Weekly Papers on Quantum Foundations (16)

Emergence-Free Duality: Phonons and Vibrating Atoms in Crystalline Solids 

from philsciFri Apr 26 2024 22:46:17 (11 hours)# 1.

Fortin, Sebastian and Pasqualini, Matias (2023) Emergence-Free Duality: Phonons and Vibrating Atoms in Crystalline Solids. [Preprint]

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Gauge Invariance Through Gauge Fixing 

from philsciFri Apr 26 2024 22:41:11 (11 hours)# 2.

Wallace, David (2024) Gauge Invariance Through Gauge Fixing. [Preprint]

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Equivalence Relations in Quantum Theory: An Objective Account of Bases and Factorizations. 

from philsciFri Apr 26 2024 22:40:47 (11 hours)# 3.

de Ronde, Christian and Massri, Cesar (2024) Equivalence Relations in Quantum Theory: An Objective Account of Bases and Factorizations. [Preprint]

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Against Self-Location 

from philsciFri Apr 26 2024 22:40:05 (11 hours)# 4.

Adlam, Emily (2024) Against Self-Location. [Preprint]

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How (Not) to Define Inertial Frames 

from philsciFri Apr 26 2024 22:39:19 (11 hours)# 5.

Jacobs, Caspar (2024) How (Not) to Define Inertial Frames. [Preprint]

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Reintroducing Dynamics into Static Causal Models 

from philsciFri Apr 26 2024 22:38:41 (11 hours)# 6.

Weinberger, Naftali (2019) Reintroducing Dynamics into Static Causal Models.

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Implications of computer science theory for the simulation hypothesis 

from physics.hist-ph by David H. WolpertFri Apr 26 2024 12:01:39 (22 hours)# 7.

arXiv:2404.16050v1 Announce Type: cross Abstract: The simulation hypothesis has recently excited renewed interest, especially in the physics and philosophy communities. However, the hypothesis specifically concerns {computers} that simulate physical universes, which means that to properly investigate it we need to couple computer science theory with physics. Here I do this by exploiting the physical Church-Turing thesis. This allows me to introduce a preliminary investigation of some of the computer science theoretic aspects of the simulation hypothesis. In particular, building on Kleene’s second recursion theorem, I prove that it is mathematically possible for us to be in a simulation that is being run on a computer \textit{by us}. In such a case, there would be two identical instances of us; the question of which of those is “really us” is meaningless. I also show how Rice’s theorem provides some interesting impossibility results concerning simulation and self-simulation; briefly describe the philosophical implications of fully homomorphic encryption for (self-)simulation; briefly investigate the graphical structure of universes simulating universes simulating universes, among other issues. I end by describing some of the possible avenues for future research that this preliminary investigation reveals.

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Counterfactuality, back-action, and information gain in multi-path interferometers 

from physics.hist-ph by Jonte R. Hance, Tomonori Matsushita, Holger F. HofmannFri Apr 26 2024 12:01:38 (22 hours)# 8.

arXiv:2404.16477v1 Announce Type: cross Abstract: The presence of an absorber in one of the paths of an interferometer changes the output statistics of that interferometer in a fundamental manner. Since the individual quantum particles detected at any of the outputs of the interferometer have not been absorbed, any non-trivial effect of the absorber on the distribution of these particles over these paths is a counterfactual effect. Here, we quantify counterfactual effects by evaluating the information about the presence or absence of the absorber obtained from the output statistics, distinguishing between classical and quantum counterfactual effects. We identify the counterfactual gain which quantifies the advantage of quantum counterfactual protocols over classical counterfactual protocols, and show that this counterfactual gain can be separated into two terms: a semi-classical term related to the amplitude blocked by the absorber, and a Kirkwood-Dirac quasiprobability assigning a joint probability to the blocked path and the output port. A negative Kirkwood-Dirac term between a path and an output port indicates that inserting the absorber into that path will have a focussing effect, increasing the probability of particles arriving at that output port, resulting in a significant enhancement of the counterfactual gain. We show that the magnitude of quantum counterfactual effects cannot be explained by a simple removal of the absorbed particles, but originates instead from a well-defined back-action effect caused by the presence of the absorber in one path, on particles in other paths.

