上午10:17 | | | Daniel J. Lum, Michael D. Mazurek, Alexander Mikhaylov, Kristen M. Parzuchowski, Ryan N. Wilson, Ralph Jimenez, Thomas Gerrits, Martin J. Stevens, Marcus T. Cicerone, Charles H. Camp Jr | | | quant-ph updates on arXiv.org |

We demonstrate the preservation of time-energy entanglement of near-IR photons through thick biological media ($\leq$1.55 mm) and tissue ($\leq$ 235 $\mu$m) at room temperature. Using a Franson-type interferometer, we demonstrate interferometric contrast of over 0.9 in skim milk, 2% milk, and chicken tissue. This work supports the many proposed opportunities for nonclassical light in biological imaging and analyses from sub-shot noise measurements to entanglement-enhanced fluorescence imaging, clearly indicating that the entanglement characteristics of photons can be maintained even after propagation through thick, turbid biological samples.

Quantum Contextuality. (arXiv:2102.13036v1 [quant-ph])

上午10:17 | | | Costantino Budroni, Adán Cabello, Otfried Gühne, Matthias Kleinmann, Jan-Åke Larsson | | | quant-ph updates on arXiv.org |

A central result in the foundations of quantum mechanics is the Kochen-Specker theorem. In short, it states that quantum mechanics is in conflict with classical models in which the result of a measurement does not depend on which other compatible measurements are jointly performed. Here, compatible measurements are those that can be performed simultaneously or in any order without disturbance. This conflict is generically called quantum contextuality. In this article, we present an introduction to this subject and its current status. We review several proofs of the Kochen-Specker theorem and different notions of contextuality. We explain how to experimentally test some of these notions and discuss connections between contextuality and nonlocality or graph theory. Finally, we review some applications of contextuality in quantum information processing.

上午10:17 | | | Patryk Lipka-Bartosik, Paul Skrzypczyk | | | quant-ph updates on arXiv.org |

Quantum catalysis is a fascinating concept which demonstrates that certain transformations can only become possible when given access to a specific resource that has to be returned unaffected. It was first discovered in the context of entanglement theory and since then applied in a number of resource-theoretic frameworks, including quantum thermodynamics. Although in that case the necessary (and sometimes also sufficient) conditions on the existence of a catalyst are known, almost nothing is known about the precise form of the catalyst state required by the transformation. In particular, it is not clear whether it has to have some special properties or be finely tuned to the desired transformation. In this work we describe a surprising property of multi-copy states: we show that in resource theories governed by majorization all resourceful states are catalysts for all allowed transformations. In quantum thermodynamics this means that the so-called “second laws of thermodynamics” do not require a fine-tuned catalyst but rather any state, given sufficiently many copies, can serve as a useful catalyst. These analytic results are accompanied by several numerical investigations that indicate that neither a multi-copy form nor a very large dimension catalyst are required to activate most allowed transformations catalytically.

Direct measurements of neutrino mass

上午10:17 | | | 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 25 February 2021

**Source:** Physics Reports

Author(s): Joseph A. Formaggio, André Luiz C. de Gouvêa, R.G. Hamish Robertson

上午10:17 | | | gr-qc updates on arXiv.org |

Authors: Nelson Falcon

The peculiarities of the inverse square law of Newtonian gravity in standard Big Bang Cosmology are discussed. It is shown that the incorporation of an additive term to Newtonian gravitation, as the inverse Yukawa-like field, allows remove the incompatibility between the flatness of the Universe and the density of matter in the Friedmann equation, provides a new approach for dark energy, and enable theoretical deduce the Hubble-Lemaitre’s law. The source of this inverse Yukawa-like field is the ordinary baryonic matter and represents the large-scale contribution of gravity in accordance with the Mach’s principle. It’s heuristically build from a specular reflection of the Yukawa potential, in agreement with astronomical and laboratory observables, result null in the inner solar system, weakly attractive in ranges of interstellar distances, very attractive in distance ranges comparable to the clusters of galaxies and repulsive in cosmic scales. Its implications in the missing mass of Zwicky, Virial Theorem, Kepler’s Third Law in Globular Clusters, rotations curves of galaxies, gravitational redshift and the Jean’s mass are discussed. The inclusion of the inverse Yukawa-like field in Newtonian gravitation predicts a graviton mass of at least 10-64 kg and could be an alternative to the paradigm of non-baryonic dark matter concomitant with the observables of the Big Bang.

上午10:17 | | | gr-qc updates on arXiv.org |

Authors: Jie Jiang, Aofei Sang, Ming Zhang

Recently, it was argued in [Phys. Rev. Lett. {\bf126}, 031102 (2021)] that the WCCC can serve as a constraint to high-order effective field theories. However, we find there exists a key error in their approximate black hole solution. After correcting it, their calculation cannot show the ability of WCCC to constrain the gravitational theories.

上午10:17 | | | gr-qc updates on arXiv.org |

Authors: Robert Brandenberger (McGill University)

I review the “Trans-Planckian Censorship Conjecture” (TCC) and its implications for cosmology, in particular for the inflationary universe scenario. Whereas the inflationary scenario is tightly constrained by the TCC, alternative early universe scenarios are not restricted.

Thermodynamics of Gambling Demons

2021年2月26日 星期五 下午6:00 | | | Gonzalo Manzano, Diego Subero, Olivier Maillet, Rosario Fazio, Jukka P. Pekola, and Édgar Roldán | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Gonzalo Manzano, Diego Subero, Olivier Maillet, Rosario Fazio, Jukka P. Pekola, and Édgar Roldán

In a new version of Maxwell’s demon, the tiny being plays the role of a gambler who knows when to quit.

[Phys. Rev. Lett. 126, 080603] Published Fri Feb 26, 2021

2021年2月26日 星期五 下午4:18 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Cuffaro, Michael E. and Doyle, Emerson P. (2020) Essay Review of Tanya and Jeffrey Bub’s Totally Random: Why Nobody Understands Quantum Mechanics: A Serious Comic on Entanglement. [Preprint]

A pragmatic approach to the ontology of models

2021年2月26日 星期五 上午8:00 | | | Latest Results for Synthese |

**Abstract**

What are scientific models? Philosophers of science have been trying to answer this question during the last three decades by putting forward a number of different proposals. Some say that models are best understood as abstract Platonic objects or fictional entities akin to Sherlock Holmes, while others focus on their mathematical nature and see them as set theoretical structures. Although each account has its own strengths in offering various insights on the nature of models, several objections have been raised against these views which still remain unanswered, making the debate on the ontology of models seem unresolvable. The primary aim of this paper is to show that a large part of these difficulties stems from an inappropriate reading of the main question on the ontology of models as a purely metaphysical question. Building on Carnap, it is argued that the question of the ontology of scientific models is either (i) an internal theoretical question within an already accepted linguistic framework or (ii) an external practical question regarding the choice of the most appropriate form of language in order to describe and explain the practice of scientific modelling. The main implication of this view is that the question of the ontology of models becomes a means of probing other related questions regarding the overall practice of scientific modelling, such as questions on the capacity of models to provide knowledge and the relation of models with background theories.

Non-equilibrium quantum dynamics and formation of the Bose polaron

2021年2月25日 星期四 上午8:00 | | | Jan J. Arlt | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 25 February 2021; doi:10.1038/s41567-021-01184-5

Quantum impurities immersed in a bosonic environment can evolve into polaronic quasiparticles, so-called polarons. Interferometric measurement reveals this transition, which involves three different regimes dominated by few-body and many-body dynamics.

I could do that in my sleep: skilled performance in dreams

2021年2月25日 星期四 上午8:00 | | | Latest Results for Synthese |

**Abstract**

The experience of skilled action occurs in dreams if we take dream reports at face value. However, what these reports indicate requires nuanced analysis. It is uncertain what it means to perform any action in a dream whatsoever. If skilled actions do occur in dreams, this has important implications for both theory of action and theory of dreaming. Here, it is argued that since some dreams generate a convincing, hallucinated world where we have virtual bodies that interact with virtual objects, there is a sense in which we can perform virtual actions. Further, we can also perform *skilfully,* although not all apparent skilful performance is as it seems. Since the dream world is generated by the dreamer’s own mind, it can be difficult to determine whether the dream world simply allows goals to be achieved without the abilities that would be required in a similar waking scenario. Because of this, individual dream reports alone are insufficient to determine what skills are demonstrated in a particular dream. However, taken with evidence from REM sleep behaviour disorder, incompetent dreams, lucid dreams and motor-skill practise, it is likely that skilled virtual dream performance at times involves both opportunity for virtual behaviour and the display of competence. Evidence from cognitive science suggests that dreamers can also lose competence through forgetting and other cognitive incapacities but, more surprisingly, it is possible to gain abilities in a robust sense, consistent with the idea that some dreams, at least, are virtual realities rather than imagination.

Grounding, Conceivability, and the Mind-Body Problem

2021年2月23日 星期二 上午11:41 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Khudairi, Hasen (2016) Grounding, Conceivability, and the Mind-Body Problem. Synthese. pp. 1-8. ISSN 0039-7857

Beyond Causal Explanation: Einstein’s Principle Not Reichenbach’s

2021年2月23日 星期二 上午11:29 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Silberstein, Michael and Stuckey, W. M. (2021) Beyond Causal Explanation: Einstein’s Principle Not Reichenbach’s. In: UNSPECIFIED.

Models of the Nucleus: Incompatible Things, Compatible Processes

2021年2月23日 星期二 上午11:26 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Penn, William (2021) Models of the Nucleus: Incompatible Things, Compatible Processes. [Preprint]

Probing Theoretical Statements with Thought Experiments

2021年2月23日 星期二 上午11:26 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

El Skaf, Rawad (2021) Probing Theoretical Statements with Thought Experiments. Synthese. ISSN 1573-0964

]]>上午7:49 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Fraser, Doreen (2021) Review of Mark Wilson, Physics Avoidance. [Preprint]

上午7:49 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Chen, Eddy Keming (2021) Fundamental Nomic Vagueness. [Preprint]

2021年2月20日 星期六 上午9:56 | | | physics.hist-ph updates on arXiv.org |

Authors: Wolfgang Bietenholz

A century ago Srinivasa Ramanujan – the great self-taught Indian genius of mathematics – died, shortly after returning from Cambridge, UK, where he had collaborated with Godfrey Hardy. Ramanujan contributed numerous outstanding results to different branches of mathematics, like analysis and number theory, with a focus on special functions and series. Here we refer to apparently weird values which he assigned to two simple divergent series, $\sum_{n \geq 1} n$ and $\sum_{n \geq 1} n^{3}$. These values are sensible, however, as analytic continuations, which correspond to Riemann’s $\zeta$-function. Moreover, they have applications in physics: we discuss the vacuum energy of the photon field, from which one can derive the Casimir force, which has been experimentally measured. We also discuss its interpretation, which remains controversial. This is a simple way to illustrate the concept of renormalization, which is vital in quantum field theory.

Agreement between observers: a physical principle?. (arXiv:2102.08966v1 [quant-ph])

2021年2月20日 星期六 上午9:56 | | | Patricia Contreras-Tejada, Giannicola Scarpa, Aleksander M. Kubicki, Adam Brandenburger, Pierfranceso La Mura | | | quant-ph updates on arXiv.org |

Is the world quantum? An active research line in quantum foundations is devoted to exploring what constraints can rule out the post-quantum theories that are consistent with experimentally observed results. We explore this question in the context of epistemics, and ask whether agreement between observers can serve as a physical principle that must hold for any theory of the world. Aumann’s seminal Agreement Theorem states that two (classical) agents cannot agree to disagree. We propose an extension of this theorem to no-signaling settings. In particular, we establish an Agreement Theorem for quantum agents, while we construct examples of (post-quantum) no-signaling boxes where agents can agree to disagree. The PR box is an extremal instance of this phenomenon. These results make it plausible that agreement between observers might be a physical principle, while they also establish links between the fields of epistemics and quantum information that seem worthy of further exploration.

2021年2月20日 星期六 上午9:56 | | | Andrei Khrennikov | | | quant-ph updates on arXiv.org |

In quantum physics, the notion of contextuality has a variety of interpretations which are typically associated with the names of their inventors, say Bohr, Bell, Kochen and Specker, and recently Dzhafarov. In fact, Bohr was the first who pointed to contextuality of quantum measurements as a part of formulation of his principle of complementarity. (Instead of “contextuality”, he considered dependence on “experimental conditions.”) Unfortunately, the contextuality counterpart of the complementarity principle was overshadowed by the issue of incompatibility of observables. And the interest for contextuality of quantum measurements rose again only in connection with the Bell inequality. The original Bohr’s contextuality, as contextuality of each quantum measurement, was practically forgotten. It was highlighted in the works of the author of this paper, with applications both to physics and cognition. In this note, the theory of open quantum systems is applied to formalization of Bohr’s contextuality within the the scheme of indirect measurements. This scheme is widely used in quantum information theory and it leads to the theory of quantum instruments (Davis-Lewis-Ozawa). In this scheme, Bohr’s viewpoint on contextuality of quantum measurements is represented in the formal mathematical framework.

