Weekly Papers on Quantum Foundations (19,20)

上午8:00 | Latest Results for Foundations of Physics

Abstract

Based on three common interpretive commitments in general relativity, I raise a conceptual problem for the usual identification, in that theory, of timelike curves as those that represent the possible histories of (test) particles in spacetime. This problem affords at least three different solutions, depending on different representational and ontological assumptions one makes about the nature of (test) particles, fields, and their modal structure. While I advocate for a cautious pluralism regarding these options, I also suggest that re-interpreting (test) particles as field processes offers the most promising route for natural integration with the physics of material phenomena, including quantum theory.

上午8:00 | Latest Results for Foundations of Physics

Abstract

The possibility question concerns the status of possibilities: do they form an irreducible category of the external reality, or are they merely features of our cognitive framework? If fundamental physics is ever to shed light on this issue, it must be done by some future theory that unifies insights of general relativity and quantum mechanics. The paper investigates one programme of this kind, namely the causal sets programme, as it apparently considers alternative developments of a given system. To evaluate this claim, we prove some algebraic facts about the sequential growth of causal sets. These facts tell against alternative developments, given that causal sets are understood as particular events. We thus interpret causal sets as multi-realisable objects, like states. This interpretation, however, is undermined by an argument for the probabilistic constraint of general covariance, as it says that multiple paths along which a causal set is produced are not physically different.

上午8:00 | Latest Results for Foundations of Physics

Abstract

In this paper non-Hausdorff manifolds as potential basic objects of General Relativity are investigated. One can distinguish four stages of identifying an appropriate mathematical structure to describe physical systems: kinematic, dynamical, physical reasonability, and empirical. The thesis of this paper is that in the context of General Relativity, non-Hausdorff manifolds pass the first two stages, as they enable one to define the basic notions of differential geometry needed to pose the problem of the evolution-distribution of matter and are not in conflict with the Einstein equations. With regard to the third stage, various potential conflicts with physical reasonability conditions are considered with a tentative conclusion that non-Hausdorff manifolds are more likely to pass this stage than is typically assumed. When dealing with some of these problems, the modal interpretation of non-Hausdorff manifolds is invoked, according to which they represent bundles of alternative possible spacetimes rather than single spacetimes.

上午8:00 | Latest Results for Foundations of Physics

Abstract

In this paper we describe a novel approach to defining an ontologically fundamental notion of co-presentness that does not go against the tenets of relativity theory. We survey the possible reactions to the problem of the present in relativity theory, introducing a terminological distinction between a static role of the present, which is served by the relation of simultaneity, and a dynamic role of the present, with the corresponding relation of co-presentness. We argue that both of these relations need to be equivalence relations, but they need not coincide. Simultaneity, the sharing of a temporal coordinate, need not have fundamental ontological import, so that a relativizing strategy with respect to simultaneity seems promising. The notion of co-presentness, on the other hand, does have ontological import, and can therefore not be relativized to an observer or to an arbitrarily chosen frame. We argue that a formal representation of indeterminism can provide the structure needed to anchor the relation of co-presentness, and that this addition is in fact congenial to the notion of dynamic time as requiring real (indeterministic) change. The resulting picture is one of an extended dynamic present, implying a formal distinction between static (coordinate) simultaneity and dynamic co-presentness. After working out the basics of our approach in the simpler framework of branching time, we provide our full analysis in the framework of branching space-times, which allows for a formal definition of modal correlations. The spatial extension of the dynamic present can reach as far as the modal correlations do. In the limit, the dynamic present could extend across a maximal space-like hypersurface.

上午8:00 | Latest Results for Foundations of Physics

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.

上午8:00 | Latest Results for Foundations of Physics

Abstract

We call attention to different formulations of how physical laws relate to what is physically possible in the philosophical literature, and argue that it may be the case that determinism fails under one formulation but reigns under the other. Whether this is so depends on our view on the nature of laws, and may also depend on the inter-theoretical relationships among our best physical theories, or so shall we argue.

