Potters, Jan and Leuridan, Bert (2017) Studying Scientific Thought Experiments in Their Context: Albert Einstein and Electromagnetic Induction. Studies in History and Philosophy of Modern Physics, 58. pp. 1-11. ISSN 1355-2198

Ackermann, Matthias (2020) Revisiting the Genesis of ‘Many-Worlds’. [Preprint]

We analyze work extraction from a qubit into a wave guide (WG) acting as a battery, where work is the coherent component of the energy radiated by the qubit. The process is stimulated by a wave packet whose mean photon number (the battery’s charge) can be adjusted. We show that the extracted work is bounded by the qubit’s ergotropy, and that the bound is saturated for a large enough battery’s charge. If this charge is small, work can still be extracted. Its amount is controlled by the quantum coherence initially injected in the qubit’s state, that appears as a key parameter when energetic resources are limited. This new and autonomous scenario for the study of quantum batteries can be implemented with state-of-the-art artificial qubits coupled to WGs.

Authors: Brett McInnes

The AdS/CFT correspondence is useful primarily when the number of colours, $N_{\textsf{c}}$, characterising the boundary field theory, is “large”, and when the mass of the bulk black hole that is usually present is “large” relative to the bulk Planck mass. But this prompts two questions: first, can these large numbers be estimated, even very approximately, in a given application? Second: if these quantities are themselves computed holographically from physical data constraining the field theory, is this computation self-consistent, in the sense that it actually produces large numbers, an outcome which is far from obvious? Here we consider these questions in the case of the application of holographic techniques to the study of the quark-gluon plasma. We find that holography in this case is able to generate estimates of the dimensionless numbers in question, and, very remarkably, they are indeed large, despite the fact that the dimensionless input data are of order unity.

Authors: Robert H. Jonsson, David Q. Aruquipa, Marc Casals, Achim Kempf, Eduardo Martín-Martínez

We study the quantum channel between two localized first-quantized systems that communicate in 3+1 dimensional Schwarzschild spacetime via a quantum field. We analyze the information carrying capacity of direct and black hole-orbiting null geodesics as well as of the timelike contributions that arise because the strong Huygens principle does not hold on the Schwarzschild background. We find, in particular, that the non-direct-null and timelike contributions, which do not possess an analog on Minkowski spacetime, can dominate over the direct null contributions. We cover the cases of both geodesic and accelerated and accelerated emitters. Technically, we apply tools previously designed for the study of wave propagation in curved spacetimes to a relativistic quantum information communication setup, first for generic spacetimes, and then for the case of Schwarzschild spacetime in particular.

Authors: Martin Bojowald

A large number of models have been analyzed in loop quantum cosmology, using mainly minisuperspace constructions and perturbations. At the same time, general physics principles from effective field theory and covariance have often been ignored. A consistent introduction of these ingredients requires substantial modifications of existing scenarios. As a consequence, none of the broader claims made mainly by the Ashtekar school — such as the genericness of bounces with astonishingly semiclassical dynamics, robustness with respect to quantization ambiguities, the realization of covariance, and the relevance of certain technical results for potential observations — hold up to scrutiny. Several useful lessons for a sustainable version of quantum cosmology can be drawn from this outcome.

Weatherall, James Owen (2018) Some Philosophical Prehistory of the (Earman-Norton) Hole Argument. [Preprint]

Abstract

Contemporary debate over laws of nature centers around Humean supervenience, the thesis that everything supervenes on the distribution of non-nomic facts. The key ingredient of this thesis is the idea that nomic-like concepts—law, chance, causation, etc.—are expressible in terms of the regularities of non-nomic facts. Inherent to this idea is the tacit conviction that regularities, “constant conjunctions” of non-nomic facts do supervene on the distribution of non-nomic facts. This paper raises a challenge for this conviction. It will be pointed out that the notion of regularity, understood as statistical correlation, has a necessary conceptual component not clearly identified before—I shall call this the “conjunctive relation” of the correlated events. On the other hand, it will be argued that there exists no unambiguous, non-circular way in which this relation could be determined. In this regard, the notion of correlation is similar to that of distant simultaneity where the necessary conceptual component is the one-way speed of light, whose value doesn’t seem to be determined by matters of (non-nomic) facts.