The Wavefunction of Continuous-Time Recurrent Neural Networks. (arXiv:2102.09399v1 [cs.LG])

2021年2月20日 星期六 上午9:56 | | | Ikjyot Singh Kohli, Michael C. Haslam | | | quant-ph updates on arXiv.org |

In this paper, we explore the possibility of deriving a quantum wavefunction for continuous-time recurrent neural network (CTRNN). We did this by first starting with a two-dimensional dynamical system that describes the classical dynamics of a continuous-time recurrent neural network, and then deriving a Hamiltonian. After this, we quantized this Hamiltonian on a Hilbert space $\mathbb{H} = L^2(\mathbb{R})$ using Weyl quantization. We then solved the Schrodinger equation which gave us the wavefunction in terms of Kummer’s confluent hypergeometric function corresponding to the neural network structure. Upon applying spatial boundary conditions at infinity, we were able to derive conditions/restrictions on the weights and hyperparameters of the neural network, which could potentially give insights on the the nature of finding optimal weights of said neural networks.

2021年2月20日 星期六 上午9:56 | | | A. D. Correia, H. T. C. Stoof, M. Moortgat | | | quant-ph updates on arXiv.org |

Extended versions of the Lambek Calculus currently used in computational linguistics rely on unary modalities to allow for the controlled application of structural rules affecting word order and phrase structure. These controlled structural operations give rise to derivational ambiguities that are missed by the original Lambek Calculus or its pregroup simplification. Proposals for compositional interpretation of extended Lambek Calculus in the compact closed category of FVect and linear maps have been made, but in these proposals the syntax-semantics mapping ignores the control modalities, effectively restricting their role to the syntax. Our aim is to turn the modalities into first-class citizens of the vectorial interpretation. Building on the directional density matrix semantics, we extend the interpretation of the type system with an extra spin density matrix space. The interpretation of proofs then results in ambiguous derivations being tensored with orthogonal spin states. Our method introduces a way of simultaneously representing co existing interpretations of ambiguous utterances, and provides a uniform framework for the integration of lexical and derivational ambiguity.

2021年2月20日 星期六 上午9:56 | | | gr-qc updates on arXiv.org |

Authors: Sachin Pandey, Narayan Banerjee

This work deals with the violation or retention of symmetries associated with the self-adjoint extension of the Hamiltonian for homogeneous but anisotropic Bianchi I cosmological model. This extension is required to make sure the quantum evolution is unitary. It is found that the scale invariance is lost, but the Noether symmetries are preserved.

2021年2月20日 星期六 上午9:56 | | | gr-qc updates on arXiv.org |

Authors: Sander M Vermeulen, Lorenzo Aiello, Aldo Ejlli, William L Griffiths, Alasdair L James, Katherine L Dooley, Hartmut Grote

Theories of quantum gravity based on the holographic principle predict the existence of quantum fluctuations of distance measurements that accumulate and exhibit correlations over macroscopic distances. This paper models an expected signal due to this phenomenology, and details the design and estimated sensitivity of co-located twin table-top 3D interferometers being built to measure or constrain it. The experiment is estimated to be sensitive to displacements $\sim10^{-19}\,\rm{m}/\sqrt{\rm{Hz}}$ in a frequency band between 1 and 250 MHz, surpassing previous experiments and enabling the possible observation of quantum gravity phenomena. The experiment will also be sensitive to MHz gravitational waves and various dark matter candidates.

Quick thinking: how Einstein did (and did not) refute the ether frame of reference

2021年2月20日 星期六 上午8:00 | | | Latest Results for Synthese |

**Abstract**

This paper addresses and proposes to resolve a longstanding problem in the philosophy of physics: whether and in what sense Albert Einstein’s *Chasing the Light* thought experiment was significant in the development of the theory of special relativity. Although Einstein granted this thought experiment pride of place in his 1949 *Autobiographical Notes*, philosophers and physicists continue to debate about what, if anything, the experiment establishes. I claim that we ought to think of *Chasing the Light* as Einstein’s first attempt to problematize the very idea of the electromagnetic ether frame, and that it thereby contributed to his eventual adoption of one of special relativity’s two foundational axioms: the “light postulate”. This interpretation requires the assumption that Einstein had presupposed special relativity’s other axiom, the “principle of relativity”, when initially considering *Chasing the Light*. This argument is novel insofar as it provides evidence that such a presupposition by Einstein is both conceptually and historically plausible. Moreover, this paper directly challenges John D. Norton’s compelling claim that *Chasing the Light* is best understood as a refutation of emission theories of light propagation; while both interpretations of the experiment are conceptually coherent, I argue that the interpretation found in this paper is supported more straightforwardly by historical evidence.

The visibility of philosophy of science in the sciences, 1980–2018

2021年2月19日 星期五 上午8:00 | | | Latest Results for Synthese |

**Abstract**

In this paper, we provide a macro level analysis of the visibility of philosophy of science in the sciences over the last four decades. Our quantitative analysis of publications and citations of philosophy of science papers, published in 17 main journals representing the discipline, contributes to the longstanding debate on the influence of philosophy of science on the sciences. It reveals the global structure of relationships that philosophy of science maintains with science, technology, engineering and mathematics (STEM) and social sciences and humanities (SSH) fields. Explored at the level of disciplines, journals and authors, this analysis of the relations between philosophy of science and a large and diversified array of disciplines allows us to answer several questions: what is the degree of openness of various disciplines to the specialized knowledge produced in philosophy of science? Which STEM and SSH fields and journals have privileged ties with philosophy of science? What are the characteristics, in terms of citation and publication patterns, of authors who get their philosophy of science papers cited outside their field? Complementing existing qualitative inquiries on the influence of specific authors, concepts or topics of philosophy of science, the bibliometric approach proposed in this paper offers a comprehensive portrait of the multiple relationships that links philosophy of science to the sciences.

2021年2月18日 星期四 下午6:00 | | | Zhibo Hou, Yan Jin, Hongzhen Chen, Jun-Feng Tang, Chang-Jiang Huang, Haidong Yuan, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Zhibo Hou, Yan Jin, Hongzhen Chen, Jun-Feng Tang, Chang-Jiang Huang, Haidong Yuan, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo

The Heisenberg scaling, which scales as N−1 in terms of the number of particles or T−1 in terms of the evolution time, serves as a fundamental limit in quantum metrology. Better scalings, dubbed as “super-Heisenberg scaling,” however, can also arise when the generator of the parameter involves many-…

[Phys. Rev. Lett. 126, 070503] Published Thu Feb 18, 2021

Probing theoretical statements with thought experiments

2021年2月18日 星期四 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Many thought experiments (TEs) are used to probe theoretical statements. One crucial strategy for doing this, or so I will argue, is the following. A TE reveals an inconsistency in part of our previously held, sometimes empirically well-established, theoretical statements. A TEer or her critic then proposes a resolution in the form of a conjecture, a hypothesis that merits further investigation. To explore this characterisation of the epistemic function of such TEs, I clarify the nature of the inconsistencies revealed by TEs, and how TEs reveal and resolve them. I argue that this can be done without settling the question of which cognitive processes are involved in performing a TE; be they propositional or non-propositional. The upshot is that TEs’ reliability, like real experiments, is to be found, in part, in their replicability by the epistemic community, not in their cognitive underpinnings.

2021年2月17日 星期三 下午2:43 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Dewar, Neil (2020) On Absolute Units. [Preprint]

A critical analysis of Markovian monism

2021年2月16日 星期二 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Free Energy Principle underlies a unifying framework that integrates theories of origins of life, cognition, and action. Recently, FEP has been developed into a Markovian monist perspective (Friston et al. in BC 102: 227–260, 2020). The paper expresses scepticism about the validity of arguments for Markovian monism. The critique is based on the assumption that Markovian models are scientific models, and while we may defend ontological theories about the nature of scientific models, we could not read off metaphysical theses about the nature of target systems (self-organising conscious systems, in the present context) from our theories of nature of scientific models (Markov blankets). The paper draws attention to different ways of understanding Markovian models, as material entities, fictional entities, and mathematical structures. I argue that none of these interpretations contributes to the defence of a metaphysical stance (either in terms of neutral monism or reductive physicalism). This is because scientific representation is a sophisticated process, and properties of Markovian models—such as the property of being neither physical nor mental—could not be projected onto their targets to determine the ontological properties of targets easily.

Mathematical Anti-Realism and Explanatory Structure

2021年2月16日 星期二 上午7:17 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Whittle, Bruno (2021) Mathematical Anti-Realism and Explanatory Structure. [Preprint]

Sensitive spin seeks single magnon

2021年2月15日 星期一 上午8:00 | | | Sophia E. Economou | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 15 February 2021; doi:10.1038/s41567-021-01176-5

A quantum dot has been used to detect a single excitation among the tens of thousands of atomic nuclear spins comprising it. This result is an important step towards treating nuclear spins as a quantum memory rather than a troublesome source of noise.

]]>上午10:05 | | | Yunzhao Wang, Kyrylo Snizhko, Alessandro Romito, Yuval Gefen, Kater Murch | | | quant-ph updates on arXiv.org |

Measurement plays a quintessential role in the control of quantum systems. Beyond initialization and readout which pertain to projective measurements, weak measurements in particular, through their back-action on the system, may enable various levels of coherent control. The latter ranges from observing quantum trajectories to state dragging and steering. Furthermore, just like the adiabatic evolution of quantum states that is known to induce the Berry phase, sequential weak measurements may lead to path-dependent geometric phases. Here we measure the geometric phases induced by sequences of weak measurements and demonstrate a topological transition in the geometric phase controlled by measurement strength. This connection between weak measurement induced quantum dynamics and topological transitions reveals subtle topological features in measurement-based manipulation of quantum systems. Our protocol could be implemented for classes of operations (e.g. braiding) which are topological in nature. Furthermore, our results open new horizons for measurement-enabled quantum control of many-body topological states.

Measuring Topological Order. (arXiv:2102.05677v1 [cond-mat.str-el])

上午10:05 | | | Parsa Bonderson | | | quant-ph updates on arXiv.org |

The topological order of a (2+1)D topological phase of matter is characterized by its chiral central charge and a unitary modular tensor category that describes the universal fusion and braiding properties of its anyonic quasiparticles. I discuss the topologically invariant quantities associated with these and identify ones that are useful for determining the topological order. I propose a variety of physical experiments that probe these quantities and detail the relation of the measured data to the topological invariants.

What makes a particle detector click. (arXiv:2102.05734v1 [quant-ph])

上午10:05 | | | Erickson Tjoa, Irene López Gutiérrez, Allison Sachs, Eduardo Martín-Martínez | | | quant-ph updates on arXiv.org |

We highlight fundamental differences in the models of light-matter interaction between the behaviour of Fock state detection in free space versus optical cavities. To do so, we study the phenomenon of resonance of detectors with Fock wavepackets as a function of their degree of monochromaticity, the number of spatial dimensions, the linear or quadratic nature of the light-matter coupling, and the presence (or absence) of cavity walls in space. In doing so we show that intuition coming from quantum optics in cavities does not straightforwardly carry to the free space case. For example, in $(3+1)$ dimensions the detector response to a Fock wavepacket will go to zero as the wavepacket is made more and more monochromatic and in coincidence with the detector’s resonant frequency. This is so even though the energy of the free-space wavepacket goes to the expected finite value of $\hbar\Omega$ in the monochromatic limit. This is in contrast to the behaviour of the light-matter interaction in a cavity (even a large one) where the probability of absorbing a Fock quantum is maximized when the quantum is more monochromatic at the detector’s resonance frequency. We trace this crucial difference to the fact that monochromatic Fock states are not normalizable in the continuum, thus physical Fock states need to be constructed out of normalizable wavepackets whose energy density goes to zero in the monochromatic limit as they get spatially delocalized.

Witnessing Wigner Negativity. (arXiv:2102.06193v1 [quant-ph])

上午10:05 | | | Ulysse Chabaud, Pierre-Emmanuel Emeriau, Frédéric Grosshans | | | quant-ph updates on arXiv.org |

Negativity of the Wigner function is arguably one of the most striking non-classical features of quantum states. Beyond its fundamental relevance, it is also a necessary resource for quantum speedup with continuous variables. As quantum technologies emerge, the need to identify and characterize the resources which provide an advantage over existing classical technologies becomes more pressing. Here we derive witnesses for Wigner negativity of quantum states, based on fidelities with Fock states, which can be reliably measured using standard detection setups. They possess a threshold expected value indicating whether the measured state exhibits the desired property or not. We phrase the problem of finding the threshold values for our witnesses as an infinite-dimensional linear optimisation. By relaxing and restricting the corresponding linear programs, we derive two hierarchies of semidefinite programs, which provide numerical sequences of increasingly tighter upper and lower bounds for the threshold values. We further show that both sequences converge to the threshold value. Moreover, our witnesses form a complete family – each Wigner negative state is detected by at least one witness – thus providing a reliable method for experimentally witnessing Wigner negativity of quantum states from few measurements. From a foundational perspective, our work provides insights on the set of positive Wigner functions which still lacks a proper characterisation.

