上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:00 | | | Latest Results for Foundations of Physics |

### Abstract

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

上午8:25 | | | Stan Gudder | | | quant-ph updates on arXiv.org |

This article considers quantum systems described by a finite-dimensional complex Hilbert space $H$. We first define the concept of a finite observable on $H$. We then discuss ways of combining observables in terms of convex combinations, post-processing and sequential products. We also define complementary and coexistent observables. We then introduce finite instruments and their related compatible observables. The previous combinations and relations for observables are extended to instruments and their properties are compared. We present four types of instruments; namely, identity, trivial, L\”uders and Kraus instruments. These types are used to illustrate different ways that instruments can act. We next consider joint probabilities for observables and instruments. The article concludes with a discussion of measurement models and the instruments they measure.

上午8:25 | | | gr-qc updates on arXiv.org |

Authors: Sayantan Choudhury, Satyaki Chowdhury, Nitin Gupta, Abinash Swain

In this paper, our prime objective is to apply the techniques of {\it parameter estimation theory} and the concept of {\it Quantum Metrology} in the form of {\it Fisher Information} to investigate the role of certain physical quantities in the open quantum dynamics of a two entangled qubit system under the Markovian approximation. There exist various physical parameters which characterize such system, but can not be treated as any quantum mechanical observable. It becomes imperative to do a detailed parameter estimation analysis to determine the physically consistent parameter space of such quantities. We apply both Classical Fisher Information (CFI) and Quantum Fisher Information (QFI) to correctly estimate these parameters, which play significant role to describe the out-of-equilibrium and the long range quantum entanglement phenomena of open quantum system. {\it Quantum Metrology}, compared to {\it classical parameter estimation theory}, plays a two-fold superior role, improving the precision and accuracy of parameter estimation. Additionally, in this paper, we present a new avenue in terms of {\it Quantum Metrology}, which beats the classical parameter estimation. We also present an interesting result of \textit{revival of out-of-equilibrium feature at the late time scales, arising due to the long-range quantum entanglement at early time scale and provide a physical interpretation for the same in terms of Bell’s Inequality Violation in early time scale giving rise to non-locality.

上午8:25 | | | gr-qc updates on arXiv.org |

Authors: Giovanni Acquaviva, Alfredo Iorio, Luca Smaldone

Assuming that the degrees of freedom of a black hole are finite in number and of fermionic nature, we naturally obtain, within a second-quantized toy model of the evaporation, that the Bekenstein bound is a consequence of the Pauli exclusion principle for these fundamental degrees of freedom. We show that entanglement, Bekenstein and thermodynamic entropies of the black hole all stem from the same approach, based on the entropy operator whose structure is the one typical of Takahashi and Umezawa’s Thermofield Dynamics. We then evaluate the von Neumann black hole–environment entropy and noticeably obtain a Page-like evolution. We finally show that this is a consequence of a duality between our model and a quantum dissipative-like fermionic system.

2020年5月29日 星期五 下午3:35 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月29日 星期五 下午3:31 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月29日 星期五 上午2:17 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月28日 星期四 下午3:07 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月28日 星期四 下午2:55 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月28日 星期四 上午8:47 | | | Mateus Araújo, Flavien Hirsch, Marco Túlio Quintino | | | quant-ph updates on arXiv.org |

In order to reject the local hidden variables hypothesis, the usefulness of a Bell inequality can be quantified by how small a p-value it will give for a physical experiment. Here we show that the expected p-value is minimized when we maximize the difference between the local and Tsirelson bounds of the Bell inequality, when it is formulated as a nonlocal game. We develop an algorithm for transforming an arbitrary Bell inequality into such an optimal nonlocal game, and show its results for the CGLMP and $I_{nn22}$ inequalities.

We present explicit examples of Bell inequalities such that the gap between their local and Tsirelson bounds is arbitrarily close to one, and show that this makes it possible to reject local hidden variables with arbitrarily small p-value in a single shot, without needing to collect statistics. We also develop a new algorithm for calculating local bounds which is significantly faster than the methods currently available, which may be of independent interest.

2020年5月28日 星期四 上午8:47 | | | Jerryman A. Gyamfi | | | quant-ph updates on arXiv.org |

The purpose of this paper is to articulate a coherent and easy-to-understand way of doing quantum mechanics in any finite-dimensional Liouville space, based on the use of Kronecker product and what we have termed the `bra-flipper’ operator. One of the greater strengths of the formalism expatiated on here is the striking similarities it bears with Dirac’s bra-ket notation. For the purpose of illustrating how the formalism can be effectively employed, we use it to solve a quantum optical master equation for a two-level quantum system and find its Kraus operator sum representation. The paper is addressed to students and researchers with some basic knowledge of linear algebra who wants to acquire a deeper understanding of the Liouville space formalism. The concepts are conveyed so as to make the application of the formalism to more complex problems in quantum physics straightforward and unencumbered.

2020年5月28日 星期四 上午8:47 | | | Pasquale Bosso | | | quant-ph updates on arXiv.org |

Quantum mechanical models with a minimal length are often described by modifying the commutation relation between position and momentum. Although this represents a small complication when described in momentum space, at least formally, the (quasi-)position representation acquires numerous issues, source of misunderstandings. In this work, we review these issues, clarifying some of the aspects of minimal length models, with particular reference to the representation of the position operator.

2020年5月28日 星期四 上午8:47 | | | physics.hist-ph updates on arXiv.org |

Authors: Andrew Knight

The assertion by Yu and Nikolic that the delayed choice quantum eraser experiment of Kim et al. empirically falsifies the consciousness-causes-collapse hypothesis of quantum mechanics is based on the unfounded and false assumption that the failure of a quantum wave function to collapse implies the appearance of a visible interference pattern.

