# A new kind of cyclic universe. (arXiv:1904.08022v1 [gr-qc] CROSS LISTED)

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on 2019-4-20 12:59am GMT

Authors: Anna Ijjas, Paul J. Steinhardt

Combining intervals of ekpyrotic (ultra-slow) contraction with a (non-singular) classical bounce naturally leads to a novel cyclic theory of the universe in which the Hubble parameter, energy density and temperature oscillate periodically, but the scale factor grows by an exponential factor from one cycle to the next. The resulting cosmology not only resolves the homogeneity, isotropy, flatness and monopole problems and generates a nearly scale invariant spectrum of density perturbations, but it also addresses a number of age-old cosmological issues that big bang inflationary cosmology does not. There may also be wider-ranging implications for fundamental physics, black holes and quantum measurement.

# The (Un)detectability of Absolute Newtonian Masses

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-19 6:22pm GMT
Martens, Niels C.M. (2019) The (Un)detectability of Absolute Newtonian Masses. [Preprint]

# Watch Now: Einstein's Scientific Revolution and the Limits of Quantum Theory

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## Scientific American Content: Global

on 2019-4-17 6:00pm GMT
Cosmologist Lee Smolin says that at certain key points, the scientific worldview is based on fallacious reasoning

show enclosure

(image/jpeg; 0.39 MB)

# Does large quantum Fisher information imply Bell correlations?

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## PRA: Fundamental concepts

on 2019-4-17 10:00am GMT

Author(s): Florian Fröwis, Matteo Fadel, Philipp Treutlein, Nicolas Gisin, and Nicolas Brunner

The quantum Fisher information (QFI) of certain multipartite entangled quantum states is larger than what is reachable by separable states, providing a metrological advantage. Are these nonclassical correlations strong enough to potentially violate a Bell inequality? Here, we present evidence from t...

[Phys. Rev. A 99, 040101(R)] Published Wed Apr 17, 2019

# Figures of light in the early history of relativity (1905-1914)

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-16 10:44pm GMT
Walter, Scott A. (2018) Figures of light in the early history of relativity (1905-1914). Beyond Einstein: Perspectives on Geometry, Gravitation, and Cosmology in the Twentieth Century (Einstein Studies 14). pp. 3-50.

# Lüders conditionalization: Conditional probability, transition probability, and updating in quantum probability theory

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-16 10:44pm GMT
Earman, John (2019) Lüders conditionalization: Conditional probability, transition probability, and updating in quantum probability theory. [Preprint]

# Why mind matters in quantum mechanics

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-16 10:41pm GMT
Gao, Shan (2019) Why mind matters in quantum mechanics. [Preprint]

# Thermodynamics of Quantum Information Flows

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

on 2019-4-16 10:00am GMT

Author(s): Krzysztof Ptaszyński and Massimiliano Esposito

We report two results complementing the second law of thermodynamics for Markovian open quantum systems coupled to multiple reservoirs with different temperatures and chemical potentials. First, we derive a nonequilibrium free energy inequality providing an upper bound for a maximum power output, wh...

[Phys. Rev. Lett. 122, 150603] Published Tue Apr 16, 2019

# Emergence of the geometric phase from quantum measurement back-action

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## Nature Physics - Issue - nature.com science feeds

on 2019-4-15 12:00am GMT

Emergence of the geometric phase from quantum measurement back-action

Emergence of the geometric phase from quantum measurement back-action, Published online: 15 April 2019; doi:10.1038/s41567-019-0482-z

Following a closed evolution in the Hilbert space, the state vector of a quantum system accumulates a geometric phase factor. A series of weak measurements reveal the origin of this in the back-action of any quantum measurement.

# Grounding the randomness of quantum measurement

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-14 4:39am GMT
Jaeger, Gregg (2016) Grounding the randomness of quantum measurement. Philosophical Transactions of the Royal Society A, 374.

# Wigner and his many friends: A new no-go result?

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-14 4:37am GMT
Fortin, Sebastian and Lombardi, Olimpia (2019) Wigner and his many friends: A new no-go result? [Preprint]

# Reformulation of quantum mechanics and strong complementarity from Bayesian inference requirements

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-14 4:34am GMT
Heartspring, William (2019) Reformulation of quantum mechanics and strong complementarity from Bayesian inference requirements. [Preprint]

# When the actual world is not even possible

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-14 4:33am GMT
Wuthrich, Christian (2019) When the actual world is not even possible. [Preprint]

# Searching for quantum black hole structure with the Event Horizon Telescope. (arXiv:1904.05287v1 [gr-qc] CROSS LISTED)

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on 2019-4-13 1:28am GMT

Authors: Steven B. Giddings

The impressive images from the Event Horizon Telescope sharpen the conflict between our observations of gravitational phenomena and the principles of quantum mechanics. Two related scenarios for reconciling quantum mechanics with the existence of black hole-like objects, with "minimal" departure from general relativity and local quantum field theory, have been explored; one of these could produce signatures visible to EHT observations. A specific target is temporal variability of images, with a characteristic time scale determined by the classical black hole radius. The absence of evidence for such variability in the initial observational span of seven days is not expected to strongly constrain such variability. Theoretical and observational next steps towards investigating such scenarios are outlined.

# Stochastic Bohmian mechanics within the Schr\"{o}dinger-Langevin framework: A trajectory analysis of wave-packet dynamics in a fluctuative-dissipative medium. (arXiv:1902.02147v2 [quant-ph] UPDATED)

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on 2019-4-13 1:28am GMT

Authors: S. V. Mousavi, S. Miret-Artés

A Bohmian analysis of the so-called Schr\"{o}dinger-Langevin or Kostin nonlinear differential equation is provided to study how thermal fluctuations of the environment affects the dynamics of the wave packet from a quantum hydrodynamical point of view. In this way, after obtaining the Schr\"{o}dinger-Langevin-Bohm equation from the Kostin equation its application to simple but physically insightful systems such as the Brownian-Bohmian motion, motion in a gravity field and transmission through a parabolic repeller is studied. % If a time-dependent Gaussian ansatz for the probability density is assumed, the effect of thermal fluctuations together with thermal wave packets leads to Bohmian stochastic trajectories. From this trajectory based analysis, quantum and classical diffusion coefficients for free particles, thermal arrival times for a linear potential and transmission probabilities and characteristic times such as arrival and dwell times for a parabolic repeller are then presented and discussed.

