Weekly Papers on Quantum Foundations (18)

Some Minimal Notes on Notation and Minima: A Comment on “How Particular is the Physics of the Free Energy Principle?” by Aguilera, Millidge, Tschantz, and Buckley. (arXiv:2204.13576v1 [cond-mat.stat-mech])

We comment on a technical critique of the free energy principle in linear systems by Aguilera, Millidge, Tschantz, and Buckley, entitled “How Particular is the Physics of the Free Energy Principle?” Aguilera and colleagues identify an ambiguity in the flow of the mode of a system, and we discuss the context for this ambiguity in earlier papers, and their proposal of a more adequate interpretation of these equations. Following that, we discuss a misinterpretation in their treatment of surprisal and variational free energy, especially with respect to their gradients and their minima. In sum, we argue that the results in the target paper are accurate and stand up to rigorous scrutiny; we also highlight that they, nonetheless, do not undermine the FEP.

Biocosmology: Biology from a cosmological perspective. (arXiv:2204.09379v2 [physics.hist-ph] UPDATED)

The Universe contains everything that exists, including life. And all that exists, including life, obeys universal physical laws. Do those laws then give adequate foundations for a complete explanation of biological phenomena? We discuss whether and how cosmology and physics must be modified to be able to address certain questions which arise at their intersection with biology. We show that a universe that contains life, in the form it has on Earth, is in a certain sense radically non-ergodic, in that the vast majority of possible organisms will never be realized. We argue from this that complete explanations in cosmology require a mixture of reductionist and functional explanations.

Could wavefunctions simultaneously represent knowledge and reality?. (arXiv:2101.06436v4 [quant-ph] UPDATED)

In discussion of the interpretation of quantum mechanics the terms ontic’ and epistemic’ are often used in the sense of pertaining to what exists, and pertaining to cognition or knowledge respectively. The terms are also often associated with the formal definitions given by Harrigan and Spekkens for the wavefunction in quantum mechanics to be $\psi$-ontic or $\psi$-epistemic in the context of the ontological models framework. The formal definitions are contradictories, so that the wavefunction can be either $\psi$-epistemic or $\psi$-ontic but not both. However, we argue, nothing about the informal ideas of epistemic and ontic interpretations rules out wavefunctions representing both reality and knowledge. The implications of the Pusey-Barrett-Rudolph theorem and many other issues may be rethought in the light of our analysis.

A Quantum-Mechanical Mechanism for Reducing the Cosmological Constant. (arXiv:2204.13124v1 [hep-th])

Authors: Nemanja KaloperAlexander Westphal

We exhibit a mechanism which dynamically adjusts cosmological constant toward $0^+$. The adjustment is quantum-mechanical, discharging cosmological constant in random discrete steps. It renders de Sitter space unstable, and triggers its decay toward Minkowski. Since the instability dynamically stops at $\Lambda = 0$, the evolution favors the terminal Minkowski space without a need for anthropics. The mechanism works for any QFT coupled to gravity.

Tests of gravity theories with pulsar timing. (arXiv:2204.13468v1 [gr-qc])

Authors: Paulo C. C. Freire

Over the last few years, a set of new results from pulsar timing has introduced much tighter constraints on violations of the strong equivalence principle (SEP), either via a direct verification of the universality of free fall for a pulsar in a triple star system, or from tests of the nature of gravitational waves, in particular a search for dipolar gravitational wave emission in a variety of binary pulsars with different masses. No deviations from the SEP have been detected in our experiments. These results introduce some of the most stringent constraints on several classes of alternative theories of gravity and complement recent results from the ground-based gravitational wave detectors.

Local Dynamical Effects of Scale Invariance: the Lunar Recession. (arXiv:2204.13560v1 [astro-ph.EP])

Authors: Andre MaederVesselin Gueorguiev

Scale invariance is expected in empty Universe models, while the presence of matter tends to suppress it. As shown recently, scale invariance is certainly absent in cosmological models with densities equal to or above the critical value $\varrho_{\mathrm{c}} =3H^2_0/(8 \pi G)$. For models with densities below $\varrho_{\mathrm{c}}$, the possibility of limited effects remains open. If present, scale invariance would be a global cosmological property. Some traces could be observable locally. For the Earth-Moon two-body system, the predicted additional lunar recession would be increased by 0.92 cm/yr, while the tidal interaction would also be slightly increased.