Positivity Bounds without Boosts. (arXiv:2102.05683v1 [hep-th])

上午10:05 | | | gr-qc updates on arXiv.org |

Authors: Tanguy Grall, Scott Melville

We derive the first positivity bounds for low-energy Effective Field Theories (EFTs) that are not invariant under Lorentz boosts. “Positivity bounds” are the low-energy manifestation of certain fundamental properties in the UV — to date they have been used to constrain a wide variety of EFTs, however since all of the existing bounds require Lorentz invariance they are not directly applicable when this symmetry is broken, such as for most cosmological and condensed matter systems. From the UV axioms of unitarity, causality and locality, we derive an infinite family of bounds which (derivatives of) the $2\to2$ EFT scattering amplitude must satisfy even when Lorentz boosts are broken (either spontaneously or explicitly). We apply these bounds to the leading-order EFT of both a superfluid and the scalar fluctuations produced during inflation, comparing in the latter case with the current observational constraints on primordial non-Gaussianity.

上午10:05 | | | gr-qc updates on arXiv.org |

Authors: Caroline Jonas, Jean-Luc Lehners

The no-boundary proposal is a theory of the initial conditions of the universe formulated in semi-classical gravity, and relying on the existence of regular (complex) solutions of the equations of motion. We show by explicit computation that regular no-boundary solutions are modified, but not destroyed, upon inclusion of expected quantum gravity corrections that involve higher powers of the Riemann tensor as well as covariant derivatives thereof. We illustrate our results with examples drawn from string theory. Our findings provide a crucial self-consistency test of the no-boundary framework.

An order-unity correction to Hawking radiation. (arXiv:2102.04930v2 [hep-th] UPDATED)

上午10:05 | | | gr-qc updates on arXiv.org |

Authors: Eanna E Flanagan

When a black hole first forms, the properties of the emitted radiation as measured by observers near future null infinity are very close to the 1974 prediction of Hawking. However, deviations grow with time, and become of order unity after a time $t \sim M_i^{7/3}$, where $M_i$ is the initial mass in Planck units. After an evaporation time the corrections are large: the angular distribution of the emitted radiation is no longer dominated by low multipoles, with an exponential fall off at high multipoles. Instead, the radiation is redistributed as a power law spectrum over a broad range of angular scales, all the way down to the scale $\Delta \theta \sim 1/M_i$, beyond which there is exponential falloff. This effect is is a quantum gravitational effect, whose origin is the spreading of the wavefunction of the black hole’s center of mass location caused by the kicks of the individual outgoing quanta, discovered by Page in 1980. The modified angular distribution of the Hawking radiation has an important consequence: the number of soft hair modes that can effectively interact with outgoing Hawking quanta increases from the handful of modes at low multipoles $l$, to a large number of modes, of order $\sim M_i^2$. We argue that this change unlocks the Hawking-Perry-Strominger mechanism for purifying the Hawking radiation.

A pragmatic approach to the ontology of models

2021年2月12日 星期五 上午9:38 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Antoniou, Antonis (2021) A pragmatic approach to the ontology of models. [Preprint]

Is the problem of molecular structure just the quantum measurement problem?

2021年2月12日 星期五 上午9:37 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Fortin, Sebastian and Lombardi, Olimpia (2021) Is the problem of molecular structure just the quantum measurement problem? [Preprint]

2021年2月11日 星期四 上午8:00 | | | Paul Skrzypczyk | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 11 February 2021; doi:10.1038/s41567-021-01177-4

Two experiments using entangled photons have successfully generated more randomness than consumed — at a level of security that is all but certain. They did so by exploiting non-locality, one of the most counterintuitive aspects of quantum mechanics.

2021年2月11日 星期四 上午4:45 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Thebault, Karim P Y (2021) On Mach On Time. [Preprint]

2021年2月11日 星期四 上午4:42 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Glick, David (2021) Book Review: French, S., & Saatsi, J. (Eds.). (2020). Scientific Realism and the Quantum. Oxford University Press. [Preprint]

Why Humean explanations are not circular

2021年2月11日 星期四 上午4:41 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Duguid, Callum (2021) Why Humean explanations are not circular.

On French on Theories and Representation

2021年2月11日 星期四 上午4:40 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Lutz, Sebastian (2021) On French on Theories and Representation. [Preprint]

Postselection-Free Entanglement Dynamics via Spacetime Duality

2021年2月9日 星期二 下午6:00 | | | Matteo Ippoliti and Vedika Khemani | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Matteo Ippoliti and Vedika Khemani

A protocol based on space-time duality is used to find the purity of a quantum state for simulations of a class of nonunitary circuits, without any postselection.

[Phys. Rev. Lett. 126, 060501] Published Tue Feb 09, 2021

Why understanding-why is contrastive

2021年2月9日 星期二 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Contrastivism about interrogative understanding is the view that ‘S understands why *p*’ posits a three-place epistemic relation between a subject S, a fact *p*, and an alternative to *p*, *q*. This thesis stands in stark opposition to the natural idea that a subject S can be said to understand why *p* *simpliciter*. I argue that contrastivism offers the best explanation for the fact that evaluations of the form ‘S understands why *p*’ vary depending on the alternatives to *p* under consideration. I also show that contrastivism offers valuable resources with which to explain the gradability of interrogative understanding attributions, as well as the sensitivity of these attributions to the perceived degree of epistemic demandingness of different contexts.

On the possibility of non-eternalism without absolute simultaneity

2021年2月8日 星期一 上午8:00 | | | Latest Results for Synthese |

**Abstract**

It has been argued that the standard formulation of the Special Theory of Relativity (hereafter STR) is not only incompatible with presentism, but also strongly indicates the truth of eternalism. We should, however, distinguish two claims concerning the ontological implications of STR: (1) STR is inconsistent with every ontology which requires an absolute relation of simultaneity; and (2) STR implies that eternalism is the only possible ontology of time. There have been a wide range of responses designed to reject these claims, both jointly and independently. For example, one way of rejecting claim (2) is by rejecting claim (1): thus, one would argue that STR can be revised or interpreted in such a way that it allows an absolute relation of simultaneity. Another way of rejecting claim (2) is by questioning the equivalency of the relation ‘being real as of’ (a relation known in the literature as relation R). The main purpose of this paper is to raise a new line of objection against concluding eternalism from the relativity of simultaneity. I argue that there is a way to deny claim (2) without denying claim (1) and also without denying the equivalency of relation R. The argument which I present rests on a metaphysical assumption concerning the relation of simultaneity (hereafter the SIM): the assumption that the SIM holds basically between space–time points as opposed to holding basically between events.

2021年2月7日 星期日 上午10:19 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Heinrich, Werner F. (2021) Why Newton’s G is not a universal Constant of Nature A reanalysis of Cavendish’s experiment to determine the density of the Earth. [Preprint]

Expanding the Empirical Realm: Constructive Empiricism and Augmented Observation

2021年2月7日 星期日 上午10:16 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Dellsén, Finnur (2021) Expanding the Empirical Realm: Constructive Empiricism and Augmented Observation. [Preprint]

Are there really no such things as theories?

2021年2月7日 星期日 上午10:15 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Dellsén, Finnur (2021) Are there really no such things as theories? [Preprint]

Identical Particles in Quantum Mechanics: Against the Received View

2021年2月7日 星期日 上午10:15 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Dieks, Dennis (2020) Identical Particles in Quantum Mechanics: Against the Received View. [Preprint]

]]>This is a dialogue between Huw Price and Travis Norsen, loosely inspired by a letter that Price received from J. S. Bell in 1988. The main topic of discussion is Bell’s views about retrocausal approaches to quantum theory, and their relevance to contemporary issues.

]]>上午10:10 | | | V. Vilasini | | | quant-ph updates on arXiv.org |

This thesis reports progress in the analysis of causality and multi-agent logical paradoxes in quantum and post-quantum theories. These research areas are highly relevant for the foundations of physics as well as the development of quantum technologies. In the first part, focussing on causality, we develop techniques for using generalised entropies to analyse distinctions between classical and non-classical causal structures. We derive new properties of Tsallis entropies of systems that follow from the relevant causal structure, and apply these to obtain new necessary constraints for classicality in the Triangle causal structure. Supplementing the method with the post-selection technique, we provide evidence that Shannon and Tsallis entropic constraints are insufficient for detecting non-classicality in Bell scenarios with non-binary outcomes. This points to the need for better methods of characterising correlations in non-classical causal structures. Further, we investigate the relationships between causality and space-time by developing a framework for modelling cyclic and fine-tuned influences in non-classical theories. We derive necessary and sufficient conditions for such causal models to be compatible with a space-time structure and for ruling out operationally detectable causal loops. In particular, this provides an operational framework for analysing post-quantum theories admitting jamming non-local correlations. In the second part, we investigate multi-agent logical paradoxes such as the Frauchiger-Renner paradox and develop a framework for analysing such paradoxes in arbitrary physical theories. Applying this to box world, a post-quantum theory, we derive a stronger paradox that does not rely on post-selection. Our results reveal that reversible evolution of agents’ memories is not necessary for deriving multi-agent paradoxes, and that certain forms of contextuality might be.

The outcomes of measurements in the de Broglie-Bohm theory. (arXiv:2102.02519v1 [quant-ph])

上午10:10 | | | G. Tastevin, F. Laloë | | | quant-ph updates on arXiv.org |

Within the de Broglie-Bohm (dBB) theory, the measurement process is usually discussed only in terms of the effect of the Bohmian positions of the measured system S, while the effects of the Bohmian positions associated with the measurements apparatus M are ignored. This article shows that the latter variables actually play an essential role in the determination of the result. Indeed, in many cases, the result of measurement is practically independent of the initial value of a Bohmian position associated with S, and determined only by those of M. The measurement then does not reveal the value of any pre-existing variable attached to S, but just the initial state of the measurement apparatus. Quantum contextuality then appears with particular clarity as a consequence of the dBB dynamics for entangled systems.

Times of Arrival and Gauge Invariance. (arXiv:2102.02661v1 [quant-ph])

上午10:10 | | | Siddhant Das, Markus Nöth | | | quant-ph updates on arXiv.org |

We revisit the arguments underlying two well-known arrival-time distributions in quantum mechanics, viz., the Aharonov-Bohm and Kijowski (ABK) distribution, applicable for freely moving particles, and the quantum flux (QF) distribution. An inconsistency in the original axiomatic derivation of Kijowski’s result is pointed out, along with an inescapable consequence of the “negative arrival times” inherent to this proposal (and generalizations thereof). The ABK free-particle restriction is lifted in a discussion of an explicit arrival-time setup featuring a charged particle moving in a constant magnetic field. A natural generalization of the ABK distribution is in this case shown to be critically gauge-dependent. A direct comparison to the QF distribution, which does not exhibit this flaw, is drawn (its acknowledged drawback concerning the quantum backflow effect notwithstanding).

上午10:10 | | | Paul Raymond-Robichaud | | | quant-ph updates on arXiv.org |

We provide a framework that describe all local-realistic theories and all no-signalling theories. We show that every local-realistic theory is a no-signalling theory. We also show that every no-signalling theory with invertible dynamics has a local-realistic model. This applies in particular to unitary quantum theory.

上午10:10 | | | Pablo L. Saldanha | | | quant-ph updates on arXiv.org |

In the seminal works from Santos and Gozalo [Europhys. Lett. $\mathbf{45}$, 418 (1999)] and Marletto and Vedral [Phys. Rev. Lett. $\mathbf{125}$, 040401 (2020)], it is shown how the Aharonov-Bohm effect can be described as the result of an exchange of virtual photons between the solenoid and the quantum charged particle along its propagation through the interferometer, where both the particle and the solenoid interact locally with the quantum electromagnetic field. This interaction results in a local and gauge-independent phase generation for the particle propagation in each path of the interferometer. Here we improve the cited treatments by using the quantum electrodynamics formalism in the Lorentz gauge, with a manifestly gauge-independent Hamiltonian for the interaction and the presence of virtual longitudinal photons. Only with this more complete and gauge-independent treatment it is possible to justify the acquired phases for interferometers with arbitrary geometries, and this is an advantage of our treatment. We also extend the results to the electric version of the Aharonov-Bohm effect. Finally, we propose an experiment that could test the locality of the Aharonov-Bohm phase generation.

Quantum Counterpart of Classical Equipartition of Energy. (arXiv:1911.06570v3 [quant-ph] UPDATED)

上午10:10 | | | Jerzy Łuczka | | | quant-ph updates on arXiv.org |

It is shown that the recently proposed quantum analogue of classical energy equipartition theorem for two paradigmatic, exactly solved models (i.e., a free Brownian particle and a dissipative harmonic oscillator) also holds true for all quantum systems which are composed of an arbitrary number of non-interacting or interacting particles, subjected to any confining potentials and coupled to thermostat with arbitrary coupling strength.

A time-symmetric formulation of quantum entanglement. (arXiv:2003.07183v3 [quant-ph] UPDATED)

上午10:10 | | | Michael B. Heaney | | | quant-ph updates on arXiv.org |

I numerically simulate and compare the entanglement of two quanta using the conventional formulation of quantum mechanics and a time-symmetric formulation that has no collapse postulate. The experimental predictions of the two formulations are identical, but the entanglement predictions are significantly different. The time-symmetric formulation reveals an experimentally testable discrepancy in the original quantum analysis of the Hanbury Brown-Twiss experiment, suggests solutions to some parts of the nonlocality and measurement problems, fixes known time asymmetries in the conventional formulation, and answers Bell’s question “How do you convert an ‘and’ into an ‘or’?'”

