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  1.  5
    Extracting Geometry From Quantum Spacetime.Yuri Bonder, Chryssomalis Chryssomalakos & Daniel Sudarsky - 2018 - Foundations of Physics 48 (9):1038-1060.
    Any acceptable quantum gravity theory must allow us to recover the classical spacetime in the appropriate limit. Moreover, the spacetime geometrical notions should be intrinsically tied to the behavior of the matter that probes them. We consider some difficulties that would be confronted in attempting such an enterprise. The problems we uncover seem to go beyond the technical level to the point of questioning the overall feasibility of the project. The main issue is related to the fact that, in the (...)
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  2.  3
    Law Without Law or “Just” Limit Theorems?Sergio Caprara & Angelo Vulpiani - 2018 - Foundations of Physics 48 (9):1112-1127.
    About 35 years ago Wheeler introduced the motto “law without law” to highlight the possibility that Physics may be understood only following regularity principles and few relevant facts, rather than relying on a treatment in terms of fundamental theories. Such a proposal can be seen as part of a more general attempt summarized by the slogan “it from bit”, which privileges the information as the basic ingredient. Apparently it seems that it is possible to obtain, without the use of physical (...)
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  3.  2
    Paul Busch 1955–2018.Stan Gudder, Pekka Lahti & Leon Loveridge - 2018 - Foundations of Physics 48 (9):1128-1130.
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  4.  3
    Quanta and Qualia.Adrian Kent - 2018 - Foundations of Physics 48 (9):1021-1037.
    I sketch a line of thought about consciousness and physics that gives some motivation for the hypothesis that conscious observers deviate—perhaps only very subtly and slightly—from quantum dynamics. Although it is hard to know just how much credence to give this line of thought, it does add motivation for a stronger and more comprehensive programme of quantum experiments involving quantum observers.
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  5.  7
    Homer Nodded: Von Neumann’s Surprising Oversight.N. David Mermin & Rüdiger Schack - 2018 - Foundations of Physics 48 (9):1007-1020.
    We review the famous no-hidden-variables theorem in von Neumann’s 1932 book on the mathematical foundations of quantum mechanics. We describe the notorious gap in von Neumann’s argument, pointed out by Hermann and, more famously, by Bell. We disagree with recent papers claiming that Hermann and Bell failed to understand what von Neumann was actually doing.
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  6.  1
    Relational Quantum Mechanics and Probability.M. Trassinelli - 2018 - Foundations of Physics 48 (9):1092-1111.
    We present a derivation of the third postulate of relational quantum mechanics from the properties of conditional probabilities. The first two RQM postulates are based on the information that can be extracted from interaction of different systems, and the third postulate defines the properties of the probability function. Here we demonstrate that from a rigorous definition of the conditional probability for the possible outcomes of different measurements, the third postulate is unnecessary and the Born’s rule naturally emerges from the first (...)
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  7.  1
    The Twofold Role of Observables in Classical and Quantum Kinematics.Federico Zalamea - 2018 - Foundations of Physics 48 (9):1061-1091.
    Observables have a dual nature in both classical and quantum kinematics: they are at the same time quantities, allowing to separate states by means of their numerical values, and generators of transformations, establishing relations between different states. In this work, we show how this twofold role of observables constitutes a key feature in the conceptual analysis of classical and quantum kinematics, shedding a new light on the distinguishing feature of the quantum at the kinematical level. We first take a look (...)
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  8. Oracles and Query Lower Bounds in Generalised Probabilistic Theories.Howard Barnum, Ciarán M. Lee & John H. Selby - 2018 - Foundations of Physics 48 (8):954-981.
    We investigate the connection between interference and computational power within the operationally defined framework of generalised probabilistic theories. To compare the computational abilities of different theories within this framework we show that any theory satisfying four natural physical principles possess a well-defined oracle model. Indeed, we prove a subroutine theorem for oracles in such theories which is a necessary condition for the oracle model to be well-defined. The four principles are: causality, purification, strong symmetry, and informationally consistent composition. Sorkin has (...)