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Completing the Quantum Reconstruction Program via the Relativity Principle 

from physics.hist-ph by W. M. Stuckey, Michael Silberstein, Timothy McDevittTue Apr 23 2024 11:39:48 (3 days)# 9.

arXiv:2404.13064v1 Announce Type: cross Abstract: We explain how the disparate kinematics of quantum mechanics (finite-dimensional Hilbert space of QM) and special relativity (Minkowski spacetime from the Lorentz transformations of SR) can both be based on one principle (relativity principle). This is made possible by the axiomatic reconstruction of QM via information-theoretic principles, which has successfully recast QM as a principle theory a la SR. That is, in the quantum reconstruction program (QRP) and SR, the formalisms (Hilbert space and Lorentz transformations, respectively) are derived from empirically discovered facts (Information Invariance & Continuity and light postulate, respectively), so QM and SR are “principle theories” as defined by Einstein. While SR has a compelling fundamental principle to justify its empirically discovered fact (relativity principle), QRP has not produced a compelling fundamental principle or causal mechanism to account for its empirically discovered fact. To unify these disparate kinematics, we show how the relativity principle (“no preferred reference frame” NPRF) can also be used to justify Information Invariance & Continuity. We do this by showing that when QRP’s operational notion of measurement is spatialized, Information Invariance & Continuity entails the empirically discovered fact that everyone measures the same value for Planck’s constant h, regardless of their relative spatial orientations or locations (Planck postulate). Since Poincare transformations relate inertial reference frames via spatial rotations and translations as well as boosts, the relativity principle justifies the Planck postulate just like it justifies the light postulate. Essentially, NPRF + c is an adynamical global constraint over the spacetime configuration of worldtubes for bodily objects while NPRF + h is an adynamical global constraint over the distribution of quanta among those bodily objects.

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Bell Correlations via Constrained Colliders — a Path from W to V 

from physics.hist-ph by Huw PriceTue Apr 23 2024 11:39:47 (3 days)# 10.

arXiv:2404.13928v1 Announce Type: cross Abstract: In previous work with Ken Wharton, I have proposed that Bell correlations are a special sort of selection artefact, explained by a combination of (i) collider bias and (ii) a boundary constraint on the collider variable. This hypothesis requires no direct causal influence outside lightcones, and may hence offer a new way to reconcile Bell nonlocality and relativity. This piece outlines a new argument for the proposal. It explains how it is valid for a special class of (W-shaped) Bell experiments involving delayed-choice entanglement swapping, and argues that it can be extended to the general (V-shaped) case.

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A review of 70 years with astrometry 

from physics.hist-ph by Erik H{\o}gTue Apr 23 2024 11:39:46 (3 days)# 11.

arXiv:2402.10996v2 Announce Type: replace-cross Abstract: In 1953 I heard of an experiment in 1925 by Bengt Str\”omgren where he observed transit times with the meridian circle at the Copenhagen University Observatory measuring the current in a photocell behind slits when a star was crossing. In 1954 just 22 years old I was given the task as a student to make first test observations with a new meridian circle of the observatory. I became fascinated by the instrument and by the importance of astrometry for astronomy. Work at four meridian circles, two in Denmark, one in Hamburg, one in Lund, and Pierre Lacroute’s vision of space astrometry in France had by 1973 created the foundation for development of the Hipparcos satellite, and Gaia followed. In 2013 I proposed a successor satellite which has gained momentum especially thanks to the efforts of David Hobbs and it has a good chance to be launched by ESA about 2045. But 70 years ago, optical astrometry was considered a dying branch of astronomy, unattractive compared with astrophysics. The following growth built on the still active interest in astrometry in Europe in those years and it was supported by ESA, the European Space Agency. This review is only about astrometry where I was personally involved.

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Why the global phase is not real 

from philsciMon Apr 22 2024 22:56:34 (4 days)# 12.

Gao, Shan (2024) Why the global phase is not real. Foundations of Physics, 54 (19). ISSN 1572-9516

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Finite frequentism explains quantum probability 

from physics.hist-ph by Simon SaundersMon Apr 22 2024 11:58:22 (4 days)# 13.

arXiv:2404.12954v1 Announce Type: cross Abstract: I show that frequentism, as an explanation of probability in classical statistical mechanics, can be extended in a natural way to a decoherent quantum history space, the analogue of a classical phase space. The result is further a form of finite frequentism, in which the Gibbs concept of an infinite ensemble of gases is replaced by the total quantum state expressed in terms of the decoherence basis, as defined by the history space. It is a form of finite and actual frequentism (as opposed to hypothetical frequentism), insofar as all the microstates exist, in keeping with the decoherence-based Everett interpretation, and some versions of pilot-wave theory.

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What is a reference frame in General Relativity? 

from physics.hist-ph by Nicola BamontiMon Apr 22 2024 11:58:21 (4 days)# 14.

arXiv:2307.09338v2 Announce Type: replace Abstract: In General Relativity, reference frames must be distinguished from coordinates. The former represent physical systems interacting with the gravitational system, aside from possible approximations, while the latter are mathematical artefacts. We propose a novel three-fold distinction between Idealised Reference Frames, Dynamical Reference Frames and Real Reference Frames. In doing so, the paper not only clarifies the physical significance of reference frames, but also sheds light on the similarities between idealised reference frames and coordinates. It also analyses the salience of reference frames to define local Dirac observables and to propose a physical interpretation to diffeomorphism gauge symmetry.

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