The Earth-Moon distance is the most systematically measured distance in the Solar System, thanks to the Lunar Laser Ranging (LLR) experiment active since 1970. The observed lunar recession from LLR amounts to 3.83 ($\pm 0.009$) cm/yr; implying a tidal change of the length-of-the-day (LOD) by 2.395 ms/cy. However, the observed change of the LOD since the Babylonian Antiquity is only 1.78 ms/cy, a result supported by paleontological data, and implying a lunar recession of 2.85 cm/yr. The significant difference of (3.83-2.85) cm/yr = 0.98 cm/yr, already pointed out by several authors over the last two decades, corresponds well to the predictions of the scale-invariant theory, which is also supported by several other astrophysical tests.

Quantum magnonics: When magnon spintronics meets quantum information science

Publication date: 26 June 2022

Source: Physics Reports, Volume 965

Author(s): H.Y. Yuan, Yunshan Cao, Akashdeep Kamra, Rembert A. Duine, Peng Yan

Objective description in physics

Halvorson, Hans (2022) Objective description in physics. [Preprint]

A simple proof that the global phase is real

Gao, Shan (2022) A simple proof that the global phase is real. [Preprint]

Reassessing the strength of a class of Wigner’s friend no-go theorems

Okon, Elias (2022) Reassessing the strength of a class of Wigner’s friend no-go theorems. [Preprint]

Where we are with quantum

Nature Physics, Published online: 28 April 2022; doi:10.1038/s41567-022-01597-w

A theoretical analysis shows how a person’s location in space could be verified by the transmission of single photons. A vital application of quantum networks may be within reach.

Quantum Relativity of Subsystems

Author(s): Shadi Ali Ahmad, Thomas D. Galley, Philipp A. Höhn, Maximilian P. E. Lock, and Alexander R. H. Smith

One of the most basic notions in physics is the partitioning of a system into subsystems and the study of correlations among its parts. In this Letter, we explore this notion in the context of quantum reference frame (QRF) covariance, in which this partitioning is subject to a symmetry constraint. W…

[Phys. Rev. Lett. 128, 170401] Published Wed Apr 27, 2022

Structuralism, indiscernibility, and physical computation

Abstract

Structuralism about mathematical objects and structuralist accounts of physical computation both face indeterminacy objections. For the former, the problem arises for cases such as the complex roots i and $$-i$$ , for which a (non-trivial) automorphism can be defined, thus establishing the structural identity of these importantly distinct mathematical objects (see e.g. Keränen in Philos Math 3:308–330, 2001). In the case of the latter, the problem arises for logical duals such as AND and OR, which have invertible structural profiles (see e.g. Shagrir in Mind 110(438):369–400, 2001). This makes their physical implementations indeterminate, in the sense that their structural profiles alone cannot establish whether a given physical component is an AND-gate or an OR-gate. Doherty (PhilPapers, https://philpapers.org/rec/DOHCI-3, 2021) has recently shown both problems to be analogous, and has argued that computational structuralism is threatened with the absurd conclusion that computational digits might be indiscernible, such that, if structural properties are all that we have to go on, the binary digit 0 must be treated as identical to the binary digit 1 (rendering pure structuralism absurd). However, we think that a solution to the indiscernibility problem for mathematical structuralists, drawing on the work of David Hilbert, can be adapted for the analogous problem in the computational case, thereby rescuing the structuralist approach to physical computation.

Nonclassical probability, convex hulls, and Dutch Books

Gil Sanchez, Michał and Gyenis, Zalán and Wronski, Leszek (2022) Nonclassical probability, convex hulls, and Dutch Books. [Preprint]

On Automorphism Criteria for Comparing Amounts of Mathematical Structure

Barrett, Thomas William and Manchak, JB and Weatherall, James Owen (2022) On Automorphism Criteria for Comparing Amounts of Mathematical Structure. [Preprint]

The Lorentz transformation in a fishbowl: a comment on Cheng and Read’s “Why not a sound postulate?”

Shanahan, Daniel The Lorentz transformation in a fishbowl: a comment on Cheng and Read’s “Why not a sound postulate?”. UNSPECIFIED.

Fine-tuning and Humean Laws: Fine-tuning as argument for a non-governing account of laws rather than for God or multiverse

Halpin, John F. (2022) Fine-tuning and Humean Laws: Fine-tuning as argument for a non-governing account of laws rather than for God or multiverse. [Preprint]