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  9.  3
    Introduction: Quantum Information Theory and Quantum Foundations.Howard Barnum, Stephanie Wehner & Alexander Wilce - 2018 - Foundations of Physics 48 (8):853-856.
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  10.  8
    On Defining the Hamiltonian Beyond Quantum Theory.Dominic Branford, Oscar C. O. Dahlsten & Andrew J. P. Garner - 2018 - Foundations of Physics 48 (8):982-1006.
    Energy is a crucial concept within classical and quantum physics. An essential tool to quantify energy is the Hamiltonian. Here, we consider how to define a Hamiltonian in general probabilistic theories—a framework in which quantum theory is a special case. We list desiderata which the definition should meet. For 3-dimensional systems, we provide a fully-defined recipe which satisfies these desiderata. We discuss the higher dimensional case where some freedom of choice is left remaining. We apply the definition to example toy (...)
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  11.  3
    Interferometric Computation Beyond Quantum Theory.Andrew J. P. Garner - 2018 - Foundations of Physics 48 (8):886-909.
    There are quantum solutions for computational problems that make use of interference at some stage in the algorithm. These stages can be mapped into the physical setting of a single particle travelling through a many-armed interferometer. There has been recent foundational interest in theories beyond quantum theory. Here, we present a generalized formulation of computation in the context of a many-armed interferometer, and explore how theories can differ from quantum theory and still perform distributed calculations in this set-up. We shall (...)
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  12.  3
    Squashed Entanglement, $$Mathbf {}$$-Extendibility, Quantum Marov Chains, and Recovery Maps.Ke Li & Andreas Winter - 2018 - Foundations of Physics 48 (8):910-924.
    Squashed entanglement :829–840, 2004) is a monogamous entanglement measure, which implies that highly extendible states have small value of the squashed entanglement. Here, invoking a recent inequality for the quantum conditional mutual information :575–611, 2015) greatly extended and simplified in various work since, we show the converse, that a small value of squashed entanglement implies that the state is close to a highly extendible state. As a corollary, we establish an alternative proof of the faithfulness of squashed entanglement. We briefly (...)
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  13.  1
    Random Constructions in Bell Inequalities: A Survey.Carlos Palazuelos - 2018 - Foundations of Physics 48 (8):857-885.
    Initially motivated by their relevance in foundations of quantum mechanics and more recently by their applications in different contexts of quantum information science, violations of Bell inequalities have been extensively studied during the last years. In particular, an important effort has been made in order to quantify such Bell violations. Probabilistic techniques have been heavily used in this context with two different purposes. First, to quantify how common the phenomenon of Bell violations is; and second, to find large Bell violations (...)
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  14.  1
    Multipartite Composition of Contextuality Scenarios.Ana Belén Sainz & Elie Wolfe - 2018 - Foundations of Physics 48 (8):925-953.
    Contextuality is a particular quantum phenomenon that has no analogue in classical probability theory. Given two independent systems, a natural question is how to represent such a situation as a single test space. In other words, how separate contextuality scenarios combine into a joint scenario. Under the premise that the the allowed probabilistic models satisfy the No Signalling principle, Foulis and Randall defined the unique possible way to compose two contextuality scenarios. When composing strictly-more than two test spaces, however, a (...)
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  15.  5
    Is Knowledge of Physical Reality Still Kantian? Some Remarks About the Transcendental Character of Loop Quantum Gravity.Luigi Laino - 2018 - Foundations of Physics 48 (7):783-802.
    In the following paper, the author will try to test the meaning of the transcendental approach in respect of the inner changes implied by the idea of quantum gravity. He will firstly describe the basic methodological Kant’s aim, viz. the grounding of a meta-science of physics as the a priori corpus of physical knowledge. After that, he will take into account the problematic physical and philosophical relationship between the theory of relativity and the quantum mechanics; in showing how the elementary (...)
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  16.  4
    The Transition From Quantum Field Theory to One-Particle Quantum Mechanics and a Proposed Interpretation of Aharonov–Bohm Effect.Benliang Li, Daniel W. Hewak & Qi Jie Wang - 2018 - Foundations of Physics 48 (7):837-852.
