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Symmetry
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Symmetries in Gravity Research: Classical and Quantum
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Symmetries in Gravity Research: Classical and Quantum

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

Deadline for manuscript submissions: 30 September 2024 | Viewed by 1666

Special Issue Editors

Prof. Dr. Carlos Frajuca

E-Mail Website
Guest Editor
Department of Mechanics, Sao Paulo Federal Institute (IFSP), Sao Paulo, Brazil
Interests: gravitation; gravitational waves detectors
Prof. Dr. Nadja Simão Magalhães

E-Mail Website
Guest Editor
Associate Professor, Department of Physics, Federal University of Sao Paulo, Diadema 09913-030, Brazil
Interests: physics (with emphasis on gravitation and astrophysics, including cosmology); engineering (with emphasis on signal analysis, mathematical modelling of systems and electromechanical transducers)

Special Issue Information

Dear Colleagues,

The analysis of symmetries is often performed to investigate, simplify and solve physical problems. For instance, in general relativity (GR), spherical symmetry is important in calculating the Schwarzschild solution, as well as in proving the nonexistence of gravitational radiation emission from a spherically pulsating star. Symmetries also relate to preserved properties as geodesics in spacetime. 

Two pillars of modern physics, GR and quantum mechanics (QM), separately agree well with experimental tests in certain domains. However, when the two theories are applied to describe the same phenomenon, they are likely to fail as GR resources do not work properly within the domains of QM. It is believed that GR is a low-gravitational field approximation to a more fundamental theory, quantum gravity (QG), which may require the development of new approaches to gravity for its full description.

In order to develop QG or to have a better understanding of gravitation, it is unavoidable to study gravity in the strong regime, which is still experimentally unattainable. One compelling option is to explore symmetries to understand gravitation in this regime.

Prof. Dr. Carlos Frajuca
Prof. Dr. Nadja Simão Magalhães
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.

Keywords

  • symmetries
  • symmetries in gravitation
  • symmetries in quantum gravity
  • preserving properties in gravitation
  • symmetries in general relativity

Published Papers (2 papers)

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Research

9 pages, 1364 KiB  
Article
Novel Phenomena of the Hartle–Hawking Wave Function
by Subeom Kang, Wan-il Park and Dong-han Yeom
Symmetry 2024, 16(4), 444; https://doi.org/10.3390/sym16040444 - 06 Apr 2024
Viewed by 319
Abstract
We find a novel phenomenon in the solution to the Wheeler–DeWitt equation by solving numerically the equation assuming O(4)-symmetry and imposing the Hartle–Hawking wave function as a boundary condition. In the slow-roll limit, as expected, the numerical solution gives [...] Read more.
We find a novel phenomenon in the solution to the Wheeler–DeWitt equation by solving numerically the equation assuming O(4)-symmetry and imposing the Hartle–Hawking wave function as a boundary condition. In the slow-roll limit, as expected, the numerical solution gives the most dominant steepest-descent that describes the probability distribution for the initial condition of a universe. The probability is consistent with the Euclidean computations, and the overall shape of the wave function is compatible with analytical approximations, although there exist novel differences in the detailed probability computation. Our approach gives an alternative point of view for the no-boundary wave function from the wave function point of view. Possible interpretations and conceptual issues of this wave function are discussed. Full article
(This article belongs to the Special Issue Symmetries in Gravity Research: Classical and Quantum)
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18 pages, 7349 KiB  
Article
Orbital Regularity of Exoplanets and the Symmetries of the Kepler Problem
by József Cseh, Phong Dang, Sándor Szilágyi and Géza Lévai
Symmetry 2023, 15(12), 2114; https://doi.org/10.3390/sym15122114 - 26 Nov 2023
Viewed by 947
Abstract
We investigate the question whether or not the orbitals of exoplanets follow the symmetry-governed sequence found by Barut from the dynamical group of the Kepler problem. In particular, we consider their star distances, periods, and velocities. Previous studies have shown the validity of [...] Read more.
We investigate the question whether or not the orbitals of exoplanets follow the symmetry-governed sequence found by Barut from the dynamical group of the Kepler problem. In particular, we consider their star distances, periods, and velocities. Previous studies have shown the validity of this regularity for our solar system, and for some selected exoplanet systems. Here, we study all the systems which are known with four or more planets. A remarkable result is found: 63 out of 100 systems show a better agreement between the theory and observation than our solar system. We discuss the relation between the symmetry-inspired transformations and the generalized Titius–Bode (gTB) rule. It turns out that the gTB rule, which has been considered purely empirical, can be obtained from the transformations corresponding to the dynamical group of the Kepler problem. Full article
(This article belongs to the Special Issue Symmetries in Gravity Research: Classical and Quantum)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Second order inflationary perturbations of the inflation potential and its symmetries
Authors: Paulo Sergio Custodio1; Cristian Ghezzi2; Nadja Simao Magalhaes3; Carlos Frajuca4
Affiliation: 1. UNIP, Sao Paulo, SP, Brazil 2. Independent Researcher, Bahia Blanca, Argentina 3. Unifesp, Diadema, SP, Brazil 4. FURG, Rio Grande, RS, Brazil
Abstract: In inflationary cosmology the form of the inflaton potential is still an open problem. In this work, second order effects of the Inflaton potential are evaluated and related to the known formula for the inflationary perturbations in a wide range of scales. It is found that the fluctuations in large scales are smaller in amplitude according to the observed pattern measured by MAP and other experiments. This effect may help to unravel the unknown Inflaton potential form and imposes new constraints on the parameters that define this potential. Symmetry conditions that are present when the signal of the inflaton changes are discussed.

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