Year:

  1.  1
    Connecting the Dots: Mott for Emulsions, Collapse Models, Colored Noise, Frame Dependence of Measurements, Evasion of the “Free Will Theorem”.Stephen L. Adler - 2018 - Foundations of Physics 48 (11):1557-1567.
    We review the argument that latent image formation is a measurement in which the state vector collapses, requiring an enhanced noise parameter in objective reduction models. Tentative observation of a residual noise at this level, plus several experimental bounds, imply that the noise must be colored, and hence frame dependent and non-relativistic. Thus a relativistic objective reduction model, even if achievable in principle, would be incompatible with experiment; the best one can do is the non-relativistic CSL model. This negative conclusion (...)
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  2.  1
    Bohmian Trajectories for Kerr–Newman Particles in Complex Space-Time.Mark Davidson - 2018 - Foundations of Physics 48 (11):1590-1616.
    Complexified Liénard–Wiechert potentials simplify the mathematics of Kerr–Newman particles. Here we constrain them by fiat to move along Bohmian trajectories to see if anything interesting occurs, as their equations of motion are not known. A covariant theory due to Stueckelberg is used. This paper deviates from the traditional Bohmian interpretation of quantum mechanics since the electromagnetic interactions of Kerr–Newman particles are dictated by general relativity. A Gaussian wave function is used to produce the Bohmian trajectories, which are found to be (...)
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  3.  2
    Heisenberg Uncertainty Relations as Statistical Invariants.Aniello Fedullo - 2018 - Foundations of Physics 48 (11):1546-1556.
    For a simple set of observables we can express, in terms of transition probabilities alone, the Heisenberg uncertainty relations, so that they are proven to be not only necessary, but sufficient too, in order for the given observables to admit a quantum model. Furthermore distinguished characterizations of strictly complex and real quantum models, with some ancillary results, are presented and discussed.
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  4.  2
    From Classical to Quantum Models: The Regularising Rôle of Integrals, Symmetry and Probabilities.Jean-Pierre Gazeau - 2018 - Foundations of Physics 48 (11):1648-1667.
    In physics, one is often misled in thinking that the mathematical model of a system is part of or is that system itself. Think of expressions commonly used in physics like “point” particle, motion “on the line”, “smooth” observables, wave function, and even “going to infinity”, without forgetting perplexing phrases like “classical world” versus “quantum world”.... On the other hand, when a mathematical model becomes really inoperative in regard with correct predictions, one is forced to replace it with a new (...)
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  5.  8
    Quantum Theory and the Limits of Objectivity.Richard Healey - 2018 - Foundations of Physics 48 (11):1568-1589.
    Three recent arguments seek to show that the universal applicability of unitary quantum theory is inconsistent with the assumption that a well-conducted measurement always has a definite physical outcome. In this paper I restate and analyze these arguments. The import of the first two is diminished by their dependence on assumptions about the outcomes of counterfactual measurements. But the third argument establishes its intended conclusion. Even if every well-conducted quantum measurement we ever make will have a definite physical outcome, this (...)
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  6.  3
    How Problematic is the Near-Euclidean Spatial Geometry of the Large-Scale Universe?M. Holman - 2018 - Foundations of Physics 48 (11):1617-1647.
    Modern observations based on general relativity indicate that the spatial geometry of the expanding, large-scale Universe is very nearly Euclidean. This basic empirical fact is at the core of the so-called “flatness problem”, which is widely perceived to be a major outstanding problem of modern cosmology and as such forms one of the prime motivations behind inflationary models. An inspection of the literature and some further critical reflection however quickly reveals that the typical formulation of this putative problem is fraught (...)
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  7.  3
    Some “No Hole” Spacetime Properties Are Unstable.J. B. Manchak - 2018 - Foundations of Physics 48 (11):1539-1545.
    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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  8.  5
    Black Holes, Gravitational Waves and Space Time Singularities.Stefano Bellucci, Alfio Bonanno, S. J. Gabriele Gionti & Fabio Scardigli - 2018 - Foundations of Physics 48 (10):1131-1133.
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  9.  5
    Black Hole Perturbations: A Review of Recent Analytical Results. [REVIEW]Donato Bini & Andrea Geralico - 2018 - Foundations of Physics 48 (10):1349-1363.
    We review the gravitational self-force program to analytically compute first-order metric perturbations in a Schwarzschild black hole spacetime in the case of a perturbing mass moving on a slightly eccentric equatorial orbit. The perturbed metric components should then be combined into gauge-invariant quantities to be associated with physical observables. In this way, for example, one determines the various “potentials” entering the Effective-One-Body model, i.e., a powerful formalism for the description of the gravitational interaction of two masses, which is currently successfully (...)
