This is a list of this week's papers on quantum foundations published in the various journals or uploaded to the preprint servers such as arxiv.org and PhilSci Archive.

Relational blockworld: Providing a realist psi-epistemic account of quantum mechanics

International Journal of Quantum Foundations » International Journal of Quantum Foundations

on 2015-6-26 8:13am GMT

*Volume 1, Issue 3, pages 123-170*

W. M. Stuckey [Show Biography], Michael Silberstein [Show Biography] and Timothy McDevitt [Show Biography]

We update our Relational Blockworld (RBW) explanation of quantum physics and argue that it provides a realist psi-epistemic account of quantum mechanics as called for by Leifer. RBW accomplishes this by employing discrete graphical amalgams of space, time and sources (“spacetimesource elements”) and an adynamical global constraint as ‘hidden variables’ that avoid the need for counterfactual definiteness in a realist account. Instead of an equation of motion governing time-evolved entities, the adynamical global constraint is used for computing the graphical transition amplitude whence a probability amplitude for our fundamental spacetimesource element. We begin with a largely conceptual and philosophical introduction to RBW’s most prominent features, i.e., adynamism, relationalism/contextualism, and the unmediated exchange of energy. This conceptual introduction includes a simple interferometer computation of the relative intensities found in a weak measurement that we compare with the authors’ computation per weak values. We use this to contrast our adynamical explanation of the experiment with the apparently dynamical, retro-time-evolved explanation of the authors’ Two State Vector Formalism. Next we use spacetimesource elements instead of paths in Dowker’s GHZ set-up to contrast RBW with Sorkin’s Many Histories account. We argue that rather than multiple paths per Many Histories, what is called for is no paths per RBW. The adynamical interpretation of these two quantum experiments, afforded by the global perspective, suggests that quantum mechanics might be underwritten adynamically. Thus, in the second part of the paper, we motivate an adynamical global constraint using coupled harmonic oscillators and then apply it to an analysis of the twin-slit experiment. This illustrates how the adynamical global constraint of our “modified lattice gauge theory” underwrites quantum field theory whence quantum mechanics. We conclude with a brief dismissal of the measurement problem and an RBW explanation of entanglement, environmental decoherence, quantum non-commutivity, quantum versus classical behavior, and the Born rule.

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Primitive ontology in a nutshell

International Journal of Quantum Foundations » International Journal of Quantum Foundations

on 2015-6-26 7:08am GMT

*Volume 1, Issue 3, pages 107-122*

Valia Allori [Show Biography]

The aim of this paper is to summarize a particular approach of doing metaphysics through physics - the primitive ontology approach. The idea is that any fundamental physical theory has a well-defined architecture, to the foundation of which there is the primitive ontology, which represents matter. According to the framework provided by this approach when applied to quantum mechanics, the wave function is not suitable to represent matter. Rather, the wave function has a nomological character, given that its role in the theory is to implement the law of evolution for the primitive ontology.

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Cosmological implications of quantum entanglement in the multiverse. (arXiv:1506.07808v1 [hep-th])

on 2015-6-26 1:03am GMT

Authors: Sugumi Kanno

We explore the cosmological implications of quantum entanglement between two causally disconnected universes in the multiverse. We first consider two causally separated de Sitter spaces with a state which is initially entangled. We derive the reduced density matrix of our universe and compute the spectrum of vacuum fluctuations. We then consider the same system with an initially non-entangled state. We find that scale dependent modulations may enter the spectrum for the case of initially non-entangled state due to quantum interference. This gives rise to the possibility that the existence of causally disconnected universes may be experimentally tested by analyzing correlators in detail.

on 2015-6-26 1:03am GMT

Authors: Ricardo Gallego Torromé

Models for deterministic quantum mechanics of Cartan-Randers type are introduced, together with the fundamental notions of the concentration of measure theory. We explain how the application of the concentration of measure to Cartan-Randers models provides a framework from which it emerge 1. The invariance under infinitesimal diffeomorphisms of the macroscopic dynamics 2. A mechanism for reduction of the quantum state and 3. The Weak Equivalence Principle.