# Entanglement, decoherence, and measurement

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-12 2:27am GMT
Hobson, Art (2019) Entanglement, decoherence, and measurement. [Preprint]

# Post-Newtonian corrections to Schrödinger equations in gravitational fields

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## Classical and Quantum Gravity - latest papers

on 2019-4-11 11:00pm GMT
In this paper we extend the WKB-like ‘non-relativistic’ expansion of the minimally coupled Klein–Gordon equation after (Kiefer and Singh 1991 Phys. Rev . D 44 1067–76; Lämmerzahl 1995 Phys. Lett . A 203 12–7; Giulini and Großardt 2012 Class. Quantum Grav . 29 215010) to arbitrary order in c −1 , leading to Schrödinger equations describing a quantum particle in a general gravitational field, and compare the results with canonical quantisation of a free particle in curved spacetime, following (Wajima et al 1997 Phys. Rev . D 55 1964–70). Furthermore, using a more operator-algebraic approach, the Klein–Gordon equation and the canonical quantisation method are shown to lead to the same results for some special terms in the Hamiltonian describing a single particle in a general stationary spacetime, without any ‘non-relativistic’ expansion.

# On the Universality of Hawking Radiation

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-11 5:03pm GMT
Gryb, Sean and Palacios, Patricia and Thebault, Karim P Y (2019) On the Universality of Hawking Radiation. [Preprint]

# Assessing Scientific Theories: The Bayesian Approach

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-11 5:02pm GMT
Dardashti, Radin and Hartmann, Stephan (2019) Assessing Scientific Theories: The Bayesian Approach. [Preprint]

# On Representational Redundancy, Surplus Structure, and the Hole Argument

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-10 8:08am GMT
Bradley, Clara and Weatherall, James Owen (2019) On Representational Redundancy, Surplus Structure, and the Hole Argument. [Preprint]

# Reformulation of quantum mechanics and strong complementarity from Bayesian inference requirements

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-10 8:03am GMT
Heartspring, William (2019) Reformulation of quantum mechanics and strong complementarity from Bayesian inference requirements. [Preprint]

# Correlations detected in a quantum vacuum

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## Nature - Issue - nature.com science feeds

on 2019-4-10 12:00am GMT

Correlations detected in a quantum vacuum

Correlations detected in a quantum vacuum, Published online: 10 April 2019; doi:10.1038/d41586-019-01083-z

A vacuum as described by quantum mechanics is perhaps the most fundamental but mysterious state in physics. The discovery of correlations between electric-field fluctuations in such a vacuum represents a major advance.

# A realist takes on quantum mechanics

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## Nature - Issue - nature.com science feeds

on 2019-4-09 12:00am GMT

A realist takes on quantum mechanics

A realist takes on quantum mechanics, Published online: 09 April 2019; doi:10.1038/d41586-019-01101-0

Graham Farmelo parses Lee Smolin’s takedown of the most successful physics theory ever.

# Friedman and Some of his Critics on the Foundations of General Relativity

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-08 4:53pm GMT
Samaroo, Ryan (2019) Friedman and Some of his Critics on the Foundations of General Relativity. [Preprint]

# Emergence and Correspondence for String Theory Black Holes

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-06 4:52am GMT
van Dongen, Jeroen and De Haro, Sebastian and Visser, Manus and Butterfield, Jeremy (2019) Emergence and Correspondence for String Theory Black Holes. [Preprint]

# Conceptual Analysis of Black Hole Entropy in String Theory

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-06 4:51am GMT
De Haro, Sebastian and van Dongen, Jeroen and Visser, Manus and Butterfield, Jeremy (2019) Conceptual Analysis of Black Hole Entropy in String Theory. [Preprint]

# Emergence, Functionalism and Pragmatic Reality in Wallacian quantum mechanics

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-06 4:49am GMT
Mulder, Ruward A. (2018) Emergence, Functionalism and Pragmatic Reality in Wallacian quantum mechanics. [Preprint]

# A Realist View of the Quantum World

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-05 8:19am GMT
Jaeger, Gregg (2019) A Realist View of the Quantum World. [Preprint]

# Reality and the Probability Wave

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-05 8:18am GMT
Shanahan, Daniel (2019) Reality and the Probability Wave. International Journal of Quantum Foundations, 5. pp. 51-68.

# Is Time Travel Too Strange to Be Possible? - Determinism and Indeterminism on Closed Timelike Curves

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-04 6:00am GMT
Mulder, Ruward A. and Dieks, Dennis (2017) Is Time Travel Too Strange to Be Possible? - Determinism and Indeterminism on Closed Timelike Curves. Determinism and Indeterminism on Closed Timelike Curves. pp. 93-114.

# The Descriptive and Normative Versions of Scientific Realism and Pessimism

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-4-04 5:55am GMT
Park, Seungbae (2019) The Descriptive and Normative Versions of Scientific Realism and Pessimism.

# Experimental Investigation of Quantum Decay at Short, Intermediate, and Long Times via Integrated Photonics

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

on 2019-4-03 10:00am GMT

Author(s): Andrea Crespi, Francesco V. Pepe, Paolo Facchi, Fabio Sciarrino, Paolo Mataloni, Hiromichi Nakazato, Saverio Pascazio, and Roberto Osellame

The decay of an unstable system is usually described by an exponential law. Quantum mechanics predicts strong deviations of the survival probability from the exponential: Indeed, the decay is initially quadratic, while at very large times it follows a power law, with superimposed oscillations. The l...