上午8:00 | Latest Results for Foundations of Physics

Abstract

The meaning and truth conditions for claims about physical modality and causation have been considered problematic since Hume’s empiricist critique. But the underlying semantic commitments that follow from Hume’s empiricism about ideas have long been abandoned by the philosophical community. Once the consequences of that abandonment are properly appreciated, the problems of physical modality and causal locutions fall away, and can be painlessly solved.

下午4:44 | ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsScienceDirect RSShttps://www.sciencedirect.com/journal/studies-in-history-and-philosophy-of-science-part-b-studies-in-history-and-philosophy-of-modern-physicsRSS for NodeWed, 24 Jul 2019 09:46:42 GMTCopyright © 2019 Elsevier Ltd. All rights reservedImprints of the underlying structure of physical theoriesPublication date: Available online 12 July 2019Source: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsAuthor(s): Jorge ManeroAbstractIn the context of scientific realism, this paper intends to provide a formal and accurate description of the structural-based ontology posited by classical mechanics, quantum mechanics and special relativity, which is preserved across the empirical domains of these theories and explain their successful predictions. Along the lines of ontic structural realism, such a description is undertaken by

Publication date: Available online 13 May 2020

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

Author(s): Marij van Strien

下午4:44 | ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsScienceDirect RSShttps://www.sciencedirect.com/journal/studies-in-history-and-philosophy-of-science-part-b-studies-in-history-and-philosophy-of-modern-physicsRSS for NodeWed, 24 Jul 2019 09:46:42 GMTCopyright © 2019 Elsevier Ltd. All rights reservedImprints of the underlying structure of physical theoriesPublication date: Available online 12 July 2019Source: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsAuthor(s): Jorge ManeroAbstractIn the context of scientific realism, this paper intends to provide a formal and accurate description of the structural-based ontology posited by classical mechanics, quantum mechanics and special relativity, which is preserved across the empirical domains of these theories and explain their successful predictions. Along the lines of ontic structural realism, such a description is undertaken by

Publication date: Available online 10 May 2020

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

Author(s): Gabriele Carcassi, Christine A. Aidala

Consider a statistical model with an epistemic restriction such that, unlike in classical mechanics, the allowed distribution of positions is fundamentally restricted by the form of an underlying momentum field. Assume an agent (observer) who wishes to estimate the momentum field given information on the conjugate positions. We discuss a classically consistent, weakly unbiased, best estimation of the momentum field minimizing the mean squared error, based on which the abstract mathematical rules of quantum mechanics can be derived. The results suggest that quantum wave function is not an objective agent-independent attribute of reality, but represents the agent’s best estimation of the momentum, given the positions, under epistemic restriction. Quantum uncertainty and complementarity between momentum and position find their epistemic origin from the trade-off between the mean squared errors of simultaneous estimations of momentum field and mean position, with the Gaussian wave function represents the simultaneous efficient estimations, achieving the Cram\’er-Rao bounds of the associated mean squared errors. We then argue that unitary time evolution and wave function collapse in measurement are normative rules for an agent to update her/his estimation given information on the experimental settings.

下午4:36 | Marian Kupczynski | quant-ph updates on arXiv.org

This short note is an introduction to the slides from our talks given in 2018 during the Advanced School of Quantum Foundations and Quantum Computation in Joao Pessoa , Brazil. In these talks, addressed to participants with a limited knowledge of quantum foundations, we defined locality, causality, randomness, counterfactual definiteness and we explained EPR-Bohm paradoxes. In particular we discussed in great detail various Bell-type inequalities and the implications of their violation in spin polarisation correlation experiments. Finally we explained why and how the predictive completeness of quantum mechanics may be tested by more careful examination of the time-series of experimental data

下午4:36 | Isaac Bowser, Ken Kiers, Erica Mitchell, Joshua Kiers | quant-ph updates on arXiv.org

The distribution of eigenvalues of the wave equation in a bounded domain is known as Weyl’s problem. We describe several computational projects related to the cumulative state number, defined as the number of states having wavenumber up to a maximum value. This quantity and its derivative, the density of states, have important applications in nuclear physics, degenerate Fermi gases, blackbody radiation, Bose-Einstein condensation and the Casimir effect. Weyl’s theorem states that, in the limit of large wavenumbers, the cumulative state number depends only on the volume of the bounding domain and not on its shape. Corrections to this behavior are well known and depend on the surface area of the bounding domain, its curvature and other features. We describe several projects that allow readers to investigate this dependence for three bounding domains – a rectangular box, a sphere, and a circular cylinder. Quasi-one- and two-dimensional systems can be analyzed by considering various limits. The projects have applications in statistical mechanics, but can also be integrated into quantum mechanics, nuclear physics, or computational physics courses.

