Hartmann, Stephan (2020) Bayes Nets and Rationality. [Preprint]

We study the effect of a logarithmic nonlinearity in the Schr\”odinger equation (SE) on the dynamics of a freely expanding Bose-Einstein condensate (BEC). The logarithmic nonlinearity was one of the first proposed nonlinear extensions to the SE which emphasized the conservation of important physical properties of the linear theory, e.g.: the separability of noninteracting states. Using this separability, we incorporate it into the description of a BEC obeying a logarithmic Gross-Pittaevskii equation. We investigate the dynamics of such BECs using variational and numerical methods and find that, using experimental techniques like delta kick collimation, experiments with extended free-fall times as available on microgravity platforms could be able to lower the bound on the strength of the logarithmic nonlinearity by at least one order of magnitude.

Authors: Hernán G. Solari, Mario A. Natiello

We analyse how the concept of the ether, playing the role of absolute space, is still present in physics. When the problem is considered in the context of classical mechanics, we show that vestiges of absolute space can be found in the standard presentation of inertial systems. We offer an alternative — fully relational — definition of inertial systems which not only eliminates the problem but it further shows that the equivalence principle is just a particular consequence of the No Arbitrariness Principle. In terms of Special Relativity, the non-existence of relative velocities implies a constructive contradiction (their existence is assumed in the construction). The problem is inherited from Lorentz’ use of the ether, developed in his interpretation of Maxwell’s electrodynamics. In summary, the velocities in the Lorentz transformations must be considered velocities relative to the ether (absolute space) if the theory is not to fall apart for being inconsistent. We discuss the relevance of the phenomenological map, and how previous works have failed to acknowledge that the consistency problem is not in the exposed part of the theory but in the supporting phenomenological map which, rather than being constructed anew, it transports concepts of classical mechanics by habit, without revising their validity in the context of Special Relativity.

Authors: Pauline Gagnon

Today, February 11, is the International Day of Women and Girls in Science, the perfect day to remember Mileva Mari\'{c} Einstein, a brilliant but largely unknown scientist. While her husband, Albert Einstein is celebrated as perhaps the best physicist of the century, one question about his career remains: How much did his first wife contribute to his groundbreaking science? While it is not possible to credit her with any specific part of his work, their letters and numerous testimonies presented in books dedicated to her $^{[1-5]}$ provide substantial evidence on how they collaborated from the time they met in 1896 up to their separation in 1914. They depict a couple united by a shared passion for physics, music and for each other. So here is her story.

Authors: Rolf Dahm

In order to ask for future concepts of relativity, one has to build upon the original concepts instead of the nowadays common formalism only, and as such recall and reconsider some of its roots in geometry. So in order to discuss 3-space and dynamics, we recall briefly Minkowski’s approach in 1910 implementing the nowadays commonly used 4-vector calculus and related tensorial representations as well as Klein’s 1910 paper on the geometry of the Lorentz group. To include microscopic representations, we discuss few aspects of Wigner’s and Weinberg’s ‘boost’ approach to describe ‘any spin’ with respect to its reductive Lie algebra and coset theory, and we relate the physical identification to objects in $P^{5}$ based on the case $(1,0)\oplus(0,1)$ of the electromagnetic field. So instead of following this — in some aspects — special and misleading ‘old’ representation theory, based on 4-vector calculus and tensors, we provide and use an alternative representation based on line geometry which — besides comprising known representation theory — is capable of both describing (classical) projective geometry of 3-space as well as it yields spin matrices and the classical Lie transfer. In addition, this geometry is capable of providing a more general route to known Lie symmetries, especially of the su(2)$\oplus$i~su(2) Lie algebra of special relativity, as well as it comprises gauge theories and affine geometry. Thus it serves as foundation for a future understanding of more general representation theory of relativity based, however, on roots known from classical projective geometry and $P^{5}$. As an application, we discuss Lorentz transformations in point space in terms of line and Complex geometry, where we can identify them as…

Authors: J. H. Kinsman, D. J. Asher

Using orbital integrations of particles ejected from Comet Halley’s passages between 1404 BC and 240 BC, the authors investigate possible outbursts of the Orionids (twin shower of the Eta Aquariids) that may have been observed in the western hemisphere. In an earlier orbital integration study the authors determined there was a high probability linking probable outbursts of the Eta Aquariid meteor shower with certain events recorded in inscriptions during the Maya Classic Period, AD 250-900. This prior examination was the first scientific inquiry of its kind into ancient meteor outbursts possibly recorded in the western hemisphere where previously no pre-Columbian observations had existed. In the current paper the aim is to describe orbital dynamics of rare but probable Orionid outbursts that would have occurred on or near applicable dates recorded in the Classic Maya inscriptions. Specifically, significant probable outbursts are found in AD 417 and 585 out of 30 possible target years. The driving mechanisms for outbursts in those two years are Jovian 1:6 and 1:7 mean motion resonances acting to maintain compact structures within the Orionid stream for over 1 kyr. Furthermore, an Orionid outburst in AD 585 recorded by China is confirmed.