[Phys. Rev. Lett. 122, 130401] Published Wed Apr 03, 2019

# About Wigner Friend’s and Hardy’s paradox in a Bohmian approach: a comment of “Quantum theory cannot consistently describe the use of itself”

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## International Journal of Quantum Foundations – International Journal of Quantum Foundations

on 2019-4-02 12:18pm GMT

Volume 5, Issue 2, pages 80-97

Aurélien Drezet [Show Biography]

Dr. Aurélien Drezet was born in Metz, France, in 1975. He received his Ph.D Degree in experimental physics from the University Joseph Fourier at Grenoble in 2002 where he was working on nano optics and near-field scanning optical microscopy. After 6 years as a post-doc in Austria and France, he is currently head of the Nano-Optics and Forces team at Institut Néel in Grenoble (which belongs to the national scientific research center-CNRS-France which is also associated with the University Joseph Fourier in Grenoble). His activities range from experimental and theoretical plasmonics to near-field scanning optical microscopy in both the classical and quantum regime. He is also strongly involved in scientific works and discussions concerning quantum foundations in general and Bohmian mechanics in particular.

This is an analysis of the recently published article “Quantum theory cannot consistently describe the use of itself” by D. Frauchiger and R. Renner [1]. Here I decipher the paradox and analyze it from the point of view of de Broglie-Bohm hidden variable theory (i.e., Bohmian mechanics). I also analyze the problem from the perspective obtained by the Copenhagen interpretation (i.e., the Bohrian interpretation) and show that both views are self consistent and do not lead to any contradiction with a `single-world’ description of quantum theory.

# Is There a Physical Reason Beyond the Imaginary i in the Quantum Mechanics Formulation?

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## International Journal of Quantum Foundations – International Journal of Quantum Foundations

on 2019-4-01 1:21am GMT

Volume 5, Issue 2, pages 69-79

Mohammed Sanduk [Show Biography]

Mohammed Sanduk is an Iraqi born British physicist. He was educated at University of Baghdad and University of Manchester. Before attending his undergraduate study, he pub-lished a book in particle physics entitled “Mesons”. Sanduk has worked in industry and academia, and his last post in Iraq was head of the Laser and Opto-electronics Engineering department at Nahrain University in Baghdad. Owing to his interest in the philosophy of science, and he was a member of the academic staff of Pontifical Babel College for Philosophy. Sanduk is working with the department of chemical and process engineering at the University of Surrey. Sanduk is interested in transport of charged particles, Magnetohydro-dynamics, and the renewable energy technology. In addition to that, Sanduk is interested in the foundation of Quantum mechanics, and the philosophy of science & technology.

The imaginary i in the formulation of the quantum mechanics is accepted within the axioms of the quantum mechanics theory, and, thus, there is no need for an explanation of its origin. Since 2012, in a non-quantum mechanics project, there has been an attempt to complexify a real function and build an analogy for relativistic quantum mechanics. In that theoretical attempt, a partial observation technique is proposed as one of the reasons behind the appearance of the imaginary i. The present article throws light on that attempt of complexification and tries to explain the logic of physics behind the complex phase factor. This physical process of partial observation acts as a process of physicalization of a virtual model. According to the positive results of analogy, the appeared imaginary i in quantum mechanics formulation may be related to a partial observation case as well.

# Reality and the Probability Wave

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## International Journal of Quantum Foundations – International Journal of Quantum Foundations

on 2019-4-01 1:19am GMT

Volume 5, Issue 2, pages 51-68

Daniel Shanahan [Show Biography]

Dan Shanahan is an independent researcher with a passion for foundational issues in quantum theory and relativity. Born in Perth, Western Australia, he studied physics at the Universities of NSW and Sydney.

Effects associated in quantum mechanics with a divisible probability wave are
explained as physically real consequences of the equal but opposite reaction
of the apparatus as a particle is measured. Taking as illustration a
Mach-Zehnder interferometer operating by refraction, it is shown that this
reaction must comprise a fluctuation in the reradiation field of complementary
effect to the changes occurring in the photon as it is projected into one or
other path. The evolution of this fluctuation through the experiment will
explain the alternative states of the particle discerned in self interference,
while the maintenance of equilibrium in the face of such fluctuations becomes
the source of the Born probabilities. In this scheme, the probability wave
is a mathematical artifact, epistemic rather than ontic, and akin in this
respect to the simplifying constructions of geometrical optics.

# Wave Function Collapse and the No-Superluminal-Signaling Principle

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## International Journal of Quantum Foundations – International Journal of Quantum Foundations

on 2019-4-01 1:15am GMT

Volume 5, Issue 2, pages 16-50

Edward J. Gillis [Show Biography]

Ed Gillis received his B. A. in Philosophy from the University of Michigan, and his Ph.D in Physics from the University of Colorado for research on the relationship between quantum nonlocality and relativity. He has authored several papers on quantum foundations, dealing, in particular, with connections between wave function collapse and elementary processes, how these connections might lead to an explanation of the no-superluminal-signaling principle in fundamental physical terms, and possible tests for collapse. He has also worked as an engineer on the development of sensor systems and control algorithms based on the information provided by those systems.

The assumption that wave function collapse is a real occurrence has very interesting consequences – both experimental and theoretical. Besides predicting observable deviations from linear evolution, it implies that these deviations must originate in nondeterministic effects at the elementary level in order to prevent superluminal signaling, as demonstrated by Gisin. This lack of determinism implies that information cannot be instantiated in a reproducible form in isolated microsystems (as illustrated by the No-cloning theorem). By stipulating that information is a reproducible and referential property of physical systems, one can formulate the no-signaling principle in strictly physical terms as a prohibition of the acquisition of information about spacelike-separated occurrences. This formulation provides a new perspective on the relationship between relativity and spacetime structure, and it imposes tight constraints on the way in which collapse effects are induced. These constraints indicate that wave function collapse results from (presumably small) nondeterministic deviations from linear evolution associated with nonlocally entangling interactions. This hypothesis can be formalized in a stochastic collapse equation and used to assess the feasibility of testing for collapse effects.