    In this article, we demonstrate a sense in which the one-particle quantum mechanics and the classical electromagnetic four-potential arise from the quantum field theory. In addition, the classical Maxwell equations are derived from the QFT scattering process, while both classical electromagnetic fields and potentials serve as mathematical tools to approximate the interactions among elementary particles described by QFT physics. Furthermore, a plausible interpretation of the Aharonov–Bohm effect is raised within the QFT framework. We provide a quantum treatment of the source (...)
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  17. Analysis of Wallace’s Proof of the Born Rule in Everettian Quantum Mechanics: Formal Aspects.André L. G. Mandolesi - 2018 - Foundations of Physics 48 (7):751-782.
    To solve the probability problem of the Many Worlds Interpretation of Quantum Mechanics, D. Wallace has presented a formal proof of the Born rule via decision theory, as proposed by D. Deutsch. The idea is to get subjective probabilities from rational decisions related to quantum measurements, showing the non-probabilistic parts of the quantum formalism, plus some rational constraints, ensure the squared modulus of quantum amplitudes play the role of such probabilities. We provide a new presentation of Wallace’s proof, reorganized to (...)
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  18.  7
    Normalized Observational Probabilities From Unnormalizable Quantum States or Phase-Space Distributions.Don N. Page - 2018 - Foundations of Physics 48 (7):827-836.
    Often it is assumed that a quantum state or a phase-space distribution must be normalizable. Here it is shown that even if it is not normalizable, one may be able to extract normalized observational probabilities from it.
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  19.  5
    Are Hidden-Variable Theories for Pilot-Wave Systems Possible?Louis Vervoort - 2018 - Foundations of Physics 48 (7):803-826.
    Recently it was shown that certain fluid-mechanical ‘pilot-wave’ systems can strikingly mimic a range of quantum properties, including single particle diffraction and interference, quantization of angular momentum etc. How far does this analogy go? The ultimate test of quantumness of such systems is a Bell-test. Here the premises of the Bell inequality are re-investigated for particles accompanied by a pilot-wave, or more generally by a resonant ‘background’ field. We find that two of these premises, namely outcome independence and measurement independence, (...)
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  20.  3
    Causality in the Classical Limit for Quantum Electrodynamics.Gregory C. Dente - 2018 - Foundations of Physics 48 (6):628-635.
    We use the path integral form of quantum electrodynamics to show that a causal classical limit to QED can be derived by functionally integrating over the photon coordinates, starting from an initial photon vacuum and ending in a final coherent radiation state driven by the anticipated classical charged particle trajectories. The resulting charged particle transition amplitude depends only on particle coordinates. When the \ limit is taken, only those particle paths that are not constrained by the final radiation state are (...)
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  21.  5
    Timeless Configuration Space and the Emergence of Classical Behavior.Henrique Gomes - 2018 - Foundations of Physics 48 (6):668-715.
    The inherent difficulty in talking about quantum decoherence in the context of quantum cosmology is that decoherence requires subsystems, and cosmology is the study of the whole Universe. Consistent histories gave a possible answer to this conundrum, by phrasing decoherence as loss of interference between alternative histories of closed systems. When one can apply Boolean logic to a set of histories, it is deemed ‘consistent’. However, the vast majority of the sets of histories that are merely consistent are blatantly nonclassical (...)
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  22.  2
    A Stochastic Version of the Noether Theorem.Alfredo González Lezcano & Alejandro Cabo Montes de Oca - 2018 - Foundations of Physics 48 (6):726-746.
    A stochastic version of the Noether theorem is derived for systems under the action of external random forces. The concept of moment generating functional is employed to describe the symmetry of the stochastic forces. The theorem is applied to two kinds of random covariant forces. One of them generated in an electrodynamic way and the other is defined in the rest frame of the particle as a function of the proper time. For both of them, it is shown the conservation (...)
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  23.  8
    Objectivity in Quantum Measurement.Sheng-Wen Li, C. Y. Cai, X. F. Liu & C. P. Sun - 2018 - Foundations of Physics 48 (6):654-667.