on 2015-6-26 1:03am GMT

Authors: Alexey E. Rastegin

We address the problem of proper quantifying an informational content in quantum theory. Brukner and Zeilinger proposed the concept of an operationally invariant measure based on measurement statistics. Their measure of information is calculated with probabilities generated in a complete set of mutually complementary observations. This approach has later been criticized for several reasons. It is related to the problem of existence of a complete set of mutually unbiased bases. In general, this open problem seems to be very hard. Another serious question concerns an inevitable role of "no-click" events in real experiments. We aim to show that some critical points can essentially be overcome by means of natural extension or reformulation of the Brukner-Zeilinger approach. In particular, this approach is shown to be connected with symmetric informationally complete measurements. The "total information" of Brukner and Zeilinger can naturally be treated in the context of mutually unbiased measurements as well as general symmetric informationally complete measurements. We also study the Brukner-Zeilinger measure of information in the case of detection inefficiencies. It is shown to be decreasing under the action of bistochastic maps. This observation may be connected with the role of unitality as the condition for the physicality of reverse processes. Relations between the non-unitality operator and the Brukner-Zeilinger total information are discussed.

Towards a Grand Unified Theory of Mathematics and Physics. (arXiv:1506.07576v1 [physics.hist-ph])

physics.hist-ph updates on arXiv.org

on 2015-6-26 1:02am GMT

Authors: Peter Woit

Wigner's "unreasonable effectiveness of mathematics" in physics can be understood as a reflection of a deep and unexpected unity between the fundamental structures of mathematics and of physics. Some of the history of evidence for this is reviewed, emphasizing developments since Wigner's time and still poorly understood analogies between number theory and quantum field theory.

Measurements according to Consistent Histories

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A

Author(s): Elias Okon , Daniel Sudarsky

We critically evaluate the treatment of the notion of measurement in the Consistent Histories approach to quantum mechanics. We find such a treatment unsatisfactory because it relies, often implicitly, on elements external to those provided by the formalism. In particular, we note that, in order for the formalism to be informative when dealing with measurement scenarios, one needs to assume that the appropriate choice of framework is such that apparatuses are always in states of well defined pointer positions after measurements. The problem is that there is nothing in the formalism to justify this assumption. We conclude that the Consistent Histories approach, contrary to what is claimed by its proponents, fails to provide a truly satisfactory resolution for the measurement problem in quantum theory.

Time and quantum theory: A history and a prospectus

on 2015-6-26 12:22am GMT

Publication date: Available online 24 April 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): Thomas Pashby

The historical part of this paper analyzes in detail how ideas and expectations regarding the role of time in quantum theory arose and evolved in the early years of quantum mechanics (from 1925 to 1927). The general theme is that expectations which seemed reasonable from the point of view of matrix mechanics and Dirac׳s q-number formalism became implausible in light of Dirac–Jordan transformation theory, and were dashed by von Neumann׳s Hilbert space formalism which came to replace it. Nonetheless, I will identify two concerns that remain relevant today, and which blunt the force of Hilgevoord׳s (2005) claim that the demand that time feature as an observable arose as the result of a simple conceptual error. First, I advocate the need for event time observables, which provide a temporal probability distribution for the occurrence of a particular event. Second, I claim that Dirac׳s use of the extended phase space to define time and (minus the) energy as conjugates is not subject to ‘Pauli׳s Theorem,’ the result that rules out time observables in von Neumann׳s formalism. I also claim that the need to define these event time observables leads to a novel motivation for considering Dirac׳s extended state space.

Modular localization and the holistic structure of causal quantum theory, a historical perspective

on 2015-6-26 12:22am GMT

Publication date: February 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49