# Less is More: Born's Rule from Quantum Frequentism. (arXiv:1903.12027v1 [quant-ph])

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on 2019-3-30 1:40am GMT

Authors: Lionel Brits

Accounting for Born's rule from first principles remains an open problem among the foundational issues in quantum mechanics. Proponents of the many-worlds interpretation have argued that histories that violate Born's rule have vanishing norms, and so are unphysical. This argument has only been made explicit for contrived situations involving measurements on infinitely many identically prepared systems. We extend this result to arbitrary preparations and show that in a system with infinitely many degrees of freedom the universal wavefunction contains no such histories.

# What we cannot learn from analogue experiments

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-29 4:36pm GMT
Crowther, Karen and Linnemann, Niels and Wuthrich, Christian (2019) What we cannot learn from analogue experiments. [Preprint]

# On Spacetime Functionalism

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-29 4:33pm GMT
Baker, David John (2019) On Spacetime Functionalism. [Preprint]

# “Wave-Packet Reduction” and the Quantum Character of the Actualization of Potentia

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-29 4:32pm GMT
Jaeger, Gregg (2017) “Wave-Packet Reduction” and the Quantum Character of the Actualization of Potentia. Entropy, 19. pp. 1-11.

# Are Virtual Particles Less Real?

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-29 4:31pm GMT
Jaeger, Gregg (2019) Are Virtual Particles Less Real? Entropy, 21. pp. 1-17. ISSN 1099-4300

# Developments in Quantum Probability and the Copenhagen Approach

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-29 4:30pm GMT
Jaeger, Gregg (2018) Developments in Quantum Probability and the Copenhagen Approach. Entropy, 20. pp. 1-19.

# A Simplified Version of Gödel’s Theorem

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-25 8:30pm GMT
Redhead, Michael (2019) A Simplified Version of Gödel’s Theorem. [Preprint]

# The Wigner function in the relativistic quantum mechanics. (arXiv:1903.08975v1 [quant-ph])

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on 2019-3-23 1:09am GMT

Authors: K. Kowalski, J. Rembielinski

A detailed study is presented of the relativistic Wigner function for a quantum spinless particle evolving in time according to the Salpeter equation.

# Quantum entanglement in physical and cognitive systems: a conceptual analysis and a general representation. (arXiv:1903.09103v1 [q-bio.NC])

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on 2019-3-23 1:08am GMT

We provide a general description of the phenomenon of entanglement in bipartite systems, as it manifests in micro and macro physical systems, as well as in human cognitive processes. We do so by observing that when genuine coincidence measurements are considered, the violation of the 'marginal laws', in addition to the Bell-CHSH inequality, is also to be expected. The situation can be described in the quantum formalism by considering the presence of entanglement not only at the level of the states, but also at the level of the measurements. However, at the "local'" level of a specific joint measurement, a description where entanglement is only incorporated in the state remains always possible, by adopting a fine-tuned tensor product representation. But contextual tensor product representations should only be considered when there are good reasons to describe the outcome-states as (non-entangled) product states. This will not in general be true, hence, the entangement resource will have to generally be allocated both in the states and in the measurements. In view of the numerous violations of the marginal laws observed in physics' laboratories, it remains unclear to date if entanglement in micro-physical systems is to be understood only as an 'entanglement of the states', or also as an 'entanglement of the measurements'. But even if measurements would also be entangled, the corresponding violation of the marginal laws (no-signaling conditions) would not for this imply that a superluminal communication would be possible.

# Interaction-Induced Wave Function Collapse Respects Conservation Laws. (arXiv:1803.02687v4 [quant-ph] UPDATED)

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on 2019-3-23 1:08am GMT

Authors: Edward J. Gillis

Because quantum measurements have probabilistic outcomes they can seem to violate conservation laws in individual experiments. Despite these appearances, strict conservation of momentum, energy, and angular momentum can be shown to follow from the assumption that the entangling interactions that constitute measurements induce a real collapse of the wave function. The essential idea is that measured systems always have some pre-existing entanglement relations with (usually larger) systems, and that apparent changes in conserved quantities in the measured system are correlated with compensating changes in these larger systems. Since wave function collapse is mediated by entanglement relations a full accounting of the relevant quantities requires a computation over all interacting, entangled systems. The demonstrations by Gemmer and Mahler[1], and by Durt[2,3], that entanglement is a generic result of interaction are central to the argument. After briefly reviewing the status of conservation laws in various interpretations of the quantum measurement process I present a stochastic collapse equation that insures conservation of the relevant quantities in all situations.

# Poincar\'e Symmetry from Heisenberg's Uncertainty Relations. (arXiv:1903.05348v2 [quant-ph] UPDATED)

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on 2019-3-23 1:08am GMT

Authors: Sibel Baskal, Young S. Kim, Marilyn E. Noz

It is noted that the single-variable Heisenberg commutation relation contains the symmetry of the $Sp(2)$ group which is isomorphic to the Lorentz group applicable to one time-like dimension and two space-like dimensions, known as the $O(2,1)$ group. According to Paul A. M. Dirac, from the uncertainty commutation relations for two variables, it possible to construct the de Sitter group $O(3,2)$, namely the Lorentz group applicable to three space-like variables and two time-like variables. By contracting one of the time-like variables in $O(3,2)$, it is possible, to construct the inhomogeneous Lorentz group $IO(3,1)$ which serves as the fundamental symmetry group for quantum mechanics and quantum field theory in the Lorentz covariant world. This $IO(3,1)$ group is commonly known as the Poincar\'e group.