下午4:36 | Giacomo Sorelli, Nicolas Treps, Frederic Grosshans, Fabrice Boust | quant-ph updates on arXiv.org

In the last decade a lot of research activity focused on the use of quantum entanglement as a resource for remote target detection, i.e. on the design of a quantum radar. The literature on this subject uses tools of quantum optics and quantum information theory, and therefore often results obscure to radar scientists. This review has been written with purpose of removing this obscurity. As such, it recollects the main advances in the quantum radar literature accompanied by a thorough introduction of the quantum optics background necessary for its understanding.

下午4:36 | David Schmid, John H. Selby, Matthew F. Pusey, Robert W. Spekkens | quant-ph updates on arXiv.org

It is useful to have a criterion for when the predictions of an operational theory should be considered classically explainable. Here we take the criterion to be that the theory admits of a generalized-noncontextual ontological model. Existing works on generalized noncontextuality have focused on experimental scenarios having a simple structure, typically, prepare-measure scenarios. Here, we formally extend the framework of ontological models as well as the principle of generalized noncontextuality to arbitrary compositional scenarios. We leverage this process-theoretic framework to prove that, under some reasonable assumptions, every generalized-noncontextual ontological model of a tomographically local operational theory has a surprisingly rigid and simple mathematical structure; in short, it corresponds to a frame representation which is not overcomplete. One consequence of this theorem is that the largest number of ontic states possible in any such model is given by the dimension of the associated generalized probabilistic theory. This constraint is useful for generating noncontextuality no-go theorems as well as techniques for experimentally certifying contextuality. Along the way, we extend known results concerning the equivalence of different notions of classicality from prepare-measure scenarios to arbitrary compositional scenarios. Specifically, we prove a correspondence between the following three notions of classical explainability of an operational theory: (i) admitting a noncontextual ontological model, (ii) admitting of a positive quasiprobability representation, and (iii) being simplex-embeddable.

We study the notion of causal orders for the cases of (classical and quantum) circuits and spacetime events. We show that every circuit can be immersed into a classical spacetime, preserving the compatibility between the two causal structures. Using the process matrix formalism, we analyse the realisations of the quantum switch using 4 and 3 spacetime events in classical spacetimes with fixed causal orders, and the realisation of a gravitational switch with only 2 spacetime events that features superpositions of different gravitational field configurations and their respective causal orders. We show that the current quantum switch experimental implementations do not feature superpositions of causal orders between spacetime events, and that these superpositions can only occur in the context of superposed gravitational fields. We also discuss a recently introduced operational notion of an event, which does allow for superpositions of respective causal orders in flat spacetime quantum switch implementations. We construct two observables that can distinguish between the quantum switch realisations in classical spacetimes, and gravitational switch implementations in superposed spacetimes. Finally, we discuss our results in the light of the modern relational approach to physics.

The Gedankenexperiment advanced by Frauchiger and Renner in their Nature paper is based on an implicit assumption that one can synchronize stochastic measurement intervals between two non-interacting systems. This hypothesis, the author demonstrates, is equivalent to the complete entanglement of these systems. Consequently, Frauchiger and Renner’s postulate Q is too broad and, in general, meaningless. Accurate reformulation of the postulate, Q1 does not seem to entail any paradoxes with measurement. This paper is agnostic with respect to particular interpretations of quantum mechanics. Nor does it refer to the collapse of the wavefunction.

