Weekly Papers on Quantum Foundations (20)

Wallace, David (2022) Philosophy of Quantum Mechanics. [Preprint]

Koberinski, Adam and Smeenk, Chris (2022) Lambda and the limits of effective field theory. [Preprint]

Dorato, Mauro and Morganti, Matteo (2022) What Ontology for Relational Quantum Mechanics? [Preprint]

Giovanelli, Marco (2020) Like Thermodynamics before Boltzmann. On the Emergence of Einstein’s Distinction between Constructive and Principle Theories. Studies In History and Philosophy of Science Part B: Studies In History and Philosophy of Modern Physics, 71. pp. 118-157. ISSN 13552198Giovanelli, Marco (2022) Geometrization vs. Unification. The Reichenbach-Einstein Quarrel about the Fernparallelismus Field Theory. Synthese, 213. ISSN 1573-0964Laudisa, Federico (2022) When Did Locality Become ‘Local Realism’? A Historical and Critical Analysis (1963-1978). [Preprint]

Gao, Shan (2022) A no-go result for wave function realism. [Preprint]

Dark matter or strong gravity?. (arXiv:2205.07153v1 [gr-qc])

下午6:38|Saurya Das, Sourav Sur|quant-ph updates on arXiv.org

We show that Newton’s gravitational potential, augmented by a logarithmic term, partly or wholly mitigates the need for dark matter. As a bonus, it also explains why MOND seems to work at galactic scales. We speculate on the origin of such a potential.

Emergent spacetimes from Hermitian and non-Hermitian quantum dynamics. (arXiv:2205.07429v1 [cond-mat.quant-gas])

下午6:38|Chenwei Lv, Qi Zhou|quant-ph updates on arXiv.org

We show that quantum dynamics of any systems with $SU(1,1)$ symmetry give rise to emergent Anti-de Sitter spacetimes in 2+1 dimensions (AdS$_{2+1}$). Using the continuous circuit depth, a quantum evolution is mapped to a trajectory in AdS$_{2+1}$. Whereas the time measured in laboratories becomes either the proper time or the proper distance, quench dynamics follow geodesics of AdS$_{2+1}$. Such a geometric approach provides a unified interpretation of a wide range of prototypical phenomena that appear disconnected. For instance, the light cone of AdS$_{2+1}$ underlies expansions of unitary fermions released from harmonic traps, the onsite of parametric amplifications, and the exceptional points that represent the $PT$ symmetry breaking in non-Hermitian systems. Our work provides a transparent means to optimize quantum controls by exploiting shortest paths in the emergent spacetimes. It also allows experimentalists to engineer emergent spacetimes and induce tunnelings between different AdS$_{2+1}$.

Einstein’s Equivalence principle for superpositions of gravitational fields and quantum reference frames. (arXiv:2012.13754v3 [quant-ph] UPDATED)

下午6:38|Flaminia Giacomini, Časlav Brukner|quant-ph updates on arXiv.org

The Principle of Equivalence, stating that all laws of physics take their special-relativistic form in any local inertial frame, lies at the core of General Relativity. Because of its fundamental status, this principle could be a very powerful guide in formulating physical laws at regimes where both gravitational and quantum effects are relevant. However, its formulation implicitly presupposes that reference frames are abstracted from classical systems (rods and clocks) and that the spacetime background is well defined. It is unclear if it continues to hold when quantum systems, which can be in a quantum relationship with other physical systems, are taken as reference frames, and in a superposition of classical spacetime structures. Here, we tackle both questions by introducing a relational formalism to describe quantum systems in a superposition of curved spacetimes. We build a unitary transformation to the quantum reference frame (QRF) of a quantum system in curved spacetime, and in a superposition thereof. In both cases, a QRF can be found such that the metric looks locally minkowskian. Hence, one cannot distinguish, with a local measurement, if the spacetime is flat or curved, or in a superposition of such spacetimes. This transformation identifies a Quantum Local Inertial Frame. We also find a spacetime path-integral encoding the dynamics of a quantum particle in spacetime and show that the state of a freely falling particle can be expressed as an infinite sum of all possible classical geodesics. We then build the QRF transformation to the Fermi normal coordinates of such freely falling quantum particle and show that the metric is locally minkowskian. These results extend the Principle of Equivalence to QRFs in a superposition of gravitational fields. Verifying this principle may pave a fruitful path to establishing solid conceptual grounds for a future theory of quantum gravity.