    The objectivity is a basic requirement for the measurements in the classical world, namely, different observers must reach a consensus on their measurement results, so that they believe that the object exists “objectively” since whoever measures it obtains the same result. We find that this simple requirement of objectivity indeed imposes an important constraint upon quantum measurements, i.e., if two or more observers could reach a consensus on their quantum measurement results, their measurement basis must be orthogonal vector sets. This (...)
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  24.  10
    Paradox Regained? A Brief Comment on Maudlin on Black Hole Information Loss.J. B. Manchak & James Owen Weatherall - 2018 - Foundations of Physics 48 (6):611-627.
    We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin's response to it.
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  25.  15
    Shan Gao: The Meaning of the Wave Function. In Search of the Ontology of Quantum Mechanics.Carlo Rovelli - 2018 - Foundations of Physics 48 (6):747-749.
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  26.  2
    Uncertainty Principle on 3-Dimensional Manifolds of Constant Curvature.Thomas Schürmann - 2018 - Foundations of Physics 48 (6):716-725.
    We consider the Heisenberg uncertainty principle of position and momentum in 3-dimensional spaces of constant curvature K. The uncertainty of position is defined coordinate independent by the geodesic radius of spherical domains in which the particle is localized after a von Neumann–Lüders projection. By applying mathematical standard results from spectral analysis on manifolds, we obtain the largest lower bound of the momentum deviation in terms of the geodesic radius and K. For hyperbolic spaces, we also obtain a global lower bound (...)
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  27.  3
    Information Graph Flow: A Geometric Approximation of Quantum and Statistical Systems.Vitaly Vanchurin - 2018 - Foundations of Physics 48 (6):636-653.
    Given a quantum system with a very large number of degrees of freedom and a preferred tensor product factorization of the Hilbert space we describe how it can be approximated with a very low-dimensional field theory with geometric degrees of freedom. The geometric approximation procedure consists of three steps. The first step is to construct weighted graphs with vertices representing subsystems and edges representing mutual information between subsystems. The second step is to deform the adjacency matrices of the information graphs (...)
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  28.  8
    The ‘Miracle’ of Applicability? The Curious Case of the Simple Harmonic Oscillator.Sorin Bangu & Robert H. C. Moir - 2018 - Foundations of Physics 48 (5):507-525.
    The paper discusses to what extent the conceptual issues involved in solving the simple harmonic oscillator model fit Wigner’s famous point that the applicability of mathematics borders on the miraculous. We argue that although there is ultimately nothing mysterious here, as is to be expected, a careful demonstration that this is so involves unexpected difficulties. Consequently, through the lens of this simple case we derive some insight into what is responsible for the appearance of mystery in more sophisticated examples of (...)
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  29.  15
    Delimiting the Unconceived.Richard Dawid - 2018 - Foundations of Physics 48 (5):492-506.
    It has been argued in Dawid that physicists at times generate substantial trust in an empirically unconfirmed theory based on observations that lie beyond the theory’s intended domain. A crucial role in the reconstruction of this argument of “non-empirical confirmation” is played by limitations to scientific underdetermination. The present paper discusses the question as to how generic the role of limitations to scientific underdetermination really is. It is argued that assessing such limitations is essential for generating trust in any theory’s (...)
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  30.  5
    On Gravitational Energy in Newtonian Theories.Neil Dewar & James Owen Weatherall - 2018 - Foundations of Physics 48 (5):558-578.
    There are well-known problems associated with the idea of gravitational energy in general relativity. We offer a new perspective on those problems by comparison with Newtonian gravitation, and particularly geometrized Newtonian gravitation. We show that there is a natural candidate for the energy density of a Newtonian gravitational field. But we observe that this quantity is gauge dependent, and that it cannot be defined in the geometrized theory without introducing further structure. We then address a potential response by showing that (...)
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  31.  7
    The Matter-Gravity Entanglement Hypothesis.Bernard S. Kay - 2018 - Foundations of Physics 48 (5):542-557.
    I outline some of my work and results on my matter-gravity entanglement hypothesis, according to which the entropy of a closed quantum gravitational system is equal to the system’s matter-gravity entanglement entropy. The main arguments presented are: that this hypothesis is capable of resolving what I call the second-law puzzle, i.e. the puzzle as to how the entropy increase of a closed system can be reconciled with the asssumption of unitary time-evolution; that the black hole information loss puzzle may be (...)