Author(s): Bert Schroer

Recent insights into the conceptual structure of localization in QFT (modular localization) led to clarifications of old unsolved problems. The oldest one is the Einstein–Jordan conundrum which led Jordan in 1925 to the discovery of quantum field theory. This comparison of fluctuations in subsystems of heat bath systems (Einstein) with those resulting from the restriction of the QFT vacuum state to an open subvolume (Jordan) leads to a perfect analogy; the globally pure vacuum state becomes upon local restriction a strongly impure KMS state. This phenomenon of localization-caused thermal behavior as well as the vacuum-polarization clouds at the causal boundary of the localization region places localization in QFT into a sharp contrast with quantum mechanics and justifies the attribute “holstic”. In fact it positions the E–J Gedankenexperiment into the same conceptual category as the cosmological constant problem and the Unruh Gedankenexperiment. The holistic structure of QFT resulting from “modular localization” also leads to a revision of the conceptual origin of the crucial crossing property which entered particle theory at the time of the bootstrap S-matrix approach but suffered from incorrect use in the S-matrix settings of the dual model and string theory. The new holistic point of view, which strengthens the autonomous aspect of QFT, also comes with new messages for gauge theory by exposing the clash between Hilbert space structure and localization and presenting alternative solutions based on the use of stringlocal fields in Hilbert space. Among other things this leads to a reformulation of the Englert–Higgs symmetry breaking mechanism.

Dissecting weak discernibility of quanta

on 2015-6-26 12:22am GMT

Publication date: May 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 50

Author(s): Tomasz Bigaj

In this paper I critically examine latest attempts to formalize quantum-mechanical relations that are supposed to weakly discern elementary particles. I argue that all of them make illegitimate and unavoidable reference to numerical identity, and therefore cannot be used as a means to ground (or derive) quantitative facts of identity/distinctness in the qualitative characteristics of quantum systems. I compare my criticism of weak discernibility with the general circularity objection known from the literature, and I show that my argument is more specific, as it is based on a particular criterion which differentiates between legitimate and illegitimate uses of identity. In the end I suggest that we should reevaluate the role of permutation invariance in expressing the facts of qualitative differences between particles. Taking into account the inevitable symmetrization requirement applied to operators in tensor product spaces, it may be claimed that particles of the same type can be absolutely discerned in some accessible states.

Berry phase and quantum structure

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A

Author(s): Holger Lyre

The paper aims to spell out the relevance of the Berry phase in view of the question what the minimal mathematical structure is that accounts for all observable quantum phenomena. The question is both of conceptual and of ontological interest. While common wisdom tells us that the quantum structure is represented by the structure of the projective Hilbert space, the appropriate structure rich enough to account for the Berry phase is the U(1) bundle over that projective space. The Berry phase is ultimately rooted in the curvature of this quantum bundle, it cannot be traced back to the Hamiltonian dynamics alone. This motivates the ontological claim in the final part of the paper that, if one strives for a realistic understanding of quantum theory including the Berry phase, one should adopt a form of ontic structural realism.

Causality and chance in relativistic quantum field theories

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part B

Author(s): Richard A. Healey

Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable algebras satisfy a relativistically motivated microcausality condition. A pragmatist view of quantum theory and an interventionist approach to causation prompt the reevaluation of local causality and microcausality. Local causality cannot be understood as a reasonable requirement on relativistic quantum field theories: it is unmotivated even if applicable to them. But microcausality emerges as a sufficient condition for the consistent application of a relativistic quantum field theory.

Does the Reeh–Schlieder theorem violate relativistic causality?

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part B

Author(s): Giovanni Valente

The Reeh–Schlieder theorem is a purely relativistic result in local quantum field theory, which is often regarded as raising a conflict with relativistic causality, namely the requirement that causal processes cannot propagate faster than light. Allegedly, under an operational interpretation, the theorem would entail non-local effects, in that by performing an operation within a region of Minkowski spacetime one could instantaneously change the state of the field over another spacelike separated region. Here, we argue that such a conflict is only apparent. Indeed, a suitable understanding of the notion of local operations helps one dissolve the puzzle. Accordingly, even if one does not exclude superluminal signalling, the latter cannot be controlled, and thus it may not be used to give rise to causal paradoxes. On the other hand, we maintain that relativistic causality is expressed by the axiom of local primitive causality, assuring no superluminal propagation of a field. The Reeh–Schlieder theorem can be shown to be fully consistent with such a condition, and hence it does not imply that matter and energy carried by a quantum field can travel faster than light. Therefore, there is no violation of relativistic causality at all.

