review the arguments that have been assumed to have established that a trajectory has no meaning in the context of quantum mechanics. We show that the conclusion that the Bohm trajectories should be called “surreal” because they are at “variance with the actual observed track” of a particle is wrong as it is based on a false argument. We also present the results of a numerical investigation of a double Stern-Gerlach experiment which shows clearly the role of the spin within the Bohm formalism and discuss situations where the appearance of the quantum potential is open to direct experimental exploration. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle What Constitutes Emergent Quantum Reality? A Complex System Exploration from Entropic Gravity and the Universal Constants
Entropy 2018, 20(5), 335; https://doi.org/10.3390/e20050335
Received: 29 March 2018 / Revised: 26 April 2018 / Accepted: 30 April 2018 / Published: 2 May 2018
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Abstract
In this work, it is acknowledged that important attempts to devise an emergent quantum (gravity) theory require space-time to be discretized at the Planck scale. It is therefore conjectured that reality is identical to a sub-quantum dynamics of ontological micro-constituents that are connected
[...] Read more.
In this work, it is acknowledged that important attempts to devise an emergent quantum (gravity) theory require space-time to be discretized at the Planck scale. It is therefore conjectured that reality is identical to a sub-quantum dynamics of ontological micro-constituents that are connected by a single interaction law. To arrive at a complex system-based toy-model identification of these micro-constituents, two strategies are combined. First, by seeing gravity as an entropic phenomenon and generalizing the dimensional reduction of the associated holographic principle, the universal constants of free space are related to assumed attributes of the micro-constituents. Second, as the effective field dynamics of the micro-constituents must eventually obey Einstein’s field equations, a sub-quantum interaction law is derived from a solution of these equations. A Planck-scale origin for thermodynamic black hole characteristics and novel views on entropic gravity theory result from this approach, which eventually provides a different view on quantum gravity and its unification with the fundamental forces. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
Open AccessFeature PaperArticle A Lenient Causal Arrow of Time?
Entropy 2018, 20(4), 294; https://doi.org/10.3390/e20040294
Received: 29 March 2018 / Revised: 13 April 2018 / Accepted: 15 April 2018 / Published: 18 April 2018
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Abstract
One of the basic assumptions underlying Bell’s theorem is the causal arrow of time, having to do with temporal order rather than spatial separation. Nonetheless, the physical assumptions regarding causality are seldom studied in this context, and often even go unmentioned, in stark
[...] Read more.
One of the basic assumptions underlying Bell’s theorem is the causal arrow of time, having to do with temporal order rather than spatial separation. Nonetheless, the physical assumptions regarding causality are seldom studied in this context, and often even go unmentioned, in stark contrast with the many different possible locality conditions which have been studied and elaborated upon. In the present work, some retrocausal toy-models which reproduce the predictions of quantum mechanics for Bell-type correlations are reviewed. It is pointed out that a certain toy-model which is ostensibly superdeterministic—based on denying the free-variable status of some of quantum mechanics’ input parameters—actually contains within it a complete retrocausal toy-model. Occam’s razor thus indicates that the superdeterministic point of view is superfluous. A challenge is to generalize the retrocausal toy-models to a full theory—a reformulation of quantum mechanics—in which the standard causal arrow of time would be replaced by a more lenient one: an arrow of time applicable only to macroscopically-available information. In discussing such a reformulation, one finds that many of the perplexing features of quantum mechanics could arise naturally, especially in the context of stochastic theories. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle The Definition of Entropy for Quantum Unstable Systems: A View-Point Based on the Properties of Gamow States
Entropy 2018, 20(4), 231; https://doi.org/10.3390/e20040231
Received: 23 November 2017 / Revised: 16 February 2018 / Accepted: 1 March 2018 / Published: 28 March 2018
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Abstract
In this paper, we review the concept of entropy in connection with the description of quantum unstable systems. We revise the conventional definition of entropy due to Boltzmann and extend it so as to include the presence of complex-energy states. After introducing a
[...] Read more.