# Local measurement uncertainties impose a limit on non-local quantum correlations. (arXiv:1809.04725v3 [quant-ph] UPDATED)

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on 2019-3-23 1:08am GMT

Authors: Holger F. Hofmann

In quantum mechanics, joint measurements of non-commuting observables are only possible if a minimal unavoidable measurement uncertainty is accepted. On the other hand, correlations between non-commuting observables can exceed classical limits, as demonstrated by the violation of Bell's inequalities. Here, the relation between the uncertainty limited statistics of joint measurements and the limits on expectation values of possible input states is analyzed. It is shown that the experimentally observable statistics of joint measurements explain the uncertainty limits of local states, but result in less restrictive bounds when applied to identify the limits of non-local correlations between two separate quantum systems. A tight upper bound is obtained for the four correlations that appear in the violation of Bell's inequalities and the statistics of pure states saturating the bound is characterized. The results indicate that the limitations of quantum non-locality are a necessary consequence of the local features of joint measurements, suggesting the possibility that quantum non-locality could be explained in terms of the local characteristics of quantum statistics.

# A Quantum Mechanics Picture. (arXiv:1612.09114v3 [quant-ph] UPDATED)

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on 2019-3-23 1:08am GMT

Authors: Jeconias Rocha Guimarães

A quantum mechanics representation based on position ($\vec{r}$), linear momentum($\vec{p}$) and energy($E$) eigenvalues is presented here. A set of equations, explicitly independent on wave function, was derived relating these observables. In this view, a particle has a known trajectory and at any point on space there is a linear momentum associated. Trajectory here, can be viewed as if a measurement were taken continuously. This picture does not change current quantum mechanics interpretation, rather it comes as a new route of calculation. Also, wave function can be retrieved performing an integration in all space for linear momentum. Equations derived in this work, present a potential dependent on linear momentum originating what we call quantum force. A particle experiences a total force whose resultant is composed by classic and quantum force, evolving on time according to it. In terms of evaluation, a single particle could be described by a set of auxiliary particles named as wave particles(WP). They will start with a range of initial conditions and will collectively describe probabilistic aspects of quantum mechanics. We expect this route could be applied to many problems, such as multi-body systems.

# Against "Reality" in Physics. (arXiv:1903.08673v1 [physics.hist-ph])

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on 2019-3-23 1:08am GMT

Authors: Stephen Boughn

The concept of "reality" is often raised in the context of philosophical foundations of physics or interpretations of quantum mechanics. When this term is so raised, it is a warning to me that I am about to be led down a rabbit hole. Such diversions usually lead nowhere unless you consider endless discussions of Schrodinger's cat, wave function collapse, quantum non-locality, and parallel universes to be useful. A prime example is the famous Einstein, Podolsky, and Rosen paper wherein they concluded that the quantum wave function cannot provide a complete description of physical reality. In this essay I suggest that, in physics discourse, the term "reality" should be avoided at all costs.

# The Noncommutative Values of Quantum Observables. (arXiv:1903.09071v1 [quant-ph])

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on 2019-3-23 1:08am GMT

Authors: Otto C. W. Kong, Wei-Yin Liu (Nat'l Central U., Taiwan)

We discuss the notion about physical quantities as having values represented by real numbers, and its limiting to describe nature to be understood in relation to our appreciation that the quantum theory is a better theory of natural phenomena than its classical analog. Getting from the algebra of physical observables to their values on a fixed state is, at least for classical physics, really a homomorphic map from the algebra into the real number algebra. The limitation of the latter to represent the values of quantum observables with noncommutating algebraic relation is obvious. We introduce and discuss the idea of the noncommutative values of quantum observables and its feasibility, arguing that at least in terms of the representation of such a value as an infinite set of complex number, the idea makes reasonable sense theoretically as well as practically.

# Quantum Simulation of Gauge Theories. (arXiv:1903.08807v1 [hep-lat])

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on 2019-3-23 1:08am GMT

Authors: Henry Lamm, Scott Lawrence, Yukari Yamauchi (for the NuQS Collaboration)

A general scheme is presented for simulating gauge theories, with matter fields, on a digital quantum computer. A Trotterized time-evolution operator that respects gauge symmetry is constructed, and a procedure for obtaining time-separated, gauge-invariant operators is detailed. We demonstrate the procedure on small lattices, including the simulation of a 2+1D non-Abelian gauge theory.

# VIP2 in LNGS - Testing the Pauli Exclusion Principle for electrons with high sensitivity. (arXiv:1903.08861v1 [quant-ph])

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on 2019-3-23 1:08am GMT

The VIP2 (VIolation of the Pauli Exclusion Principle) experiment at the Gran Sasso underground laboratory (LNGS) is searching for possible violations of standard quantum mechanics predictions in atoms at very high sensitivity. We investigate atomic transitions with precision X-ray spectroscopy in order to test the Pauli Exclusion Principle (PEP) and therefore the related spin-statistics theorem. We will present our experimental method for the search for "anomalous" (i.e. Pauli-forbidden) X-ray transitions in copper atoms, produced by "new" electrons, which could have tiny probability to undergo Pauli-forbidden transition to the ground state already occupied by two electrons. We will describe the VIP2 experimental setup, which is taking data at LNGS presently. The goal of VIP2 is to test the PEP for electrons with unprecedented accuracy, down to a limit in the probability that PEP is violated at the level of 10$^{-31}$. We will present current experimental results and discuss implications of a possible violation.

# From a Lost History to a New Future: Is a Phenomenological Approach to Quantum Physics Viable?

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-22 7:35pm GMT
French, Steven (2019) From a Lost History to a New Future: Is a Phenomenological Approach to Quantum Physics Viable? [Preprint]

# Learning from Conditionals

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-20 7:30pm GMT
Eva, Benjamin and Hartmann, Stephan and Rafiee Rad, Soroush (2019) Learning from Conditionals. [Preprint]

# Experimental Demonstration of Quantum Effects in the Operation of Microscopic Heat Engines

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

on 2019-3-20 10:00am GMT

Author(s): James Klatzow, Jonas N. Becker, Patrick M. Ledingham, Christian Weinzetl, Krzysztof T. Kaczmarek, Dylan J. Saunders, Joshua Nunn, Ian A. Walmsley, Raam Uzdin, and Eilon Poem

Experiments demonstrate a quantum-coherence-induced power increase for quantum heat engines over their classical counterparts.