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  10. Gravitational Collapse in Quantum Einstein Gravity.Alfio Bonanno, Benjamin Koch & Alessia Platania - 2018 - Foundations of Physics 48 (10):1393-1406.
    The existence of spacetime singularities is one of the biggest problems of nowadays physics. According to Penrose, each physical singularity should be covered by a “cosmic censor” which prevents any external observer from perceiving their existence. However, classical models describing the gravitational collapse usually results in strong curvature singularities, which can also remain “naked” for a finite amount of advanced time. This proceedings studies the modifications induced by asymptotically safe gravity on the gravitational collapse of generic Vaidya spacetimes. It will (...)
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  11.  2
    Horizon Quantum Mechanics: Spherically Symmetric and Rotating Sources.Roberto Casadio, Andrea Giugno, Andrea Giusti & Octavian Micu - 2018 - Foundations of Physics 48 (10):1204-1218.
    The Horizon Quantum Mechanics is an approach that allows one to analyse the gravitational radius of spherically symmetric systems and compute the probability that a given quantum state is a black hole. We first review the formalism and show how it reproduces a gravitationally inspired GUP relation. This results leads to unacceptably large fluctuations in the horizon size of astrophysical black holes if one insists in describing them as central singularities. On the other hand, if they are extended systems, like (...)
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  12.  6
    On Quantum Life of Black Holes.Gia Dvali - 2018 - Foundations of Physics 48 (10):1219-1225.
    We review some ideas about the quantum physics of black hole information storage and processing in terms of a general phenomenon of quantum criticality.
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  13.  3
    Status of the Asymptotic Safety Paradigm for Quantum Gravity and Matter.Astrid Eichhorn - 2018 - Foundations of Physics 48 (10):1407-1429.
    In the asymptotic safety paradigm, a quantum field theory reaches a regime with quantum scale invariance in the ultraviolet, which is described by an interacting fixed point of the Renormalization Group. Compelling hints for the viability of asymptotic safety in quantum gravity exist, mainly obtained from applications of the functional Renormalization Group. The impact of asymptotically safe quantum fluctuations of gravity at and beyond the Planck scale could at the same time induce an ultraviolet completion for the Standard Model of (...)
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  14.  19
    The Standard Cosmological Model: Achievements and Issues.George Ellis - 2018 - Foundations of Physics 48 (10):1226-1245.
    The present day standard cosmological model is a great theoretical achievement. This chapter surveys the main themes that have arisen and issues that are still oustanding.
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  15. The X-Ray Chirp of a Compact Black Hole Binary.Zoltán Haiman - 2018 - Foundations of Physics 48 (10):1430-1445.
    The gravitational waves from a binary black hole with masses \ can be detected with the Laser Interferometer Space Antenna once their orbital frequency exceeds 10\–10\ Hz. The binary separation at this stage is \R_{\mathrm{g}}\), and the orbital speed is \\). I argue that at this stage, the binary will be producing bright electromagnetic radiation via gas bound to the individual BHs. Both BHs will have their own photospheres in X-ray and possibly also in optical bands. Relativistic Doppler modulations and (...)
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  16.  5
    Virtual Black Holes and Space–Time Structure.Gerard ’T. Hooft - 2018 - Foundations of Physics 48 (10):1134-1149.
    In the standard formalism of quantum gravity, black holes appear to form statistical distributions of quantum states. Now, however, we can present a theory that yields pure quantum states. It shows how particles entering a black hole can generate firewalls, which however can be removed, replacing them by the ‘footprints’ they produce in the out-going particles. This procedure can preserve the quantum information stored inside and around the black hole. We then focus on a subtle but unavoidable modification of the (...)
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  17.  2
    From the Sky to the Fundamental Physics.Renata Kallosh - 2018 - Foundations of Physics 48 (10):1279-1290.
    We discuss the relation between string theory/supergravity and the observational data in cosmology, as well as at LHC, past and future. We pay particular attention to the possibility of the future detection of primordial gravitational waves and how this might affect our understanding of fundamental physics.
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  18.  1
    Singularity Crossing, Transformation of Matter Properties and the Problem of Parametrization in Field Theories.A. Yu Kamenshchik - 2018 - Foundations of Physics 48 (10):1159-1176.
    We investigate particular cosmological models, based either on tachyon fields or on perfect fluids, for which soft future singularities arise in a natural way. Our main result is the description of a smooth crossing of the soft singularity in models with an anti-Chaplygin gas or with a particular tachyon field in the presence of dust. Such a crossing is made possible by certain transformations of matter properties. We discuss and compare also different approaches to the problem of crossing of the (...)
