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Symmetry
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Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational
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Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 11751

Special Issue Editor

Prof. Dr. Stephen A. Fulling

E-Mail Website
Guest Editor
Department of Mathematics, Texas A&M University, College Station, TX, USA
Interests: quantum field theory in curved space-time;quantum vacuum energy;quantum graphs;semiclassical approximations in quantum mechanics

Special Issue Information

Dear Colleagues,

The process of radiation by a uniformly accelerated charge, although both fundamental and elementary, has long been a subject of controversy. The conceptual issues are intensified when gravity is brought into the picture, and they have come even more to the fore now that a related effect in quantum theory (named after Unruh), which usually deals with a neutral system with internal degrees of freedom rather than a charge, has attracted sustained attention and has a close relation to the Hawking effect of black-hole evaporation. These issues also have implications for two major current experimental projects: LIGO (for the detection of gravitational waves) and DUNE (for the study of neutrino mixing). Furthermore, Unruh-like effects in the behavior of atoms falling into a black hole are a topic of current research uniting general-relativity and quantum-optics researchers. The crucial (and counterintuitive) point in these various situations is that the acceleration of the observer, or measuring instrument, is as relevant as that of the source. The time has come to consolidate a world-wide consensus in this important, and unnecessarily confused, area.

Prof. Dr. Stephen A. Fulling
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • acceleration
  • radiation
  • bremsstrahlung
  • Unruh effect
  • Larmor formula
  • horizon
  • Rindler space
  • vacuum
  • particle detector
  • two-level atom

Published Papers (6 papers)