[Phys. Rev. Lett. 122, 110601] Published Wed Mar 20, 2019

# Formulations of Classical Mechanics

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## Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2019-3-20 5:09am GMT
North, Jill (2019) Formulations of Classical Mechanics. [Preprint]

# Quantum mechanics, time and ontology

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

on 2019-3-17 1:07am GMT

Publication date: Available online 8 March 2019

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

Author(s): Valia Allori

##### Abstract

Against what is commonly accepted in many contexts, it has been recently suggested that both deterministic and indeterministic quantum theories are not time-reversal invariant, and thus time is handed in a quantum world. In this paper, I analyze these arguments and evaluate possible reactions to them. In the context of deterministic theories, first I show that this conclusion depends on the controversial assumption that the wave-function is a physically real scalar field in configuration space. Then I argue that answers which restore invariance by assuming the wave-function is a ray in Hilbert space fall short. Instead, I propose that one should deny that the wave-function represents physical systems, along the lines proposed by the so-called primitive ontology approach. Moreover, in the context of indeterministic theories, I argue that time-reversal invariance can be restored suitably redefining its meaning.

# Emergence and topological order in classical and quantum systems

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

on 2019-3-17 1:07am GMT

Publication date: Available online 9 March 2019

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

Author(s): Tom McLeish, Mark Pexton, Tom Lancaster

##### Abstract

There has been growing interest in systems in condensed matter physics as a potential source of examples of both epistemic and ontological emergence. One of these case studies is the fractional quantum Hall state (FQHS). In the FQHS a system of electrons displays a type of holism due to a pattern of long-range quantum entanglement that some argue is emergent. Indeed, in general, quantum entanglement is sometimes cited as the best candidate for one form of ontological emergence. In this paper we argue that there are significant formal and physical parallels between the quantum FQHS and classical polymer systems. Both types of system cannot be explained simply by considering an aggregation of local microphysical properties alone, since important features of each are globally determined by topological features. As such, we argue that if the FQHS is a case of ontological emergence then it is not due to the quantum nature of the system and classical polymer systems are ontologically emergent as well.

# Universal quantum uncertainty relations: Minimum-uncertainty wave packet depends on measure of spread

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## ScienceDirect Publication: Physics Letters A

on 2019-3-17 1:07am GMT

Publication date: Available online 15 March 2019

Source: Physics Letters A

Author(s): Anindita Bera, Debmalya Das, Aditi Sen(De), Ujjwal Sen

##### Abstract

Based on the statistical concept of the median, we propose a quantum uncertainty relation between semi-interquartile ranges of the position and momentum distributions of arbitrary quantum states. The relation is universal, unlike that based on the mean and standard deviation, as the latter may become non-existent or ineffective in certain cases. We show that the median-based one is not saturated for Gaussian distributions in position. Instead, the Cauchy-Lorentz distributions in position turn out to be the one with the minimal uncertainty, among the states inspected, implying that the minimum-uncertainty state is not unique but depends on the measure of spread used. Even the ordering of the states with respect to the distance from the minimum uncertainty state is altered by a change in the measure. We invoke the completeness of Hermite polynomials in the space of all quantum states to probe the median-based relation. The results have potential applications in a variety of studies including those on the quantum-to-classical boundary and on quantum cryptography.

# Entropic Energy-Time Uncertainty Relation

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

on 2019-3-12 10:00am GMT

Author(s): Patrick J. Coles, Vishal Katariya, Seth Lloyd, Iman Marvian, and Mark M. Wilde

Energy-time uncertainty plays an important role in quantum foundations and technologies, and it was even discussed by the founders of quantum mechanics. However, standard approaches (e.g., Robertson’s uncertainty relation) do not apply to energy-time uncertainty because, in general, there is no Herm...

[Phys. Rev. Lett. 122, 100401] Published Tue Mar 12, 2019

# The best of many worlds, or, is quantum decoherence the manifestation of a disposition?

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

on 2019-3-09 1:21am GMT

Publication date: Available online 4 March 2019

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

Author(s): Florian J. Boge

##### Abstract

In this paper I investigate whether the phenomenon of quantum decoherence, the vanishing of interference and detectable entanglement on quantum systems in virtue of interactions with the environment, can be understood as the manifestation of a disposition. I will highlight the advantages of this approach as a realist interpretation of the quantum formalism, and demonstrate how such an approach can benefit from advances in the metaphysics of dispositions. I will also confront some commonalities with and differences to the many worlds interpretation, and address the difficulties induced by quantum non-locality. I conclude that there are ways to deal with these issues and that the proposal hence is an avenue worth pursuing.