The second law of thermodynamics as a deterministic theorem for quantum spin systems. (arXiv:2112.01175v4 [math-ph] UPDATED)

下午6:38|Walter F. Wreszinski|quant-ph updates on arXiv.org

We review our approach to the second law of thermodynamics, viewed as a theorem asserting the growth of the mean (Gibbs-von Neumann) entropy of quantum spin systems undergoing automorphic (unitary) adiabatic transformations. Non-automorphic interactions with the environment, although known to produce on the average a strict reduction of the entropy of systems with finite number of degrees of freedom, are proved to conserve the mean entropy on the average. The results depend crucially on two properties of the mean entropy, proved by Robinson and Ruelle for classical systems, and Lanford and Robinson for quantum lattice systems: upper semicontinuity and affinity.

The Cavendish Computors: The women working in scientific computing for Radio Astronomy. (arXiv:2205.07267v1 [astro-ph.IM])

下午6:38|physics.hist-ph updates on arXiv.org

Authors: Verity Allan

A discussion of the history of scientific computing for Radio Astronomy in the Cavendish Laboratory of the University of Cambridge in the decades after the Second World War. This covers the development of the aperture synthesis technique for Radio Astronomy and how that required using the new computing technology developed by the University’s Mathematical Laboratory: the EDSAC, EDSAC 2 and TITAN computers. It looks at the scientific advances made by the Radio Astronomy group, particularly the assembling of evidence which contradicted the Steady State Hypothesis. It also examines the software advances that allowed bigger telescopes to be built: the Fast Fourier Transform (FFT) and the degridding algorithm. Throughout, the contribution of women is uncovered, from the diagrams they drew for scientific publications, through programming and operating computers, to writing scientific papers.

A Discrete Analog of General Covariance — Part 2: Despite what you’ve heard, a perfectly Lorentzian lattice theory. (arXiv:2205.07701v1 [gr-qc])

下午6:38|physics.hist-ph updates on arXiv.org

Authors: Daniel Grimmer

A crucial step in the history of General Relativity was Einstein’s adoption of the principle of general covariance which demands a coordinate independent formulation for our spacetime theories. General covariance helps us to disentangle a theory’s substantive content from its merely representational artifacts. It is an indispensable tool for a modern understanding of spacetime theories. Motivated by quantum gravity, one may wish to extend these notions to quantum spacetime theories (whatever those are). Relatedly, one might want to extend these notions to discrete spacetime theories (i.e., lattice theories). This paper delivers such an extension with surprising consequences, extending Part 1 (arXiv:2204.02276) to a Lorentzian setting.

This discrete analog of general covariance reveals that lattice structure is rather less like a fixed background structure and rather more like a coordinate system, i.e., merely a representational artifact. This discrete analog is built upon a rich analogy between the lattice structures appearing in our discrete spacetime theories and the coordinate systems appearing in our continuum spacetime theories. I argue that properly understood there are no such things as lattice-fundamental theories, rather there are only lattice-representable theories. It is well-noted by the causal set theory community that no theory on a fixed spacetime lattice is Lorentz invariant, however as I will discuss this is ultimately a problem of representational capacity, not of physics. There is no need for the symmetries of our representational tools to latch onto the symmetries of the thing being represented. Nothing prevents us from using Cartesian coordinates to describe rotationally invariant states/dynamics. As this paper shows, the same is true of lattices in a Lorentzian setting: nothing prevents us from defining a perfectly Lorentzian lattice(-representable) theory.

Regarding Flows Under the Free Energy Principle: A Comment on “How Particular is the Physics of the Free Energy Principle?” by Aguilera, Millidge, Tschantz, and Buckley. (arXiv:2205.07793v1 [cond-mat.stat-mech])

下午6:38|physics.hist-ph updates on arXiv.org

Authors: Dalton A R Sakthivadivel

In a recent technical critique of the free energy principle (FEP) due to Aguilera-Millidge-Tschantz-Buckley, it is argued that there are a number of instances where the FEP\textemdash as conventionally written, in terms of densities over states\textemdash is uninformative about the dynamics of many physical systems, and by extension, many `things.’ In this informal comment on their critique, I highlight two points of interest where their derivations are largely correct, but where their arguments are not fatal to the FEP. I go on to conjecture that a path-based formulation of the FEP has key features which restore its explanatory power in broad physical regimes. Correspondingly, this piece takes the position that the application of a state-based formulation of the FEP is inappropriate for certain simple systems, but, that the FEP can be expected to hold regardless.