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  32.  4
    Against Laplacian Reduction of Newtonian Mass to Spatiotemporal Quantities.Niels C. M. Martens - 2018 - Foundations of Physics 48 (5):591-609.
    Laplace wondered about the minimal choice of initial variables and parameters corresponding to a well-posed initial value problem. Discussions of Laplace’s problem in the literature have focused on choosing between spatiotemporal variables relative to absolute space or merely relative to other material bodies and between absolute masses or merely mass ratios. This paper extends these discussions of Laplace’s problem, in the context of Newtonian Gravity, by asking whether mass needs to be included in the initial state at all, or whether (...)
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  33.  3
    Had We But World Enough, and Time... But We Don’T!: Justifying the Thermodynamic and Infinite-Time Limits in Statistical Mechanics.Patricia Palacios - 2018 - Foundations of Physics 48 (5):526-541.
    In this paper, I compare the use of the thermodynamic limit in the theory of phase transitions with the infinite-time limit in the explanation of equilibrium statistical mechanics. In the case of phase transitions, I will argue that the thermodynamic limit can be justified pragmatically since the limit behavior also arises before we get to the limit and for values of N that are physically significant. However, I will contend that the justification of the infinite-time limit is less straightforward. In (...)
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  34.  2
    Equivalent Theories and Changing Hamiltonian Observables in General Relativity.J. Brian Pitts - 2018 - Foundations of Physics 48 (5):579-590.
    Change and local spatial variation are missing in Hamiltonian general relativity according to the most common definition of observables as having 0 Poisson bracket with all first-class constraints. But other definitions of observables have been proposed. In pursuit of Hamiltonian–Lagrangian equivalence, Pons, Salisbury and Sundermeyer use the Anderson–Bergmann–Castellani gauge generator G, a tuned sum of first-class constraints. Kuchař waived the 0 Poisson bracket condition for the Hamiltonian constraint to achieve changing observables. A systematic combination of the two reforms might use (...)
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  35.  41
    Physics Needs Philosophy. Philosophy Needs Physics.Carlo Rovelli - 2018 - Foundations of Physics 48 (5):481-491.
    Contrary to claims about the irrelevance of philosophy for science, I argue that philosophy has had, and still has, far more influence on physics than is commonly assumed. I maintain that the current anti-philosophical ideology has had damaging effects on the fertility of science. I also suggest that recent important empirical results, such as the detection of the Higgs particle and gravitational waves, and the failure to detect supersymmetry where many expected to find it, question the validity of certain philosophical (...)
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  36.  8
    A General Theorem on Temporal Foliations of Causal Sets.Ali Bleybel & Abdallah Zaiour - 2018 - Foundations of Physics 48 (4):456-478.
    Causal sets are a particular class of partially ordered sets, which are proposed as basic models of discrete space-time, specially in the field of quantum gravity. In this context, we show the existence of temporal foliations for any causal set, or more generally, for a causal space. Moreover, we show that automorphisms of a large class of infinite causal sets fall into two classes 1) Automorphisms of spacelike hypersurfaces in some given foliation, or 2) Translations in time. More generally, we (...)
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  37.  5
    Energy and Uncertainty in General Relativity.F. I. Cooperstock & M. J. Dupre - 2018 - Foundations of Physics 48 (4):387-394.
    The issue of energy and its potential localizability in general relativity has challenged physicists for more than a century. Many non-invariant measures were proposed over the years but an invariant measure was never found. We discovered the invariant localized energy measure by expanding the domain of investigation from space to spacetime. We note from relativity that the finiteness of the velocity of propagation of interactions necessarily induces indefiniteness in measurements. This is because the elements of actual physical systems being measured (...)
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  38.  7
    Generalized Stefan–Boltzmann Law.Gilles Montambaux - 2018 - Foundations of Physics 48 (4):395-410.