Time-travelling billiard ball clocks: a quantum model. (arXiv:2007.12677v2 [quant-ph] UPDATED)

上午10:10 | | | Lachlan G. Bishop, Fabio Costa, Timothy C. Ralph | | | quant-ph updates on arXiv.org |

General relativity predicts the existence of closed timelike curves (CTCs), along which an object could travel to its own past. A consequence of CTCs is the failure of determinism, even for classical systems: one initial condition can result in multiple evolutions. Here we introduce a new quantum formulation of a classic example, where a billiard ball can travel along two possible trajectories: one unperturbed and one, along a CTC, where it collides with its past self. Our model includes a vacuum state, allowing the ball to be present or absent on each trajectory, and a clock, which provides an operational way to distinguish the trajectories. We apply the two foremost quantum theories of CTCs to our model: Deutsch’s model (D-CTCs) and post-selected teleportation (P-CTCs). We find that D-CTCs reproduce the classical solution multiplicity in the form of a mixed state, while P-CTCs predict an equal superposition of the two trajectories, supporting a conjecture by Friedman et al. [Phys. Rev. D 42, 1915 (1990)].

Schr\”odinger’s Cat. (arXiv:2102.01808v2 [quant-ph] UPDATED)

上午10:10 | | | Matthew F. Brown | | | quant-ph updates on arXiv.org |

The basic idea here is that observation (or one’s experience) is fundamental and the `atomic world’ is postulated as the source of such observation. Once this source has been inferred to exist one may attempt to explicitly derive its structure in such a way that the observation itself can be reproduced. And so here is a purely quantum mechanical model of observation coupled to its supposed source, and the observation itself is realised as a projection of this quantum system.

Lapsing Quickly into Fatalism: Bell on Backward Causation. (arXiv:2102.02392v1 [quant-ph])

上午9:24 | | | physics.hist-ph updates on arXiv.org |

Authors: Travis Norsen, Huw Price

This is a dialogue between Huw Price and Travis Norsen, loosely inspired by a letter that Price received from J. S. Bell in 1988. The main topic of discussion is Bell’s views about retrocausal approaches to quantum theory, and their relevance to contemporary issues.

Why Do You Think It is a Black Hole?. (arXiv:2102.02592v1 [physics.hist-ph])

上午9:24 | | | physics.hist-ph updates on arXiv.org |

Authors: Galina Weinstein

This paper analyzes the experiment presented in 2019 by the Event Horizon Telescope (EHT) Collaboration that revealed the first image of the supermassive black hole at the center of galaxy M87. The very first question asked by the EHT Collaboration is: What is the compact object at the center of galaxy M87? Does it have a horizon? Is it a Kerr black hole? In order to answer these questions, the EHT Collaboration first endorses the working hypothesis that the central object is a black hole described by the Kerr metric, i.e. a spinning Kerr black hole as predicted by classical general relativity. They choose this hypothesis based on previous research and observations of the galaxy M87. After having adopted the Kerr black hole hypothesis, the EHT Collaboration proceeds to test it. They confront this hypothesis with the data collected in the 2017 EHT experiment. They then compare the Kerr rotating black hole hypothesis with alternative explanations and finally find that their hypothesis is consistent with the data. In this paper I describe the complex methods used to test the spinning Kerr black hole hypothesis. I conclude this paper with a discussion of the implications of the findings presented here with respect to Hawking radiation.

Reconstructing the graviton. (arXiv:2102.02217v1 [hep-th])

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: Alfio Bonanno, Tobias Denz, Jan M. Pawlowski, Manuel Reichert

We reconstruct the Lorentzian graviton propagator in asymptotically safe quantum gravity from Euclidean data. The reconstruction is applied to both the dynamical fluctuation graviton and the background graviton propagator. We prove that the spectral function of the latter necessarily has negative parts similar to, and for the same reasons, as the gluon spectral function. In turn, the spectral function of the dynamical graviton is positive. We argue that the latter enters cross sections and other observables in asymptotically safe quantum gravity. Hence, its positivity may hint at the unitarity of asymptotically safe quantum gravity.

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: Alireza Allahyari, Lijing Shao

We perform an observational test of no-hair theorem using quasi-periodic oscillations within the relativistic precession model. Two well motivated metrics we apply are Kerr-Q and Hartle-Thorne metrics in which the quadrupole is the parameter that possibly encodes deviations from the Kerr black hole. The expressions for the quasi-periodic frequencies are derived before comparing the models with the observation. We encounter a degeneracy in constraining spin and quadrupole parameters that makes it difficult to measure their values. In particular, we here propose a novel test of no-hair theorem by adapting the Hartle-Thorne metric. It turns out that a Kerr black hole is a good description of the central object in GRO J1655$-$40 given the present observational precisions.

Probing Hawking radiation through capacity of entanglement. (arXiv:2102.02425v1 [hep-th])

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: Kohki Kawabata, Tatsuma Nishioka, Yoshitaka Okuyama, Kento Watanabe

We consider the capacity of entanglement in models related with the gravitational phase transitions. The capacity is labeled by the replica parameter which plays a similar role to the inverse temperature in thermodynamics. In the end of the world brane model of a radiating black hole the capacity has a peak around the Page time indicating the phase transition between replica wormhole geometries of different types of topology. Similarly, in a moving mirror model describing Hawking radiation the capacity typically shows a discontinuity when the dominant saddle switches between two phases, which can be seen as a formation of island regions. In either case we find the capacity can be an invaluable diagnostic for a black hole evaporation process.

Analogue Hawking temperature of a laser-driven plasma. (arXiv:2102.02556v1 [gr-qc])

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: C. Fiedler, D.A. Burton

We present a method for exploring analogue Hawking radiation using a laser pulse propagating through an underdense plasma. The propagating fields in the Hawking effect are local perturbations of the plasma density and laser amplitude. We derive the dependence of the resulting Hawking temperature on the dimensionless amplitude of the laser and the behaviour of the spot area of the laser at the analogue event horizon. We demonstrate one possible way of obtaining the analogue Hawking temperature in terms of the plasma wavelength, and our analysis shows that for a high intensity near-IR laser the analogue Hawking temperature is less than approximately 25K for a reasonable choice of parameters.

Diving inside a hairy black hole. (arXiv:2102.02707v1 [gr-qc])

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: Nicolás Grandi, Ignacio Salazar Landea

We investigate the interior of the Einstein-Gauss-Bonnet charged black-hole with scalar hair. We find a variety of dynamical epochs, with the particular important feature that the Cauchy horizon is not present. This makes the violation of the no-hair theorem a possible tool to understand how might the strong cosmic censorship conjecture work.

上午9:24 | | | gr-qc updates on arXiv.org |

Authors: G. A. Ummarino, A. Gallerati

We calculate the possible interaction between a superconductor and the static Earth’s gravitational fields, making use of the gravito-Maxwell formalism combined with the time-dependent Ginzburg-Landau theory. We try to estimate which are the most favourable conditions to enhance the effect, optimizing the superconductor parameters characterizing the chosen sample. We also give a qualitative comparison of the behaviour of high-$T_\text{c}$ and classical low-$T_\text{c}$ superconductors with respect to the gravity/superfluid interplay.

Knowledge is closed under analytic content

2021年2月5日 星期五 上午8:00 | | | Latest Results for Synthese |

**Abstract**

I am concerned with epistemic closure—the phenomenon in which some knowledge requires other knowledge. In particular, I defend a version of the closure principle in terms of analyticity; if an agent *S* knows that *p* is true and that *q* is an analytic part of *p*, then *S* knows that *q*. After targeting the relevant notion of analyticity, I argue that this principle accommodates intuitive cases and possesses the theoretical resources to avoid the preface paradox.

A Principle Explanation of Bell State Entanglement

2021年2月4日 星期四 上午9:23 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Stuckey, W. M. and Silberstein, Michael and McDevitt, Timothy (2021) A Principle Explanation of Bell State Entanglement. In: UNSPECIFIED.

No-go Theorems: What are they good for?

2021年2月4日 星期四 上午9:22 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Dardashti, Radin (2021) No-go Theorems: What are they good for? [Preprint]

Spacetime singularities and a novel formulation of indeterminism

2021年2月4日 星期四 上午9:21 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Azhar, Feraz and Namjoo, Mohammad Hossein (2021) Spacetime singularities and a novel formulation of indeterminism. [Preprint]

The Concept of Time: A Grand Unified Reaction Platform

2021年2月4日 星期四 上午9:20 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Hamidreza, Simchi (2019) The Concept of Time: A Grand Unified Reaction Platform. [Preprint]

Demystifying mysteries. How metaphors and analogies extend the reach of the human mind

2021年2月4日 星期四 上午6:37 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Boudry, Maarten and Vlerick, Michael and Edis, Taner (2021) Demystifying mysteries. How metaphors and analogies extend the reach of the human mind. [Preprint]

The Local versus the Global in the History of Relativity: The Case of Belgium

2021年2月2日 星期二 下午3:56 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

ten Hagen, Sjang L. (2020) The Local versus the Global in the History of Relativity: The Case of Belgium. [Preprint]

Clarifying the New Problem for Quantum Mechanics: Reply to Vaidman

2021年1月30日 星期六 下午6:28 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Meehan, Alexander (2020) Clarifying the New Problem for Quantum Mechanics: Reply to Vaidman. [Preprint]

Probing Theoretical Statements with Thought Experiments

2021年1月30日 星期六 下午6:25 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

El Skaf, Rawad (2021) Probing Theoretical Statements with Thought Experiments. [Preprint]

]]>上午10:14 | | | Ismael L. Paiva, Yakir Aharonov, Jeff Tollaksen, Mordecai Waegell | | | quant-ph updates on arXiv.org |

The interaction between a quantum charge and a quantized source of a magnetic field is considered in the Aharonov-Bohm scenario. It is shown that, if the source has a relatively small uncertainty while the particle encircles it, an effective magnetic vector potential arises and the final state of the joint system is approximately a tensor product. Furthermore, if a post-selection of the source is considered, the effective vector potential is, in general, complex-valued. This leads to a new prediction in the Aharonov-Bohm scenario before the magnetic field is fully enclosed that has a parallel with Berry phases in open quantum systems. Also, new insights into the correspondence principle, which makes complex vector potentials relevant in the study of classical systems, are discussed.

Inertial Theorem: Overcoming the quantum adiabatic limit. (arXiv:1810.12094v3 [quant-ph] UPDATED)

上午10:14 | | | Roie Dann, Ronnie Kosloff | | | quant-ph updates on arXiv.org |

We present a new theorem describing stable solutions for a driven quantum system. The theorem, coined `inertial theorem’, is applicable for fast driving, provided the acceleration rate is small. The theorem states that in the inertial limit eigenoperators of the propagator remain invariant throughout the dynamics, accumulating dynamical and geometric phases. The proof of the theorem utilizes the structure of Liouville space and a closed Lie algebra of operators. We demonstrate applications of the theorem by studying three explicit solutions of a harmonic oscillator, a two-level and three-level system models. These examples demonstrate that the inertial solution is superior to that obtained with the adiabatic approximation. Inertial protocols can be combined to generate a new family of solutions. The inertial theorem is then employed to extend the validity of the Markovian Master equation to strongly driven open quantum systems. In addition, we explore the consequence of new geometric phases associated with the driving parameters.

Collapse and Measures of Consciousness. (arXiv:2009.13224v3 [quant-ph] UPDATED)

上午10:14 | | | Adrian Kent (Centre for Quantum Information and Foundations, DAMTP, University of Cambridge, Perimeter Institute for Theoretical Physics) | | | quant-ph updates on arXiv.org |

There has been an upsurge of interest lately in developing Wigner’s hypothesis that conscious observation causes collapse by exploring dynamical collapse models in which some purportedly quantifiable aspect(s) of consciousness resist superposition. Kremnizer-Ranchin, Chalmers-McQueen and Okon-Sebasti\’an have explored the idea that collapse may be associated with a numerical measure of consciousness. More recently, Chalmers-McQueen have argued that any single measure is inadequate because it will allow superpositions of distinct states of equal consciousness measure to persist. They suggest a satisfactory model needs to associate collapse with a set of measures quantifying aspects of consciousness, such as the “Q-shapes” defined by Tononi et al. in their “integrated information theory” (IIT) of consciousness. I argue here that Chalmers-McQueen’s argument against associating a single measure with collapse requires a precise symmetry between brain states associated with different experiences and thus does not apply to the only case where we have strong intuitions, namely human (or other terrestrial biological) observers. In defence of Chalmers-McQueen’s stance, it might be argued that idealized artificial information processing networks could display such symmetries. However, I argue that any theory (such as IIT) that postulates a map from network states to mind states should assign identical mind states to isomorphic network states (as IIT does). This suggests that, if such a map exists, no familiar components of mind states, such as viewing different colours, or experiencing pleasure or pain, are likely to be related by symmetries.