Authors: Bob Osano

The evolution of the Universe is traditionally examined by monitoring how its material content evolves as it expands. This model of an isolated system is as expressed as the equation of motion of the bulk but segmented into different epochs. In particular, the evolution of the Friedman-Leimetre-Robertson-Walker (FRLW) Universe is separated into different epochs that are characterised by the dynamics of whichever mass-energy constituent is dominant at the time. The standard analysis of the evolution of the Universe in a particular epoch often considers the evolution of the dominant energy density only; disregarding all others. Whereas this represents the limiting case, in principle the contributions from others cannot always be disregarded particularly in the vicinity of the equality of the various mass-energy densities or the transition periods between epochs. We examine the evolution of the total energy density rather than individual energy densities during the different epochs. We find that taking into account the contributions from the various constituents leads to a broader range of possibilities evolution histories which enriches the standard picture. This article looks at these possibilities.

Authors: Donald Marolf, Henry Maxfield

In the 1980’s, work by Coleman and by Giddings and Strominger linked the physics of spacetime wormholes to `baby universes’ and an ensemble of theories. We revisit such ideas, using features associated with a negative cosmological constant and asymptotically AdS boundaries to strengthen the results, introduce a change in perspective, and connect with recent replica wormhole discussions of the Page curve. A key new feature is an emphasis on the role of null states. We explore this structure in detail in simple topological models of the bulk that allow us to compute the full spectrum of associated boundary theories. The dimension of the asymptotically AdS Hilbert space turns out to become a random variable $Z$, whose value can be less than the naive number $k$ of independent states in the theory. For $k>Z$, consistency arises from an exact degeneracy in the inner product defined by the gravitational path integral, so that many a priori independent states differ only by a null state. We argue that a similar property must hold in any consistent gravitational path integral. We also comment on other aspects of extrapolations to more complicated models, and on possible implications for the black hole information problem in the individual members of the above ensemble.

Author(s): T. M. Wintermantel, Y. Wang, G. Lochead, S. Shevate, G. K. Brennen, and S. Whitlock

We propose a physical realization of quantum cellular automata (QCA) using arrays of ultracold atoms excited to Rydberg states. The key ingredient is the use of programmable multifrequency couplings which generalize the Rydberg blockade and facilitation effects to a broader set of nonadditive, unita…

[Phys. Rev. Lett. 124, 070503] Published Fri Feb 21, 2020

Author(s): Daniel Szombati, Alejandro Gomez Frieiro, Clemens Müller, Tyler Jones, Markus Jerger, and Arkady Fedorov

The state of a superconducting qubit can be preserved by increasing the drive strength, thus introducing further control over decoherence processes.

[Phys. Rev. Lett. 124, 070401] Published Thu Feb 20, 2020

Gao, Shan (2020) A thought experiment in many worlds. [Preprint]

The Minkowski vacuum $|0\rangle_M$, which for an inertial observer is devoid of particles, is treated as a thermal bath by Rindler observers living in a single Rindler wedge, as a result of the discrepancy in the definition of positive frequency between the two classes of observers and a strong entanglement between degrees of freedom in the left and right Rindler wedges. We revisit, in the context of a free scalar Klein-Gordon field, the problem of quantification of the correlations between an inertial observer Alice and left/right Rindler observes Rob/AntiRob. We emphasize the analysis of informational quantities, like the locally accessible and locally inaccessible information, and a closely associated entanglement measure, the entanglement of formation. We conclude that, with respect to the correlation structure probed by inertial observers alone, the introduction of a Rindler observer gives rise to a correlation redistribution which can be quantified by the entanglement of formation.

Under the assumption that every material object can ultimately be described by quantum theory, we ask how a probe system evolves in a device prepared and kept in a superposition state of values of its classical parameter. We find that, under ideal conditions, the evolution of the system would be unitary, generated by an effective Hamiltonian. We describe also an incoherent use of the device that achieves the same effective evolution on an ensemble. The effective Hamiltonian thus generated may have qualitatively different features from that associated to a classical value of the parameter.

