Weekly Papers on Quantum Foundations (50)

Volume 4, Issue 1, pages 147-157

Jean Bricmont [Show Biography]

I was born 12 April 1952 in Belgium; I got my phD in 1977 at the University of Louvain in Belgium. I worked at Rutgers and Princeton universities and have been a professor of theoretical physics at the university of Louvain, but I am now retired. I worked on statistical mechanics, the renormalization group and nonlinear partial differential equations. I am also interested in making sense of quantum mechanics, see http://www.springer.com/gp/book/9783319258874.

This is a review of Travis Norsen’s book \emph{Foundations of Quantum Mechanics: An Exploration of the Physical Meaning of Quantum Theory} (Springer, 2017).

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Volume 4, Issue 1, pages 142-146

Louis Marchildon [Show Biography]

Louis Marchildon is Professor of Physics (Emeritus) at Université du Québec à Trois-Rivières (UQTR). He obtained his B.Sc. and M.Sc. from UQTR, and his Ph.D. from Yale University in 1978. After postdoctoral work at Institut des hautes études scientifiques (France), he returned to UQTR where, in addition to research in relativity, he collaborated with a group investigating dielectric properties of materials. His book Quantum Mechanics: From Basic Principles to Numerical Methods and Applications was published by Springer in 2002. He served as President of the Canadian Association of Physicists in 2007-2008. He has now been working on quantum foundations for more than 15 years, and is also interested in science popularization.

Kastner (this issue) and Kastner and Cramer (arXiv:1711.04501) argue that the Relativistic Transactional Interpretation (RTI) of quantum mechanics provides a clear definition of absorbers and a solution to the measurement problem. I briefly examine how RTI stands with respect to unitarity in quantum mechanics. I then argue that a specific proposal to locate the origin of nonunitarity is flawed, at least in its present form.

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Volume 4, Issue 1, pages 128-141

Ruth E. Kastner [Show Biography]

Ruth E. Kastner earned her M.S. in Physics and Ph.D. in Philosophy (History and Philosophy of Science) and the University of Maryland, College Park (1999). She has taught a variety of philosophy and physics courses throughout the Baltimore-Washington corridor, and currently is a member of the Foundations of Physics group at UMCP. She is also an Affiliate of the physics department at the SUNY Albany campus. She specializes in time-symmetry and the Transactional Interpretation (TI) of quantum mechanics, and in particular has extended the original TI of John Cramer to the relativistic domain. Her interests and publications include topics in thermodynamics and statistical mechanics, quantum ontology, counterfactuals, spacetime emergence, and free will. She is the author of two books: The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility (Cambridge, 2012) and Understanding Our Unseen Reality: Solving Quantum Riddles (Imperial College Press, 2015). She is also an Editor of the collected volume Quantum Structural Studies (World Scientific, 2016).

In view of a resurgence of concern about the measurement problem, it is pointed out that the Relativistic Transactional Interpretation (RTI) remedies issues previously considered as drawbacks or refutations of the original Transactional Interpretation (TI). Specifically, once one takes into account relativistic processes that are not representable at the non-relativistic level (such as particle creation and annihilation, and virtual propagation), absorption is quantitatively defined in unambiguous physical terms. In addition, specifics of the relativistic transactional model demonstrate that the Maudlin ‘contingent absorber’ challenge to the original TI cannot even be mounted: basic features of established relativistic field theories (in particular, the asymmetry between field sources and the bosonic fields, and the fact that slow-moving bound states, such as atoms, are not offer waves) dictate that the ‘slow-moving offer wave’ required for the challenge scenario cannot exist. It is concluded that issues previously considered obstacles for the Transactional Interpretation are no longer legitimately viewed as such, and that reconsideration of the model is warranted in connection with solving the measurement problem.
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Volume 4, Issue 1, pages 117-127

Andreas Schlatter [Show Biography]

Born in Zurich, Switzerland, Andreas Schlatter was educated at the Swiss Federal Institute of Technology in Zurich, where he studied mathematics. He got his PhD in 1994 with work in partial differential equations. He subsequently held a research position at Princeton University, where he did further work mainly on the Yang-Mills heat equation. In 1997 Andreas joined the Asset Management industry and pursued a distinguished career over twenty years, which brought him into the Executive Committee of one of the world’s large Asset Management firms. Today Andreas does consulting work and holds a number of independent board seats. Andreas has been doing research and published during his professional life, mainly in the area of Quantum Foundations and Relativity but also in Finance.

There are so called MOND corrections to the general relativistic laws of gravity, able to explain phenomena like the rotation of large spiral galaxies or gravitational lensing by certain galaxy clusters. We show that these corrections can be derived in the framework of synchronizing thermal clocks. We develop a general formula, which reproduces the deep MOND correction at large scales and defines the boundary-acceleration beyond which corrections are necessary.