上午10:14 | | | Giacomo Mauro D’Ariano, Federico Faggin | | | quant-ph updates on arXiv.org |

We explore definite theoretical assertions about consciousness, starting from a non-reductive psycho-informational solution of David Chalmers’s ‘hard problem’, based on the hypothesis that a fundamental property of ‘information’ is its experience by the supporting ‘system’. The kind of information involved in consciousness needs to be quantum for multiple reasons, including its intrinsic privacy and its power of building up thoughts by entangling qualia states. As a result we reach a quantum-information-based panpsychism, with classical physics supervening on quantum physics, quantum physics supervening on quantum information, and quantum information supervening on consciousness. We then argue that the internally experienced quantum state, since it corresponds to a definite experience-not to a random choice-must be pure, and we call it ontic, in contrast with the state predictable from the outside (i.e. the state describing the knowledge of the experience from the point of view of an external observer) which we call epistemic and is generally mixed. Purity of the ontic state requires an evolution that is purity preserving, namely a so-called ‘atomic’ quantum operation. The latter is generally probabilistic, and its particular outcome is interpreted as the free will, which is unpredictable even in principle since quantum probability cannot be interpreted as lack of knowledge. The same purity of state and evolution allows solving the ‘combination problem’ of panpsychism. Quantum state evolution accounts for a short-term buffer of experience and contains itself quantum-to-classical and classical-to-quantum information transfers. Long term memory, on the other hand, is classical, and needs memorization and recall processes that are quantum-to-classical and classical-to-quantum, respectively…

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Ioanna Kourkoulou, Alberto Nicolis, Guanhao Sun

The near vanishing of the cosmological constant is one of the most puzzling open problems in theoretical physics. We consider a system, the so-called framid, that features a technically similar problem. Its stress-energy tensor has a Lorentz-invariant expectation value on the ground state, yet there are no standard, symmetry-based selection rules enforcing this, since the ground state spontaneously breaks boosts. We verify the Lorentz invariance of the expectation value in question with explicit one-loop computations. These, however, yield the expected result only thanks to highly nontrivial cancellations, which are quite mysterious from the low-energy effective theory viewpoint.

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Harvey S. Reall

This paper considers diffeomorphism invariant theories of gravity coupled to matter, with second order equations of motion. This includes Einstein-Maxwell and Einstein-scalar field theory with (after field redefinitions) the most general parity-symmetric four-derivative effective field theory corrections. A gauge-invariant approach is used to study the characteristics associated to the physical degrees of freedom in an arbitrary background solution. The symmetries of the principal symbol arising from diffeomorphism invariance and the action principle are determined. For gravity coupled to a single scalar field (i.e. a Horndeski theory) it is shown that causality is governed by a characteristic polynomial of degree $6$ which factorises into a product of quadratic and quartic polynomials. The former is defined in terms of an “effective metric” and is associated with a “purely gravitational” polarisation, whereas the latter generically involves a mixture of gravitational and scalar field polarisations. The “fastest” degrees of freedom are associated with the quartic polynomial, which defines a surface analogous to the Fresnel surface in crystal optics. In contrast with optics, this surface is generically non-singular except on certain surfaces in spacetime. It is shown that a Killing horizon is an example of such a surface. It is also shown that a Killing horizon satisfies the zeroth law of black hole mechanics. The characteristic polynomial defines a cone in the cotangent space and a dual cone in the tangent space. The latter is used to define basic notions of causality and to provide a definition of a dynamical black hole in these theories.

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Flaminia Giacomini

In general relativity, the description of spacetime relies on idealised rods and clocks, which identify a reference frame. In any concrete scenario, reference frames are associated to physical systems, which are ultimately quantum in nature. A relativistic description of the laws of physics hence needs to take into account such quantum reference frames, through which spacetime can be given an operational meaning.

Here, we introduce the notion of a spacetime quantum reference frame, associated to a quantum particle in spacetime, and we give a manifestly covariant formulation of physical laws from the perspective of such a quantum reference frame. In particular, we consider a system of $N$ relativistic quantum particles in a weak gravitational field, and introduce a timeless formulation in which the global state of the $N$ particles appears “frozen”, but the dynamical evolution is recovered in terms of relational quantities. We describe both the external and the internal degrees of freedom of the particles. The external degrees of freedom are used to fix the quantum reference frame via a transformation to the local frame of the particle such that the metric is locally flat at the origin of the quantum reference frame. The internal degrees of freedom are used as clocks keeping the proper time in the local frame of the particle. We then show how the remaining particles evolve dynamically in the relational variables from the perspective of the quantum reference frame. The construction proposed here includes the Page-Wootters mechanism for non interacting clocks when the external degrees of freedom are neglected. Finally, we find that a quantum superposition of gravitational redshifts and a quantum superposition of special-relativistic time dilations can be observed in the quantum reference frame.

Testing quantum gravity with interactive information sensing. (arXiv:2101.11629v1 [quant-ph])

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Daniel Carney, Holger Müller, Jacob M. Taylor

We suggest a test of a central prediction of perturbatively quantized general relativity: the coherent communication of quantum information between massive objects through gravity. To do this, we introduce the concept of interactive quantum information sensing, a protocol tailored to the verification of dynamical entanglement generation between a pair of systems. Concretely, we propose to monitor the periodic wavefunction collapse and revival in an atomic interferometer which is gravitationally coupled to a mechanical oscillator. We prove a theorem which shows that, under the assumption of time-translation invariance, this collapse and revival is possible if and only if the gravitational interaction forms an entangling channel. Remarkably, as this approach improves at moderate temperatures and relies primarily upon atomic coherence, our numerical estimates indicate feasibility with current devices.

Quantum information probes of charge fractionalization. (arXiv:2101.11636v1 [hep-th])

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Brandon S. DiNunno, Niko Jokela, Juan F. Pedraza, Arttu Pönni

We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of gauge theories. For concreteness, we focus on a simple holographic $(2+1)$-dimensional strongly coupled electron fluid whose charged states organize themselves into a fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To overcome this challenge, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a $U(1)$ gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic $c$-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.

Energy-mass equivalence from Maxwell equations. (arXiv:2101.11923v1 [gr-qc])

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Alejandro Perez, Salvatore Ribisi

Since the appearance of Einstein’s paper {\em”On the Electrodynamics of Moving Bodies”} and the birth of special relativity, it is understood that the theory was basically coded within Maxwell’s equations. The celebrated mass-energy equivalence relation, $E=mc^2$, is derived by Einstein using thought experiments involving the kinematics of the emission of light (electromagnetic energy) and the relativity principle. Text book derivations often follow paths similar to Einstein’s, or the analysis of the kinematics of particle collisions interpreted from the perspective of different inertial frames. All the same, in such derivations the direct dynamical link with hypothetical fundamental fields describing matter (e.g. Maxwell theory or other) is overshadowed by the use of powerful symmetry arguments, kinematics, and the relativity principle.

Here we show that the formula can be derived directly form the dynamical equations of a massless matter model confined in a box (which can be thought of as a toy model of a composite particle). The only assumptions in the derivation are that the field equations hold and the energy-momentum tensor admits a universal interpretation in arbitrary coordinate systems. The mass-energy equivalence relation follows from the inertia or (taking the equivalence principle for granted) weight of confined field radiation. The present derivation offers an interesting pedagogical perspective on the formula providing a simple toy model on the origin of mass and a natural bridge to the foundations of general relativity.

Emergent gauge symmetries: Yang-Mills theory. (arXiv:2101.12188v1 [hep-th])

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Carlos Barceló, Raúl Carballo-Rubio, Luis J. Garay, Gerardo García-Moreno

Gauge symmetries are typically interpreted as redundancies in our description of a physical system, needed in order to make Lorentz invariance explicit when working with fields of spin 1 or higher. However, another perspective on gauge symmetries is that they represent an effective decoupling of some degrees of freedom of the theory. In this work we discuss the extension of a mechanism for the emergence of gauge symmetries proposed in a previous article \cite{barcelo2016} in order to account for non-Abelian gauge symmetries. We begin by examining the linearized theory and then move on to discuss the possible non-linear extensions via a perturbative bootstrapping process. In particular, we show that the bootstrapping procedure is essential in order to determine the physical principles under which the decoupling observed at the linear level (and therefore, the emergence of gauge symmetries) extends to the non-linear scenario. These principles are the following: low-energy Lorentz invariance, emergence of massless vector fields describable by an action quadratic in those fields and their derivatives, and self-coupling to a conserved current. This serves as a step-forward in the emergent gravity program.

上午10:14 | | | gr-qc updates on arXiv.org |

Authors: Rouzbeh Allahverdi, Mustafa A. Amin, Asher Berlin, Nicolás Bernal, Christian T. Byrnes, M. Sten Delos, Adrienne L. Erickcek, Miguel Escudero, Daniel G. Figueroa, Katherine Freese, Tomohiro Harada, Dan Hooper, David I. Kaiser, Tanvi Karwal, Kazunori Kohri, Gordan Krnjaic, Marek Lewicki, Kaloian D. Lozanov, Vivian Poulin, Kuver Sinha, Tristan L. Smith, Tomo Takahashi, Tommi Tenkanen, James Unwin, Ville Vaskonen, Scott Watson

It is commonly assumed that the energy density of the Universe was dominated by radiation between reheating after inflation and the onset of matter domination 54,000 years later. While the abundance of light elements indicates that the Universe was radiation dominated during Big Bang Nucleosynthesis (BBN), there is scant evidence that the Universe was radiation dominated prior to BBN. It is therefore possible that the cosmological history was more complicated, with deviations from the standard radiation domination during the earliest epochs. Indeed, several interesting proposals regarding various topics such as the generation of dark matter, matter-antimatter asymmetry, gravitational waves, primordial black holes, or microhalos during a nonstandard expansion phase have been recently made. In this paper, we review various possible causes and consequences of deviations from radiation domination in the early Universe – taking place either before or after BBN – and the constraints on them, as they have been discussed in the literature during the recent years.

Entanglement View of Dynamical Quantum Phase Transitions

2021年1月29日 星期五 下午6:00 | | | Stefano De Nicola, Alexios A. Michailidis, and Maksym Serbyn | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Stefano De Nicola, Alexios A. Michailidis, and Maksym Serbyn

The analogy between an equilibrium partition function and the return probability in many-body unitary dynamics has led to the concept of dynamical quantum phase transition (DQPT). DQPTs are defined by nonanalyticities in the return amplitude and are present in many models. In some cases, DQPTs can b…

[Phys. Rev. Lett. 126, 040602] Published Fri Jan 29, 2021

2021年1月29日 星期五 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Philosophers now seem to agree that frequentism is an untenable strategy to explain the meaning of probabilities. Nevertheless, I want to revive frequentism, and I will do so by grounding probabilities on typicality in the same way as the thermodynamic arrow of time can be grounded on typicality within statistical mechanics. This account, which I will call *typicality frequentism*, will evade the major criticisms raised against previous forms of frequentism. In this theory, probabilities arise within a physical theory from statistical behavior of almost all initial conditions. The main advantage of typicality frequentism is that it shows which kinds of probabilities (that also have empirical relevance) can be derived from physics. Although one cannot recover all probability talk in this account, this is rather a virtue than a vice, because it shows which types of probabilities can in fact arise from physics and which types need to be explained in different ways, thereby opening the path for a pluralistic account of probabilities.

The life of an analogue black hole

2021年1月28日 星期四 上午8:00 | | | Giovanni Modugno | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 28 January 2021; doi:10.1038/s41567-020-01160-5

Table-top superfluid experiments offer a way of bringing the physics of astrophysical black holes into the lab. But the presence of two event horizons in these superfluid black holes complicates matters — and makes them more interesting.

Muon colliders to expand frontiers of particle physics

2021年1月28日 星期四 上午8:00 | | | V. Shiltsev | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 28 January 2021; doi:10.1038/s41567-020-01130-x

Muon colliders offer enormous potential for the exploration of the particle physics frontier but are challenging to realize. A new international collaboration is forming to make such a muon collider a reality.

A hydrodynamic instability drives protein droplet formation on microtubules to nucleate branches

2021年1月28日 星期四 上午8:00 | | | Sabine Petry | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 28 January 2021; doi:10.1038/s41567-020-01141-8

Branching microtubule nucleation plays a major part in cellular processes driving eukaryotic cell division. A combination of microscopy approaches and hydrodynamic theory is used to show how the condensed protein TPX2 on a microtubule reorganizes according to the Rayleigh–Plateau instability.

In Praise of Clausius Entropy: Reassessing the Foundations of Boltzmannian Statistical Mechanics

2021年1月28日 星期四 上午4:16 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Weaver, Christopher (2020) In Praise of Clausius Entropy: Reassessing the Foundations of Boltzmannian Statistical Mechanics. [Preprint]

Phenomenology and the unity of consciousness

2021年1月27日 星期三 上午8:00 | | | Latest Results for Synthese |

**Abstract**

The phenomenology of the unity of consciousness can be analyzed in terms of perceptual spatial and object unity. Subject unity—what we commonly understand by “the unity of consciousness”—has no attendant phenomenology. The further, non-phenomenological, effects of unity can be analyzed in terms of the functional notion of access unity. The unity of consciousness in general can therefore be analyzed in terms of access unity. As a consequence, we can avoid the theoretical introduction of problematic notions such as subsumptive or phenomenal unity.

