# Weekly Papers on Quantum Foundations (46)

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PhilSci-Archive: No conditions. Results ordered -Date Deposited.

Sat Nov 12 2022 03:48:12 (6 hours)

# 1.

Dieks, Dennis (2022) Perspectival Quantum Realism. Foundations of Physics, 52 (95). ISSN 1572-9516

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Sat Nov 12 2022 03:47:00 (6 hours)

# 2.

Dieks, Dennis (2022) Identical Particles in Quantum Mechanics: Against the Received View (version 2022). [Preprint]

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Fedele Lizzi

Fri Nov 11 2022 09:51:14 (1 day)

# 3.

A room, a teacher and many friends.

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Dennis Dieks

Fri Nov 11 2022 09:51:12 (1 day)

# 4.

The theories of pre-quantum physics are standardly seen as representing physical systems and their properties. Quantum mechanics in its standard form is a more problematic case: here, interpretational problems have led to doubts about the tenability of realist views. Thus, QBists and Quantum Pragmatists maintain that quantum mechanics should not be thought of as representing physical systems, but rather as an agent-centered tool for updating beliefs about such systems. It is part and parcel of such views that different agents may have different beliefs and may assign different quantum states. What results is a collection of agent-centered perspectives rather than a unique representation of the physical world.

In this paper we argue that the problems identified by QBism and Quantum Pragmatism do not necessitate abandoning the ideal of representing the physical world. We can avail ourselves of the same puzzle-solving strategies as employed by QBists and pragmatists by adopting a \emph{perspectival quantum realism}. According to this perspectivalism (close to the relational interpretation of quantum mechanics) objects may possess different, but equally objective properties with respect to different physically defined perspectives. We discuss two options for such a perspectivalism, a local and a nonlocal one, and apply them to Wigner’s friend and EPR scenarios. Finally, we connect quantum perspectivalism to the recently proposed philosophical position of \emph{fragmentalism}.

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Dennis Dieks

Fri Nov 11 2022 09:51:11 (1 day)

# 5.

According to the Received View identical quantum particles are a previously unknown kind of objects that do not possess individuality. In this Chapter we discuss this view, criticize it, and propose an alternative. According to this alternative view so-called identical quantum particles should in many cases not be seen as objects (particles) at all. However, there are situations in which a particle picture does become applicable. But the particles that emerge in these cases are distinguishable individuals, unlike the particles of the Received View.

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Hiroki Matsui, Shinji Mukohyama, Atsushi Naruko

Fri Nov 11 2022 09:51:07 (1 day)

# 6.

In minisuperspace quantum cosmology, the Lorentzian path integral formulations of the no-boundary and tunneling proposals have recently been analyzed. But it has been pointed out that the wave function of linearized perturbations around a homogeneous and isotropic background is of an inverse Gaussian form and thus that their correlation functions are divergent. In this paper, we revisit this issue and consider the problem of perturbations in Lorentzian quantum cosmology by modifying the dispersion relation based on trans-Planckian physics. We consider two modified dispersion relations, the generalized Corley-Jacobson dispersion relation with higher momentum terms and the Unruh dispersion relation with a trans-Planckian mode cut-off, as examples. We show that the inverse Gaussian problem of perturbations in Lorentzian quantum cosmology is hard to overcome with the trans-Planckian physics modifying the dispersion relation at short distances.

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Andrzej Góźdź, Marcin Kisielowski, Włodzimierz Piechocki

Fri Nov 11 2022 09:51:04 (1 day)

# 7.

The quantum dynamics of a self-gravitating thin matter shell in vacuum has been considered. Quantum Hamiltonian of the system is positive definite. Within chosen set of parameters, the quantum shell bounces above the horizon. Considered quantum system does not collapse to the gravitational singularity of the corresponding classical system.

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Arnau Bas i Beneito, Gianluca Calcagni, Lesław Rachwał

Fri Nov 11 2022 09:50:59 (1 day)

# 8.

This chapter of the Handbook of Quantum Gravity aims to illustrate how nonlocality can be implemented in field theories, as well as the manner it solves fundamental difficulties of gravitational theories. We review Stelle’s quadratic gravity, which achieves multiplicative renormalizability successfully to remove quantum divergences by modifying the Einstein’s action but at the price of breaking the unitarity of the theory and introducing Ostrogradski’s ghosts. Utilizing nonlocal operators, one is able not only to make the theory renormalizable, but also to get rid of these ghost modes that arise from higher derivatives. We start this analysis by reviewing the classical scalar field theory and highlighting how to deal with this new kind of nonlocal operators. Subsequently, we generalize these results to classical nonlocal gravity and, via the equations of motion, we derive significant results about the stable vacuum solutions of the theory. Furthermore, we discuss the way nonlocality could potentially solve the singularity problem of Einstein’s gravity. In the final part, we examine how nonlocality induced by exponential and asymptotically polynomial form factors preserves unitarity and improves the renormalizability of the theory.

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Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Fri Nov 11 2022 09:50:57 (1 day)

# 9.

We summarize our work on spherically symmetric midi-superspaces in loop quantum gravity. Our approach is based on using inhomogeneous slicings that may penetrate the horizon in case there is one and on a redefinition of the constraints so the Hamiltonian has an Abelian algebra with itself. We discuss basic and improved quantizations as is done in loop quantum cosmology. We discuss the use of parameterized Dirac observables to define operators associated with kinematical variables in the physical space of states, as a first step to introduce an operator associated with the space-time metric. We analyze the elimination of singularities and how they are replaced by extensions of the space-times. We discuss the charged case and potential observational consequences in quasinormal modes. We also analyze the covariance of the approach. Finally, we comment on other recent approaches of quantum black holes, including mini-superspaces motivated by loop quantum gravity.