下午4:36 | Steffen Gielen, Lucía Menéndez-Pidal | quant-ph updates on arXiv.org

We study the quantum cosmology of a flat FLRW universe filled with a (free) massless scalar field and a perfect fluid that represents radiation or a cosmological constant whose value is not fixed by the action, as in unimodular gravity. We study two versions of the quantum theory: the first is based on a time coordinate conjugate to the radiation/dark energy matter component, i.e., conformal time (for radiation) or unimodular time. As shown by Gryb and Th\’ebault, this quantum theory achieves a type of singularity resolution; we illustrate this and other properties of this theory. The theory is then contrasted with a second type of quantisation in which the logarithm of the scale factor serves as time, which has been studied in the context of the “perfect bounce” for quantum cosmology. Unlike the first quantum theory, the second one contains semiclassical states that follow classical trajectories and evolve into the singularity without obstruction, thus showing no singularity resolution. We discuss how a complex scale factor best describes the semiclassical dynamics. This cosmological model serves as an illustration of the problem of time in quantum cosmology.

Authors: Wyman Kwok

An indeterministic interpretation of classical physics has been proposed recently, in which the argument relies on the claim that real numbers cannot represent physical reality. This paper aims at showing that the defenses for this claim are fallacious, and hence the argument has a loophole.

下午4:34 | physics.hist-ph updates on arXiv.org

Authors: Emil KhalisiJoachim Gripp

The obscuration of a celestial body that covers another object in the background will be called a “hierarchical eclipse”. The most obvious case is that a star or a planet will be hidden from sight by the moon during a lunar eclipse. We investigate this phenomenon with respect to the region of visibility and periodicity. There exists a parallax field constraining the chances for viewing. A historic account from the Middle Ages is preserved that we analyse from different observational places. Furthermore, we provide a list of events from 0 to 4000 AD. From this, it is apparent that Jupiter is most often involved in such spectacles because its orbit inclination is small. High-inclination orbits reduce the probability of coinciding the occultation with a lunar eclipse.

Authors: Mohammadtaher SafarzadehKenta Hotokezaka

The LIGO/Virgo Scientific Collaboration recently announced the detection of a compact object binary merger, GW190412, as the first asymmetric binary black hole (BBH) merger with mass ratio $q\approx0.25$. Other than the mass ratio, this BBH has shown to have a positive effective spin of around $\chi_{\rm eff}\approx0.28$. Assuming a field formation channel, associating this effective spin to either the primary or the secondary BH each has its implications: If the spin of the BBH comes form the primary BH, it would imply that the angular momentum transport in the formation of massive BHs operates such that high spin massive BHs are born abundantly. If, on the other hand, the spin is due to the secondary BH through tidal spin up processes, one has to note that such processes have very short delay times and low local star formation rate at sufficiently low metallicities. We show that the predicted merger rate density from this channel is $\lesssim 0.3~\rm Gpc^{-3} yr^{-1}$ and in tension with the rather high local merger rate of such systems which we estimate from this single event to be $\sim 2.5^{+3.5}_{-0.5}~\rm Gpc^{-3} yr^{-1}$ (90\% confidence interval). Large natal kicks ($v\gtrsim 500\,{\rm km/s}$) would be required to get such BBHs with in-plane spin component to account for the marginal detection of precession in GW190412. However, this would only exacerbate the tension as the estimated local merger rate would be further decreased. Similarly, the formation of such systems through the dynamical assembly is exceedingly rare, leaving this system a dilemma hard to account for with the currently accepted paradigms of BBH formation.

Authors: Sebastian BahamondeMir FaizalJames Q. QuachRichard A. Norte

We will use Fisher information to properly analyze the quantum weak equivalence principle. We argue that gravitational waves will be partially reflected by superconductors. This will occur as the violation of the weak equivalence principle in Cooper pairs is larger than the surrounding ionic lattice. Such reflections of virtual gravitational waves by superconductors can produce a gravitational Casimir effect, which may be detected using currently available technology.

Authors: Wen-Cong GanFu-Wen Shu

Unitary evolution makes pure state on one Cauchy surface evolve to pure state on another Cauchy surface. Outgoing Hawking radiation is only subsystem on the late Cauchy surface. The requirement that Hawking radiation to be pure amounts to require purity of subsystem when total system is pure. We will see this requirement will lead to firewall even in \textit{flat} spacetime, and thus is invalid. Information is either stored in the entanglement between field modes inside black hole and the outgoing modes or stored in correlation between geometry and Hawking radiation when singularity is resolved by quantum gravity effects. We will give a simple argument that even in semi-classical regime, information is (at least partly) stored in correlation between geometry and Hawking radiation.

