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Symmetry
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Symmetry in Quantum Theory of Gravity
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Symmetry in Quantum Theory of Gravity

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

Deadline for manuscript submissions: closed (15 December 2021) | Viewed by 13360

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Chris Fields

E-Mail Website
Guest Editor
Allen Discovery Center, Tufts University, Medford, MA 02155, USA
Interests: decoherence; holography; quantum gravity; quantum information
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Antonino Marciano

E-Mail Website
Guest Editor
Center for Field Theory and Particle Physics and Department of Physics, Fudan University, Shanghai 200433, China
Interests: early cosmology; inflation; dark energy; quantum comsology and quantum gravity; quantum gravity phenomenology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Symmetries are at the origin of modern comprehension of fundamental interactions in physics. Internal symmetries both dictate the dynamics of the degrees of freedom of quantum systems and specify how such systems interact. External symmetries—more precisely, diffeomorphism symmetries—provide strong constraints on physical observables, as accurately confirmed by a plethora of high-precision experiments. Our comprehension of quantum gravity models is thus intertwined with the fate of symmetries at high-energy (Planckian) scales. At the same time, the breakdown of global symmetries in quantum gravity might also lead to stringent phenomenological predictions, with observable implications on the mass spectroscopy of dark matter candidates. The reconceptualization of quantum theory in informational terms suggests, on the other hand, that all classical information, including local values of spacetime curvature, results from breaking a symmetry. This offers an appealing scenario in which the structure of spacetime itself could be emergent via some decoherence process or quantum field condensation. 

This Special Issue of Symmetry solicits papers from all relevant theoretical perspectives, including novel approaches to information topology and/or geometry. Topics of interest include but are not limited to discrete symmetries in quantum gravity, breakdown of global symmetries in quantum gravity, hypersurface constraint algebra and canonical quantization of gravity, decoherence mechanisms that record curvature information locally in spacetime, “erasure” of curvature through recoherence, the generation of gravitational waves, renormalization group flow, encoding of curvature information in dark energy, dark matter, or supertranslation or other “soft mode” symmetries, spontaneous symmetry breaking and radiative corrections, and the description of scattering or other processes within spacetime from a quantum-computational perspective.

Submit your paper and select the Journal “Symmetry” and the Special Issue “Symmetry in Quantum Theory of Gravity” via: MDPI submission system. Our papers will be published on a rolling basis and we will be pleased to receive your submission once you have finished it.

Dr. Chris Fields
Prof. Dr. Antonino Marciano
Guest Editors

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.

Published Papers (7 papers)

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Editorial

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3 pages, 167 KiB  
Editorial
Symmetry in Quantum Theory of Gravity
by Chris Fields
Symmetry 2022, 14(4), 775; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14040775 - 8 Apr 2022
Cited by 1 | Viewed by 1380
Abstract
Nicolas Gisin [...] Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)