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  19.  5
    Quantum Gravity, Information Theory and the CMB.Achim Kempf - 2018 - Foundations of Physics 48 (10):1191-1203.
    We review connections between the metric of spacetime and the quantum fluctuations of fields. We start with the finding that the spacetime metric can be expressed entirely in terms of the 2-point correlator of the fluctuations of quantum fields. We then discuss the open question whether the knowledge of only the spectra of the quantum fluctuations of fields also suffices to determine the spacetime metric. This question is of interest because spectra are geometric invariants and their quantization would, therefore, have (...)
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  20.  6
    Georges Lemaître, Pioneer of Modern Theoretical Cosmology.Helge Kragh - 2018 - Foundations of Physics 48 (10):1333-1348.
    No other scientist may have had a greater impact on modern cosmology than the Belgian physicist, astronomer and priest Georges Lemaître. In 1927 he predicted the expansion of the universe on the basis of the cosmological field equations; and four years later he proposed what he called the primeval-atom hypothesis, the first version of the later big bang universe. In all his work on cosmology the cosmological constant Λ played a significant role. A recognized expert in the theory of general (...)
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  21.  1
    On the Problem of Initial Conditions for Inflation.Andrei Linde - 2018 - Foundations of Physics 48 (10):1246-1260.
    I review the present status of the problem of initial conditions for inflation and describe several ways to solve this problem for many popular inflationary models, including the recent generation of the models with plateau potentials favored by cosmological observations.
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  22.  1
    Cosmological Constraints From Low-Redshift Data.Vladimir V. Luković, Balakrishna S. Haridasu & Nicola Vittorio - 2018 - Foundations of Physics 48 (10):1446-1485.
    In this paper we summarise the constraints that low-redshift data—such as supernovae Ia, baryon acoustic oscillations and cosmic chronometers —are able to set on the concordance model and its extensions, as well as on inhomogeneous but isotropic models. We provide a broad overlook into these cosmological scenarios and several aspects of data analysis. In particular, we review a number of systematic issues of SN Ia analysis that include magnitude correction techniques, selection bias and their influence on the inferred cosmological constraints. (...)
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  23.  5
    Non-Local Effects of Conformal Anomaly.Krzysztof A. Meissner & Hermann Nicolai - 2018 - Foundations of Physics 48 (10):1150-1158.
    It is shown that the nonlocal anomalous effective actions corresponding to the quantum breaking of the conformal symmetry can lead to observable modifications of Einstein’s equations. The fact that Einstein’s general relativity is in perfect agreement with all observations including cosmological or recently observed gravitational waves imposes strong restrictions on the field content of possible extensions of Einstein’s theory: all viable theories should have vanishing conformal anomalies. It is shown that a complete cancellation of conformal anomalies in \ for both (...)
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  24.  1
    3D Spacetimes Construction From $$$$D Kitaev Superconductor Model.Miok Park - 2018 - Foundations of Physics 48 (10):1486-1499.
    This is a proceedings based on the talk that was made in the workshop “Black Holes, Gravitational Waves and Spacetime Singularities” at Vatican Observatory on 9–12 May 2017. Since then we have constructed some corrections, hence this paper includes them. Here we employ the \\)D Kitaev superconductor model and perform the Wilsonian renormalization group transformation in a real space. We regard the running energy scale or the repetition number of RG transformation as a new emergent direction of the spacetime, thus (...)
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  25.  12
    The Big Bang and its Dark-Matter Content: Whence, Whither, and Wherefore.Roger Penrose - 2018 - Foundations of Physics 48 (10):1177-1190.
    The singularity theorems of the 1960s showed that Lemaître’s initial symmetry assumptions were not essential for deriving a big-bang origin for a vast multitude of relativistic universe models. Yet the actual universe accords remarkably closely with models of Lemaître’s type. This is a mystery closely related to the form taken by the 2nd law of thermodynamics and is not explained by currently conventional inflationary cosmology. Conformal cyclic cosmology provides another perspective on these issues, one consequence being the necessary initial presence (...)
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  26.  1
    Unimodular Quantum Gravity and the Cosmological Constant.R. Percacci - 2018 - Foundations of Physics 48 (10):1364-1379.
    It is shown that the one-loop effective action of unimodular gravity is the same as that of ordinary gravity, restricted to unimodular metrics. The only difference is in the treatment of the global scale degree of freedom and of the cosmological term. A constant vacuum energy does not gravitate, addressing one aspect of the cosmological constant problem.
