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Universe
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Spacetime Symmetry
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Spacetime Symmetry

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Field Theory".

Deadline for manuscript submissions: closed (10 December 2022) | Viewed by 8540

Special Issue Editors

Dr. Stefano Viaggiu

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Guest Editor
Dipartimento di Scienze Ingegneristiche, Università degli Studi Guglielmo Marconi, Via Plinio 44, I-00193 Roma, Italy
Interests: general relativity; cosmology; quantum gravity; statistical mechanics
Dr. Fabio Rinaldi

E-Mail Website
Guest Editor
Dipartimento di Scienze Ingegneristiche, University degli Studi Guglielmo Marconi, Via Plinio 44, I-00193 Rome, Italy
Interests: Schroedinger equation; quantum mechanics; functional analysis; point interactions; renormalization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

As well known, symmetries in physics represent a useful and powerful tool to solve or simplify many physical problems, ranging from classical to quantum physics. For example, spacetime symmetries are essential for understanding, interpreting, classifying, and finding exact solutions in general relativity, or exploring possible formulations of quantum gravity.

This Special Issue aims to collect papers representing both original research and reviews on recent progress on a broad range of arguments, from the use of spacetime symmetries in general relativity, modified and loop quantum gravity, string theory, non-commutative spacetimes, gauge theories, extensions of the standard particle model, and modular theory. It also includes, for example, issues related to the implementation or deformation of classical symmetries at a quantum level or the study of supertranslations for black hole physics.

We would like to address these issues and arguments in this Special Issue. We thus invite our colleagues to submit their articles covering the above topics and arguments or related ones. All submitted articles, including review articles, should include clear purposes, results, and conclusions.

Dr. Stefano Viaggiu
Dr. Fabio Rinaldi
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. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. 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

  • spacetime symmetries
  • spacetime isometries
  • exact solutions in general relativity
  • exact solutions in modified gravity
  • symmetries at quantum level
  • symmetries in quantum gravity
  • symmetries in non-commutative spacetimes
  • symmetries in modified gravity
  • symmetries in string theory
  • symmetries in loop gravity

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Published Papers (4 papers)

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Research

17 pages, 336 KiB  
Article
Isotropic Perfect Fluids in Modified Gravity
by Shavani Naicker, Sunil D. Maharaj and Byron P. Brassel
Universe 2023, 9(1), 47; https://doi.org/10.3390/universe9010047 - 11 Jan 2023
Cited by 10 | Viewed by 2019
Abstract
We generate the Einstein–Gauss–Bonnet field equations in higher dimensions for a spherically symmetric static spacetime. The matter distribution is a neutral fluid with isotropic pressure. The condition of isotropic pressure, an Abel differential equation of the second kind, is transformed to a first [...] Read more.
We generate the Einstein–Gauss–Bonnet field equations in higher dimensions for a spherically symmetric static spacetime. The matter distribution is a neutral fluid with isotropic pressure. The condition of isotropic pressure, an Abel differential equation of the second kind, is transformed to a first order nonlinear canonical differential equation. This provides a mechanism to generate exact solutions systematically in higher dimensions. Our solution generating algorithm is a different approach from those considered earlier. We show that a specific choice of one potential leads to a new solution for the second potential for all spacetime dimensions. Several other families of exact solutions to the condition of pressure isotropy are found for all spacetime dimensions. Earlier results are regained from our treatments. The difference with general relativity is highlighted in our study. Full article
(This article belongs to the Special Issue Spacetime Symmetry)
19 pages, 460 KiB  
Article
Study of Anisotropic Fluid Distributed Hyperbolically in f(R,T,Q) Gravity
by Hamna Asad and Zeeshan Yousaf
Universe 2022, 8(12), 630; https://doi.org/10.3390/universe8120630 - 28 Nov 2022
Cited by 20 | Viewed by 1534
Abstract
The core of this manuscript is to conduct a broad investigation into the features of static matter configurations with hyperbolical symmetry, which might possibly serve as formation of corresponding spacetime within the limits of f(R,T,Q) gravity, where (Q ≡ RασT [...] Read more.
The core of this manuscript is to conduct a broad investigation into the features of static matter configurations with hyperbolical symmetry, which might possibly serve as formation of corresponding spacetime within the limits of f(R,T,Q) gravity, where (Q ≡ RασTασ). We recognize that such matter distributions can be anisotropic in pressure, with just two primary stresses unequal and a negative energy density. Usually, negative matter densities are suggested in extreme cosmological and astrophysical situations, particularly with regard to quantum occurrences that might occur within the horizon. Eventually, we construct a generic formalism that allows every static hyperbolically symmetric (HS) fluid solution to be expressed with respect to two generating functions (GFs). Full article
(This article belongs to the Special Issue Spacetime Symmetry)
10 pages, 279 KiB  
Article
Curvature Inheritance Symmetry in Ricci Flat Spacetimes
by Mohammad Salman, Musavvir Ali and Mohd Bilal
Universe 2022, 8(8), 408; https://doi.org/10.3390/universe8080408 - 4 Aug 2022
Cited by 2 | Viewed by 1761
Abstract
In this article, we study curvature inheritance symmetry in Ricci flat spacetimes. We show that, if Ricci flat spacetimes are not of Petrov type N, and admit curvature inheritance symmetries, then the only existing symmetries are conformal motions. We also prove that the [...] Read more.
In this article, we study curvature inheritance symmetry in Ricci flat spacetimes. We show that, if Ricci flat spacetimes are not of Petrov type N, and admit curvature inheritance symmetries, then the only existing symmetries are conformal motions. We also prove that the only Ricci flat spacetime that admits a proper curvature inheritance symmetry and is of Petrov type other than N is the flat spacetime. Next, we find that the vacuum pp-waves of Petrov type N if admit curvature inheritance symmetry, then conformal motion implies homothetic motion. Full article
(This article belongs to the Special Issue Spacetime Symmetry)
31 pages, 1271 KiB  
Article
Non-Static Fluid Spheres Admitting a Conformal Killing Vector: Exact Solutions
by Luis Herrera, Alicia Di Prisco and Justo Ospino
Universe 2022, 8(6), 296; https://doi.org/10.3390/universe8060296 - 24 May 2022
Cited by 23 | Viewed by 2059
Abstract
We carry on a general study on non-static spherically symmetric fluids admitting a conformal Killing vector (CKV). Several families of exact analytical solutions are found for different choices of the CKV in both the dissipative and the adiabatic regime. To specify the solutions, [...] Read more.
We carry on a general study on non-static spherically symmetric fluids admitting a conformal Killing vector (CKV). Several families of exact analytical solutions are found for different choices of the CKV in both the dissipative and the adiabatic regime. To specify the solutions, besides the fulfillment of the junction conditions on the boundary of the fluid distribution, different conditions are imposed, such as a vanishing complexity factor and quasi-homologous evolution. A detailed analysis of the obtained solutions and its prospective applications to astrophysical scenarios, as well as alternative approaches to obtain new solutions, are discussed. Full article
(This article belongs to the Special Issue Spacetime Symmetry)
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