On Abstraction in Mathematics and Indefiniteness in Quantum Mechanics

2021年1月24日 星期日 上午8:18 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Ellerman, David (2021) On Abstraction in Mathematics and Indefiniteness in Quantum Mechanics. [Preprint]

The relativity of indetermininacy

2021年1月23日 星期六 下午6:11 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Del Santo, Flavio and Gisin, Nicolas (2021) The relativity of indetermininacy. [Preprint]

Beyond Causal Explanation: Einstein’s Principle Not Reichenbach’s

by Michael Silberstein^{ 1,2,*},William Mark Stuckey^{ 3} andTimothy McDevitt

**Abstract**

Our account provides a local, realist and fully non-causal principle explanation for EPR correlations, contextuality, no-signalling, and the Tsirelson bound. Indeed, the account herein is fully consistent with the causal structure of Minkowski spacetime. We argue that retrocausal accounts of quantum mechanics are problematic precisely because they do not fully transcend the assumption that causal or constructive explanation must always be fundamental. Unlike retrocausal accounts, our principle explanation is a complete rejection of Reichenbach’s Principle. Furthermore, we will argue that the basis for our principle account of quantum mechanics is the physical principle sought by quantum information theorists for their reconstructions of quantum mechanics. Finally, we explain why our account is both fully realist and psi-epistemic. View Full-Text

]]>We present a simple and rigorous derivation of the free wave equations such as the Klein-Gordon equation based on spacetime translation invariance and relativistic invariance. The new analysis may help underdstand the physical origin and significance of the laws of motion in quantum mechanics.

]]>We give an argument for the “inexistence” of the interior of Schwarzschild black holes and for the corresponding interpretation of the event horizon as an edge of space-time. In order to do that, we interpret findings from the theory of general relativity by means of realist models of quantum-events. Our approach also sheds light on the information paradox and establishes a link between black holes and the question of dark energy and dark matter.

]]>上午9:07 | | | Martin Plávala, Matthias Kleinmann | | | quant-ph updates on arXiv.org |

We construct a toy model for the harmonic oscillator that is neither classical nor quantum. The model features a discrete energy spectrum, a ground state with sharp position and momentum, an eigenstate with non-positive Wigner function as well as a state that has tunneling properties. The underlying formalism exploits that the Wigner-Weyl approach to quantum theory and the Hamilton formalism in classical theory can be formulated in the same operational language, which we then use to construct generalized theories with well-defined phase space. The toy model demonstrates that operational theories are a viable alternative to operator-based approaches for building physical theories.

Quantum Correlations in Space-Time: Foundations and Applications. (arXiv:2101.08693v1 [quant-ph])

上午9:07 | | | Tian Zhang | | | quant-ph updates on arXiv.org |

The absolute/relative debate on the nature of space and time is ongoing for thousands of years. Here we attempt to investigate space and time from the information theoretic point of view to understand spatial and temporal correlations under the relative assumption. Correlations, as a measure of relationship between two quantities, do not distinguish space and time in classical probability theory; quantum correlations in space are well-studied but temporal correlations are not well understood. The thesis investigates quantum correlations in space-time, by treating temporal correlations equally in form as spatial correlations and unifying quantum correlations in space and time. In particular, we follow the pseudo-density matrix formalism in which quantum states in spacetime are properly defined by correlations from measurements. We first review classical correlations, quantum correlations in space and time, to motivate the pseudo-density matrix formalism in finite dimensions. Next we generalise the pseudo-density matrix formulation to the Gaussian case, general continuous variables via Wigner representations, and general measurement processes like weak measurements. Then we compare the pseudo-density matrix formalism with other spacetime formulations: indefinite causal structures, consistent histories, generalised non-local games, out-of-time-order correlation functions, and path integrals. We argue that in non-relativistic quantum mechanics, different spacetime formulations are closely related via quantum correlations, except path integrals. Finally, we apply the pseudo-density matrix formulation to time crystals. By defining time crystals as long-range order in time, we analyse continuous and discrete time translation symmetry as well as discuss the existence of time crystals from an algebraic point of view. Finally, we summarise our work and provide the outlook for future directions.

Indefinite global time. (arXiv:2101.08739v1 [quant-ph])

上午9:07 | | | Tom Holden-Dye, Sandu Popescu | | | quant-ph updates on arXiv.org |

By studying the set of correlations that are theoretically possible between physical systems without allowing for signalling of information backwards in time, we here identify correlations that can only be achieved if the time ordering between the systems is fundamentally indefinite. These correlations, if they exist in nature, must result from non-classical, non-deterministic time, and so may have relevance for quantum (or post-quantum) gravity, where a definite global time might not exist.

上午9:07 | | | Xu Zheng, Baowen Li | | | quant-ph updates on arXiv.org |

We propose that the optomechanical systems can be potential platforms to implement the Fr\”{o}hlich condensate of phonons. We consider a one-dimensional array of membranes coupled to the cavity field via a quadratic interaction, and the cavity is pumped by an external laser. Analytical and numerical results predict that the high phonon occupancy of the lowest or highest mechanical mode is achievable depending on the detuning of the driving laser, the optomechnical strength, and the temperature. The decoherence of the Fr\”{o}hlich condensate can be largely suppressed by the large number of membranes. Our results shed light on narrow-linewidth phonon laser, energy conversion/transfer, and efficient multimode cooling.

上午9:07 | | | Jules Tilly, Ryan J. Marshman, Anupam Mazumdar, Sougato Bose | | | quant-ph updates on arXiv.org |

Recently a theoretical and an experimental protocol known as quantum gravity induced entanglement of masses (QGEM) has been proposed to test the quantum nature of gravity using two mesoscopic masses each placed in a superposition of two locations. If, after eliminating all non-gravitational interactions between them, the particles become entangled, one can conclude that the gravitational potential is induced via a quantum mediator, i.e. a virtual graviton. In this paper, we examine a range of different experimental set-ups, considering different geometries and the number of spatially superposed states taken, in order to determine which would generate entanglement faster. We conclude that without decoherence, and given a maximum distance $\Delta x$ between any two spatial states of a superposition, a set of two qubits placed in spatial superposition parallel to one another will outperform all other models given realistic experimental parameters. Furthermore, when a sufficiently high decoherence rate is introduced, multi-component superpositions can outperform the two-qubit set-up. This is further verified with an experimental simulation, showing that $O(10^3)$ measurements are required to reject the no entanglement hypothesis with a parallel qubits set-up without decoherence at a 99.9$\%$ confidence level. The number of measurements increases when decoherence is introduced. When the decoherence rate reaches $0.125$~Hz, 6-dimensional qudits are required as the two-qubit system entanglement cannot be witnessed anymore. However, in this case, $O(10^6)$ measurements will be required. One can group the witness operators to measure in order to reduce the number of measurements (up to ten-fold). However, this may be challenging to implement experimentally.

Observations and predictions from past lightcones. (arXiv:2101.08324v1 [gr-qc])

上午9:07 | | | gr-qc updates on arXiv.org |

Authors: Martin Lesourd

In a general Lorentzian manifold M, the past lightcone of a point is a proper subset of M that does not carry enough information to determine the rest of M. That said, if M is a globally hyperbolic Cauchy development of vacuum initial data on a Cauchy surface S and there is a point whose past lightcone contains S, then the contents of such a lightcone determines all of M (up to isometry). We show some results that describe what properties of M guarantee that past lightcones do indeed determine all or at least significant portions of M. Null lines and observer horizons, which are well known features of the de-Sitter spacetime, play a prominent role.

上午9:07 | | | gr-qc updates on arXiv.org |

Authors: Jean-Pierre Luminet (Laboratoire d’Astrophysique de Marseille)

I give a historical survey of the discussions about the existence of closed timelike curves in general relativistic models of the universe, opening the physical possibility of time travel in the past, as first recognized by K. G\”odel in his rotating universe model of 1949. I emphasize that journeying into the past is intimately linked to spacetime models devoid of timelike singularities. Since such singularities arise as an inevitable consequence of the equations of general relativity given physically reasonable assumptions, time travel in the past becomes possible only when one or another of these assumptions is violated. It is the case with wormhole-type solutions. S. Hawking and other authors have tried to “save” the paradoxical consequences of time travel in the past by advocating physical mechanisms of chronological protection; however, such mechanisms remain presently unknown, even when quantum fluctuations near horizons are taken into account. I close the survey by a brief and pedestrian discussion of Causal Dynamical Triangulations, an approach to quantum gravity in which causality plays a seminal role.

The 6th Post-Newtonian Potential Terms at $O(G_N^4)$. (arXiv:2101.08630v1 [gr-qc])

上午9:07 | | | gr-qc updates on arXiv.org |

Authors: J. Blümlein, A. Maier, P. Marquard, G. Schäfer

We calculate the potential contributions of the Hamiltonian in harmonic coordinates up 6PN for binary mass systems to $O(G_N^4)$ and perform comparisons to recent results in the literature \cite{Bern:2021dqo} and \cite{Bini:2020nsb}.

Modified general relativity. (arXiv:1904.10803v7 [gr-qc] UPDATED)

上午9:07 | | | gr-qc updates on arXiv.org |

Authors: Gary Nash

In a Lorentzian spacetime there exists a smooth regular line element field $(\bm{X},-\bm{X}) $ and a unit vector $ \bm{u} $ collinear with one of the pair of vectors in the line element field. An orthogonal decomposition of symmetric tensors can be constructed in terms of the Lie derivative along $ \bm{X} $ of the metric and a product of the unit vectors; and a linear sum of divergenceless symmetric tensors. A modified Einstein equation of general relativity is then obtained by using the principle of least action, the decomposition and a fundamental postulate of general relativity. The decomposition introduces a new symmetric tensor $ \varPhi_{\alpha\beta} $ which describes the energy-momentum of the gravitational field. It completes Einstein’s equation and addresses the energy localization problem. Variation of the action with respect to $ X^{\mu} $ restricts $u_{\mu}$ to a particular value, which defines the possible Lorentzian metrics. $ \Phi $, the trace of $ \varPhi_{\alpha\beta} $, describes dark energy. The cosmological constant is dynamically replaced by $ \Phi $. A cyclic universe that developed after the Big Bang is described. The dark energy density provides a natural explanation of why the vacuum energy density is so small, and why it dominates the present epoch. Assuming dark matter does not exist, a solution to the modified Einstein equation introduces two additional terms into the Newtonian radial force equation, from which the baryonic Tully-Fisher relation is obtained.

Yet Again, Quantum Indeterminacy is not Worldly Indecision

2021年1月22日 星期五 上午3:40 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Corti, Alberto (2021) Yet Again, Quantum Indeterminacy is not Worldly Indecision. [Preprint]

Scientific Realism and Dark Matter: Conflicts In Theory Confirmation

2021年1月21日 星期四 上午3:37 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Allzén, Simon (2021) Scientific Realism and Dark Matter: Conflicts In Theory Confirmation. [Preprint]

Out of Nowhere: Introduction: The emergence of spacetime

2021年1月19日 星期二 下午4:17 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Huggett, Nick and Wuthrich, Christian (2021) Out of Nowhere: Introduction: The emergence of spacetime. [Preprint]

The infinite and contradiction: A history of mathematical physics by dialectical approach

2021年1月19日 星期二 上午5:12 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Ueki, Ichiro (2021) The infinite and contradiction: A history of mathematical physics by dialectical approach. [Preprint]

Decay and recurrence of non-Gaussian correlations in a quantum many-body system

2021年1月18日 星期一 上午8:00 | | | Jörg Schmiedmayer | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 18 January 2021; doi:10.1038/s41567-020-01139-2

Starting from a strongly correlated state, with highly non-Gaussian correlations, a Gaussian state can emerge dynamically over time. Experiments with ultracold atoms show how the mixing between phase and density fluctuations plays the crucial role.

Missing the point in noncommutative geometry

2021年1月18日 星期一 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Noncommutative geometries generalize standard smooth geometries, parametrizing the noncommutativity of dimensions with a fundamental quantity with the dimensions of area. The question arises then of whether the concept of a region smaller than the scale—and ultimately the concept of a point—makes sense in such a theory. We argue that it does not, in two interrelated ways. In the context of Connes’ spectral triple approach, we show that arbitrarily small regions are not definable in the formal sense. While in the scalar field Moyal–Weyl approach, we show that they cannot be given an operational definition. We conclude that points do not exist in such geometries. We therefore investigate (a) the metaphysics of such a geometry, and (b) how the appearance of smooth manifold might be recovered as an approximation to a fundamental noncommutative geometry.

Does general relativity highlight necessary connections in nature?

2021年1月18日 星期一 上午8:00 | | | Latest Results for Synthese |

**Abstract**

The dynamics of general relativity is encoded in a set of ten differential equations, the so-called *Einstein field equations*. It is usually believed that Einstein’s equations represent a physical law describing the coupling of spacetime with material fields. However, just six of these equations actually describe the coupling mechanism: the remaining four represent a set of differential relations known as *Bianchi identities*. The paper discusses the physical role that the Bianchi identities play in general relativity, and investigates whether these identities—*qua* part of a physical law—highlight some kind of *a posteriori* necessity in a Kripkean sense. The inquiry shows that general relativistic physics has an interesting bearing on the debate about the metaphysics of the laws of nature.

上午9:07 | | | Martin Plávala, Matthias Kleinmann | | | quant-ph updates on arXiv.org |

We construct a toy model for the harmonic oscillator that is neither classical nor quantum. The model features a discrete energy spectrum, a ground state with sharp position and momentum, an eigenstate with non-positive Wigner function as well as a state that has tunneling properties. The underlying formalism exploits that the Wigner-Weyl approach to quantum theory and the Hamilton formalism in classical theory can be formulated in the same operational language, which we then use to construct generalized theories with well-defined phase space. The toy model demonstrates that operational theories are a viable alternative to operator-based approaches for building physical theories.