Integrated Information Theory is one of the leading models of consciousness. It aims to describe both the quality and quantity of the conscious experience of a physical system, such as the brain, in a particular state. In this contribution, we propound the mathematical structure of the theory, separating the essentials from auxiliary formal tools. We provide a definition of a generalized IIT which has IIT 3.0 of Tononi et. al., as well as the Quantum IIT introduced by Zanardi et. al. as special cases. This provides an axiomatic definition of the theory which may serve as the starting point for future formal investigations and as an introduction suitable for researchers with a formal background.

It is well established that simulating a perfect quantum computer with a classical computer requires computing resources that scale exponentially with the number of qubits $N$ or the depth $D$ of the circuit. Conversely, a perfect quantum computer could potentially provide an exponential speed up with respect to classical hardware. Real quantum computers however are not perfect: they are characterized by a small error rate $\epsilon$ per operation, so that the fidelity of the many-qubit quantum state decays exponentially as $ {\cal{F}} \sim (1-\epsilon)^{ND}$. Here, we discuss a set of classical algorithms based on matrix product states (MPS) which closely mimic the behavior of actual quantum computers. These algorithms require resources that scale linearly in $N$ and $D$ at the cost of making a small error $\epsilon$ per two-qubit gate. We illustrate our algorithms with simulations of random circuits for qubits connected in both one and two dimensional lattices. We find that $\epsilon$ can be decreased at a polynomial cost in computing power down to a minimum error $\epsilon_\infty$. Getting below $\epsilon_\infty$ requires computing resources that increase exponentially with $\epsilon_\infty/\epsilon$. For a two dimensional array of $N=54$ qubits and a circuit with Control-Z gates of depth $D=20$, a fidelity ${\cal F}\ge 0.002$ can be reached on a single core computer in a few hours. It is remarkable that such a high fidelity can be obtained using a variational ansatz that only spans a tiny fraction $(\sim 10^{-8})$ of the full Hilbert space. Our results show how the actual computing power harvested by noisy quantum computers is controlled by the error rate $\epsilon$.

In 2007, and in a series of later papers, Joy Christian claimed to refute Bell’s theorem, presenting an alleged local realistic model of the singlet correlations using techniques from Geometric Algebra (GA). Several authors published papers refuting his claims, and Christian’s ideas did not gain acceptance. However, he recently succeeded in publishing yet more ambitious and complex versions of his theory in fairly mainstream journals. How could this be? The mathematics and logic of Bell’s theorem is simple and transparent and has been intensely studied and debated for over 50 years. Christian claims to have a mathematical counterexample to a purely mathematical theorem. Each new version of Christian’s model used new devices to circumvent Bell’s theorem or depended on a new way to misunderstand Bell’s work. These devices and misinterpretations are in common use by other Bell critics, so it useful to identify and name them. I hope that this paper can serve as a useful resource to those who need to evaluate new “disproofs of Bell’s theorem”. Christian’s fundamental idea is simple and quite original: he gives a probabilistic interpretation of the fundamental GA equation a.b = (ab + ba)/2. After that, ambiguous notation and technical complexity allow sign errors to be hidden from sight, and new mathematical errors can be introduced. This version: as published, but with correction note added.

I identify a number of errors in Richard Gill’s purported refutation (arXiv:1203.1504) of my disproof of Bell’s theorem. In particular, I point out that his central argument is based, not only on a rather trivial misreading of my counterexample to Bell’s theorem, but also on a simple oversight of a freedom of choice in the orientation of a Clifford algebra. What is innovative and original in my counterexample is thus mistaken for an error, at the expense of the professed universality and generality of Bell’s theorem.

A true quantum reason for why people fib on April first.

Bell’s Theorem rules out many potential reformulations of quantum mechanics, but within a generalized framework, it does not exclude all “locally-mediated” models. Such models describe the correlations between entangled particles as mediated by intermediate parameters which track the particle world-lines and respect Lorentz covariance. These locally-mediated models require the relaxation of an arrow-of-time assumption which is typically taken for granted. Specifically, some of the mediating parameters in these models must functionally depend on measurement settings in their future, i.e., on input parameters associated with later times. This option (often called “retrocausal”) has been repeatedly pointed out in the literature, but the exploration of explicit locally-mediated toy-models capable of describing specific entanglement phenomena has begun only in the past decade. A brief survey of such models is included here. These models provide a continuous and consistent description of events associated with spacetime locations, with aspects that are solved “all-at-once” rather than unfolding from the past to the future. The tension between quantum mechanics and relativity which is usually associated with Bell’s Theorem does not occur here. Unlike conventional quantum models, the number of parameters needed to specify the state of a system does not grow exponentially with the number of entangled particles. The promise of generalizing such models to account for all quantum phenomena is identified as a grand challenge.