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Research

53 pages, 3121 KiB  
Article
Vortical Effects for Free Fermions on Anti-De Sitter Space-Time
by Victor E. Ambrus and Elizabeth Winstanley
Symmetry 2021, 13(11), 2019; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13112019 - 25 Oct 2021
Cited by 8 | Viewed by 1634
Abstract
Here, we study a quantum fermion field in rigid rotation at finite temperature on anti-de Sitter space. We assume that the rotation rate Ω is smaller than the inverse radius of curvature ℓ−1, so that there is no speed of [...] Read more.
Here, we study a quantum fermion field in rigid rotation at finite temperature on anti-de Sitter space. We assume that the rotation rate Ω is smaller than the inverse radius of curvature ℓ−1, so that there is no speed of light surface and the static (maximally-symmetric) and rotating vacua coincide. This assumption enables us to follow a geometric approach employing a closed-form expression for the vacuum two-point function, which can then be used to compute thermal expectation values (t.e.v.s). In the high temperature regime, we find a perfect analogy with known results on Minkowski space-time, uncovering curvature effects in the form of extra terms involving the Ricci scalar R. The axial vortical effect is validated and the axial flux through two-dimensional slices is found to escape to infinity for massless fermions, while for massive fermions, it is completely converted into the pseudoscalar density −iψ¯γ5ψ. Finally, we discuss volumetric properties such as the total scalar condensate and the total energy within the space-time and show that they diverge as [1−ℓ2Ω2]−1 in the limit Ω→ℓ−1. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
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20 pages, 8883 KiB  
Article
The Unruh Effect in Slow Motion
by Silas Vriend, Daniel Grimmer and Eduardo Martín-Martínez
Symmetry 2021, 13(11), 1977; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13111977 - 20 Oct 2021
Cited by 12 | Viewed by 1879
Abstract
We show under what conditions an accelerated detector (e.g., an atom/ion/molecule) thermalizes while interacting with the vacuum state of a quantum field in a setup where the detector’s acceleration alternates sign across multiple optical cavities. We show (non-perturbatively) in what regimes the probe [...] Read more.
We show under what conditions an accelerated detector (e.g., an atom/ion/molecule) thermalizes while interacting with the vacuum state of a quantum field in a setup where the detector’s acceleration alternates sign across multiple optical cavities. We show (non-perturbatively) in what regimes the probe ‘forgets’ that it is traversing cavities and thermalizes to a temperature proportional to its acceleration, the same as it would in free space. Then we analyze in detail how this thermalization relates to the renowned Unruh effect. Finally, we use these results to propose an experimental testbed for the direct detection of the Unruh effect at relatively low probe speeds and accelerations, potentially orders of magnitude below previous proposals. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
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11 pages, 290 KiB  
Article
Falling from Rest: Particle Creation in a Dropped Cavity
by Francesco Sorge
Symmetry 2021, 13(7), 1139; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13071139 - 25 Jun 2021
Viewed by 1034
Abstract
We discuss the process of particle creation in the case of a scalar quantum field confined to a small cavity, initially at rest, which is suddenly dropped in a static gravitational field. We show that, due to the transition from a Schwarzschild to [...] Read more.
We discuss the process of particle creation in the case of a scalar quantum field confined to a small cavity, initially at rest, which is suddenly dropped in a static gravitational field. We show that, due to the transition from a Schwarzschild to a Minkowski background, as perceived by a comoving observer, field particles are excited out of the quantum vacuum. The density of the created quanta depends on the proper gravitational acceleration as well as on a parameter α≃1/Δt, with Δt representing the typical time duration of the transition. For the specific acceleration profile considered, the energy spectrum of the created quanta roughly resembles a two-dimensional Planckian distribution, whose equivalent temperature mimics the Hawking-Unruh temperature, with the detector acceleration (or the black hole surface gravity) replaced by the parameter cα. We briefly comment on possible issues related to local Lorentz symmetry. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
22 pages, 404 KiB  
Article
Interpretations and Naturalness in the Radiation-Reaction Problem
by Carlos Barceló, Luis J. Garay and Jaime Redondo-Yuste
Symmetry 2021, 13(4), 658; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13040658 - 12 Apr 2021
Viewed by 1747
Abstract
After more than a century of history, the radiation-reaction problem in classical electrodynamics still surprises and puzzles new generations of researchers. Here, we revise and explain some of the paradoxical issues that one faces when approaching the problem, mostly associated with regimes of [...] Read more.
After more than a century of history, the radiation-reaction problem in classical electrodynamics still surprises and puzzles new generations of researchers. Here, we revise and explain some of the paradoxical issues that one faces when approaching the problem, mostly associated with regimes of uniform proper acceleration. The answers we provide can be found in the literature and are a synthesis of a large body of research. We only present them in a personal way that may help in their understanding. Besides, after the presentation of the standard answers, we motivate and present a twist to those ideas. The physics of emission of radiation by extended charges (charges with internal structure) might proceed in a surprising oscillating fashion. This hypothetical process could open up new research paths and a new take on the equivalence principle. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
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16 pages, 680 KiB  
Article
Quantum Power Distribution of Relativistic Acceleration Radiation: Classical Electrodynamic Analogies with Perfectly Reflecting Moving Mirrors
by Abay Zhakenuly, Maksat Temirkhan, Michael R. R. Good and Pisin Chen
Symmetry 2021, 13(4), 653; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13040653 - 12 Apr 2021
Cited by 17 | Viewed by 2117
Abstract
We find the quantum power emitted and distribution in 3 + 1-dimensions of relativistic acceleration radiation using a single perfectly reflecting mirror via Lorentz invariance, demonstrating close analogies to point charge radiation in classical electrodynamics. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
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15 pages, 1025 KiB  
Article
Discrepancy between Power Radiated and the Power Loss Due to Radiation Reaction for an Accelerated Charge
by Ashok K. Singal
Symmetry 2020, 12(11), 1833; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12111833 - 05 Nov 2020
Cited by 4 | Viewed by 1981
Abstract
We examine here the discrepancy between the radiated power, calculated from the Poynting flux at infinity, and the power loss due to radiation reaction for an accelerated charge. It is emphasized that one needs to maintain a clear distinction between the electromagnetic power [...] Read more.
We examine here the discrepancy between the radiated power, calculated from the Poynting flux at infinity, and the power loss due to radiation reaction for an accelerated charge. It is emphasized that one needs to maintain a clear distinction between the electromagnetic power received by distant observers and the mechanical power loss undergone by the charge. In the literature, both quantities are treated as almost synonymous; the two in general could, however, be quite different. It is shown that in the case of a periodic motion, the two formulations do yield the power loss in a time averaged sense to be the same, even though, the instantaneous rates are quite different. It is demonstrated that the discordance between the two power formulas merely reflects the difference in the power going in self-fields of the charge between the retarded and present times. In particular, in the case of a uniformly accelerated charge, power going into the self-fields at the present time is equal to the power that was going into the self-fields at the retarded time plus the power going in acceleration fields, usually called radiation. From a study of the fields in regions far off from the time retarded positions of the uniformly accelerated charge, it is shown that effectively the fields, including the acceleration fields, remain around the ‘present’ position of the charge which itself is moving toward infinity due to its continuous constant acceleration, with no other Poynting flow that could be termed as ‘radiation emitted’ by the charge. Full article
(This article belongs to the Special Issue Acceleration and Radiation: Classical and Quantum, Electromagnetic and Gravitational)
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