]]>上午11:33 | | | Huw Price, Ken Wharton | | | quant-ph updates on arXiv.org |

A 2015 experiment by Hanson and his Delft colleagues provided new confirmation that the quantum world violates the Bell inequalities, closing some loopholes left open by previous experiments. The experiment was also taken to provide new evidence of quantum nonlocality. Here we argue for caution about the latter claim. The Delft experiment relies on entanglement swapping, and our main point is that this introduces new loopholes in the argument from violation of the Bell inequalities to nonlocality. As we explain, the sensitivity of such experiments to these new loopholes depends on the temporal relation between the entanglement swapping measurement C and the two measurements A and B between which we seek to infer nonlocality. If the C is in the future of A and B, the loopholes loom large. If C is in the past, they are less of a threat. The Delft experiment itself is the intermediate case, in which the separation is spacelike. We argue that this still leaves it vulnerable to the new loopholes, unable to establish conclusively that it avoids them.

Quantum logics close to Boolean algebras. (arXiv:2101.05501v1 [quant-ph])

上午11:33 | | | Mirko Navara, Pavel Pták | | | quant-ph updates on arXiv.org |

We consider orthomodular posets endowed with a symmetric difference. We call them ODPs. Expressed in the quantum logic language, we consider quantum logics with an XOR-type connective. We study three classes of “almost Boolean” ODPs, two of them defined by requiring rather specific behaviour of infima and the third by a Boolean-like behaviour of Frink ideals. We establish a (rather surprising) inclusion between the three classes, shadding thus light on their intrinsic properties. (More details can be found in the Introduction that follows.) Let us only note that the orthomodular posets pursued here, though close to Boolean algebras (i.e., close to standard quantum logics), still have a potential for an arbitrarily high degree of non-compatibility and hence they may enrich the studies of mathematical foundations of quantum mechanics.

Entangled Kernels — Beyond Separability. (arXiv:2101.05514v1 [cs.LG])

上午11:33 | | | Riikka Huusari, Hachem Kadri | | | quant-ph updates on arXiv.org |

We consider the problem of operator-valued kernel learning and investigate the possibility of going beyond the well-known separable kernels. Borrowing tools and concepts from the field of quantum computing, such as partial trace and entanglement, we propose a new view on operator-valued kernels and define a general family of kernels that encompasses previously known operator-valued kernels, including separable and transformable kernels. Within this framework, we introduce another novel class of operator-valued kernels called entangled kernels that are not separable. We propose an efficient two-step algorithm for this framework, where the entangled kernel is learned based on a novel extension of kernel alignment to operator-valued kernels. We illustrate our algorithm with an application to supervised dimensionality reduction, and demonstrate its effectiveness with both artificial and real data for multi-output regression.

Layers of classicality in the compatibility of measurements. (arXiv:2101.05752v1 [quant-ph])

上午11:33 | | | Arindam Mitra | | | quant-ph updates on arXiv.org |

The term “Layers of classicality” in the context of quantum measurements, is introduced in [T. Heinosaari, Phys. Rev. A \textbf{93}, 042118 (2016)]. The strongest layer among these consists of the sets of observables that can be broadcast and the weakest layer consists of the sets of compatible observables. There are several other layers in between those two layers. In this work, we show the differences and similarities in their mathematical and geometric properties. We also show the relations among these layers.

上午11:33 | | | T.H.A. van der Reep, L. Rademaker, X.G.A. Le Large, R.H. Guis, T.H. Oosterkamp | | | quant-ph updates on arXiv.org |

The read-out of a microwave qubit state occurs using an amplification chain that enlarges the quantum state to a signal detectable with a classical measurement apparatus. However, at what point in this process is the quantum state really ‘measured’? In order to investigate whether the `measurement’ takes place in the amplification chain, in which a parametric amplifier is often chosen as the first amplifier, it is proposed to construct a microwave interferometer that has such an amplifier added to each of its arms. Feeding the interferometer with single photons, the interference visibility depends on the gain of the amplifiers and whether a measurement collapse has taken place during the amplification process. The visibility as given by standard quantum mechanics is calculated as a function of gain, insertion loss and temperature. We find a visibility of 1/3 in the limit of large gain without taking into account losses, which is reduced to 0.26 in case the insertion loss of the amplifiers is 2.2 dB at a temperature of 50 mK. It is shown that if the wave function collapses within the interferometer, the measured visibility is reduced compared to its magnitude predicted by standard quantum mechanics once this collapse process sets in.

Introducing the inverse hoop conjecture for black holes. (arXiv:2101.05290v1 [gr-qc])

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Shahar Hod

It is conjectured that stationary black holes are characterized by the inverse hoop relation ${\cal A}\leq {\cal C}^2/\pi$, where ${\cal A}$ and ${\cal C}$ are respectively the black-hole surface area and the circumference length of the smallest ring that can engulf the black-hole horizon in every direction. We explicitly prove that generic Kerr-Newman-(anti)-de Sitter black holes conform to this conjectured area-circumference relation.

Generalized gravity theory with curvature, torsion and nonmetricity. (arXiv:2101.05318v1 [gr-qc])

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: K. Yesmakhanova, S. Myrzakul, G. Yergaliyeva, K. Myrzakulov, K. Yerzhanov, R. Myrzakulov

In this article, the generalized gravity theory with the curvature, torsion and nonmetricy was studied. For the FRW spacetime case, in particular, the Lagrangian, Hamilatonian and gravitational equations are obtained. The particular case $F(R,T)=\alpha R+\beta T+\mu Q+\nu{\cal T}$ is investigated in detail. In quantum case, the corresponding Wheeler-DeWitt equation is obtained. Finally, some gravity theories with the curvature, torsion and nonmetricity are presented.

Gravitationally induced uncertainty relations in curved backgrounds. (arXiv:2101.05552v1 [gr-qc])

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Luciano Petruzziello, Fabian Wagner

This paper aims at investigating the influence of space-time curvature on the uncertainty relation. In particular, relying on previous findings, we assume the quantum wave function to be confined to a geodesic ball on a given space-like hypersurface whose radius is a measure of the position uncertainty. On the other hand, we concurrently work out a viable physical definition of the momentum operator and its standard deviation in the non-relativistic limit of the 3+1 formalism. Finally, we evaluate the uncertainty relation which to second order depends on the Ricci scalar of the effective 3-metric and the corresponding covariant derivative of the shift vector. For the sake of illustration, we apply our general result to a number of examples arising in the context of both general relativity and extended theories of gravity.

A cosmic shadow on CSL. (arXiv:1906.04405v4 [quant-ph] UPDATED)

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Jerome Martin, Vincent Vennin

The Continuous Spontaneous Localisation (CSL) model solves the measurement problem of standard quantum mechanics, by coupling the mass density of a quantum system to a white-noise field. Since the mass density is not uniquely defined in general relativity, this model is ambiguous when applied to cosmology. We however show that most natural choices of the density contrast already make current measurements of the cosmic microwave background incompatible with other laboratory experiments.

IR dynamics and entanglement entropy. (arXiv:1910.07847v3 [hep-th] UPDATED)

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Theodore N Tomaras, Nicolaos Toumbas

We consider scattering of Faddeev-Kulish electrons in QED and study the entanglement between the hard and soft particles in the final state at the perturbative level. The soft photon spectrum naturally splits into two parts: i) soft photons with energies less than a characteristic infrared scale $E_d$ present in the clouds accompanying the asymptotic charged particles, and ii) sufficiently low energy photons with energies greater than $E_d$, comprising the soft part of the emitted radiation. We construct the density matrix associated with tracing over the radiative soft photons and calculate the entanglement entropy perturbatively. We find that the entanglement entropy is free of any infrared divergences order by order in perturbation theory. On the other hand infrared divergences in the perturbative expansion for the entanglement entropy appear upon tracing over the entire spectrum of soft photons, including those in the clouds. To leading order the entanglement entropy is set by the square of the Fock basis amplitude for real single soft photon emission, which leads to a logarithmic infrared divergence when integrated over the photon momentum. We argue that the infrared divergences in the entanglement entropy (per particle flux per unit time) in this latter case persist to all orders in perturbation theory in the infinite volume limit.

Conserved charges in general relativity. (arXiv:2005.13233v3 [gr-qc] UPDATED)

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Sinya Aoki, Tetsuya Onogi, Shuichi Yokoyama

We present a precise definition of a conserved quantity from an arbitrary covariantly conserved current available in a general curved spacetime with Killing vectors. This definition enables us to define energy and momentum for matter by the volume integral. As a result we can compute charges of Schwarzschild and BTZ black holes by the volume integration of a delta function singularity. Employing the definition we also compute the total energy of a static compact star. It contains both the gravitational mass known as the Misner-Sharp mass in the Oppenheimer-Volkoff equation and the gravitational binding energy. We show that the gravitational binding energy has the negative contribution at maximum by 68% of the gravitational mass in the case of a constant density. We finally comment on a definition of generators associated with a vector field on a general curved manifold.

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Kaushik Y. Bhagat, Baibhab Bose, Sayantan Choudhury, Satyaki Chowdhury, Rathindra N. Das, Saptarshhi G. Dastider, Nitin Gupta, Archana Maji, Gabriel D. Pasquino, Swaraj Paul

The concept of out-of-time-ordered correlation (OTOC) function is treated as a very strong theoretical probe of quantum randomness, using which one can study both chaotic and non-chaotic phenomena in the context of quantum statistical mechanics. In this paper, we define a general class of OTOC, which can perfectly capture quantum randomness phenomena in a better way. Further we demonstrate an equivalent formalism of computation using a general time independent Hamiltonian having well defined eigenstate representation for integrable supersymmetric quantum systems. We found that one needs to consider two new correlators apart from the usual one to have a complete quantum description. To visualize the impact of the given formalism we consider the two well known models viz. Harmonic Oscillator and one dimensional potential well within the framework of supersymmetry. For the Harmonic Oscillator case we obtain similar periodic time dependence but dissimilar parameter dependences compared to the results obtained from both micro-canonical and canonical ensembles in quantum mechanics without supersymmetry. On the other hand, for one dimensional potential well problem we found significantly different time scale and the other parameter dependence compared to the results obtained from non-supersymmetric quantum mechanics. Finally, to establish the consistency of the prescribed formalism in the classical limit, we demonstrate the phase space averaged version of the classical version of OTOCs from a model independent Hamiltonian along with the previously mentioned these well cited models.

Quantum Detection of Inertial Frame Dragging. (arXiv:2009.10584v3 [gr-qc] UPDATED)

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Wan Cong, Jiri Bicak, David Kubiznak, Robert B. Mann

A relativistic theory of gravity like general relativity produces phenomena differing fundamentally from Newton’s theory. An example, analogous to electromagnetic induction, is gravitomagnetism, or the dragging of inertial frames by mass-energy currents. These effects have recently been confirmed by classical observations. Here we show, for the first time, that they can be observed by a quantum detector. We study the response function of Unruh De-Witt detectors placed in a slowly rotating shell. We show that the response function picks up the presence of rotation even though the spacetime inside the shell is flat and the detector is locally inertial. The detector can distinguish between the static situation when the shell is non-rotating and the stationary case when the shell rotates and the dragging of inertial frames, i.e. gravitomagnetic effects, arise. Moreover, it can do so when the detector is switched on for a finite time interval within which a light signal cannot travel to the shell and back to convey the presence of rotation.

String Theory, the Dark Sector and the Hierarchy Problem. (arXiv:2010.15610v2 [hep-th] UPDATED)

上午10:33 | | | gr-qc updates on arXiv.org |

Authors: Per Berglund, Tristan Hübsch, Djordje Minic

We discuss dark energy, dark matter and the hierarchy problem in the context of a general non-commutative formulation of string theory. In this framework dark energy is generated by the dynamical geometry of the dual spacetime while dark matter, on the other hand, comes from the degrees of freedom dual to the visible matter. This formulation of string theory is sensitive both to the IR and UV scales and the Higgs scale is radiatively stable by being a geometric mean of radiatively stable UV and IR scales. We also comment on various phenomenological signatures of this novel approach to dark energy, dark matter and the hierarchy problem. We find that this new view on the hierarchy problem is realized in a toy model based on a non-holomorphic deformation of the stringy cosmic string. Finally, we discuss a proposal for a new non-perturbative formulation of string theory, which sheds light on M theory and F theory, as well as on supersymmetry and holography.

The history of LHCb. (arXiv:2101.05331v1 [physics.hist-ph])

上午10:33 | | | physics.hist-ph updates on arXiv.org |

Authors: I. Belyaev, G. Carboni, N. Harnew, C. Matteuzzi. F. Teubert

In this paper we describe the history of the LHCb experiment over the last three decades, and its remarkable successes and achievements. LHCb was conceived primarily as a b-physics experiment, dedicated to CP violation studies and measurements of very rare b decays, however the tremendous potential for c-physics was also clear. At first data taking, the versatility of the experiment as a general-purpose detector in the forward region also became evident, with measurements achievable such as electroweak physics, jets and new particle searches in open states. These were facilitated by the excellent capability of the detector to identify muons and to reconstruct decay vertices close to the primary pp interaction region. By the end of the LHC Run 2 in 2018, before the accelerator paused for its second long shut down, LHCb had measured the CKM quark mixing matrix elements and CP violation parameters to world-leading precision in the heavy-quark systems. The experiment had also measured many rare decays of b and c quark mesons and baryons to below their Standard Model expectations, some down to branching ratios of order 10-9. In addition, world knowledge of b and c spectroscopy had improved significantly through discoveries of many new resonances already anticipated in the quark model, and also adding new exotic four and five quark states.

