# Weekly Papers on Quantum Foundations (18)

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.

Mathematical formalism of many-worlds quantum mechanics. (arXiv:1504.08059v1 [quant-ph])

on 2015-5-02 9:40am GMT

Authors: Zeqian Chen

We combine the ideas of Dirac’s orthonormal representation, Everett’s relative state, and ‘t Hooft’s ontological basis to define the notion of a world for quantum mechanics. Mathematically, for a quantum system $\mathcal{Q}$ with an associated Hilbert space $\mathbb{H},$ a world of $\mathcal{Q}$ is defined to be an orthonormal basis of $\mathbb{H}.$ The evolution of the system is governed by Schr\”{o}dinger’s equation for the worlds of it. An observable in a certain world is a self-adjoint operator diagonal under the corresponding basis. Moreover, a state is defined in an associated world but can be uniquely extended to the whole system as proved recently by Marcus, Spielman, and Srivastava. Although the states described by unit vectors in $\mathbb{H}$ may be determined in different worlds, there are the so-called topology-compact states which must be determined by the totality of a world. Experimentally realization of such a topology-compact state may verify the existence of the worlds for $\mathcal{Q}.$ We can apply the Copenhagen interpretation to a world instead of a quantum state and obtain the Born rule of random outcomes. In particular, our reformulation excludes that quantum mechanics requires some “spooky action at a distance”, as shown in the conventional formulation of non-locality, such as the EPR paradox and various Bell’s theorems. Therefore, we present a mathematical formalism for the many-worlds interpretation of quantum mechanics.

Refined Applications of the “Collapse of the Wavefunction”. (arXiv:1412.7353v2 [hep-ph] UPDATED)

on 2015-5-02 9:40am GMT

Authors: Leo Stodolsky

In a two-part system the “collapse of the wavefunction” of one part can put the other part in a state which would be difficult or impossible to achieve otherwise, in particular one sensitive to small effects in the collapse’ interaction.

We present some applications to the very symmeteric and experimentally accessible situations of the decays $\phi(1020)\to K^oK^o$, $\psi(3770)\to D^oD^o$, or $\Upsilon(4s)\to B^oB^o$, involving the internal state of the two-state $K^o$, $D^o$ or $B^o$ mesons. The “collapse of the wavefunction” occasioned by a decay of one member of the pair (away side’) fixes the state vector of that side’s two-state system. Bose-Einstein statistics then determines the state of the recoiling meson (near side’), whose evolution can then be followed further.

In particular the statistics requirement dictates that the away side’ and near side’ internal states must be orthogonal at the time of the “collapse”. Thus a CP violation in the away side’, decay implies a complementary CP impurity on the `near side’, which can be detected in the further evolution. The CP violaion so manifested is necessarily direct CP violation, since neither the mass matrix nor time evolution was involved in the “collapse”.

A parametrization of the direct CP violation is given and various manifestations are presented. Certain rates or combination of rates are identified which are nonzero only if there is direct CP violation.

The very explicit and detailed use made of “collapse of the wavefunction” makes the procedure interesting with respect to the fundamentals of quantum mechanics. We note an experimental consistency test for our treatment of the “collapse of the wavefunction”, which can be carried out by a certain measurement of partial decay rates.

Niels Bohr as philosopher of experiment: Does decoherence theory challenge Bohr׳s doctrine of classical concepts?

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Does the Reeh–Schlieder theorem violate relativistic causality?

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

On the relation between the probabilistic characterization of the common cause and Bell׳s notion of local causality

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Causality and chance in relativistic quantum field theories

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Berry phase and quantum structure

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

The utility of Naturalness, and how its application to Quantum Electrodynamics envisages the Standard Model and Higgs boson

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Time in fundamental physics

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm GMT

Publication date: Available online 3 October 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Abhay Ashtekar
The first three sections of this paper contain a broad brush summary of the profound changes in the notion of time in fundamental physics that were brought about by three revolutions: the foundations of mechanics distilled by Newton in his Principia, the discovery of special relativity by Einstein and its reformulation by Minkowski, and, finally, the fusion of geometry and gravity in Einstein׳s general relativity. The fourth section discusses two aspects of yet another deep revision that waits in the wings as we attempt to unify general relativity with quantum physics.

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

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Four tails problems for dynamical collapse theories

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Entanglement and disentanglement in relativistic quantum mechanics

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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): Jeffrey A. Barrett
A satisfactory formulation of relativistic quantum mechanics requires that one be able to represent the entangled states of spacelike separated systems and describe how such states evolve. This paper presents two stories that one must be able to tell coherently in order to understand relativistic entangled systems. These stories help to illustrate why one׳s understanding of entanglement in relativistic quantum mechanics must ultimately depend on the details of one׳s strategy for addressing the quantum measurement problem.