    We reconsider the thermodynamic derivation by L. Boltzmann of the Stefan law and we generalize it for various different physical systems whose chemical potential vanishes. Being only based on classical arguments, therefore independent of the quantum statistics, this derivation applies as well to the saturated Bose gas in various geometries as to “compensated” Fermi gas near a neutrality point, such as a gas of Weyl Fermions. It unifies in the same framework the thermodynamics of many different bosonic or fermionic non-interacting (...)
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  39.  6
    Losing Stuff Down a Black Hole.Elias Okon & Daniel Sudarsky - 2018 - Foundations of Physics 48 (4):411-428.
    Over the years, the so-called black hole information loss paradox has generated an amazingly diverse set of proposals. However, 40 years after the introduction of Hawking’s radiation, there continues to be a debate regarding whether the effect does, in fact, lead to an actual problem. In this paper we try to clarify some aspect of the discussion by describing two possible perspectives regarding the landscape of the information loss issue. Moreover, we advance a fairly conservative point of view regarding the (...)
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  40.  8
    Can We Make Sense of Relational Quantum Mechanics?Quentin Ruyant - 2018 - Foundations of Physics 48 (4):440-455.
    The relational interpretation of quantum mechanics proposes to solve the measurement problem and reconcile completeness and locality of quantum mechanics by postulating relativity to the observer for events and facts, instead of an absolute “view from nowhere”. The aim of this paper is to clarify this interpretation, and in particular, one of its central claims concerning the possibility for an observer to have knowledge about other observer’s events. I consider three possible readings of this claim, and develop the most promising (...)
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  41.  5
    Decoherence and Determinism in a One-Dimensional Cloud-Chamber Model.Jean-Marc Sparenberg & David Gaspard - 2018 - Foundations of Physics 48 (4):429-439.
    The hypothesis that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model. In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and (...)
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  42.  7
    Completing the Physical Representation of Quantum Algorithms Provides a Quantitative Explanation of Their Computational Speedup.Giuseppe Castagnoli - 2018 - Foundations of Physics 48 (3):333-354.
    The usual representation of quantum algorithms, limited to the process of solving the problem, is physically incomplete. We complete it in three steps: extending the representation to the process of setting the problem, relativizing the extended representation to the problem solver to whom the problem setting must be concealed, and symmetrizing the relativized representation for time reversal to represent the reversibility of the underlying physical process. The third steps projects the input state of the representation, where the problem solver is (...)
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  43.  12
    What is Quantum Mechanics? A Minimal Formulation.R. Friedberg & P. C. Hohenberg - 2018 - Foundations of Physics 48 (3):295-332.
    This paper presents a minimal formulation of nonrelativistic quantum mechanics, by which is meant a formulation which describes the theory in a succinct, self-contained, clear, unambiguous and of course correct manner. The bulk of the presentation is the so-called “microscopic theory”, applicable to any closed system S of arbitrary size N, using concepts referring to S alone, without resort to external apparatus or external agents. An example of a similar minimal microscopic theory is the standard formulation of classical mechanics, which (...)
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  44.  6
    Generalized Ehrenfest Relations, Deformation Quantization, and the Geometry of Inter-Model Reduction.Joshua Rosaler - 2018 - Foundations of Physics 48 (3):355-385.
    This study attempts to spell out more explicitly than has been done previously the connection between two types of formal correspondence that arise in the study of quantum–classical relations: one the one hand, deformation quantization and the associated continuity between quantum and classical algebras of observables in the limit \, and, on the other, a certain generalization of Ehrenfest’s Theorem and the result that expectation values of position and momentum evolve approximately classically for narrow wave packet states. While deformation quantization (...)
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  45.  3
    On the Boltzmann–Grad Limit for Smooth Hard-Sphere Systems.Massimo Tessarotto, Claudio Cremaschini, Michael Mond, Claudio Asci, Alessandro Soranzo & Gino Tironi - 2018 - Foundations of Physics 48 (3):271-294.
    The problem is posed of the prescription of the so-called Boltzmann–Grad limit operator ) for the N-body system of smooth hard-spheres which undergo unary, binary as well as multiple elastic instantaneous collisions. It is proved, that, despite the non-commutative property of the operator \, the Boltzmann equation can nevertheless be uniquely determined. In particular, consistent with the claim of Uffink and Valente that there is “no time-asymmetric ingredient” in its derivation, the Boltzmann equation is shown to be time-reversal symmetric. The (...)