A new approach of quantum gravity based on the world function (invariant distance) is presented. The approach takes a relational scalar quantity as a basic variable, conveniently incorporates matter, and facilitates the study of quantum causal structure of spacetime. The core of the approach is an application of Parker’s observation that under a Feynman sum, a gravitational phase can be traded into the Van Vleck-Morette determinant — a functional of the world function. A formula for quantum amplitudes of processes on quantum spacetime is obtained. Quantum gravity not only modifies the form of the matter propagators, but also break them into smaller pieces.

Authors: R. Folk, Yu. Holovatch

Scientific research is and was at all times a transnational activity. In this respect it crosses several borders: national, cultural, and ideological. Even in times when physical borders separated the scientific community, scientists kept their minds open and tried to communicate despite all obstacles. An example of such activities in the field of physics is the travel in the year 1838 of a group of three scientists through the Western Europe: Andreas Ettingshausen (professor at the University of Vienna), August Kunzek (professor at the University of Lviv) and P. Marian Koller (director of the observatory in Chremsminster, Upper Austria).

$155$ years later a vivid scientific exchange between physicists from Austria and Ukraine and in particular between the Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine in Lviv and the Institute for Theoretical Physics of Johannes Kepler University Linz began. This became possible due to programs financed by national institutions, but it had its scientific background in already knotted historic scientific networks, when Lviv was an international center of mathematics and in Vienna the `School of Statistical Thought’ arose.

In this paper, we discuss the above examples of scientific cooperation pursuing several goals: to record less known facts from the history of science in a general culturological context, to trace the rise of studies that resulted, with a span of time, in an emergence of statistical and condensed matter physics, to follow development of multilayer networking structures that join scientists and enable their research. It is our pleasure to submit this paper to the Festschrift devoted to the 60th birthday of a renowned physicist, our good colleague and friend Ihor Mryglod. In fact, his activities contributed a lot into strengthening the networks we describe in this paper.

Coffey, Kevin (2020) On the Ontology of Particle Mass and Energy in Special Relativity. [Preprint]

Koshkin, Sergiy (2020) Wittgenstein, Peirce, and paradoxes of mathematical proof. Analytic Philosophy. ISSN 2153-960X

French, Steven (2020) Metaphysical Underdetermination as a Motivational Device. [Preprint]

Zafiris, Elias and Karakostas, Vassilios (2019) Category-Theoretic Interpretative Framework of the Complementarity Principle in Quantum Mechanics. International Journal of Theoretical Physics, 58. pp. 4208-4234. ISSN 0020-7748

Authors: Andras Patkos

This lecture recalls the memory of Baron Roland Eotvos, an outstanding figure of the experimental exploration of the gravitational interaction.

Authors: Lydia Patton

The multiple detections of gravitational waves by LIGO (the Laser Interferometer Gravitational-Wave Observatory), operated by Caltech and MIT, have been acclaimed as confirming Einstein’s prediction, a century ago, that gravitational waves propagating as ripples in spacetime would be detected. Yunes and Pretorius (2009) investigate whether LIGO’s template-based searches encode fundamental assumptions, especially the assumption that the background theory of general relativity is an accurate description of the phenomena detected in the search. They construct the parametrized post-Einsteinian (ppE) framework in response, which broadens those assumptions and allows for wider testing under more flexible assumptions. Their methods are consistent with work on confirmation and testing found in Carnap (1936), Hempel (1969), and Stein (1992, 1994), with the following principles in common: that confirmation is distinct from testing, and that, counterintuitively, revising a theory’s formal basis can make it more broadly empirically testable. These views encourage a method according to which theories can be made abstract, to define families of general structures for the purpose of testing. With the development of the ppE framework and related approaches, multi-messenger astronomy is a catalyst for deep reasoning about the limits and potential of the theoretical framework of general relativity.

We address estimation of the minimum length arising from gravitational theories. In particular, we provide bounds on precision and assess the use of quantum probes to enhance the estimation performances. At first, we review the concept of minimum length and show how it induces a perturbative term appearing in the Hamiltonian of any quantum system, which is proportional to a parameter depending on the minimum length. We then systematically study the effects of this perturbation on different state preparations for several 1-dimensional systems, and we evaluate the Quantum Fisher Information in order to find the ultimate bounds to the precision of any estimation procedure. Eventually, we investigate the role of dimensionality by analysing the use of two-dimensional square well and harmonic oscillator systems to probe the minimal length. Our results show that quantum probes are convenient resources, providing potential enhancement in precision. Additionally, our results provide a set of guidelines to design possible future experiments to detect minimal length.