Measurements according to Consistent Histories

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Dissecting weak discernibility of quanta

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

The quantum Hall effects: Philosophical approach

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

MichaelEppersonEliasZafirisFoundations of Relational Realism: A Topological Approach to Quantum Mechanics and the Philosophy of Nature2013Lexington Books978-0-7391-8032-7419pp.US$110.00 (hard back), US$109.99 (e-book)

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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): Chris Heunen
Waiting for the quantum bus: The flow of negative probability

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Time and quantum theory: A history and a prospectus

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Can the ontological models framework accommodate Bohmian mechanics?

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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.

Retrocausal models for EPR

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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): Richard Corry
This paper takes up Huw Price׳s challenge to develop a retrocausal toy model of the Bell-EPR experiment. I develop three such models which show that a consistent, local, hidden-variables interpretation of the EPR experiment is indeed possible, and which give a feel for the kind of retrocausation involved. The first of the models also makes clear a problematic feature of retrocausation: it seems that we cannot interpret the hidden elements of reality in a retrocausal model as possessing determinate dispositions to affect the outcome of experiments. This is a feature which Price has embraced, but Gordon Belot has argued that this feature renders retrocausal interpretations “unsuitable for formal development”, and the lack of such determinate dispositions threatens to undermine the motivation for hidden-variables interpretations in the first place. But Price and Belot are both too quick in their assessment. I show that determinate dispositions are indeed consistent with retrocausation. What is more, I show that the ontological economy allowed by retrocausation holds out the promise of a classical understanding of spin and polarization.

Reply to Fleming: Symmetries, observables, and the occurrence of events

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm GMT

Publication date: Available online 5 October 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Thomas Pashby
In this article I reply to Fleming׳s response to my ‘Time and quantum theory: a history and a prospectus.’ I take issue with two of his claims: (i) that quantum theory concerns the (potential) properties of eternally persisting objects; (ii) that there is an underdetermination problem for Positive Operator Valued Measures (POVMs). I advocate an event-first view which regards the probabilities supplied by quantum theory as probabilities for the occurrence of physical events rather than the possession of properties by persisting objects.

Ontological aspects of the Casimir Effect

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-5-01 11:19pm 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): William M.R. Simpson
The role of the vacuum, in the Casimir Effect, is a matter of some dispute: the Casimir force has been variously described as a phenomenon resulting “from the alteration, by the boundaries, of the zero-point electromagnetic energy” (Bordag, Mohideen, &amp; Mostepanenko, 2001), or a “van der Waals force between the metal plates” that can be “computed without reference to zero point energies” (Jaffe, 2005). Neither of these descriptions is grounded in a consistently quantum mechanical treatment of matter interacting with the electromagnetic field. However, the Casimir Effect has been canonically described within the framework of macroscopic quantum electrodynamics (Philbin, 2010). On this general account, the force is seen to arise due to the coupling of fluctuating currents to the zero-point radiation, and it is in this restricted sense that the phenomenon requires the existence of zero-point fields. The conflicting descriptions of the Casimir Effect, on the other hand, appear to arise from ontologies in which an unwarranted metaphysical priority is assigned either to the matter or the fields, and this may have a direct bearing on the problem of the cosmological constant.

[Report] Observation of isolated monopoles in a quantum field

Science: Current Issue

on 2015-5-01 12:00am GMT

Topological defects play important roles throughout nature, appearing in contexts as diverse as cosmology, particle physics, superfluidity, liquid crystals, and metallurgy. Point defects can arise naturally as magnetic monopoles resulting from symmetry breaking in grand unified theories. We devised an experiment to create and detect quantum mechanical analogs of such monopoles in a spin-1 Bose-Einstein condensate. The defects, which were stable on the time scale of our experiments, were identified from spin-resolved images of the condensate density profile that exhibit a characteristic dependence on the choice of quantization axis. Our observations lay the foundation for experimental studies of the dynamics and stability of topological point defects in quantum systems. Authors: M. W. Ray, E. Ruokokoski, K. Tiurev, M. Möttönen, D. S. Hall

A new vacuum for loop quantum gravity

Classical and Quantum Gravity – latest papers

on 2015-5-01 12:00am GMT

We construct a new vacuum and representation for loop quantum gravity. Because the new vacuum is based on BF theory, it is physical for (2+1)-dimensional gravity, and much closer to the spirit of spin foam quantization in general. To construct this new vacuum and the associated representation of quantum observables, we introduce a modified holonomy–flux algebra that is cylindrically consistent with respect to the notion of refinement by time evolution suggested in Dittrich and Steinhaus (2013 arXiv: 1311.7565 [http://arXiv.org/abs/1311.7565] ). This supports the proposal for a construction of the physical vacuum made in Dittrich and Steinhaus (2013 arXiv: 1311.7565 [http://arXiv.org/abs/1311.7565] ) and Dittrich (2012 New J. Phys. 14 [http://dx.doi.org/10.1088/1367-2630/14/12/123004] 123004 ), and for (3+1)-dimensional gravity. We expect that the vacuum introduced here will facilitate the extraction of large scale physics and cosmologi…

Casimir effect in a quantum space–time

Classical and Quantum Gravity – latest papers

on 2015-5-01 12:00am GMT

We apply quantum field theory in quantum space–time techniques to study the Casimir effect for large spherical shells. As background we use the recently constructed exact quantum solution for spherically symmetric vacuum space–time in loop quantum gravity. All calculations are finite and one recovers the usual results without the need for regularization or renormalization. This is an example of how loop quantum gravity provides a natural resolution to the infinities of quantum field theories.