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  46.  15
    The Relativistic Geometry and Dynamics of Electrons.M. F. Atiyah & J. Malkoun - 2018 - Foundations of Physics 48 (2):199-208.
    Atiyah and Sutcliffe made a number of conjectures about configurations of N distinct points in hyperbolic 3-space, arising from ideas of Berry and Robbins. In this paper we prove all these conjectures, purely geometrically, but we also provide a physical interpretation in terms of Electrons.
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  47.  9
    A Note on the Problem of Proper Time in Weyl Space–Time.R. Avalos, F. Dahia & C. Romero - 2018 - Foundations of Physics 48 (2):253-270.
    We discuss the question of whether or not a general Weyl structure is a suitable mathematical model of space–time. This is an issue that has been in debate since Weyl formulated his unified field theory for the first time. We do not present the discussion from the point of view of a particular unification theory, but instead from a more general standpoint, in which the viability of such a structure as a model of space–time is investigated. Our starting point is (...)
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  48.  11
    How Not to Establish the Non-Renormalizability of Gravity.Juliusz Doboszewski & Niels Linnemann - 2018 - Foundations of Physics 48 (2):237-252.
    General relativity cannot be formulated as a perturbatively renormalizable quantum field theory. An argument relying on the validity of the Bekenstein–Hawking entropy formula aims at dismissing gravity as non-renormalizable per se, against hopes that d-dimensional GR could turn out to have a non-perturbatively renormalizable d–dimensional quantum field theoretic formulation. In this note we discuss various forms of highly problematic semi-classical extrapolations assumed by both sides of the debate concerning what we call The Entropy Argument, and show that a large class (...)
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  49.  8
    Symmetry, Reference Frames, and Relational Quantities in Quantum Mechanics.Leon Loveridge, Takayuki Miyadera & Paul Busch - 2018 - Foundations of Physics 48 (2):135-198.
    We propose that observables in quantum theory are properly understood as representatives of symmetry-invariant quantities relating one system to another, the latter to be called a reference system. We provide a rigorous mathematical language to introduce and study quantum reference systems, showing that the orthodox “absolute” quantities are good representatives of observable relative quantities if the reference state is suitably localised. We use this relational formalism to critique the literature on the relationship between reference frames and superselection rules, settling a (...)
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  50.  8
    The Dynamics of Difference.Lee Smolin - 2018 - Foundations of Physics 48 (2):121-134.
    A proposal is made for a fundamental theory, in which the history of the universe is constituted of diverse views of itself. Views are attributes of events, and the theory’s only be-ables; they comprise information about energy and momentum transferred to an event from its causal past. A dynamics is proposed for a universe constituted of views of events, which combines the energetic causal set dynamics with a potential energy based on a measure of the distinctiveness of the views, called (...)
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  51.  10
    Particle Trajectories for Quantum Field Theory.Jeroen C. Vink - 2018 - Foundations of Physics 48 (2):209-236.
    The formulation of quantum mechanics developed by Bohm, which can generate well-defined trajectories for the underlying particles in the theory, can equally well be applied to relativistic quantum field theories to generate dynamics for the underlying fields. However, it does not produce trajectories for the particles associated with these fields. Bell has shown that an extension of Bohm’s approach can be used to provide dynamics for the fermionic occupation numbers in a relativistic quantum field theory. In the present paper, Bell’s (...)
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  52.  7
    Interaction-Free Effects Between Distant Atoms.Yakir Aharonov, Eliahu Cohen, Avshalom C. Elitzur & Lee Smolin - 2018 - Foundations of Physics 48 (1):1-16.
    A Gedanken experiment is presented where an excited and a ground-state atom are positioned such that, within the former’s half-life time, they exchange a photon with 50% probability. A measurement of their energy state will therefore indicate in 50% of the cases that no photon was exchanged. Yet other measurements would reveal that, by the mere possibility of exchange, the two atoms have become entangled. Consequently, the “no exchange” result, apparently precluding entanglement, is non-locally established between the atoms by this (...)