# Going quantum with radio waves

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## Science current issue

on 2019-3-07 6:41pm GMT

# Naturalness, Wilsonian renormalization, and “fundamental parameters” in quantum field theory

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

on 2019-3-02 12:24am GMT

Publication date: Available online 26 February 2019

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

Author(s): Joshua Rosaler, Robert Harlander

##### Abstract

The Higgs naturalness principle served as the basis for the so far failed prediction that signatures of physics beyond the Standard Model (SM) would be discovered at the LHC. One influential formulation of the principle, which prohibits fine tuning of bare Standard Model (SM) parameters, rests on the assumption that a particular set of values for these parameters constitute the “fundamental parameters” of the theory, and serve to mathematically define the theory. On the other hand, an old argument by Wetterich suggests that fine tuning of bare parameters merely reflects an arbitrary, inconvenient choice of expansion parameters and that the choice of parameters in an EFT is therefore arbitrary. We argue that these two interpretations of Higgs fine tuning reflect distinct ways of formulating and interpreting effective field theories (EFTs) within the Wilsonian framework: the first takes an EFT to be defined by a single set of physical, fundamental bare parameters, while the second takes a Wilsonian EFT to be defined instead by a whole Wilsonian renormalization group (RG) trajectory, associated with a one-parameter class of physically equivalent parametrizations. From this latter perspective, no single parametrization constitutes the physically correct, fundamental parametrization of the theory, and the delicate cancellation between bare Higgs mass and quantum corrections appears as an eliminable artifact of the arbitrary, unphysical reference scale with respect to which the physical amplitudes of the theory are parametrized. While the notion of fundamental parameters is well motivated in the context of condensed matter field theory, we explain why it may be superfluous in the context of high energy physics.

# Reply to “Comment on ‘Past of a quantum particle revisited’ ”

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## PRA: Fundamental concepts

on 2019-2-27 10:00am GMT

Author(s): Berthold-Georg Englert, Kelvin Horia, Jibo Dai, Yink Loong Len, and Hui Khoon Ng

We stand by our findings in Phys. Rev. A 96, 022126 (2017). In addition to refuting the invalid objections raised by Peleg and Vaidman, we report a retrocausation problem inherent in Vaidman's definition of the past of a quantum particle.

[Phys. Rev. A 99, 026104] Published Wed Feb 27, 2019

# Comment on “Past of a quantum particle revisited”

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## PRA: Fundamental concepts

on 2019-2-27 10:00am GMT

Author(s): Uri Peleg and Lev Vaidman

The recent criticism of Vaidman's proposal for the analysis of the past of a particle in the nested interferometer is refuted. It is shown that the definition of the past of the particle adopted by Englert et al. [B. G. Englert et al., Phys. Rev. A 96, 022126 (2017)] is applicable only to a tiny fra...

[Phys. Rev. A 99, 026103] Published Wed Feb 27, 2019

# Experimental Test of Contextuality in Quantum and Classical Systems

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

on 2019-2-26 10:00am GMT

Author(s): Aonan Zhang, Huichao Xu, Jie Xie, Han Zhang, Brian J. Smith, M. S. Kim, and Lijian Zhang

Contextuality is considered as an intrinsic signature of nonclassicality and a crucial resource for achieving unique advantages of quantum information processing. However, recently, there have been debates on whether classical fields may also demonstrate contextuality. Here, we experimentally config...

[Phys. Rev. Lett. 122, 080401] Published Tue Feb 26, 2019

# Can We Probe Planckian Corrections at the Horizon Scale with Gravitational Waves?

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## PRL Editors' Suggestions

on 2019-2-25 10:00am GMT

Author(s): Andrea Addazi, Antonino Marcianò, and Nicolás Yunes

A theoretical study quantifies future challenges for probing the horizon structure of merging black holes using gravitational waves as a tool to study quantum gravity.

[Phys. Rev. Lett. 122, 081301] Published Mon Feb 25, 2019

# Quantum particle in a split box: Excitations to the ground state

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## PRA: Fundamental concepts

on 2019-2-20 10:00am GMT

Author(s): Vegard B. Sørdal and Joakim Bergli

We discuss two different approaches for splitting the wave function of a single-particle box (SPB) into two equal parts. Adiabatic insertion of a barrier in the center of a SPB in order to make two compartments which each have probability 1/2 of finding the particle in it is one of the key steps for...

[Phys. Rev. A 99, 022121] Published Wed Feb 20, 2019

# The case for black hole thermodynamics part II: Statistical mechanics

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

on 2019-2-20 1:54am GMT

Publication date: Available online 14 February 2019

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

Author(s): David Wallace

##### Abstract

I present in detail the case for regarding black hole thermodynamics as having a statistical-mechanical explanation in exact parallel with the statistical-mechanical explanation believed to underlie the thermodynamics of other systems. (Here I presume that black holes are indeed thermodynamic systems in the fullest sense; I review the evidence for that conclusion in the prequel to this paper.) I focus on three lines of argument: (i) zero-loop and one-loop calculations in quantum general relativity understood as a quantum field theory, using the path-integral formalism; (ii) calculations in string theory of the leading-order terms, higher-derivative corrections, and quantum corrections, in the black hole entropy formula for extremal and near-extremal black holes; (iii) recovery of the qualitative and (in some cases) quantitative structure of black hole statistical mechanics via the AdS/CFT correspondence. In each case I briefly review the content of, and arguments for, the form of quantum gravity being used (effective field theory; string theory; AdS/CFT) at a (relatively) introductory level: the paper is aimed at readers with some familiarity with thermodynamics, quantum mechanics and general relativity but does not presume advanced knowledge of quantum gravity. My conclusion is that the evidence for black hole statistical mechanics is as solid as we could reasonably expect it to be in the absence of a directly-empirically-verified theory of quantum gravity.

# Very strong evidence in favor of quantum mechanics and against local hidden variables from a Bayesian analysis

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## PRA: Fundamental concepts

on 2019-2-13 10:00am GMT

Author(s): Yanwu Gu, Weijun Li, Michael Evans, and Berthold-Georg Englert

The data of four recent experiments—conducted in Delft, Vienna, Boulder, and Munich with the aim of refuting nonquantum hidden-variables alternatives to the quantum-mechanical description—are evaluated from a Bayesian perspective of what constitutes evidence in statistical data. We find that each of...

[Phys. Rev. A 99, 022112] Published Wed Feb 13, 2019

# Necessary and sufficient condition for contextuality from incompatibility

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## Recent Articles in Phys. Rev. A

on 2019-2-12 10:00am GMT

Author(s): Zhen-Peng Xu and Adán Cabello

Measurement incompatibility is the most basic resource that distinguishes quantum from classical physics. Contextuality is the critical resource behind the power of some models of quantum computation and is also a necessary ingredient for many applications in quantum information. A fundamental probl...