Four tails problems for dynamical collapse theories

on 2015-6-26 12:22am GMT

Publication date: February 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49

Author(s): Kelvin J. McQueen

The primary quantum mechanical equation of motion entails that measurements typically do not have determinate outcomes, but result in superpositions of all possible outcomes. Dynamical collapse theories (e.g. GRW) supplement this equation with a stochastic Gaussian collapse function, intended to collapse the superposition of outcomes into one outcome. But the Gaussian collapses are imperfect in a way that leaves the superpositions intact. This is the tails problem. There are several ways of making this problem more precise. But many authors dismiss the problem without considering the more severe formulations. Here I distinguish four distinct tails problems. The first (bare tails problem) and second (structured tails problem) exist in the literature. I argue that while the first is a pseudo-problem, the second has not been adequately addressed. The third (multiverse tails problem) reformulates the second to account for recently discovered dynamical consequences of collapse. Finally the fourth (tails problem dilemma) shows that solving the third by replacing the Gaussian with a non-Gaussian collapse function introduces new conflict with relativity theory.

Calling time on digital clocks

on 2015-6-26 12:22am GMT

Publication date: Available online 18 April 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): David Sloan

I explore two logical possibilities for the discretization of time, termed “instantaneous” and “smeared”. These are found by discretizing a continuous theory, and the resulting structure of configuration space and velocities are described. It is shown that results known in numerical methods for integration of dynamical systems preclude the existence of a system with fixed discrete time step which conserves fundamental charges universally, and a method of avoidance of this “no-go” theorem is constructed. Finally the implications of discrete time upon quantum cosmology are discussed.

on 2015-6-26 12:22am GMT

Publication date: August 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 51

Author(s): Edward Anderson

I previously showed that Kendall׳s work on shape geometry is in fact also the geometrical description of Barbour׳s relational mechanics׳ reduced configuration spaces (alias shape spaces). I now describe the extent to which Kendall׳s subsequent statistical application to e.g. the ‘standing stones problem׳ realizes further ideas along the lines of Barbour-type timeless records theories, albeit just at the classical level.

on 2015-6-26 12:22am GMT

Publication date: February 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49

Author(s): James D. Wells

With the Higgs boson discovery and no new physics found at the LHC, confidence in Naturalness as a guiding principle for particle physics is under increased pressure. We wait to see if it proves its mettle in the LHC upgrades ahead, and beyond. In the meantime, I present a justification a posteriori of the Naturalness criterion by suggesting that uncompromising application of the principle to Quantum Electrodynamics leads toward the Standard Model and Higgs boson without additional experimental input. Potential lessons for today and future theory building are commented upon.

on 2015-6-26 12:22am GMT

Publication date: February 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49

Author(s): Gábor Hofer-Szabó

In this paper the relation between the standard probabilistic characterization of the common cause (used for the derivation of the Bell inequalities) and Bell׳s notion of local causality will be investigated in the isotone net framework borrowed from algebraic quantum field theory. The logical role of two components in Bell׳s definition will be scrutinized; namely that the common cause is localized in the intersection of the past of the correlated events; and that it provides a complete specification of the ‘beables’ of this intersection.

on 2015-6-26 12:22am GMT

Publication date: February 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49

Author(s): Kristian Camilleri , Maximilian Schlosshauer

Niels Bohr׳s doctrine of the primacy of “classical concepts” is arguably his most criticized and misunderstood view. We present a new, careful historical analysis that makes clear that Bohr׳s doctrine was primarily an epistemological thesis, derived from his understanding of the functional role of experiment. A hitherto largely overlooked disagreement between Bohr and Heisenberg about the movability of the “cut” between measuring apparatus and observed quantum system supports the view that, for Bohr, such a cut did not originate in dynamical (ontological) considerations, but rather in functional (epistemological) considerations. As such, both the motivation and the target of Bohr׳s doctrine of classical concepts are of a fundamentally different nature than what is understood as the dynamical problem of the quantum-to-classical transition. Our analysis suggests that, contrary to claims often found in the literature, Bohr׳s doctrine is not, and cannot be, at odds with proposed solutions to the dynamical problem of the quantum–classical transition that were pursued by several of Bohr׳s followers and culminated in the development of decoherence theory.

Waiting for the quantum bus: The flow of negative probability

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A

Author(s): A.J. Bracken , G.F. Melloy

It is 45 years since the discovery of the peculiar quantum effect known as ‘probability backflow’, and it is 20 years since the greatest possible size of the effect was characterized. Recently an experiment has been proposed to observe it directly, for the first time, by manipulating ultra-cold atoms. Here a non-technical description is given of the effect and its interpretation in terms of the flow of negative probability.