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  27.  3
    Functional Renormalization Group Flows on Friedman–Lemaître–Robertson–Walker Backgrounds.Alessia Platania & Frank Saueressig - 2018 - Foundations of Physics 48 (10):1291-1304.
    We revisit the construction of the gravitational functional renormalization group equation tailored to the Arnowitt–Deser–Misner formulation emphasizing its connection to the covariant formulation. The results obtained from projecting the renormalization group flow onto the Einstein–Hilbert action are reviewed in detail and we provide a novel example illustrating how the formalism may be connected to the causal dynamical triangulations approach to quantum gravity.
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  28.  5
    Dark Matter in Galaxies: Evidences and Challenges.Paolo Salucci - 2018 - Foundations of Physics 48 (10):1517-1537.
    The evidence of the phenomenon for which, in galaxies, the gravitating mass is distributed differently than the luminous mass, increases as new data become available. Furthermore, this discrepancy is well structured and it depends on the magnitude and the compactness of the galaxy and on the radius, in units of its luminous size \, where the measure is performed. For the disk systems with \ all this leads to an amazing scenario, revealed by the investigation of individual and coadded rotation (...)
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  29.  5
    Towards the Limits of Cosmology.Joseph Silk - 2018 - Foundations of Physics 48 (10):1305-1332.
    One of our greatest challenges in cosmology is understanding the origin of the structure of the universe. I will describe how the cosmic microwave background has provided a window for probing the initial conditions from which structure evolved and seeded the formation of the galaxies, and the outstanding issues that remain to be resolved. I will address our optimal choice of future strategy in order to make further progress on understanding our cosmic origins.
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  30.  3
    Probing the Strong Gravitational Field of Accreting Black Holes with X-Ray Observations.Luigi Stella - 2018 - Foundations of Physics 48 (10):1500-1516.
    High throughput time-resolved observations of accreting collapsed objects at X-ray energies provide key information on the motions of matter orbiting a few gravitational radii away from black holes. Predictions of general relativity in the strong field regime, such as relativistic epicyclic motions, precession, light bending and the presence and radius of an innermost stable circular orbit in the close vicinity of a black hole can be verified by making use of two powerful diagnostics, namely relativistically broadened \ lines and variability (...)
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  31.  2
    $$\Lambda $$ΛCDM: Much More Than We Expected, but Now Less Than What We Want.Michael S. Turner - 2018 - Foundations of Physics 48 (10):1261-1278.
    The \CDM cosmological model is remarkable: with just six parameters it describes the evolution of the Universe from a very early time when all structures were quantum fluctuations on subatomic scales to the present, and it is consistent with a wealth of high-precision data, both laboratory measurements and astronomical observations. However, the foundation of \CDM involves physics beyond the standard model of particle physics: particle dark matter, dark energy and cosmic inflation. Until this ‘new physics’ is clarified, \CDM is at (...)
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  32.  3
    Measuring the Last Burst of Non-Singular Black Holes.Francesca Vidotto - 2018 - Foundations of Physics 48 (10):1380-1392.
    Non-perturbative quantum gravity prevents the formation of curvature singularities and may allow black holes to decay with a lifetime shorter than evaporation time. This, in connection with the existence of primordial black holes, could open a new window for quantum-gravity phenomenology. I discuss the possibility of observing astrophysical emissions from the explosion of old black holes in the radio and in the gamma wavelengths. These emissions can be discriminated from other astrophysical sources because of a peculiar way the emitted wavelength (...)
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  33.  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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  34.  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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  35.  2
    Paul Busch 1955–2018.Stan Gudder, Pekka Lahti & Leon Loveridge - 2018 - Foundations of Physics 48 (9):1128-1130.
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  36.  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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  37.  8
    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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  38.  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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  39.  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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  40.  1
    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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  41.  4
    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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  42.  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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  43.  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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  44.  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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  45.  2
    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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  46.  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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  47.  6
    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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  48.  5
    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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  49. 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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  50.  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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  51.  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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  52.  4
    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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  53.  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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  54.  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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  55.  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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  56.  11
    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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  57.  18
    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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  58.  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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  59.  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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  60.  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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  61.  18
    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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  62.  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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  63.  10
    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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  64.  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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  65.  10
    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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  66.  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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  67.  44
    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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  68.  10
    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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  69.  6
    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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  70.  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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  71.  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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  72.  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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  73.  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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  74.  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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  75.  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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  76.  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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  77.  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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  78.  27
    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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  79.  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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  80.  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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  81.  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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  82.  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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  83.  11
    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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  84.  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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  85.  11
    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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  86.  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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  87.  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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  88.  18
    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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  89.  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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  90.  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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