Weekly Papers on Quantum Foundations (6)

History of Lattice Field Theory from a Statistical Perspective 

from physics.hist-ph by Wolfgang BietenholzFri Feb 16 2024 13:58:48 (20 hours)# 1.

arXiv:2402.09628v1 Announce Type: cross Abstract: Researchers working in lattice field theory constitute an established community since the early 1990s, and around the same time the online open-access e-print repository arXiv was created. The fact that this field has a specific arXiv section, hep-lat, which is comprehensively used, provides a unique opportunity for a statistical study of its evolution over the last three decades. We present data for the number of entries, $E$, published papers, $P$, and citations, $C$, in total and separated by nations. We compare them to six other arXiv sections (hep-ph, hep-th, gr-qc, nucl-th, quant-ph, cond-mat) and to two socio-economic indices of the nations involved: the Gross Domestic Product (GDP) and the Education Index (EI). We present rankings, which are based either on the Hirsch Index H, or on the linear combination $\Sigma = E + P + 0.05 C$. We consider both extensive and intensive national statistics, i.e. absolute and relative to the population or to the GDP.

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Cellular automaton ontology, bits, qubits, and the Dirac equation 

from physics.hist-ph by Hans-Thomas ElzeFri Feb 16 2024 13:58:46 (20 hours)# 2.

arXiv:2401.08253v2 Announce Type: replace-cross Abstract: Cornerstones of the Cellular Automaton Interpretation of Quantum Mechanics are its ontological states that evolve by permutations, in this way never creating would-be quantum mechanical superposition states. We review and illustrate this with a classical Ising spin chain. It is shown that it can be related to the Weyl equation in the continuum limit. Yet, the model of discrete spins or bits unavoidably becomes a model of qubits by generating superpositions, if only slightly deformed. We study modifications of its signal velocity which, however, do not relate to mass terms. To incorporate the latter, we consider the Dirac equation in 1+1 dimensions and sketch an underlying discrete deterministic “necklace of necklaces” automaton that qualifies as ontological.

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Quantum gravity phenomenology and the blackbody radiation 

from gr-qc by R. Turcati, I. Soares, S. B. DuarteFri Feb 16 2024 13:58:43 (20 hours)# 3.

arXiv:2402.09918v1 Announce Type: new Abstract: We analyze the problem of blackbody radiation in the presence of quantum gravity effects encoded in modified dispersion relations. In this context, the spectral radiance and the generalized Stefan-Boltzmann law are studied. Furthermore, the regime of low temperatures is contemplated as well, where features related to the blackbody thermal laws and the thermodynamics quantities such as energy, pressure, entropy, and specific heat are obtained. Possible implications in compact objects such as neutron stars are also discussed.

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Cosmic Topology, Underdetermination, and Spatial Infinity 

from philsciFri Feb 16 2024 13:22:51 (21 hours)# 4.

Patrick, Ryan (2024) Cosmic Topology, Underdetermination, and Spatial Infinity. [Preprint]

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Same-diff? Conceptual similarities between gauge transformations and diffeomorphisms. Part III: Representational conventions and relationism 

from physics.hist-ph by Henrique GomesThu Feb 15 2024 09:15:46 (2 days)# 5.

arXiv:2402.09198v1 Announce Type: new Abstract: The following questions are germane to our understanding of gauge-(in)variant quantities and physical possibility: in which ways are gauge transformations and spacetime diffeomorphisms similar, and in which are they different? Sophistication is the most popular attitude towards some of these questions: roughly, it takes models related by these symmetries to represent the same physical possibility. In the previous paper in this series, I discussed obstacles to sophistication and then showed how these obstacles are overcome by theories that fulfill three Desiderata (i-iii). But this resolution still leaves open two main worries about sophistication: (a) it allows the individuation of structure-tokens to remain intractably prolix and thus of limited use, which is why practising physicists frequently invoke ‘relational, symmetry-invariant observables’; and (b) it leaves us with no formal framework for expressing counterfactual statements about the world. Here I will show that a third Desideratum, (iii), answers these worries. The new Desideratum requires a `relational’ understanding \emph{of coordinates} (or frames, etc).

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What is the Q of a Blackbody? A small contribution to Gustav Robert Kirchhoff’s bicentennial 

from physics.hist-ph by Arthur Ballato, John BallatoThu Feb 15 2024 09:15:45 (2 days)# 6.

arXiv:2402.08691v1 Announce Type: cross Abstract: The blackbody spectrum “half-power points” are used to assign effective Q “quality factor” values that are found to be less than unity whether frequency or wavelength scaling is used. A comparison with values for coherent oscillators is made. This exercise blends two of Kirchhoff’s interests, and is instructive in its own right, as it bridges the often mutually exclusive engineering and scientific disciplines.

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Thinking twice inside the box: is Wigner’s friend really quantum? 

from physics.hist-ph by Caroline L. Jones, Markus P. MuellerThu Feb 15 2024 09:15:44 (2 days)# 7.

arXiv:2402.08727v1 Announce Type: cross Abstract: There has been a surge of recent interest in the Wigner’s friend paradox, sparking several novel thought experiments and no-go theorems. The main narrative has been that Wigner’s friend highlights a counterintuitive feature that is unique to quantum theory, and which is closely related to the quantum measurement problem. Here, we challenge this view. We argue that the gist of the Wigner’s friend paradox can be reproduced without assuming quantum physics, and that it underlies a much broader class of enigmas in the foundations of physics and philosophy. To show this, we first consider several recently proposed extended Wigner’s friend scenarios, and demonstrate that their implications for the absoluteness of observations can be reproduced by classical thought experiments that involve the duplication of agents. Crucially, some of these classical scenarios are technologically much easier to implement than their quantum counterparts. Then, we argue that the essential structural ingredient of all these scenarios is a feature that we call “Restriction A”: essentially, that a physical theory cannot give us a probabilistic description of the observations of all agents. Finally, we argue that this difficulty is at the core of other puzzles in the foundations of physics and philosophy, and demonstrate this explicitly for cosmology’s Boltzmann brain problem. Our analysis suggests that Wigner’s friend should be studied in a larger context, addressing a frontier of human knowledge that exceeds the boundaries of quantum physics: to obtain reliable predictions for experiments in which these predictions can be privately but not intersubjectively verified.