2020年5月28日 星期四 上午8:47 | | | 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. This definition enables us to define energy and momentum for matter by the volume integral. As a result we can compute charges of well-known black holes just as an electric charge of an electron in electromagnetism by the volume integration of a delta function singularity. As a byproduct we show that the definition leads to a correction to the known mass formula of a compact star in the Oppenheimer-Volkoff equation. We finally comment on a definition of generators associated with a vector field on a general curved manifold.

2020年5月28日 星期四 上午8:47 | | | gr-qc updates on arXiv.org |

Authors: Metin Gurses, Yaghoub Heydarzade, Bayram Tekin

We show that (1) the Einstein field equations with a perfect fluid source admit a nonlinear superposition of two distinct homogenous Friedman-Lemaitre-Robertson-Walker (FLRW) metrics as a solution, (2) the superposed solution is an inhomogeneous geometry in general, (3) it reduces to a homogeneous one in the two asymptotes which are the early and the late stages of the universe as described by two different FLRW metrics, (4) the solution possesses a scale factor inversion symmetry and (5) the solution implies two kinds of topology changes: one during the time evolution of the superposed universe and the other occurring in the asymptotic region of space.

2020年5月28日 星期四 上午8:47 | | | gr-qc updates on arXiv.org |

Authors: Mark P. Hertzberg, Jacob A. Litterer, McCullen Sandora

It is known that local, Lorentz invariant, unitary theories involving particles with spin 1 demand that the matter sector they couple to are organized by internal physical symmetries and the associated charge conservation, while spin 3/2 demands supersymmetry. However, the introduction of a spin 2 graviton does not obviously demand new symmetries of the matter sector (although it does demand a universal coupling). In this work we relax the assumption of Lorentz boost symmetry, while maintaining a basic notion of locality that there is no instantaneous signaling at a distance. This extends and complements our accompanying work in Part 1 on related issues for spin 1 particles in electromagnetism. In order to avoid potential problems with longitudinal modes of the graviton, we choose to project them out, leaving only two degrees of freedom. We study large classes of theories that a priori may violate Lorentz boost invariance. By requiring the tree-level exchange action be local, we find that consistency demands that the Lorentz boost symmetry must be satisfied by the graviton and the matter sector, and in turn we recover general relativity at this order of analysis.

2020年5月28日 星期四 上午8:00 | | | Latest Results for Synthese |

### Abstract

The debate between Einstein and Bergson is a salient episode in the history of modern physics and a telling example of the interaction between science and philosophy. This paper initially discusses five reasons why Bergson criticised Einstein for giving up absolute time. The most important one was Bergson’s commitment to an intuitionist, anti-Kantian metaphysics informed by common sense. Apart from that, he knew that the theory of special relativity permits “duration” (*durée*) in the form of the passage of proper time, to which Bergson referred as “real time”. Neither static eternalism (which excludes temporal passage) nor dynamic eternalism (which, like the former, claims the existence of the future) are acceptable from Bergson’s philosophical perspective, which acknowledges the role of temporal experience and everyday thinking in addition to science and metaphysics. He understood temporal passage as creation of new existence, anticipating what later became known as the growing block theory of time. The pointy relativistic variant of this theory, which divides the universe into blocks of growing past light cones, does justice to large parts of his philosophy, including the distinction between the actual and the virtual. Supporters of Bergson’s account of duration should adopt this theory of time.

2020年5月27日 星期三 上午11:06 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月27日 星期三 上午10:58 | | | Philsci-Archive: No conditions. Results ordered -Date Deposited. |

2020年5月27日 星期三 上午8:00 | | | Latest Results for Synthese |

### Abstract

Reality is hierarchically structured, or so proponents of the metaphysical posit of grounding argue. The less fundamental facts obtain in virtue of, or are grounded in, the more fundamental facts. But what exactly is it for one fact to be more fundamental than another? The aim of this paper is to provide a measure of relative fundamentality. I develop and defend an account of the metaphysical hierarchy that assigns to each fact a set of ordinals representing the levels on which it occurs. The account allows one to compare any two facts with respect to their fundamentality and it uses immediate grounding as its sole primitive. In the first section, I will set the stage and point to some shortcomings of a rival account proposed by Karen Bennett. The second section will present my own proposal and the third section will discuss how it can be extended to non-foundationalist settings. The fourth section discusses potential objections.

2020年5月26日 星期二 上午8:00 | | | Lenka Zdeborová | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 26 May 2020; doi:10.1038/s41567-020-0929-2

Automated learning from data by means of deep neural networks is finding use in an ever-increasing number of applications, yet key theoretical questions about how it works remain unanswered. A physics-based approach may help to bridge this gap.

2020年5月25日 星期一 上午8:00 | | | Manuel Endres | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 25 May 2020; doi:10.1038/s41567-020-0903-z

High entanglement fidelity between neutral atoms is achieved using highly excited Rydberg states. The unique electron structure provided by alkaline-earth atoms makes it a promising platform for various quantum-technology-based applications.

2020年5月25日 星期一 上午8:00 | | | Wenhui Li | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 25 May 2020; doi:10.1038/s41567-020-0907-8

Systems of neutral atoms are gradually gaining currency as a promising candidate for realizing large-scale quantum computing. The achievement of a record-high fidelity in quantum operation with alkaline-earth Rydberg atoms is a case in point.