[Phys. Rev. A 99, 020103(R)] Published Tue Feb 12, 2019

# Closed timelike curves and the second law of thermodynamics

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## PRA: Quantum information

on 2019-2-05 10:00am GMT

Author(s): Małgorzata Bartkiewicz, Andrzej Grudka, Ryszard Horodecki, Justyna Łodyga, and Jacek Wychowaniec

One out of many emerging implications from solutions of Einstein's general relativity equations are closed timelike curves (CTCs), which are trajectories through space-time that allow for time travel to the past without exceeding the speed of light. Two main quantum models of computation with the us...

[Phys. Rev. A 99, 022304] Published Tue Feb 05, 2019

# What is the Integrated Information Theory of Consciousness?: A Catalogue of Questions

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## Latest Issue of JOURNAL OF CONSCIOUSNESS STUDIES

on 2019-2-02 2:21am GMT

# Strong Quantum Nonlocality without Entanglement

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

on 2019-2-01 10:00am GMT

Author(s): Saronath Halder, Manik Banik, Sristy Agrawal, and Somshubhro Bandyopadhyay

Quantum nonlocality is usually associated with entangled states by their violations of Bell-type inequalities. However, even unentangled systems, whose parts may have been prepared separately, can show nonlocal properties. In particular, a set of product states is said to exhibit “quantum nonlocalit...

[Phys. Rev. Lett. 122, 040403] Published Fri Feb 01, 2019

# Quantum foundations

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on 2019-2-01 8:01am GMT
Physics Today, Volume 72, Issue 2, Page 50-51, February 2019.
More than a century after the birth of quantum mechanics, physicists and philosophers are still debating what a “measurement” really means.

# Four Meta-methods for the Study of Qualia

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## Latest Results for Erkenntnis

on 2019-2-01 12:00am GMT

### Abstract

In this paper, we describe four broad ‘meta-methods’ (as we shall call them) employed in scientific and philosophical research of qualia. These are the theory-centred metamethod, the property-centred meta-method, the argument-centred meta-method, and the event-centred meta-method. Broadly speaking, the theory-centred meta-method is interested in the role of qualia as some theoretical entities picked out by our folk psychological theories; the property-centred meta-method is interested in some metaphysical properties of qualia that we immediately observe through introspection (e.g., intrinsic, non-causal, ineffable); the argument-centred meta-method is interested in the role of qualia in some arguments for non-physicalism; the event-centred metamethod is interested in the role of qualia as some natural events whose nature is hidden and must be uncovered empirically. We will argue that the event-centred metamethod is the most promising route to a comprehensive scientific conception of qualia because of the flexibility of ontological and methodological assumptions it can provide. We also reveal the hidden influences of the different meta-methods and in doing so show why consideration of meta-methods has value for the study of consciousness.

# The Notion of Locality in Relational Quantum Mechanics

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## Latest Results for Foundations of Physics

on 2019-1-29 12:00am GMT

### Abstract

The term ‘locality’ is used in different contexts with different meanings. There have been claims that relational quantum mechanics is local, but it is not clear then how it accounts for the effects that go under the usual name of quantum non-locality. The present article shows that the failure of ‘locality’ in the sense of Bell, once interpreted in the relational framework, reduces to the existence of a common cause in an indeterministic context. In particular, there is no need to appeal to a mysterious space-like influence to understand it.

# Some remarks on the mentalistic reformulation of the measurement problem: a reply to S. Gao

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## Latest Results for Synthese

on 2019-1-25 12:00am GMT

### Abstract

Gao (Synthese, 2017. https://doi.org/10.1007/s11229-017-1476-y) presents a new mentalistic reformulation of the well-known measurement problem affecting the standard formulation of quantum mechanics. According to this author, it is essentially a determinate-experience problem, namely a problem about the compatibility between the linearity of the Schrödinger’s equation, the fundamental law of quantum theory, and definite experiences perceived by conscious observers. In this essay I aim to clarify (i) that the well-known measurement problem is a mathematical consequence of quantum theory’s formalism, and that (ii) its mentalistic variant does not grasp the relevant causes which are responsible for this puzzling issue. The first part of this paper will be concluded claiming that the “physical” formulation of the measurement problem cannot be reduced to its mentalistic version. In the second part of this work it will be shown that, contrary to the case of quantum mechanics, Bohmian mechanics and GRW theories provide clear explanations of the physical processes responsible for the definite localization of macroscopic objects and, consequently, for well-defined perceptions of measurement outcomes by conscious observers. More precisely, the macro-objectification of states of experimental devices is obtained exclusively in virtue of their clear ontologies and dynamical laws without any intervention of human observers. Hence, it will be argued that in these theoretical frameworks the measurement problem and the determinate-experience problem are logically distinct issues.

# Quantum Space

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## Physics

on 2019-1-22 12:00am GMT
Author: Jim Baggott
ISBN: 9780198809111
Binding: Hardcover
Publication Date: 22 January 2019

# Why Be regular?, part I

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

on 2018-11-17 7:55am GMT

Publication date: Available online 16 November 2018

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

Author(s): Benjamin Feintzeig, J.B. Le Manchak, Sarita Rosenstock, James Owen Weatherall

##### Abstract

We provide a novel perspective on “regularity” as a property of representations of the Weyl algebra. We first critique a proposal by Halvorson [2004, “Complementarity of representations in quantum mechanics”, Studies in History and Philosophy of Modern Physics35 (1), pp. 45–56], who argues that the non-regular “position” and “momentum” representations of the Weyl algebra demonstrate that a quantum mechanical particle can have definite values for position or momentum, contrary to a widespread view. We show that there are obstacles to such an intepretation of non-regular representations. In Part II, we propose a justification for focusing on regular representations, pace Halvorson, by drawing on algebraic methods.