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A Note on the Origin of Inertia 

from physics.hist-ph by A. Schlatter, R. E. KastnerThu Feb 15 2024 09:15:43 (2 days)# 8.

arXiv:2402.09365v1 Announce Type: cross Abstract: The question of where the inertial properties of matter come from has been open for a long time. Isaac Newton considered inertia an intrinsic property of matter. Ernst Mach held a different view whereby the inertia of a body comes from its interaction with the rest of the universe. This idea is known today as Mach’s principle. We discuss Mach’s principle based on transactional gravity, the recently developed completion of the entropic gravity program by the physics of quantum events induced by transactions. A consequence of the analysis is a fundamental relation between the gravitational constant G and the total mass in the causal universe, derived by means of entropic principles.

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Bohmian Mechanics as a Practical Tool 

from physics.hist-ph by Xabier Oianguren-Asua, Carlos F. Destefani, Matteo Villani, David K. Ferry, Xavier OriolsThu Feb 15 2024 09:15:42 (2 days)# 9.

arXiv:2212.09671v3 Announce Type: replace-cross Abstract: In this chapter, we will take a trip around several hot-spots where Bohmian mechanics and its capacity to describe the microscopic reality, even in the absence of measurements, can be harnessed as computational tools, in order to help in the prediction of phenomenologically accessible information (also useful for the followers of the Copenhagen theory). As a first example, we will see how a Stochastic Schr\”odinger Equation, when used to compute the reduced density matrix of a non-Markovian open quantum system, necessarily seems to employ the Bohmian concept of a conditional wavefunction. We will see that by dressing these conditional wavefunctions with an interpretation, the Bohmian theory can prove to be a useful tool to build general quantum frameworks, like a high-frequency electron transport model. As a second example, we will introduce how a Copenhagen “observable operator” can be derived from numerical properties of the Bohmian trajectories, which within Bohmian mechanics, are well-defined even for an “unmeasured” system. Most importantly in practice, even if these numbers are given no ontological meaning, not only we will be able to simulate (thus, predict and talk about) them, but we will see that they can be operationally determined in a weak value experiment. Therefore, they will be practical numbers to characterize a quantum system irrespective of the followed quantum theory.

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The measurement in classical and quantum theory 

from philsciThu Feb 15 2024 02:16:09 (2 days)# 10.

Kryukov, Alexey (2023) The measurement in classical and quantum theory. Journal of Physics.

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Can the Schro ̈dinger dynamics explain measurement? 

from philsciThu Feb 15 2024 02:15:49 (2 days)# 11.

Kryukov, Alexey (2023) Can the Schro ̈dinger dynamics explain measurement? Journal of Physics.

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Schro ̈dinger dynamics of a two-state system under measurement 

from philsciThu Feb 15 2024 02:15:19 (2 days)# 12.

Kryukov, Alexey (2024) Schro ̈dinger dynamics of a two-state system under measurement. [Preprint]

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Making Sense of Gravitational Thermodynamics 

from philsciThu Feb 15 2024 02:12:45 (2 days)# 13.

Lorenzetti, Lorenzo (2024) Making Sense of Gravitational Thermodynamics. [Preprint]

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Are observers reducible to structures? 

from philsciWed Feb 14 2024 03:19:31 (3 days)# 14.

Stoica, Ovidiu Cristinel (2023) Are observers reducible to structures? [Preprint]

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Why the wavefunction already is an object on space 

from philsciWed Feb 14 2024 03:18:09 (3 days)# 15.

Stoica, Ovidiu Cristinel (2024) Why the wavefunction already is an object on space. [Preprint]

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Independent Evidence in Multi-messenger Astrophysics 

from philsciTue Feb 13 2024 16:26:42 (3 days)# 16.

Elder, Jamee (2024) Independent Evidence in Multi-messenger Astrophysics. [Preprint]

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Flipping Arrows 

from philsciTue Feb 13 2024 16:25:21 (3 days)# 17.

Thebault, Karim P Y (2024) Flipping Arrows. [Preprint]

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On the Hole Argument and the physical interpretation of General Relativity 

from physics.hist-ph by Jaume de HaroTue Feb 13 2024 08:54:35 (4 days)# 18.

Einstein presented the Hole Argument against General Covariance, understood as invariance with respect to a change of coordinates, as a consequence of his initial failure to obtain covariant equations that, in the weak static limit, contain Newton’s law. Fortunately, about two years later, Einstein returned to General Covariance and found these famous equations of gravity. However, the rejection of his Hole Argument carries a totally different vision of space-time. Its substantivalism notion, which is an essential ingredient in Newtonian theory and also in his special theory of relativity, has to be replaced, following Descartes and Leibniz’s relationalism, by a set of “point-coincidences.”

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Symmetry matters 

from nature-physics by Maximilian PrüferMon Feb 12 2024 19:00:00 (4 days)# 19.

Nature Physics, Published online: 13 February 2024; doi:10.1038/s41567-024-02395-2Quantum simulators can provide new insights into the complicated dynamics of quantum many-body systems far from equilibrium. A recent experiment reveals that underlying symmetries dictate the nature of universal scaling dynamics.

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