Special Issue "Recent Advances in Quantum Gravity"

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

Deadline for manuscript submissions: 31 October 2020.

Special Issue Editor

Prof. Dr. Roberto Casadio
Website
Guest Editor
Department of Physics and Astronomy, Alma Mater Studiorum Università di Bologna, Bologna, Italy
Interests: theoretical physics; cosmology; generalised theories of gravity

Special Issue Information

Dear Colleagues,

This Special Issue is devoted to new and recent theoretical investigations aiming at understanding physical aspects of the fundamental gravitational interaction which should be relevant at the quantum level, both from top–down (mathematical methods and general theory to phenomenology) as well as bottom–up (studies of specific systems to general theory) approaches, and with applications to the astrophysics of very compact and exotic objects, black hole physics, and the issue of space-time singularities, gravitational wave production in black hole mergers, and cosmology of the early and present Universe.

Prof. Dr. Roberto Casadio
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 papers will be 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 1400 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

  • Black holes
  • Binary mergers
  • Compact astrophysical objects
  • Dark energy
  • Dark matter
  • Early cosmology
  • Effective field theory of gravity

Published Papers (2 papers)

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Research

Open AccessArticle
Unsettling Physics in the Quantum-Corrected Schwarzschild Black Hole
Symmetry 2020, 12(8), 1264; https://doi.org/10.3390/sym12081264 - 01 Aug 2020
Abstract
We study a quantum-corrected Schwarzschild black hole proposed recently in Loop Quantum Gravity. Prompted by the fact that corrections to the innermost stable circular orbit of Schwarzschild diverge, we investigate time-like and null radial geodesics. Massive particles moving radially outwards are confined, while [...] Read more.
We study a quantum-corrected Schwarzschild black hole proposed recently in Loop Quantum Gravity. Prompted by the fact that corrections to the innermost stable circular orbit of Schwarzschild diverge, we investigate time-like and null radial geodesics. Massive particles moving radially outwards are confined, while photons make it to infinity with infinite redshift. This unsettling physics, which deviates radically from both Schwarzschild (near the horizon) and Minkowski (at infinity) is due to repulsion by the negative quantum energy density that makes the quasilocal mass vanish as one approaches spatial infinity. Full article
(This article belongs to the Special Issue Recent Advances in Quantum Gravity)
Open AccessArticle
MGD Dirac Stars
Symmetry 2020, 12(4), 508; https://doi.org/10.3390/sym12040508 - 01 Apr 2020
Cited by 6
Abstract
The method of geometric deformation (MGD) is here employed to study compact stellar configurations, which are solutions of the effective Einstein–Dirac coupled field equations on fluid branes. Non-linear, self-interacting, fermionic fields are then employed to derive MGD Dirac stars, whose properties are analyzed [...] Read more.
The method of geometric deformation (MGD) is here employed to study compact stellar configurations, which are solutions of the effective Einstein–Dirac coupled field equations on fluid branes. Non-linear, self-interacting, fermionic fields are then employed to derive MGD Dirac stars, whose properties are analyzed and discussed. The MGD Dirac star maximal mass is shown to increase as a specific function of the spinor self-interaction coupling constant, in a realistic model involving the most strict phenomenological current bounds for the brane tension. Full article
(This article belongs to the Special Issue Recent Advances in Quantum Gravity)
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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.

1) Title: Long Range Quantum Gravity Autors: Mariano Cadoni and Matteo Tuveri
Abstract: It is a tantalising possibility that quantum gravity states remaining coherent at astrophysical, galactic and cosmological scales could exist and that they could play crucial role in understanding macroscopic gravitational effects. In this essay we review recent attempts along this direction and discuss this possibility in a critical way. We also show how key features of the gravitational interaction such as black hole thermodynamics, holography and the galactic phenomena currently attributed to dark matter can be explained in this framework.

2) Title: MGD-decoupled Dirac stars Author: Roldao da Rocha
Abstract: In the membrane paradigm of AdS/CFT, encompassing General Relativity (GR), the method of geometric deformation (MGD) is used to study Dirac compact stellar solutions of the effective Einstein field equations on the brane. Fermionic fields are employed to derive regular stationary asymptotically flat solutions, corresponding to MGD-decoupled compact objects. Our solutions encompass stellar distributions of Chandrasekhar mass order. Analysis of the MGD-decoupled Dirac stars with the GR Dirac stars therefore provides signatures of the MGD-decoupling paradigm.

3) Title: Lorentz Invariance Violation from cosmological entanglement entropy Authors: Salvatore Capozziello and Orlando Luongo
Abstract: In the framework of quantum decoherence, the existence of quantum entanglement between cosmological eras has been conjectured. As a byproduct, a further Von Neumann entropy naturally emerges, with the property of being additive with respect to the standard thermodynamical entropy. The consequence of this fact, in a homogeneous and isotropic universe, may lead to Lorentz Invariance Violation (LIV), manifesting in terms of energy dependent modification of standard relativistic dispersion relation. We investigate the specific modification inferred from our picture by investigating the energy dependent time offsets in different energy bands on a sample of high energetic sources. We show the expected differences, under modifications of given cosmological backgrounds. We provide weak indications towards LIV evidences at early stages of the universe evolution and discuss the possible consequences on observational cosmology.

4) Title: Glimpses on the micro black hole Planck phase
Author: Fabio Scardigli
Abstract: Mass thresholds, lifetimes, entropy and heat capacity for micro black holes close to their
late Schwarzschild phase are computed using two different generalized uncertainty principles,
in the framework of models with extra spatial dimensions. Emission of both photons and
gravitons (in the bulk) are taken into account. Results are discussed and compared.

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