Coarse-grained modelling out of equilibrium

下午6:38|ScienceDirect Publication: Physics ReportsScienceDirect RSShttps://www.sciencedirect.com/journal/physics-reportsRSS for NodeTue, 23 Jul 2019 10:02:48 GMTCopyright © 2019 Elsevier B.V. All rights reservedRapid solidification as non-ergodic phenomenonPublication date: 20 July 2019Source: Physics Reports, Volume 818Author(s): P.K. Galenko, D. JouAbstractRapid solidification is a relevant physical phenomenon in material sciences, whose theoretical analysis requires going beyond the limits of local equilibrium statistical physics and thermodynamics and, in particular, taking account of ergodicity breaking and of generalized formulation of thermodynamics. The ergodicity breaking is related to the time symmetry breaking and to the presence of some kinds of fluxes and gradient flows making that an average of microscopic variables along time is different than an average over some chosen statistical ensemble. In fast processes, this is due, for instance, to the fact that the system has no time enough to explore the who

Publication date: 19 August 2022

Source: Physics Reports, Volume 972

Author(s): Tanja Schilling

Effective field theory from Relativistic Generalized Uncertainty. (arXiv:2205.06878v1 [gr-qc])

下午6:38|gr-qc updates on arXiv.org

Authors: Vasil TodorinovSaurya DasPasquale Bosso

Theories of Quantum Gravity predict a minimum measurable length and a corresponding modification of the Heisenberg Uncertainty Principle to the so-called Generalized Uncertainty Principle (GUP). However, this modification is usually formulated in non-relativistic language, making it unclear whether the minimum length is Lorentz invariant. We have formulated a Relativistic Generalized Uncertainty Principle, resulting in a Lorentz invariant minimum measurable length and the resolution of the composition law problem. This proved to be an important step in the formulation of Quantum Field Theory with minimum length. We derived the Lagrangians consistent with the existence of minimal length and describing the behaviour of scalar, spinor, and U(1) gauge fields. We calculated the Feynman rules (propagators and vertices) associated with these Lagrangians. Furthermore, we calculated the Quantum Gravity corrected scattering cross-sections for a lepton-lepton scattering. Finally, we compared our results with current experiments, which allowed us to improve the bounds on the scale at which quantum gravity phenomena will become relevant.

Causal completions as Lorentzian pre-length spaces. (arXiv:2205.07148v1 [gr-qc])

下午6:38|gr-qc updates on arXiv.org

Authors: L. Ake HauSaul BurgosDidier A. Solis

In this work we revisit the notion of the (future) causal completion of a globally hyperbolic spacetime and endow it with the structure of a Lorentzian pre-length space. We further carry out this construction for a certain class of generalized Robertson-Walker spacetimes.

Entanglement between two evaporating black holes. (arXiv:2111.11688v2 [hep-th] UPDATED)

下午6:38|gr-qc updates on arXiv.org

Authors: Akihiro MiyataTomonori Ugajin

We study a thermo-field double type entangle state on two disjoint gravitating universes, say A and B, with an eternal black hole on each. As was shown previously, its entanglement entropy of the universe A is computed by the generalized entropy on a new spacetime constructed by suitably gluing the black holes on A and B. We study such spacetime gluings when universes are asymptotically flat and AdS cases, especially when the masses of these black holes are different. We also clarify the rule to construct such a glued spacetime in more general settings from the gravitational path integral view point.

Unruh-DeWitt detectors in cosmological spacetimes. (arXiv:2204.00359v2 [gr-qc] UPDATED)

下午6:38|gr-qc updates on arXiv.org

Authors: Aindriú Conroy

We analyse the response and thermal behaviour of an Unruh-DeWitt detector as it travels through cosmological spacetimes, with special reference to the question of how to define surface gravity and temperature in dynamical spacetimes. Working within the quantum field theory on curved spacetime approximation, we consider a detector as it travels along geodesic and accelerated Kodama trajectories in de Sitter and asymptotically de Sitter FLRW spacetimes. By modelling the temperature of the detector using the detailed-balance form of the Kubo–Martin–Schwinger (KMS) conditions as it thermalises, we can better understand the thermal behaviour of the detector as it interacts with the quantum field, and use this to compare competing definitions of surface gravity and temperature that persist in the literature. These include the approaches of Hayward-Kodama, Ashtekar et al., Fodor et al., and Nielsen-Visser. While these are most often examined within the context of a dynamical black hole, here we shift focus to surface gravity on the evolving cosmological horizon.