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Apollonas S. Matsoukas-Roubeas, Federico Roccati, Julien Cornelius, Zhenyu Xu, Aurelia Chenu, Adolfo del Campo

Fri Nov 11 2022 09:50:57 (1 day)

# 10.

The construction of exactly-solvable models has recently been advanced by considering integrable $T\bar{T}$ deformations and related Hamiltonian deformations in quantum mechanics. We introduce a broader class of non-Hermitian Hamiltonian deformations in a nonrelativistic setting, to account for the description of a large class of open quantum systems, which includes, e.g., arbitrary Markovian evolutions conditioned to the absence of quantum jumps. We relate the time evolution operator and the time-evolving density matrix in the undeformed and deformed theories in terms of integral transforms with a specific kernel. Non-Hermitian Hamiltonian deformations naturally arise in the description of energy diffusion that emerges in quantum systems from time-keeping errors in a real clock used to track time evolution. We show that the latter can be related to an inverse $T\bar{T}$ deformation with a purely imaginary deformation parameter. In this case, the integral transforms take a particularly simple form when the initial state is a coherent Gibbs state or a thermofield double state, as we illustrate by characterizing the purity, R\’enyi entropies, logarithmic negativity, and the spectral form factor. As the dissipative evolution of a quantum system can be conveniently described in Liouville space, we further discuss the spectral properties of the Liouvillians, i.e., the dynamical generators associated with the deformed theories. As an application, we discuss the interplay between decoherence and quantum chaos in non-Hermitian deformations of random matrix Hamiltonians and the Sachdev-Ye-Kitaev model.

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Fri Nov 11 2022 03:11:51 (1 day)

# 11.

Abrams, Marshall (2022) Random foraging and perceived randomness. In: UNSPECIFIED.

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Fri Nov 11 2022 03:10:42 (1 day)

# 12.

Adlam, Emily and Linnemann, Niels and Read, James (2022) Constructive Axiomatics in Spacetime Physics Part II: Constructive Axiomatics in Context. [Preprint]

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Fri Nov 11 2022 03:08:46 (1 day)

# 13.

Hildebrand, Tyler (2022) The Ideology of Pragmatic Humeanism. In: UNSPECIFIED.

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PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

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Fergus Barratt, Utkarsh Agrawal, Andrew C. Potter, Sarang Gopalakrishnan, and Romain Vasseur

Thu Nov 10 2022 18:00:00 (1 day)

# 14.

Author(s): Fergus Barratt, Utkarsh Agrawal, Andrew C. Potter, Sarang Gopalakrishnan, and Romain Vasseur

We consider monitored quantum systems with a global conserved charge, and ask how efficiently an observer (“eavesdropper”) can learn the global charge of such systems from local projective measurements. We find phase transitions as a function of the measurement rate, depending on how much informatio…

[Phys. Rev. Lett. 129, 200602] Published Thu Nov 10, 2022

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PhilSci-Archive: No conditions. Results ordered -Date Deposited.

Thu Nov 10 2022 02:19:25 (2 days)

# 15.

Szabo, Laszlo E. (2021) Physicalism without the idols of mathematics. [Preprint]

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Lorenzo Lorenzetti

Wed Nov 09 2022 10:17:44 (2 days)

# 16.

Functionalism is the view that being x is to play the role of x. This paper defends a functionalist account of three-dimensional entities in the context of Wave Function Realism (WFR), that can explain in detail how we can recover three-dimensional entities out of the wavefunction. In particular, the essay advocates for a novel version of WFR in terms of a functional reductionist approach in the style of David Lewis. This account entails reduction of the upper entities to the bottom ones, when the latter behave appropriately. As applied to WFR, it shows how the wavefunction can turn out to be identical to three-dimensional objects, provided certain conditions. The first major goal of the paper is thus to put forward an improved and more rigorous version of WFR, which dissolves several extant issues about the theory, and can serve as a starting point for the future literature about the topic. Moreover, the second major goal of the article is to take WFR as a case study to demonstrate the pros of functional reductionism, especially in the form defended here, thereby helping to bring this view back in the philosophy of science debate. The positive upshots of this paper suggest a possible application of functional reductionism also to other contexts.

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Nature Physics

by

Peter Sidaway

Mon Nov 07 2022 08:00:00 (5 days)

# 17.

Nature Physics, Published online: 07 November 2022; doi:10.1038/s41567-022-01817-3

Units of length have come a long way: from countless local variants to standardized measures. Peter Sidaway looks back at some milestones.

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Nature Physics

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Luyi Yang

Mon Nov 07 2022 08:00:00 (5 days)

# 18.

Nature Physics, Published online: 07 November 2022; doi:10.1038/s41567-022-01774-x

Optical experiments reveal nematicity and broken time-reversal symmetry in the charge density waves in kagome metals.

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Nature Physics

Mon Nov 07 2022 08:00:00 (5 days)

# 19.

Nature Physics, Published online: 07 November 2022; doi:10.1038/s41567-022-01847-x

The 2022 Nobel Prize in Physics has been awarded “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science”, a long-anticipated topic for the prize.