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Volume 4, Issue 1, pages 1-116

Per Östborn [Show Biography]

Born in Lund, Sweden, Per Östborn was educated at Lund University. He got his PhD at the Division of Mathematical Physics in 2003. The subject of the dissertation was phase transitions toward synchrony in large lattices of limit cycle oscillators. Such phase transitions are examples of phase transitions in non-equilibrium systems. More recently he has held a cross-disciplinary research position at the Department of Archaeology and Ancient History at Lund University. He has developed and used network-based methods to analyze the diffusion of innovations in antiquity. Per works outside academia as well, mostly with environmental issues relating to transport. Interest in the philosophical foundations was the reason why he started to study physics, but this is his first publication in this field.

We derive the Hilbert space formalism of quantum mechanics from epistemic principles. A key assumption is that a physical theory that relies on entities or distinctions that are unknowable in principle gives rise to wrong predictions. An epistemic formalism is developed, where concepts like individual and collective knowledge are used, and knowledge may be actual or potential. The physical state S corresponds to the collective potential knowledge. The state S is a subset of a state space S = {Z}, such that S always contains several elements Z, which correspond to unattainable states of complete potential knowledge of the world. The evolution of S cannot be determined in terms of the individual evolution of the elements Z, unlike the evolution of an ensemble in classical phase space. The evolution of S is described in terms of sequential time n belonging to N, which is updated according to n -> n+1 each time potential knowledge changes. In certain experimental contexts C, there is knowledge at the start of the experiment at time n that a given series of properties P, P’,… will be observed within a given time frame, meaning that a series of values p, p’,… of these properties will become known. At time n, it is just known that these values belong to predefined, finite sets {p},{p’},… In such a context C, it is possible to define a complex Hilbert space HC on top of S, in which the elements are contextual state vectors Sc. Born’s rule to calculate the probabilities to find the values p,p’,… is derived as the only generally applicable such rule. Also, we can associate a self-adjoint operator P with eigenvalues {p} to each property P observed within C. These operators obey [P, P’] = 0 if and only if the precise values of P and P’ are simultaneoulsy knowable. The existence of properties whose precise values are not simultaneously knowable follows from the hypothesis that collective potential knowledge is always incomplete, corresponding to the above-mentioned statement that S always contains several elements Z.

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Authors: Andrea AddaziPierluigi BelliRita BernabeiAntonino Marciano

We propose to deploy limits that arise from different tests of the Pauli Exclusion Principle in order: i) to provide theories of quantum gravity with an experimental guidance; ii) to distinguish among the plethora of possible models the ones that are already ruled out by current data; iii) to direct future attempts to be in accordance with experimental constraints. We firstly review experimental bounds on nuclear processes forbidden by the Pauli Exclusion Principle, which have been derived by several experimental collaborations making use of different detector materials. Distinct features of the experimental devices entail sensitivities on the constraints hitherto achieved that may differ one another by several orders of magnitude. We show that with choices of these limits, renown examples of flat noncommutative space-time instantiations of quantum gravity can be heavily constrained, and eventually ruled out. We devote particular attention to the analysis of the $\kappa$-Minkowski and $\theta$-Minkowski noncommutative spacetimes. These are deeply connected to some scenarios in string theory, loop quantum gravity and noncommutative geometry. We emphasize that the severe constraints on these quantum spacetimes, although cannot rule out theories of top-down quantum gravity to whom are connected in various way, provide a powerful limitations of those models that it will make sense to focus on in the future.

Authors: F. Becattini (University of Florence and INFN)

We address the problem of thermodynamic equilibrium with constant acceleration along the velocity field lines in a quantum relativistic statistical mechanics framework. We show that for a free scalar quantum field, after vacuum subtraction, all mean values vanish when the local temperature T is as low as the Unruh temperature T_U = A/2\pi where A is the magnitude of the acceleration four-vector. We argue that the Unruh temperature is an absolute lower bound for the temperature of any accelerated fluid at global thermodynamic equilibrium. We discuss the conditions of this bound to be applicable in a local thermodynamic equilibrium situation.

Authors: A. FabbriN. Pavloff

We study the two-body momentum correlation signal in a quasi one dimensional Bose-Einstein condensate in the presence of a sonic horizon. We identify the relevant correlation lines in momentum space and compute the intensity of the corresponding signal. We consider a set of different experimental procedures and identify the specific issues of each measuring process. We show that some inter-channel correlations, in particular the Hawking quantum/partner one, are particularly well adapted for witnessing quantum non-separability, being resilient to the effects of temperature and/or quantum quenches.