Authors: Sergey L. CherkasVladimir L. Kalashnikov

The essay is devoted to the problem of time in the context of quantum cosmology, which acquires a philosophical level to date. At an example of the minisuperspace model, we show that this problem is illusive in the sense that it does not prevent to calculate mean values of the operators over the quantum state of the universe. Contrariwise, the different approaches to the description of these time-dependent mean values give similar results.

下午4:34 | gr-qc updates on arXiv.org

Authors: D. GrumillerM. M. Sheikh-JabbariC. Zwikel

Horizons of black holes or cosmologies are peculiar loci of spacetime where interesting physical effects takes place, some of which are probed by recent (EHT and LIGO) and future experiments (ET and LISA). We discuss that there are boundary degrees of freedom residing at the horizon. We describe their symmetries and their interactions with gravitational waves. This fits into a larger picture of boundary plus bulk degrees of freedom and their interactions in gauge theories. Existence and dynamics of the near horizon degrees of freedom could be crucial to address fundamental questions and apparent paradoxes in black holes physics.

Authors: Yen Chin Ong

The singularity theorems of Hawking and Penrose tell us that singularities are common place in general relativity. Singularities not only occur at the beginning of the Universe at the Big Bang, but also in complete gravitational collapses that result in the formation of black holes. If singularities – except the one at the Big Bang – ever become “naked”, i.e., not shrouded by black hole horizons, then it is expected that problems would arise and render general relativity indeterministic. For this reason, Penrose proposed the cosmic censorship conjecture, which states that singularities should never be naked. Various counterexamples to the conjecture have since been discovered, but it is still not clear under which kind of physical processes one can expect violation of the conjecture. In this short review, I briefly examine some progresses in spacetime singularities and cosmic censorship conjecture. In particular, I shall discuss why we should still care about the conjecture, and whether we should be worried about some of the counterexamples. This is not meant to be a comprehensive review, but rather to give an introduction to the subject, which has recently seen an increase of interest.

Authors: Claudio F. Paganini

We prove in a semi-classical setting that in the context of the Events, Trees, Histories (ETH) approach to Quantum Theory points on closed causal curves are physically indistinguishable. Therefore there is no observation that could be made by an observer to tell any two points on a closed causal curve apart. We thus conclude that closed causal curves have no physical significance and one can assume that time travel will forever remain a fantasy.

2020年5月15日 星期五 上午8:00 | Latest Results for Synthese

Abstract

A common adage runs that, given a theory manifesting symmetries, the syntax of that theory should be modified in order to construct a new theory, from which symmetry-variant structure of the original theory has been excised. Call this strategy for explicating the underlying ontology of symmetry-related models reduction. Recently, Dewar has proposed an alternative to reduction as a means of articulating the ontology of symmetry-related models—what he calls (external) sophistication, in which the semantics of the original theory is modified, and symmetry-related models of that theory are treated as if they are isomorphic. In this paper, we undertake a critical evaluation of sophistication about symmetries—we find the programme underdeveloped in a number of regards. In addition, we clarify the interplay between sophistication about symmetries, and a separate debate to which Dewar has contributed—viz., that between interpretational versus motivational approaches to symmetry transformations.

2020年5月14日 星期四 下午6:00 | Xiaobin Zhao, Yuxiang Yang, and Giulio Chiribella | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Author(s): Xiaobin Zhao, Yuxiang Yang, and Giulio Chiribella

We address the study of quantum metrology enhanced by indefinite causal order, demonstrating a quadratic advantage in the estimation of the product of two average displacements in a continuous variable system. We prove that no setup where the displacements are used in a fixed order can have root-mea…

[Phys. Rev. Lett. 124, 190503] Published Thu May 14, 2020

2020年5月14日 星期四 下午3:18 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
McCutcheon, Randall (2020) On Equitable Non-Anonymous Review. [Preprint]
2020年5月14日 星期四 上午8:00 | Latest Results for Synthese