The fate of causal structure under time reversal

2022年5月15日 星期日 下午3:50|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Williams, Porter (2022) The fate of causal structure under time reversal. THEORIA. An International Journal for Theory, History and Foundations of Science, 37 (1). pp. 87-102. ISSN 0495-4548

Bi-directionality and time in causal relationships

2022年5月15日 星期日 下午3:50|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Samaniego, Fernanda (2022) Bi-directionality and time in causal relationships. THEORIA. An International Journal for Theory, History and Foundations of Science, 37 (1). pp. 103-109. ISSN 0495-4548

Watch out for the W

2022年5月13日 星期五 上午8:00|Stefanie Reichert|Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 13 May 2022; doi:10.1038/s41567-022-01617-9

Watch out for the W

Geometrization vs. unification: the Reichenbach–Einstein quarrel about the Fernparallelismus field theory

2022年5月9日 星期一 上午8:00|Latest Results for Synthese


This study reconstructs the 1928–1929 correspondence between Reichenbach and Einstein about the latter’s latest distant parallelism-unified field theory, which attracted considerable public attention at the end of the 1920s. Reichenbach, who had recently become a Professor in Berlin, had the opportunity to discuss the theory with Einstein and therefore sent him a manuscript with some comments for feedback. The document has been preserved among Einstein’s papers. However, the subsequent correspondence took an unpleasant turn after Reichenbach published a popular article on distant parallelism in a newspaper. Einstein directly wrote to the Editorial Board complaining about Reichenbach’s unfair use of off-the-record information. While Reichenbach’s reply demonstrates a sense of personal betrayal at Einstein’s behavior, his published writings of that period point to a sense of intellectual betrayal of their shared philosophical ideals. In his attempts to unify both electricity and gravitation, Einstein had abandoned the physical heuristic that guided him to the relativity theory, to embrace a more speculative, mathematical heuristic that he and Reichenbach had both previously condemned. A decade-long personal and intellectual friendship grew fainter and then never recovered. This study, relying on archival material, aims to revisit the Reichenbach–Einstein relationship in the late 1920s in light of Reichenbach’s neglected contributions to the epistemology of the unified field theory program. Thereby, it hopes to provide a richer account of Reichenbach’s philosophy of space and time.

Schrödinger’s Equation as a Consequence of the Central Limit Theorem Without Assuming Prior Physical Laws [Foundations of Physics volume 52, Article number: 50 (2022)]

P. M. Grinwald

The central limit theorem has been found to apply to random vectors in complex Hilbert space. This amounts to sufficient reason to study the complex–valued Gaussian, looking for relevance to quantum mechanics. Here we show that the Gaussian, with all terms fully complex, acting as a propagator, leads to Schrödinger’s non-relativistic equation including scalar and vector potentials, assuming only that the norm is conserved. No physical laws need to be postulated a priori. It thereby presents as a process of irregular motion analogous to the real random walk but executed under the rules of the complex number system. There is a standard view that Schrödinger’s equation is deterministic, whereas wavefunction “collapse” is probabilistic (by Born’s rule)—we have now a demonstrated linkage to the central limit theorem, indicating a stochastic picture at the foundation of Schrödinger’s equation itself. It may be an example of Wheeler’s “It from bit” with “No underlying law”. Reasons for the primary role of C are open to discussion. The present derivation is compared with recent reconstructions of the quantum formalism, which have the aim of rationalizing its obscurities.

Discretised Hilbert Space and Superdeterminism [arXiv:2204.05763 (quant-ph)]

T.N. Palmer

In computational physics it is standard to approximate continuum systems with discretised representations. Here we consider a specific discretisation of the continuum complex Hilbert space of quantum mechanics – a discretisation where squared amplitudes and complex phases are rational numbers. The fineness of this discretisation is determined by a finite (prime-number) parameter p. As p→∞, unlike standard discretised representations in computational physics, this model does not tend smoothly to the continuum limit. Instead, the state space of quantum mechanics is a singular limit of the discretised model at p=∞. Using number theoretic properties of trigonometric functions, it is shown that for large enough values of p, discretised Hilbert space accurately describes ensemble representations of quantum systems within an inherently superdeterministic framework, one where the Statistical Independence assumption in Bell’s theorem is formally violated. In this sense, the discretised model can explain the violation of Bell inequalities without appealing to nonlocality or indefinite reality. It is shown that this discretised framework is not fine tuned (and hence not conspiratorial) with respect to its natural state-space p-adic metric. As described by Michael Berry, old theories of physics are typically the singular limits of new theories as a parameter of the new theory is set equal to zero or infinity. Using this, we can answer the challenge posed by Scott Aaronson, critic of superderminism: to explain when a great theory in physics (here quantum mechanics) has ever been grudgingly accommodated' rather thangloriously explained’ by its candidate successor theory (here a superdeterministic theory of quantum physics based on discretised Hilbert space).

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