Publication date: Available online 21 December 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): R. Hermens, O.J.E. Maroney
Macroscopic realism is the thesis that macroscopically observable properties must always have definite values. The idea was introduced by Leggett and Garg (1985), who wished to show a conflict with the predictions of quantum theory, by using it to derive an inequality that quantum theory violates. However, Leggett and Garg’s analysis required not just the assumption of macroscopic realism per se, but also that the observable properties could be measured non-invasively. In recent years there has been increasing interest in experimental tests of the violation of the Leggett-Garg inequality, but it has remained a matter of controversy whether this second assumption is a reasonable requirement for a macroscopic realist view of quantum theory. In a recent critical assessment Maroney and Timpson (2014) identified three different categories of macroscopic realism, and argued that only the simplest category could be ruled out by Leggett-Garg inequality violations. Allen, Maroney, and Gogioso (2016) then showed that the second of these approaches was also incompatible with quantum theory in Hilbert spaces of dimension 4 or higher. However, we show that the distinction introduced by Maroney and Timpson between the second and third approaches is not noise tolerant, so unfortunately Allen’s result, as given, is not directly empirically testable. In this paper we replace Maroney and Timpson’s three categories with a parameterization of macroscopic realist models, which can be related to experimental observations in a noise tolerant way, and recover the original definitions in the noise-free limit. We show how this parameterization can be used to experimentally rule out classes of macroscopic realism in Hilbert spaces of dimension 3 or higher, without any use of the non-invasive measurability assumption. Even for relatively low precision experiments, this will rule out the original category of macroscopic realism, that is tested by the Leggett-Garg inequality, while as the precision of the experiments increases, all cases of the second category and many cases of the third category, will become experimentally ruled out.
Esfeld, Michael (2017) ‘Thing’ and ‘non-thing’ ontologies. [Preprint]
Dardashti, Radin and Hartmann, Stephan and Thebault, Karim P Y and Winsberg, Eric (2015) Hawking Radiation and Analogue Experiments: A Bayesian Analysis. [Preprint]
Dawid, Richard (2017) Delimiting the Unconceived. [Preprint]
The black hole firewall paradox has been vexing physicists for years. But if quantum laws lead to the creation of other universes, the headache disappears

Author(s): Zhi-Xin Chen, Jun-Li Li, Qiu-Cheng Song, Hui Wang, S. M. Zangi, and Cong-Feng Qiao

The uncertainty relation is a distinguishing feature of quantum theory, characterizing the incompatibility of noncommuting observables in the preparation of quantum states. Recently, many uncertainty relations were proposed with improved lower bounds and were deemed capable of incorporating multiple…
[Phys. Rev. A 96, 062123] Published Wed Dec 20, 2017

Author(s): A. Alexandradinata and Leonid Glazman

A generalization of the Bohr-Sommerfeld quantization rule unifies geometric phase, orbital magnetic moment, and tunneling between Fermi surfaces in topological metals near the metal-insulator transition.

[Phys. Rev. Lett. 119, 256601] Published Tue Dec 19, 2017

Author(s): Adrian Kent

We further investigate postulates for realist versions of relativistic quantum theory and quantum field theory in Minkowski space and other background spacetimes. According to these postulates, quantum theory is supplemented by local variables that depend on possible outcomes of hypothetical measure…
[Phys. Rev. A 96, 062121] Published Mon Dec 18, 2017


It has been suggested that puzzles in the interpretation of quantum mechanics motivate consideration of entities that are numerically distinct but do not stand in a relation of identity with themselves or non-identity with others. Quite apart from metaphysical concerns, I argue that talk about such entities is either meaningless or not about such entities. It is meaningless insofar as we attempt to take the foregoing characterization literally. It is meaningful, however, if talk about entities without identity is taken as elliptical for either nominal or predicative use of a special class of mass terms.


A recent paper from Brun et al. has argued that access to a closed timelike curve (CTC) would allow for the possibility of perfectly distinguishing nonorthogonal quantum states. This result can be used to develop a protocol for instantaneous nonlocal signaling. Several commenters have argued that nonlocal signaling must fail in this and in similar cases, often citing consistency with relativity as the justification. I argue that this objection fails to rule out nonlocal signaling in the presence of a CTC. I argue that the reason these authors are motivated to exclude the prediction of nonlocal signaling is because the No Signaling principle is considered to a fundamental part of the formulation of the quantum information approach. I draw out the relationship between nonlocal signaling, quantum information, and relativity, and argue that the principle theory formulation of quantum mechanics, which is at the foundation of the quantum information approach, is in tension with foundational assumptions of Deutsch’s D-CTC model, on which this protocol is based.

Walter, Scott A. (2017) Figures of light in the early history of relativity (1905-1914). [Preprint]
Rochefort-Maranda, Guillaume (2013) Statistical Power and P-values: An Epistemic Interpretation Without Power Approach Paradoxes. [Preprint]
Hangleiter, Dominik and Carolan, Jacques and Thebault, Karim P Y (2017) Analogue Quantum Simulation: A Philosophical Prospectus. [Preprint]
ROVELLI, Carlo (2017) “Space is blue and birds fly through it”. [Preprint]

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