Abstract

In this paper I interrogate the notion of `debunking conspiracy theories’, arguing that the term `debunk’ carries with it pejorative implications, given that the verb `to debunk’ is commonly understood as `to show the wrongness of a thing or concept’. As such, the notion of `debunking conspiracy theories’ builds in the notion that such theories are not just wring but ought to be shown as being wrong. I argue that we should avoid the term `debunk’ (and other such loaded terms) and focus on investigating conspiracy theories. Looking at recent research work in epistemology on conspiracy theory, I argue that the best way to avoid talk of `debunking’ conspiracy theories is by (a) working with a non-pejorative definition of `conspiracy theory’, and (b) forming communities of inquiry which allow us to investigate the warrant of such theories without the prejudice associated with working with a pejorative definition.

Abstract

Large scale experiments at CERN’s Large Hadron Collider (LHC) rely heavily on computer simulations (CSs), a fact that has recently caught philosophers’ attention. CSs obviously require appropriate modeling, and it is a common assumption among philosophers that the relevant models can be ordered into hierarchical structures. Focusing on LHC’s ATLAS experiment, we will establish three central results here: (a) with some distinct modifications, individual components of ATLAS’ overall simulation infrastructure can be ordered into hierarchical structures. Hence, to a good degree of approximation, hierarchical accounts remain valid at least as descriptive accounts of initial modeling steps. (b) In order to perform the epistemic function Winsberg (in Magnani L, Nersessian N, Thagard P (eds) Model-based reasoning in scientific discovery. Kluwer Academic/Plenum Publishers, New York, pp 255–269, 1999) assigns to models in simulation—generate knowledge through a sequence of skillful but non-deductive transformations—ATLAS’ simulation models have to be considered part of a network rather than a hierarchy, in turn making the associated simulation modeling messy rather than motley. Deriving knowledge-claims from this ‘mess’ requires two sources of justification: (i) holistic validation (also Lenhard and Winsberg in Stud Hist Philos Sci Part B Stud Hist Philos Modern Phys 41(3):253–262, 2010; in Carrier M, Nordmann A (eds) Science in the context of application. Springer, Berlin, pp 115–130, 2011), and (ii) model coherence. As it turns out, (c) the degree of model coherence sets HEP apart from other messy, simulation-intensive disciplines such as climate science, and the reasons for this are to be sought in the historical, empirical and theoretical foundations of the respective discipline.

2020年5月13日 星期三 上午8:00 | Latest Results for Synthese

Abstract

Beginning at the end of the nineteenth century, systematic scientific abstracting played a crucial role in reconfiguring the sciences on an international scale. For mathematicians, the 1931 launch of the Zentralblatt für Mathematik and 1940 launch of Mathematical Reviews marked and intensified a fundamental transformation, not just to the geographic scale of professional mathematics but to the very nature of mathematicians’ research and theories. It was not an accident that mathematical abstracting in this period coincided with an embrace across mathematical research fields of a distinctive form of symbolic and conceptual abstraction. This essay examines the historical, institutional, embodied, and conceptual bases of mathematical abstracting and abstraction in the mid-twentieth century, placing them in historical context within the first half of the twentieth century and then examining their consequences and legacies for the second half of the twentieth century and beyond. Focused on scale, media, and the relationship between mathematical knowledge and its forms of articulation, my analysis connects the changing social structure of modern mathematical research communities to their changing domains of investigation and resources for representation and collective understanding.

2020年5月11日 星期一 上午8:00 | Hui Zhai | Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 11 May 2020; doi:10.1038/s41567-020-0889-6

Generalization of linear response theory to the non-Hermitian case turns dissipation into a new tool for detecting equilibrium phases. The prediction from this theory remarkably agrees with a recent cold atom experiment.

2020年5月8日 星期五 下午4:37 | 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: Available online 4 May 2020

Source: Physics Reports

Author(s): Markus Q. Huber

2020年5月8日 星期五 下午4:37 | gr-qc updates on arXiv.org

Authors: Omar GallegosTonatiuh Matos

We rewrite the Klein-Gordon (KG) equation in an arbitrary space-time transforming it into a generalized Schr\”odinger equation. Then we take the weak field limit and show that this equation has some differences with the traditional Schr\”odinger equation plus a gravitational field. Thus, this procedure shows that the Schr\”odinger equation derived in a covariant manner is different from the traditional one. With this new Schr\”odinger equation, we study the KG equation in a Newtonian space-time to describe the behavior of a scalar particle in an inertial system. We give some examples where it is possible to study the energy levels, effective potential and the wave function of the systems, these results contain the gravitational effects due to the curvature of space-time. We show that it is possible to verify experimentally these effects in a laboratory using non-inertial reference frames.

