Symmetry in Gravity Theories and Cosmology

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

Deadline for manuscript submissions: 30 April 2024 | Viewed by 869

Special Issue Editors


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Guest Editor
Associate Professor, Department of Physics, Indira Gandhi Institute of Technology, Sarang, Dhenkanal 759146, India
Interests: gravitation and cosmology; astrophysics, nuclear equation of state

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Guest Editor
Department of Physics, Indira Gandhi Institute of Technology, Sarang, Dhenkanal 759146, Odisha, India
Interests: theoretical nuclear physics; cosmology

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Guest Editor
Associate Professor, Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), University of Maragheh, Maragheh, Iran
Interests: gravity; cosmology; quantum mechanics; gravity analogue; astrophysics

Special Issue Information

Dear Colleagues,

The late-time cosmic speed-up phenomenon, as witnessed in recent observations, has triggered the development of new ideas and concepts. Einstein’s general relativity (GR) theory is able to explain such a phenomenon through the incorporation of additional dynamical degrees of freedom, such as quintessence, tachyons, phantom fields, etc., usually dubbed as dark energy candidates. However, geometrically modified theories of gravity can handle this issue without the need for any dark energy candidates. On the other hand, theoretical shortcomings and tensions between different cosmological observations have raised questions about GR, at least at the large energy scale. Additionally, questions about the symmetrical expansion of the universe have arisen. In this context, symmetry plays an important role in addressing many issues arising in the fields of cosmology and astrophysics. Usually, for a dynamical system, different symmetries, such Noether symmetry and the non-local conservation laws, help to simplify the system of equations, allowing physical systems to be studied in an analytic manner.

This Special Issue aims to present the role played by symmetries and conservation laws in addressing issues in gravitation and cosmology concerning recent research challenges.

Dr. Sunil Kumar Tripathy
Dr. Dipanjali Behera
Dr. Hooman Moradpour
Guest Editors

Manuscript Submission Information

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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

  • wormholes
  • Casimir wormholes
  • modified theories of gravity
  • bouncing cosmological models
  • observational constraints on modified gravity theories
  • dark energy models
  • Noether symmetry
  • scalar field cosmology
  • exact solutions

Published Papers (1 paper)

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Research

22 pages, 330 KiB  
Article
The Post-Quasi-Static Approximation: An Analytical Approach to Gravitational Collapse
by Luis Herrera, Alicia Di Prisco and Justo Ospino
Symmetry 2024, 16(3), 341; https://doi.org/10.3390/sym16030341 - 12 Mar 2024
Viewed by 553
Abstract
A seminumerical approach proposed many years ago for describing gravitational collapse in the post-quasi-static approximation is modified in order to avoid the numerical integration of the basic differential equations the approach is based upon. For doing that we have to impose some restrictions [...] Read more.
A seminumerical approach proposed many years ago for describing gravitational collapse in the post-quasi-static approximation is modified in order to avoid the numerical integration of the basic differential equations the approach is based upon. For doing that we have to impose some restrictions on the fluid distribution. More specifically, we shall assume the vanishing complexity factor condition, which allows for analytical integration of the pertinent differential equations and leads to physically interesting models. Instead, we show that neither the homologous nor the quasi-homologous evolution are acceptable since they lead to geodesic fluids, which are unsuitable for being described in the post-quasi-static approximation. Also, we prove that, within this approximation, adiabatic evolution also leads to geodesic fluids, and therefore, we shall consider exclusively dissipative systems. Besides the vanishing complexity factor condition, additional information is required for a full description of models. We shall propose different strategies for obtaining such an information, which are based on observables quantities (e.g., luminosity and redshift), and/or heuristic mathematical ansatz. To illustrate the method, we present two models. One model is inspired in the well-known Schwarzschild interior solution, and another one is inspired in Tolman VI solution. Full article
(This article belongs to the Special Issue Symmetry in Gravity Theories and Cosmology)

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: A review of wormhole stabilization in f(R) gravity theories
Authors: Ramesh Radhakrishnan, Patrick Brown, Jacob Matulevich and Gerald Cleaver
Affiliation: 1. Early Universe, Cosmology and Strings (EUCOS) Group, Center for Astrophysics, Space Physics and Engineering Research (CASPER), Baylor University, Waco, TX 76798 2. Department of Physics, Baylor University, Waco, TX 76798, USA
Abstract: It has been proven that in standard Einstein gravity, exotic matter (i.e. matter violating the weak and null energy conditions) is required to stabilize traversable wormholes. Quantum field theory does, theoretically, permit these violations. In the case of the Casimir effect, these violations have been experimentally proven. However, it is still unknown if it is possible to create these violations on a macroscopic scale. Therefore, it is advantageous to investigate methods of minimizing the use of exotic matter. One such area of interest is extended theories of Einstein gravity. It has been claimed that in some extended theories, stable traversable wormholes solutions can be found without the use of exotic matter. There are many extended theories of gravity. In this review paper we first explore f(R) theories and then explore some wormhole solutions in f(R) theories including Einstein-Gauss-Bonnet gravity and Lovelock gravity.

Title: THE POST–QUASI–STATIC APPROXIMATION: AN ANALYTICAL APPROACH TO GRAVITATIONAL COLLAPSE
Authors: Luis Herrera; Alicia Di Prisco; Justo Ospino
Affiliation: Instituto Universitario de Física Fundamental y Matemáticas, Universidad de Salamanca, 37007 Salamanca, Spain
Abstract: A semi–numerical approach proposed many years ago for describing gravitational collapse in the post–quasi–static approximation , , , , is modified in order to avoid the numerical integration of the basic differential equations the approach is based upon. For doing that we have to impose some restrictions on the fluid distribution. More specifically, we shall assume the vanishing complexity factor condition, which allows for analytical integration of the pertinent differential equations and leads to physically interesting models. Instead, we show that neither the homologous nor the quasi–homologous evolution are acceptable since they lead to geodesic fluids, which are unsuitable for being described in the post–quasi–static approximation. Also, we prove that, within this approximation, adiabatic evolution also leads to geodesic fluids and therefore we shall consider exclusively dissipative systems. Besides the vanishing complexity factor condition, additional information is required for a full description of models. We shall propose different strategies for obtaining such an information, which are based on observables quantities (e.g. luminosity and redshift), and/or heuristic mathematical ansatz. To illustrate the method, we present two models. One model is inspired in the well known Schwarzschild interior solution, and another one is inspired in Tolman VI solution.

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