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Bruno de S. L. Torres

Thu Oct 26 2023 09:32:00 (1 day)

# 1.

Using the Schwinger-Keldysh path integral, we draw a connection between localized quantum field theories and more commonly used models of local probes in Relativistic Quantum Information (RQI). By integrating over and then tracing out the inaccessible modes of the localized field being used as a probe, we show that, at leading order in perturbation theory, the dynamics of any finite number of modes of the probe field is exactly that of a finite number of harmonic-oscillator Unruh-DeWitt (UDW) detectors. The equivalence is valid for a rather general class of input states of the probe-target field system, as well as for any arbitrary number of modes included as detectors. The path integral also provides a closed-form expression which gives us a systematic way of obtaining the corrections to the UDW model at higher orders in perturbation theory due to the existence of the additional modes that have been traced out. This approach vindicates and extends a recently proposed bridge between detector-based and field-theory-based measurement frameworks for quantum field theory [__arXiv:2308.11698__], and also points to potential connections between particle detector models in RQI and other areas of physics where path integral methods are more commonplace — in particular, the Wilsonian approach to the renormalization group and effective field theories.

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Koki Tokeshi, Vincent Vennin

Thu Oct 26 2023 09:31:46 (1 day)

# 2.

Most high-energy constructions that realise a phase of cosmic inflation contain many degrees of freedom. Yet, cosmological observations are all consistent with single-field embeddings. We show how volume selection effects explain this apparent paradox. Due to quantum diffusion, different regions of space inflate by different amounts. In regions that inflate most, and eventually dominate the volume of the universe, a generic mechanism is unveiled that diverts the inflationary dynamics towards single-field attractors. The formalism of constrained stochastic inflation is developed to this end.

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Alessandro Coppo, Alessandro Cuccoli, Paola Verrucchi

Mon Oct 23 2023 10:28:14 (4 days)

# 3.

We present an implementation of a recently proposed procedure for defining time, based on the description of the evolving system and its clock as non-interacting, entangled systems, according to the Page and Wootters approach. We study how the quantum dynamics transforms into a classical-like behaviour when conditions related with macroscopicity are met by the clock alone, or by both the clock and the evolving system. In the description of this emerging behaviour finds its place the classical notion of time, as well as that of phase-space and trajectories on it. This allows us to analyze and discuss the relations that must hold between quantities that characterize system and clock separately, in order for the resulting overall picture be that of a physical dynamics as we mean it.

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Daniel Canarutto

Mon Oct 23 2023 10:28:13 (4 days)

# 4.

A sketch of some of the fundamental notions related to the nature of knowledge is offered, with special focus on the role of mathematics and my own opinions. No single idea exposed here is entirely original; indeed, this topic has been explored by legions of philosophers, mathematicians, and scientists throughout history — I listed a few related books among the references. I look forward to observations and criticisms that may serve to improve this exposition.

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Oliver Davis Johns

Mon Oct 23 2023 10:28:12 (4 days)

# 5.

The Feynman demonstration that electromagnetic field momentum is real-even for static fields-can be made more pedagogically useful by simplifying its geometry. Instead of Feynman’s disk with charged balls on its surface, this article uses the geometry of a hollow non-conducting sphere with uniform surface charge density. With only methods available in a typical upper-division electrodynamics course, the initial field angular momentum and the final mechanical angular momentum can then be calculated in closed form and shown to be equal.

This simplified geometry also provides a counterexample for the idea that electromagnetic field momentum is due to the flow of an electromagnetic inertial mass, defined as the energy density divided by the square of the speed of light. The curved flow lines of an inertial field momentum would require a centripetal force to bend them, but no such force can be identified.

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Mon Oct 23 2023 06:36:58 (5 days)

# 6.

Toader, Iulian D. (2023) Rules and Meaning in Quantum Mechanics. [Preprint]

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Mon Oct 23 2023 06:33:21 (5 days)

# 7.

Cairns, Monte (2023) Electronegativity as a New Case for Emergence and a New Problem for Reductionism. [Preprint]

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Sat Oct 21 2023 13:32:23 (6 days)

# 8.

Wu, Jingyi and Weatherall, James Owen (2023) Between a Stone and a Hausdorff Space. [Preprint]