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  53.  10
    Realistic Clocks for a Universe Without Time.K. L. H. Bryan & A. J. M. Medved - 2018 - Foundations of Physics 48 (1):48-59.
    There are a number of problematic features within the current treatment of time in physical theories, including the “timelessness” of the Universe as encapsulated by the Wheeler–DeWitt equation. This paper considers one particular investigation into resolving this issue; a conditional probability interpretation that was first proposed by Page and Wooters. Those authors addressed the apparent timelessness by subdividing a faux Universe into two entangled parts, “the clock” and “the remainder of the Universe”, and then synchronizing the effective dynamics of the (...)
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  54.  4
    Non-Minimal Coupling of the Higgs Boson to Curvature in an Inflationary Universe.Xavier Calmet, Iberê Kuntz & Ian G. Moss - 2018 - Foundations of Physics 48 (1):110-120.
    In the absence of new physics around \ GeV, the electroweak vacuum is at best metastable. This represents a major challenge for high scale inflationary models as, during the early rapid expansion of the universe, it seems difficult to understand how the Higgs vacuum would not decay to the true lower vacuum of the theory with catastrophic consequences if inflation took place at a scale above \ GeV. In this paper we show that the non-minimal coupling of the Higgs boson (...)
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  55.  8
    Self-Accelerated Universe Induced by Repulsive Effects as an Alternative to Dark Energy and Modified Gravities.Orlando Luongo & Hernando Quevedo - 2018 - Foundations of Physics 48 (1):17-26.
    The existence of current–time universe’s acceleration is usually modeled by means of two main strategies. The first makes use of a dark energy barotropic fluid entering by hand the energy–momentum tensor of Einstein’s theory. The second lies on extending the Hilbert–Einstein action giving rise to the class of extended theories of gravity. In this work, we propose a third approach, derived as an intrinsic geometrical effect of space–time, which provides repulsive regions under certain circumstances. We demonstrate that the effects of (...)
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  56.  17
    Quantum Locality, Rings a Bell?: Bell’s Inequality Meets Local Reality and True Determinism.Natalia Sánchez-Kuntz & Eduardo Nahmad-Achar - 2018 - Foundations of Physics 48 (1):27-47.
    By assuming a deterministic evolution of quantum systems and taking realism into account, we carefully build a hidden variable theory for Quantum Mechanics based on the notion of ontological states proposed by ’t Hooft. We view these ontological states as the ones embedded with realism and compare them to the quantum states that represent superpositions, viewing the latter as mere information of the system they describe. Such a deterministic model puts forward conditions for the applicability of Bell’s inequality: the usual (...)
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  57.  11
    A Local-Realistic Model of Quantum Mechanics Based on a Discrete Spacetime.Antonio Sciarretta - 2018 - Foundations of Physics 48 (1):60-91.
    This paper presents a realistic, stochastic, and local model that reproduces nonrelativistic quantum mechanics results without using its mathematical formulation. The proposed model only uses integer-valued quantities and operations on probabilities, in particular assuming a discrete spacetime under the form of a Euclidean lattice. Individual particle trajectories are described as random walks. Transition probabilities are simple functions of a few quantities that are either randomly associated to the particles during their preparation, or stored in the lattice nodes they visit during (...)
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  58.  3
    Quantum Bit Commitment and the Reality of the Quantum State.R. Srikanth - 2018 - Foundations of Physics 48 (1):92-109.
    Quantum bit commitment is insecure in the standard non-relativistic quantum cryptographic framework, essentially because Alice can exploit quantum steering to defer making her commitment. Two assumptions in this framework are that: Alice knows the ensembles of evidence E corresponding to either commitment; and system E is quantum rather than classical. Here, we show how relaxing assumption or can render her malicious steering operation indeterminable or inexistent, respectively. Finally, we present a secure protocol that relaxes both assumptions in a quantum teleportation (...)
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  59.  1
    Some “No Hole” Spacetime Properties Are Unstable.J. B. Manchak - 2018 - Foundations of Physics:1-7.
    We show a sense in which the spacetime property of effective completeness—a type of “local hole-freeness” or “local inextendibility”—is not stable.
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