On the Relationship Between Modelling Practices and Interpretive Stances in Quantum Mechanics

2021年1月14日 星期四 下午2:12 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Ruyant, Quentin (2021) On the Relationship Between Modelling Practices and Interpretive Stances in Quantum Mechanics. Foundations of Science. ISSN 1233-1821

Efficient Simulation of Loop Quantum Gravity: A Scalable Linear-Optical Approach

2021年1月11日 星期一 下午6:00 | | | Lior Cohen, Anthony J. Brady, Zichang Huang, Hongguang Liu, Dongxue Qu, Jonathan P. Dowling, and Muxin Han | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Lior Cohen, Anthony J. Brady, Zichang Huang, Hongguang Liu, Dongxue Qu, Jonathan P. Dowling, and Muxin Han

The problem of simulating complex quantum processes on classical computers gave rise to the field of quantum simulations. Quantum simulators solve problems, such as boson sampling, where classical counterparts fail. In another field of physics, the unification of general relativity and quantum theor…

[Phys. Rev. Lett. 126, 020501] Published Mon Jan 11, 2021

Truth and beauty in physics and biology

2021年1月11日 星期一 上午8:00 | | | Ben D. MacArthur | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 11 January 2021; doi:10.1038/s41567-020-01132-9

Physicists and biologists have different conceptions of beauty. A better appreciation of these differences may bring the disciplines closer and help develop a more integrated view of life.

2021年1月10日 星期日 下午4:18 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Chua, Eugene Y. S. and Callender, Craig (2020) No Time for Time from No-Time. [Preprint]

Humean Laws of Nature: The End of the Good Old Days

2021年1月10日 星期日 下午4:16 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Callender, Craig (2021) Humean Laws of Nature: The End of the Good Old Days. [Preprint]

2021年1月10日 星期日 下午4:04 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Woodward, James (2021) Downward Causation Defended. [Preprint]

]]>上午9:31 | | | Leon V. Biguaa, Vladimir V. Kassandrov | | | quant-ph updates on arXiv.org |

We substantiate the need for account of the proper electromagnetic field of the electron in the canonical problem of hydrogen in relativistic quantum mechanics. From mathematical viewpoint, the goal is equivalent to determination of the spectrum of everywhere regular solutions to the self-consistent system of Dirac and Maxwell equations (with external Coulomb potential). We demonstrate that only particular classes of solutions, “nonlinear” analogues of s- and p-states, can be obtained through decomposition of a solution in a series, with respect to the fine structure constant parameter $\alpha$. In the zero approximation at $\alpha \rightarrow 0$ the reduction to the self-consistent non-relativistic system of Schr\”odinger-Poisson equations takes place. For the latter, using both numerical and variational methods, we obtain the solutions corresponding to the ground and set of excited states. Spectrum of the binding energies with remarkable precision reproduces the “Bohrian” dependence $W_n = W/ n^2$. For this, the ionization energy $W$ proves to be universal yet about two times smaller than its observed value. Possibility of the renormalization procedure and the problem of account for relativistic corrections to the binding energies of order $\alpha^2$ are considered

上午9:31 | | | Armin Hochrainer, Mayukh Lahiri, Manuel Erhard, Mario Krenn, Anton Zeilinger | | | quant-ph updates on arXiv.org |

Two photon-pair creation processes can be arranged such that the paths of the emitted photons are identical. Thereby the path information is not erased but is never born in the first place. In addition to its implications for fundamental physics, this concept has recently led to a series of discoveries in the fields of imaging, spectroscopy, and quantum information science. Here we present the idea of path identity and provide a comprehensive review of the recent developments.

上午9:31 | | | J.-B. Bru, W. de Siqueira Pedra | | | quant-ph updates on arXiv.org |

During the last three decades, P. B\'{o}na has developed a non-linear generalization of quantum mechanics, based on symplectic structures for normal states and offering a general setting which is convenient to study the emergence of macroscopic classical dynamics from microscopic quantum processes. We propose here a new mathematical approach to Bona’s one, with much brother domain of applicability. It highlights the central role of self-consistency. This leads to a mathematical framework in which the classical and quantum worlds are naturally entangled. We build a Poisson bracket for the polynomial functions on the hermitian weak$^{\ast }$ continuous functionals on any $C^{\ast }$-algebra. This is reminiscent of a well-known construction for finite-dimensional Lie algebras. We then restrict this Poisson bracket to states of this $C^{\ast }$-algebra, by taking quotients with respect to Poisson ideals. This leads to densely defined symmetric derivations on the commutative $C^{\ast }$-algebras of real-valued functions on the set of states. Up to a closure, these are proven to generate $C_{0}$-groups of contractions. As a matter of fact, in general commutative $C^{\ast }$-algebras, even the closableness of unbounded symmetric derivations is a non-trivial issue. Some new mathematical concepts are introduced, which are possibly interesting by themselves: the convex weak $^{\ast }$ G\^{a}teaux derivative, state-dependent $C^{\ast }$-dynamical systems and the weak$^{\ast }$-Hausdorff hypertopology, a new hypertopology used to prove, among other things, that convex weak$^{\ast }$-compact sets generically have weak$^{\ast }$-dense extreme boundary in infinite dimension. Our recent results on macroscopic dynamical properties of lattice-fermion and quantum-spin systems with long-range, or mean-field, interactions corroborate the relevance of the general approach we present here.

上午9:31 | | | Michael E. Tobar, Raymond Y. Chiao, Maxim Goryachev | | | quant-ph updates on arXiv.org |

To understand the creation of electromagnetic energy (or a photonic degree of freedom) from an external energy source, an electromotive force must be generated, capable of separating positive and negative charges. The separation of charges (free or bound) may be modelled as a permanent polarization, which has a non-zero electric vector curl, created by an external force per unit charge, sometimes referred as an impressed electric field. The resulting system forms a physical dipole in the static case, or a Hertzian dipole in the time dependent case. This system is the electrical dual of the magnetic solenoid described by a magnetic vector potential and excited by an electrical current. Correspondingly, the creation of an electric dipole, from the forceful separation of positive and negative charge, may be described by an electric flux density, which exhibits an electric vector potential and a magnetic current boundary source, within the frame work of two-potential theory without the need for the existence of the magnetic monopole. From this result we derive the Dual electric Aharanov-Bohm (DAB) Berry phase and make the conjecture that it should be equivalent to the geometric phase that is described in modern electric polarization theory, which also describes the nature of the permanent polarization of a ferroelectric. This work gives a formal meaning to the electric vector potential that defines the DAB geometric phase, and determines that a permanent polarization has both a scalar and vector potential component, and we show that it must be considered to fully describe the nature of a physical electric dipole, which inevitably is a generator of electricity. Additionally, we show that Faraday’s and Ampere’s law may be derived from the time rate of change of the Aharanov-Bohm phase and the DAB phase respectively, independent of the electromagnetic gauge.

Discovery of the Relativistic Schr\”odinger Equation. (arXiv:2012.12467v2 [physics.hist-ph] UPDATED)

上午9:01 | | | physics.hist-ph updates on arXiv.org |

Authors: Kamal Barley, José Vega-Guzmán, Sergei K. Suslov

We discuss the discovery of the relativistic wave equation for a spin-zero charged particle in the Coulomb field by Erwin Schr\”odinger (and elaborate on why he didn’t publish it).

A simple characterization of doubly twisted spacetimes. (arXiv:2101.02208v1 [gr-qc])

上午9:01 | | | gr-qc updates on arXiv.org |

Authors: Carlo Alberto Mantica, Luca Guido Molinari

In this note we characterize 1+n doubly twisted spacetimes in terms of `doubly torqued’ vector fields. They extend Bang-Yen Chen’s characterization of twisted and generalized Robertson-Walker spacetimes with torqued and concircular vector fields. The result is a simple classification of 1+n doubly-twisted, doubly-warped, twisted and generalized Robertson-Walker spacetimes.

上午9:01 | | | gr-qc updates on arXiv.org |

Authors: Klaas Landsman

In the light of his recent (and fully deserved) Nobel Prize, this pedagogical paper draws attention to a fundamental tension that drove Penrose’s work on general relativity. His 1965 singularity theorem (for which he got the prize) does not in fact imply the existence of black holes (even if its assumptions are met). Similarly, his versatile definition of a singular space-time does not match the generally accepted definition of a black hole (derived from his concept of null infinity). To overcome this, Penrose launched his cosmic censorship conjecture(s), whose evolution we discuss. In particular, we review both his own (mature) formulation and its later, inequivalent reformulation in the PDE literature. As a compromise, one might say that in “generic” or “physically reasonable” space-times, weak cosmic censorship postulates the appearance and stability of event horizons, whereas strong cosmic censorship asks for the instability and ensuing disappearance of Cauchy horizons. As an encore, an appendix by Erik Curiel reviews the early history of the definition of a black hole.

上午9:01 | | | gr-qc updates on arXiv.org |

Authors: S.N. Mayburov

Several experimental groups reported the evidence of multiple periodic modulations of nuclear decay constants which amplitudes are of the order 0.05% and have periods of one year, 24 hours or about one month. We argue that these deviations from radioactive decay law can be explained as the effect of small nonlinear corrections to standard quantum mechanics, in particular, to Hamiltonian of quantum system interaction with gravitational field. It’s shown that modified Doebner-Goldin nonlinear model predicts the similar decay parameter variations under influence of Sun gravity.

上午9:01 | | | gr-qc updates on arXiv.org |

Authors: Flaminia Giacomini, Časlav Brukner

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

Does General Relativity Highlight Necessary Connections in Nature?

2021年1月8日 星期五 上午9:09 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Vassallo, Antonio (2021) Does General Relativity Highlight Necessary Connections in Nature? [Preprint]

2021年1月8日 星期五 上午8:00 | | | Wendy S. Parker | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 08 January 2021; doi:10.1038/s41567-020-01138-3

Simulations are as much a part of science as hypothesis and experiment. But can their outcomes be considered observations? Wendy S. Parker investigates.

Thermodynamic Uncertainty Relation for General Open Quantum Systems

2021年1月5日 星期二 下午6:00 | | | Yoshihiko Hasegawa | | | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. |

Author(s): Yoshihiko Hasegawa

We derive a thermodynamic uncertainty relation for general open quantum dynamics, described by a joint unitary evolution on a composite system comprising a system and an environment. By measuring the environmental state after the system-environment interaction, we bound the counting observables in t…

[Phys. Rev. Lett. 126, 010602] Published Tue Jan 05, 2021

A challenge to the second law of thermodynamics from cognitive science and vice versa

2021年1月5日 星期二 上午8:00 | | | Latest Results for Synthese |

**Abstract**

We show that the so-called *Multiple*–*Computations Theorem* in cognitive science and philosophy of mind challenges Landauer’s Principle in physics. Since the orthodox wisdom in statistical physics is that Landauer’s Principle is *implied* by, or is the mechanical *equivalent* of, the Second Law of thermodynamics, our argument shows that the Multiple-Computations Theorem challenges the universal validity of the Second Law of thermodynamics itself. We construct two examples of computations carried out by one and the same dynamical process with respect to which Landauer’s principle implies c*ontradictory* predictions concerning the entropy increase. Our two examples are based on a weak version of the Multiple-Computations Theorem, which is quite uncontroversial, and therefore they amount to a clear refutation of the universal validity of Landauer’s Principle. We consider some responses to this argument that do not attempt to single out one computation over the others, and we show that they do not work. We further consider ways out of the argument by externalist approaches supporting the computational theory of the mind who propose that the interaction of a computing system with the environment is enough to select a single computation over the others. We show on physical grounds that this approach fails too. We then reverse the direction of our challenge and formulate a dilemma for supporters of the computational theory of the mind: (i) they must *reject* (or amend somehow) the causal closure of physic; or else (ii) they must accept on a priori grounds that Landauer’s Principle and the Second Law of thermodynamics are *not* universally valid. Finally, we present our version of a type–type mind-brain identity theory called *Flat Physicalism*, which is based on the paradigm case of statistical mechanics, and we show that it circumvents the challenge from Landauer’s Principle and the Multiple-Computations Theorem and does not fall prey to our dilemma.

The Relativistic Transactional Interpretation and The Quantum Direct-Action Theory

2021年1月4日 星期一 上午3:31 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

Kastner, Ruth (2021) The Relativistic Transactional Interpretation and The Quantum Direct-Action Theory. [Preprint]

The Empirical Under-determination Argument Against Scientific Realism for Dual Theories

2021年1月4日 星期一 上午3:29 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

De Haro, Sebastian (2021) The Empirical Under-determination Argument Against Scientific Realism for Dual Theories. [Preprint]

2021年1月4日 星期一 上午3:28 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

de Ronde, Christian (2021) The Power of Inconsistency in Anti-Realist Realisms about Quantum Mechanics (Or: Lessons on How to Capture and Defeat Smoky Dragons). [Preprint]

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