Abstract

A recent no-go theorem gives an extension of the Wigner’s Friend argument that purports to prove the “Quantum theory cannot consistently describe the use of itself.” The argument is complex and thought provoking, but fails in a straightforward way if one treats QM as a statistical theory in the most fundamental sense, i.e. if one applies the so-called ensemble interpretation. This explanation is given here at an undergraduate level, which can be edifying for experts and students alike. A recent paper has already shown that the no-go theorem is incorrect with regard to the de Broglie Bohm theory and misguided in some of its general claims. This paper’s contribution is three fold. It shows how the extended Wigner’s Friend argument fails in the ensemble interpretation. It also makes more evident how natural a consistent statistical treatment of the wave function is. In this way, the refutation of the argument is useful for bringing out the core statistical nature of QM. It, in addition, manifests the unnecessary complications and problems introduced by the collapse mechanism that is part of the Copenhagen interpretation. The paper uses the straightforwardness of the ensemble interpretation to make the no-go argument and its refutation more accessible.

According to a radical account of quantum metaphysics that I label ‘high-dimensionalism’, ordinary objects are the ‘shadows’ of high-dimensional fundamental ontology (for example, Albert [2013], [unpublished-b]; Ney [2015]). Critics—especially Maudlin ([2007], [2010], [2019])—allege that high-dimensionalism cannot provide a satisfactory explanation of the manifest image. In this paper, I examine the two main ideas behind these criticisms: that high-dimensionalist connections between fundamental and non-fundamental are 1) inscrutable, and 2) arbitrary. In response to the first, I argue that there is no metaphysically significant contrast regarding the scrutability of low- and high-dimensionalist connections. In response to the second, I argue that the arbitrariness of high-dimensionalist connections has been overstated, and what arbitrariness there is afflicts low-dimensionalist connections too. Thus, the debate should not be focused on whether high-dimensionalism can provide a satisfactory explanation of the manifest image—as it has been in recent literature—but rather on the broader question of whether there is good all-things-considered reason to prefer low-dimensionalist theories.

Authors: Yaakov Zik, Giora Hon, Ilan Manulis

The question, Did Simon Marius (1573-1625) observe Jupiter’s satellites on January 8, 1610 (December 29, 1609 in the Julian calendar) is moot, for he did not disclose his research method and the instrument he used. To resolve this issue we apply astronomical codes and evaluate the visual performance of a replica of the telescope that Galileo Galilei (1564-1642) had used.

Explicit construction of local observable algebras in quasi-Hermitian quantum theories is derived in both the tensor product model of locality and in models of free fermions. The latter construction is applied to several cases of a $\mathcal{PT}$-symmetric toy model of particle-conserving free fermions on a 1-dimensional lattice, with nearest neighbour interactions and open boundary conditions. Despite the locality of the Hamiltonian, local observables do not exist in generic collections of sites in the lattice. The collections of sites which do contain nontrivial observables depends strongly depends on the complex potential.

We investigate the first-order theory of closed subspaces of complex Hilbert spaces in the signature $(\lor,\perp,0,1)$, where `$\perp$’ is the orthogonality relation. Our main result is that already its quasi-identities are undecidable: there is no algorithm to decide whether an implication between equations and orthogonality relations implies another equation. This is a corollary of a recent result of Slofstra in combinatorial group theory. It follows upon reinterpreting that result in terms of the hypergraph approach to quantum contextuality, for which it constitutes a proof of the inverse sandwich conjecture. It can also be interpreted as stating that a certain quantum satisfiability problem is undecidable.