In this paper, we review the concept of entropy in connection with the description of quantum unstable systems. We revise the conventional definition of entropy due to Boltzmann and extend it so as to include the presence of complex-energy states. After introducing a generalized basis of states which includes resonances, and working with amplitudes instead of probabilities, we found an expression for the entropy which exhibits real and imaginary components. We discuss the meaning of the imaginary part of the entropy on the basis of the similarities existing between thermal and time evolutions. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
Open AccessArticle Generalized Lagrangian Path Approach to Manifestly-Covariant Quantum Gravity Theory
Entropy 2018, 20(3), 205; https://doi.org/10.3390/e20030205
Received: 10 January 2018 / Revised: 25 February 2018 / Accepted: 8 March 2018 / Published: 19 March 2018
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Abstract
A trajectory-based representation for the quantum theory of the gravitational field is formulated. This is achieved in terms of a covariant Generalized Lagrangian-Path (GLP) approach which relies on a suitable statistical representation of Bohmian Lagrangian trajectories, referred to here as GLP-representation. The
[...] Read more.
A trajectory-based representation for the quantum theory of the gravitational field is formulated. This is achieved in terms of a covariant Generalized Lagrangian-Path (GLP) approach which relies on a suitable statistical representation of Bohmian Lagrangian trajectories, referred to here as GLP-representation. The result is established in the framework of the manifestly-covariant quantum gravity theory (CQG-theory) proposed recently and the related CQG-wave equation advancing in proper-time the quantum state associated with massive gravitons. Generally non-stationary analytical solutions for the CQG-wave equation with non-vanishing cosmological constant are determined in such a framework, which exhibit Gaussian-like probability densities that are non-dispersive in proper-time. As a remarkable outcome of the theory achieved by implementing these analytical solutions, the existence of an emergent gravity phenomenon is proven to hold. Accordingly, it is shown that a mean-field background space-time metric tensor can be expressed in terms of a suitable statistical average of stochastic fluctuations of the quantum gravitational field whose quantum-wave dynamics is described by GLP trajectories. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
Open AccessArticle Why Bohmian Mechanics? One- and Two-Time Position Measurements, Bell Inequalities, Philosophy, and Physics
Entropy 2018, 20(2), 105; https://doi.org/10.3390/e20020105
Received: 21 December 2017 / Revised: 21 January 2018 / Accepted: 31 January 2018 / Published: 2 February 2018
Cited by 3 | PDF Full-text (533 KB) | HTML Full-text | XML Full-text
Abstract
In Bohmian mechanics, particles follow continuous trajectories, so two-time position correlations have been well defined. However, Bohmian mechanics predicts the violation of Bell inequalities. Motivated by this fact, we investigate position measurements in Bohmian mechanics by coupling the particles to macroscopic pointers. This
[...] Read more.
In Bohmian mechanics, particles follow continuous trajectories, so two-time position correlations have been well defined. However, Bohmian mechanics predicts the violation of Bell inequalities. Motivated by this fact, we investigate position measurements in Bohmian mechanics by coupling the particles to macroscopic pointers. This explains the violation of Bell inequalities despite two-time position correlations. We relate this fact to so-called surrealistic trajectories that, in our model, correspond to slowly moving pointers. Next, we emphasize that Bohmian mechanics, which does not distinguish between microscopic and macroscopic systems, implies that the quantum weirdness of quantum physics also shows up at the macro-scale. Finally, we discuss the fact that Bohmian mechanics is attractive to philosophers but not so much to physicists and argue that the Bohmian community is responsible for the latter. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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Open AccessArticle Spooky Action at a Temporal Distance
Entropy 2018, 20(1), 41; https://doi.org/10.3390/e20010041
Received: 25 November 2017 / Revised: 5 January 2018 / Accepted: 9 January 2018 / Published: 10 January 2018
Cited by 1 | PDF Full-text (275 KB) | HTML Full-text | XML Full-text
Abstract
Since the discovery of Bell’s theorem, the physics community has come to take seriously the possibility that the universe might contain physical processes which are spatially nonlocal, but there has been no such revolution with regard to the possibility of temporally nonlocal processes.
[...] Read more.
Since the discovery of Bell’s theorem, the physics community has come to take seriously the possibility that the universe might contain physical processes which are spatially nonlocal, but there has been no such revolution with regard to the possibility of temporally nonlocal processes. In this article, we argue that the assumption of temporal locality is actively limiting progress in the field of quantum foundations. We investigate the origins of the assumption, arguing that it has arisen for historical and pragmatic reasons rather than good scientific ones, then explain why temporal locality is in tension with relativity and review some recent results which cast doubt on its validity. Full article
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
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