Research

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17 pages, 351 KiB  
Article
Theory of Spinors in Curved Space-Time
by Ying-Qiu Gu
Symmetry 2021, 13(10), 1931; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13101931 - 14 Oct 2021
Cited by 5 | Viewed by 2284
Abstract
By means of Clifford Algebra, a unified language and tool to describe the rules of nature, this paper systematically discusses the dynamics and properties of spinor fields in curved space-time, such as the decomposition of the spinor connection, the classical approximation of the [...] Read more.
By means of Clifford Algebra, a unified language and tool to describe the rules of nature, this paper systematically discusses the dynamics and properties of spinor fields in curved space-time, such as the decomposition of the spinor connection, the classical approximation of the Dirac equation, the energy-momentum tensor of spinors and so on. To split the spinor connection into the Keller connection Υμ∈Λ1 and the pseudo-vector potential Ωμ∈Λ3 not only makes the calculation simpler, but also highlights their different physical meanings. The representation of the new spinor connection is dependent only on the metric, but not on the Dirac matrix. Only in the new form of connection can we clearly define the classical concepts for the spinor field and then derive its complete classical dynamics, that is, Newton’s second law of particles. To study the interaction between space-time and fermion, we need an explicit form of the energy-momentum tensor of spinor fields; however, the energy-momentum tensor is closely related to the tetrad, and the tetrad cannot be uniquely determined by the metric. This uncertainty increases the difficulty of deriving rigorous expression. In this paper, through a specific representation of tetrad, we derive the concrete energy-momentum tensor and its classical approximation. In the derivation of energy-momentum tensor, we obtain a spinor coefficient table Sabμν, which plays an important role in the interaction between spinor and gravity. From this paper we find that Clifford algebra has irreplaceable advantages in the study of geometry and physics. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
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7 pages, 288 KiB  
Article
Spontaneous Lorentz Violation from Infrared Gravity
by Fabrizio Illuminati, Gaetano Lambiase and Luciano Petruzziello
Symmetry 2021, 13(10), 1854; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13101854 - 3 Oct 2021
Cited by 4 | Viewed by 1261
Abstract
In this paper, we investigate a novel implication of the non-negligible spacetime curvature at large distances when its effects are expressed in terms of a suitably modified form of the Heisenberg uncertainty relations. Specifically, we establish a one-to-one correspondence between this modified uncertainty [...] Read more.
In this paper, we investigate a novel implication of the non-negligible spacetime curvature at large distances when its effects are expressed in terms of a suitably modified form of the Heisenberg uncertainty relations. Specifically, we establish a one-to-one correspondence between this modified uncertainty principle and the Standard Model Extension (SME), a string-theoretical effective field theory that accounts for both explicit and spontaneous breaking of Lorentz symmetry. This tight correspondence between string-derived effective field theory and modified quantum mechanics with extended uncertainty relations is validated by comparing the predictions concerning a deformed Hawking temperature derived from the two models. Moreover, starting from the experimental bounds on the gravity sector of the SME, we derive the most stringent constraint achieved so far on the value of the free parameter in the extended Heisenberg uncertainty principle. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
22 pages, 410 KiB  
Article
Extended Chern–Simons Model for a Vector Multiplet
by Dmitry S. Kaparulin, Simon L. Lyakhovich and Oleg D. Nosyrev
Symmetry 2021, 13(6), 1004; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13061004 - 3 Jun 2021
Cited by 3 | Viewed by 1519
Abstract
We consider a gauge theory of vector fields in 3D Minkowski space. At the free level, the dynamical variables are subjected to the extended Chern–Simons (ECS) equations with higher derivatives. If the color index takes n values, the third-order model admits a [...] Read more.
We consider a gauge theory of vector fields in 3D Minkowski space. At the free level, the dynamical variables are subjected to the extended Chern–Simons (ECS) equations with higher derivatives. If the color index takes n values, the third-order model admits a 2n-parameter series of second-rank conserved tensors, which includes the canonical energy–momentum. Even though the canonical energy is unbounded, the other representatives in the series have a bounded from below the 00-component. The theory admits consistent self-interactions with the Yang–Mills gauge symmetry. The Lagrangian couplings preserve the energy–momentum tensor that is unbounded from below, and they do not lead to a stable non-linear theory. The non-Lagrangian couplings are consistent with the existence of a conserved tensor with a 00-component bounded from below. These models are stable at the non-linear level. The dynamics of interacting theory admit a constraint Hamiltonian form. The Hamiltonian density is given by the 00-component of the conserved tensor. In the case of stable interactions, the Poisson bracket and Hamiltonian do not follow from the canonical Ostrogradski construction. Particular attention is paid to the “triply massless” ECS theory, which demonstrates instability even at the free level. It is shown that the introduction of extra scalar field, serving as Higgs, can stabilize the dynamics in the vicinity of the local minimum of energy. The equations of motion of the stable model are non-Lagrangian, but they admit the Hamiltonian form of dynamics with a Hamiltonian that is bounded from below. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
7 pages, 260 KiB  
Communication
Holographic Foam Cosmology: From the Late to the Early Universe
by Yee Jack Ng
Symmetry 2021, 13(3), 435; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13030435 - 8 Mar 2021
Cited by 3 | Viewed by 1331
Abstract
Quantum fluctuations endow spacetime with a foamy texture. The degree of foaminess is dictated by black hole physics to be of the holographic type. Applied to cosmology, the holographic foam model predicts the existence of dark energy with critical energy density in the [...] Read more.
Quantum fluctuations endow spacetime with a foamy texture. The degree of foaminess is dictated by black hole physics to be of the holographic type. Applied to cosmology, the holographic foam model predicts the existence of dark energy with critical energy density in the current (late) universe, the quanta of which obey infinite statistics. Furthermore, we use the deep similarities between turbulence and the spacetime foam phase of strong quantum gravity to argue that the early universe was in a turbulent regime when it underwent a brief cosmic inflation with a “graceful” transition to a laminar regime. In this scenario, both the late and the early cosmic accelerations have their origins in spacetime foam. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
19 pages, 1257 KiB  
Article
Reference Frame Induced Symmetry Breaking on Holographic Screens
by Chris Fields, James F. Glazebrook and Antonino Marcianò
Symmetry 2021, 13(3), 408; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13030408 - 3 Mar 2021
Cited by 17 | Viewed by 2372
Abstract
Any interaction between finite quantum systems in a separable joint state can be viewed as encoding classical information on an induced holographic screen. Here we show that when such an interaction is represented as a measurement, the quantum reference frames (QRFs) deployed to [...] Read more.
Any interaction between finite quantum systems in a separable joint state can be viewed as encoding classical information on an induced holographic screen. Here we show that when such an interaction is represented as a measurement, the quantum reference frames (QRFs) deployed to identify systems and pick out their pointer states induce decoherence, breaking the symmetry of the holographic encoding in an observer-relative way. Observable entanglement, contextuality, and classical memory are, in this representation, logical and temporal relations between QRFs. Sharing entanglement as a resource requires a priori shared QRFs. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
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Other

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11 pages, 969 KiB  
Brief Report
A Note on Effects of Generalized and Extended Uncertainty Principles on Jüttner Gas
by Hooman Moradpour, Sarah Aghababaei and Amir Hadi Ziaie
Symmetry 2021, 13(2), 213; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13020213 - 28 Jan 2021
Cited by 10 | Viewed by 1787
Abstract
In recent years, the implications of the generalized (GUP) and extended (EUP) uncertainty principles on Maxwell–Boltzmann distribution have been widely investigated. However, at high energy regimes, the validity of Maxwell–Boltzmann statistics is under debate and instead, the Jüttner distribution is proposed as the [...] Read more.
In recent years, the implications of the generalized (GUP) and extended (EUP) uncertainty principles on Maxwell–Boltzmann distribution have been widely investigated. However, at high energy regimes, the validity of Maxwell–Boltzmann statistics is under debate and instead, the Jüttner distribution is proposed as the distribution function in relativistic limit. Motivated by these considerations, in the present work, our aim is to study the effects of GUP and EUP on a system that obeys the Jüttner distribution. To achieve this goal, we address a method to get the distribution function by starting from the partition function and its relation with thermal energy which finally helps us in finding the corresponding energy density states. Full article
(This article belongs to the Special Issue Symmetry in Quantum Theory of Gravity)
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