Ten years of Nature Physics: From spooky foundations

Nature Physics – Issue – nature.com science feeds

on 2015-4-30 12:00am GMT

Nature Physics 11, 383 (2015). doi:10.1038/nphys3318

Author: Sebastian Deffner

Quantum entanglement is as confounding as it is potentially useful. A paper in 2006 suggested that its utility might extend to making sense of a fundamental puzzle in statistical mechanics.

Identities for Entropy Change Associated with the Time-Evolution of an Open System

Latest Results for Foundations of Physics

on 2015-4-29 12:00am GMT

Abstract

A general relation between entropy and an evolutionary superoperator is derived based on the theory of the real-time formulation. The formulation establishing the relation relies only on the framework of quantum statistical mechanics and the standard definition of the von Neumann entropy. Applying the theory of the imaginary-time formulation, a similar relation is obtained for the entropy change due to the change in reservoir temperatures. To show the usefulness of these formulas, we derived the expression for the entropy production induced by some dissipation in an open quantum system as the exemplary model system.

Review of ‘Quantum Information Theory and the Foundations of Quantum Mechanics’, by Christopher G. Timpson

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

on 2015-4-28 10:16pm GMT

Felline, Laura (2014) Review of ‘Quantum Information Theory and the Foundations of Quantum Mechanics’, by Christopher G. Timpson. [Published Article]

A conjecture concerning determinism and phases in quantum mechanics

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

on 2015-4-28 10:10pm GMT

Jabs, Arthur (2015) A conjecture concerning determinism and phases in quantum mechanics. [Preprint]

Quantum mechanics in terms of realism

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

on 2015-4-28 10:08pm GMT

Jabs, Arthur (2015) Quantum mechanics in terms of realism. [Preprint]

Entanglement and thermodynamics in general probabilistic theories. (arXiv:1504.07045v1 [quant-ph])

on 2015-4-28 1:00am GMT

Entanglement is one of the most striking features of quantum mechanics, and yet it is not specifically quantum. It shows up in a number of alternative theories, such as the theory of nonlocal boxes, where it provides a powerful information-theoretic resource. Here we explore the ways in which this resource can be manipulated in a general physical theory, searching for operational links between transformations of entanglement and thermodynamic transformations. We first address the question whether an entangled state can be transformed into another by means of local operations and classical communication (LOCC). Under two operational requirements, we prove an analogue of the Lo-Popescu theorem, stating that every LOCC protocol acting on a pure bipartite state can be simulated by a protocol that uses a single round of classical communication. We then introduce an ordering of single-system states according to their degree of mixedness, providing an operational version of the majorization criterion.

Based on this notion, we show that the degree of entanglement of a pure bipartite state coincides with the degree of mixedness of its marginals in every physical theory where all processes arise from pure states and reversible interactions at the fundamental level.

Quantum set theory extending standard probabilistic interpretation of quantum theory. (arXiv:1504.06838v1 [quant-ph])

on 2015-4-28 1:00am GMT

Authors: Masanao Ozawa

The notion of equality between two observables will play many important roles in foundations of quantum theory. However, the standard probabilistic interpretation based on the conventional Born formula does not give the probability of equality relation for a pair of arbitrary observables, since the Born formula gives the probability distribution only for a commuting family of observables. In this paper, quantum set theory developed by Takeuti and the present author is used to systematically extend the probabilistic interpretation of quantum theory to define the probability of equality relation for a pair of arbitrary observables. Applications of this new interpretation to quantum measurement theory are discussed briefly.

On the Importance of Interpretation in Quantum Physics: A Reply to Elise Crull

Latest Results for Foundations of Physics

on 2015-4-28 12:00am GMT

Abstract

Elise Crull (Found Phys. doi:10.1007/s10701-014-9847-4, 2014) claims that by invoking decoherence it is possible (i) to obviate many “fine grained” issues often conflated under the common designation of measurement problem, and (ii) to make substantial progresses in the fields of quantum gravity and quantum cosmology, without any early incorporation of a particular interpretation in the quantum formalism. We point out that Crull is mistaken about decoherence and tacitly assumes some kind of interpretation of the quantum formalism.

Bohmian Dispositions

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

on 2015-4-26 6:13pm GMT

Suárez, Mauricio (2015) Bohmian Dispositions. [Preprint]