Publication date: Available online 8 February 2020

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

Author(s): Ana-Maria Creţu

Publication date: Available online 7 February 2020

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

Author(s): Lydia Patton

Authors: Sandipan Sengupta

We set up a theory of gravity in vacuum with an extra dimension of vanishing proper length. The most general solution to the field equations are presented. By construction, this extra-dimensional formulation is free of Kaluza-Klein modes and does not allow any propagation along the fifth direction. The associated emergent theory exhibits a geometric stress-tensor composed of a vacuum energy, radiation and a vector-tensor multiplet. Based on the distinctive features of this multiplet, namely, its coupling to gravity, its natural inertness and its equation of state as an ideal fluid, it is proposed to supercede the hypothetical `dark matter’. A purely geometric model of the galactic halo is built upon this framework, which predicts flat rotation curves at sufficiently large distance.

Authors: R. Chan, M. F. A. da Silva, V. H. Satheeshkumar

How do the global properties of a Lorentzian manifold change when endowed with a vector field? This interesting question is tackled in this paper within the framework of Einstein-Aether (EA) theory which has the most general diffeomorphism-invariant action involving a spacetime metric and a vector field. After classifying all the possible nine vacuum solutions with and without cosmological constant in Friedmann-Lema{\^{\i}}tre-Robertson-Walker (FLRW) cosmology, we show that there exist three singular solutions in the EA theory which are not singular in the General Relativity (GR), all of them for $k=-1$, and another singular solution for $k=1$ in EA theory which does not exist in GR. This result is cross-verified by showing the focusing of timelike geodesics using the Raychaudhuri equation. These new singular solutions show that GR and EA theories can be completely different, even for the FLRW solutions when we go beyond flat geometry ($k=0$). In fact, they have different global structures. In the case where $\Lambda=0$ ($k=\pm 1$) the vector field defining the preferred direction is the unique source of the curvature.

Barrett, Jeffrey A. and Huttegger, Simon (2020) Quantum Randomness and Underdetermination. [Preprint]

Patton, Lydia (2020) Expanding theory testing in general relativity: LIGO and parametrized theories. Studies in History and Philosophy of Modern Physics. ISSN 1355-2198

de Ronde, Christian and Massri, Cesar (2020) Beyond Purity and Mixtures in Categorical Quantum Mechanics. [Preprint]

Author(s): M. Isoard and N. Pavloff

We study the quantum fluctuations in a one-dimensional Bose-Einstein condensate realizing an analogous acoustic black hole. The taking into account of evanescent channels and of zero modes makes it possible to accurately reproduce recent experimental measurements of the density correlation function….

[Phys. Rev. Lett. 124, 060401] Published Mon Feb 10, 2020

Nature Physics, Published online: 10 February 2020; doi:10.1038/s41567-020-0784-1

Mode-locking of lasers can be understood as self-organization, and the three-dimensional case of spatiotemporal mode-locking can described using attractor dissection theory, which helps develop an intuition for this complex case.

Abstract

We address a recent proposal concerning ‘surplus structure’ due to Nguyen et al. (Br J Phi Sci, 2018). We argue that the sense of ‘surplus structure’ captured by their formal criterion is importantly different from—and in a sense, opposite to—another sense of ‘surplus structure’ used by philosophers. We argue that minimizing structure in one sense is generally incompatible with minimizing structure in the other sense. We then show how these distinctions bear on Nguyen et al.’s arguments about Yang-Mills theory and on the hole argument.

Abstract

This paper discusses an outstanding issue in philosophy of physics concerning the relation between quantum symmetries and the notion of physical equivalence. Specifically, it deals with a dilemma arising for quantum symmetry breaking that was posed by Baker (Philos Sci 78:128–148, 2011), who claimed that if two ground states are connected by a symmetry, even when it is broken, they must be physically equivalent. However, I argue that the dilemma is just apparent. In fact, I object to Baker’s conclusion by showing that the two thermodynamical phases of a ferromagnet, which are connected by the so-called flip-flop symmetry, are physically inequivalent, thereby providing a counter-example to his claim.

ROVELLI, Carlo (2019) Neither Presentism nor Eternalism. Foundations of Physics, 49 (12). pp. 1325-1335. ISSN 0015-9018

Bacciagaluppi, Guido and Hermens, Ronnie (2020) Reverse Bell’s Theorem and Relativity of Pre- and Postselection. [Preprint]

Jodoin, Laurent (2020) A Justification of the Probabilistic Explanation of the Entropy Principle. [Preprint]