Can the ontological models framework accommodate Bohmian mechanics?

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A

Author(s): Benjamin Feintzeig

The ontological models framework has been proposed as a tool to prove general results about many competing interpretations of quantum mechanics at once. I argue that the ontological models framework is at best ambiguous, and at worst unable to accomplish its task of representing even the most well known interpretations of quantum mechanics. I show that when the framework is made mathematically precise, it cannot accommodate Bohmian mechanics, a well known interpretation of quantum mechanics in terms of hidden variables.

The quantum Hall effects: Philosophical approach

on 2015-6-26 12:22am GMT

Publication date: May 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 50

Author(s): P. Lederer

The Quantum Hall Effects offer a rich variety of theoretical and experimental advances. They provide interesting insights on such topics as gauge invariance, strong interactions in Condensed Matter physics, emergence of new paradigms. This paper focuses on some related philosophical questions. Various brands of positivism or agnosticism are confronted with the physics of the Quantum Hall Effects. Hacking׳s views on Scientific Realism, Chalmers׳ on Non-Figurative Realism are discussed. It is argued that the difficulties with those versions of realism may be resolved within a dialectical materialist approach. The latter is argued to provide a rational approach to the phenomena, theory and ontology of the Quantum Hall Effects.

A categorial approach to relativistic locality

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part B

Author(s): Miklós Rédei

Relativistic locality is interpreted in this paper as a web of conditions expressing the compatibility of a physical theory with the underlying causal structure of spacetime. Four components of this web are distinguished: spatiotemporal locality, along with three distinct notions of causal locality, dubbed CL-Independence, CL-Dependence, and CL-Dynamic. These four conditions can be regimented using concepts from the categorical approach to quantum field theory initiated by Brunetti, Fredenhagen, and Verch (2003). A covariant functor representing a general quantum field theory is defined to be causally local if it satisfies the three CL conditions. Any such theory is viewed as fully compliant with relativistic locality. We survey current results indicating the extent to which an algebraic quantum field theory satisfying the Haag–Kastler axioms is causally local.

No superluminal propagation for classical relativistic and relativistic quantum fields

on 2015-6-26 12:22am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part B

Author(s): John Earman

A criterion is proposed to ensure that classical relativistic fields do not propagate superluminally. If this criterion does indeed serve as a sufficient condition for no superluminal propagation it follows that various other criteria found in the physics literature cannot serve as necessary conditions since they can fail although the proffered condition holds. The rejected criteria rely on energy conditions that are believed to hold for most classical fields used in actual applications. But these energy conditions are known to fail at small scales for quantum fields. It is argued that such a failure is not necessarily a cause for concern about superluminal propagation in the quantum regime since the proffered criterion of no superluminal propagation for classical fields has a natural analog for quantum fields and, further, this quantum analog condition provably holds for some quantum fields despite the violation of energy conditions. The apparatus developed here also offers a different approach to treating the Reichenbach–Salmon cases of “pseudo-causal processes” and helps to clarify the issue of whether relativity theory is consistent with superluminal propagation.

[This Week in Science] A quantum twist on classical optics

on 2015-6-26 12:00am GMT

Author: Ian S. Osborne

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2015-6-24 7:32pm GMT

de Ronde, Christian (2015) Probabilistic Knowledge as Objective Knowledge in Quantum Mechanics: Potential Powers Instead of Actual Properties. [Preprint]

Reality of the quantum state: A new proof in terms of protective measurements

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2015-6-24 7:26pm GMT

Gao, Shan (2015) Reality of the quantum state: A new proof in terms of protective measurements. [Preprint]

Necessary and Sufficient Condition for Quantum State-Independent Contextuality

PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

on 2015-6-24 2:00pm GMT

Author(s): Adán Cabello, Matthias Kleinmann, and Costantino Budroni

We solve the problem of whether a set of quantum tests reveals state-independent contextuality and use this result to identify the simplest set of the minimal dimension. We also show that identifying state-independent contextuality graphs [R. Ramanathan and P. Horodecki, Phys. Rev. Lett. **112**, 040404…

[Phys. Rev. Lett. 114, 250402] Published Wed Jun 24, 2015

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