Authors: Naouel Boulkaboul

In this study, we provide an alternatively reformulated interpretation of Gibbons-Hawking radiation as well as inflation. By using a spacetime quantization procedure, proposed recently by L.C. C\’eleri et al., in anti-de Sitter space we show that Gibbons-Hawking radiation is an intrinsic property of the concerned space, that arises due to the existence of a scalar field whose quanta “carry” a length $l$ (i.e. the radius of the hyperboloid curvature). Furthermore, within the context of Tsallis q-framework, we propose an inflationary model that depends on the non-extensive parameter $q$. The main source of such an inflation is the same scalar field mentioned before. Being constrained by the observational data, the q-parameter along with the rest of the model’s parameters has been used to estimate the time at which inflation ends as well as the reheating temperature. The latter is found to be related to Gibbons-Hawking temperature. Thus, the present model offers an alternative perspective regarding the nature of the cosmic background radiation (CMB).

2020年5月8日 星期五 上午7:54 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Swanson, Noel (2020) Can Quantum Thermodynamics Save Time? [Preprint]
2020年5月8日 星期五 上午5:40 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Swanson, Noel (2020) Antiunitary Equivalence. [Preprint]
2020年5月7日 星期四 上午5:57 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Carcassi, Gabriele and Aidala, Christine A (2019) Hamiltonian mechanics is conservation of information entropy. [Preprint]

Abstract

The empirical coherence problem of quantum gravity is the worry that a theory which does not fundamentally contain local beables located in space and time—such as is arguably the case for certain approaches to quantum gravity—cannot be connected to measurements (which are actually carried out in space and time) and thus has its prospects of being empirically adequate undermined. Spacetime functionalism à la Lam and Wüthrich (Stud Hist Philos Mod Phys 64:39–51, 2018) is said to solve this empirical coherence problem as well as bridging a (putatively) severe conceptual gap between spatiotemporal structures of classical spacetime theories on the one hand, and the (so-called) non-spatiotemporal structures in quantum gravity approaches on the other hand (call this the spatiotemporal gap problem). The aim of this essay is to offer a deflationary account of both the empirical coherence problem and the spatiotemporal gap problem as they are claimed to arise at least prima facie for current theories of quantum gravity by Huggett and Wüthrich (Stud Hist Philos Mod Phys 44(3):276–285, 2013), Lam and Wüthrich (2018) and Le Bihan (Synthese 2019. https://doi.org/10.1007/s11229-019-02449-6). I defend the view that (1) spacetime functionalism is set up to address a problem (the empirical coherence problem) which can usually be solved without it; and that (2) it is wrongly claimed to (dis)solve another problem which for any actual account of quantum gravity is in fact currently non-existent anyway (the spatiotemporal gap problem).

2020年5月5日 星期二 下午3:41 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Ben-Yami, Hanoch The Structure of Space and Time, and Physical Indeterminacy. UNSPECIFIED.
2020年5月4日 星期一 上午8:00 | Latest Results for Foundations of Physics

Abstract

The essence of the path integral method in quantum physics can be expressed in terms of two relations between unitary propagators, describing perturbations of the underlying system. They inherit the causal structure of the theory and its invariance properties under variations of the action. These relations determine a dynamical algebra of bounded operators which encodes all properties of the corresponding quantum theory. This novel approach is applied to non-relativistic particles, where quantum mechanics emerges from it. The method works also in interacting quantum field theories and sheds new light on the foundations of quantum physics.

2020年5月4日 星期一 上午5:21 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Cocco, Lorenzo and Babic, Joshua (2020) A system of axioms for Minkowski spacetime. [Preprint]

Article written by

editor

Please comment with your real name using good manners.

Leave a Reply

You must be logged in to post a comment.