We investigate the first law of complexity proposed in arXiv:1903.04511, i.e., the variation of complexity when the target state is perturbed, in more detail. Based on Nielsen’s geometric approach to quantum circuit complexity, we find the variation only depends on the end of the optimal circuit. We apply the first law to gain new insights into the quantum circuits and complexity models underlying holographic complexity. In particular, we examine the variation of the holographic complexity for both the complexity=action and complexity=volume conjectures in perturbing the AdS vacuum with coherent state excitations of a free scalar field. We also examine the variations of circuit complexity produced by the same excitations for the free scalar field theory in a fixed AdS background. In this case, our work extends the existing treatment of Gaussian coherent states to properly include the time dependence of the complexity variation. We comment on the similarities and differences of the holographic and QFT results.

We show that localisation microscopy of multiple weak, incoherent point sources with possibly different intensities in one spatial dimension is equivalent to estimating the amplitudes of a classical mixture of coherent states of a simple harmonic oscillator. This enables us to bound the multi-parameter covariance matrix for an unbiased estimator for the locations in terms of the quantum Fisher information matrix, which we obtained analytically. In the regime of arbitrarily small separations we find it to be no more than rank two — implying that no more than two independent parameters can be estimated irrespective of the number of point sources. We use the eigenvalues of the classical and quantum Fisher information matrices to compare the performance of spatial-mode demultiplexing and direct imaging in localisation microscopy with respect to the quantum limits.

This work provides a comprehensive method to analyze the entanglement between subsystems generated by identical particles that preserves superselection rules (SSR), i.e., particle number SSR (NSSR) for bosons and parity SSR (PSSR) for fermions. Contrary to the common belief that the quantification of identical particles’ entanglement needs some special techniques, it can be treated in a fundamentally equivalent manner to the non-identical particles’ entanglement, which is achieved by the combination of symmetric/exterior algebra (SEA) and microcausality. We also show that the total Hilbert space of identical particles is factorized according to the local distribution of subsystems. This formal correspondence between identical and non-identical particle systems turns out very useful to quantify the non-locality generated by identical particles, such as the maximal Bell inequality violation and the GHJW theorem of identical particles.

Publication date: Available online 15 February 2020

Source: Physics Reports

Author(s): Noemi Frusciante, Louis Perenon

Abstract

Abstract

Contextual emergence was originally proposed as an inter-level relation between different levels of description to describe an epistemic notion of emergence in physics. Here, we discuss the ontic extension of this relation to different domains or levels of physical reality using the properties of temperature and molecular shape (chirality) as detailed case studies. We emphasize the concepts of stability conditions and multiple realizability as key features of contextual emergence. Some broader implications contextual emergence has for the foundations of physics and cognitive and neural sciences are given in the concluding discussion. Relevant facts about algebras of observables are found in the appendices along with an abstract definition of Kubo-Martin-Schwinger states.

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Abstract

Presentists believe that only present things exist. Their theories, at first glance, seem to offer many admirable features: a simple ontology, and a meaningful, objective status for key temporal phenomena, such as the present moment and the passage of time. So intuitive is this theory that, as John Bigelow puts it, presentism was “believed by everyone…until at least the nineteenth century” (1996, p. 35). Yet, in the last 200 years presentism has been beset by criticisms from both physicists and metaphysicians. One of the most significant criticisms is that presentists cannot provide an acceptable system of truthmaking. If there is no past, how can there still be truths about the past? In this paper, I introduce a new theory of presentism, which addresses this problem in a novel way: by simply denying that there are any truths about the past. While prima facie an unintuitive position, I will argue that a sensible presentist philosophy of this kind can be described, so long as it is accompanied by an appropriate system of physics. I will also indicate at certain points that adopting presentism could allow us to understand fundamental physics in new, more intuitive ways. By the end of the paper, I hope to not only show that hard presentism is a defensible theory of time, but also that it could offer a number of advantages to the physicist and the philosopher alike.

Mazurek, Leszek (2020) Division by zero. [Preprint]

Poldrack, Russell A. (2020) The physics of representation. [Preprint]

Potters, Jan (2019) Heuristics versus Norms: On the Relativistic Responses to the Kaufmann Experiments. Studies in History and Philosophy of Modern Physics, 66. pp. 69-89. ISSN 1355-2198