Modified Gravity, Supergravity and Cosmological Applications

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

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 5499

Special Issue Editor

1. DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
2. INFN, Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy
Interests: theoretical high-energy physics; fundamental symmetries; supergravity; modified gravity; gauge field theory; relational formalism; differential geometry
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Special Issue Information

Dear Colleagues,

The term “modified gravity” has now become standard for gravitational theories differing from general relativity, whose rigorous mathematical formulation resides in Riemannian geometry. In this context, generalizations and extensions of Riemannian geometry have been proposed, releasing, for instance, the Riemannian assumptions of metric compatibility and torsionlessness of the affine connection. This gives rise to the framework of non-Riemannian geometry, in which several modified (alternative) theories of gravity going beyond general relativity have been developed over the years.

A guiding principle in both Einstein’s well-celebrated theory and modified gravity is the concept of symmetry, a common thread that leads us to introduce another prominent extension of general relativity, proposed in the 1970s: supergravity, where invariance under general coordinate transformations follows from a key symmetry principle that goes under the name of supersymmetry. For a given field content and spacetime dimensions, supersymmetry totally determines the spectrum and interactions of supergravity. The latter inherits non-renormalizability from general relativity and, even if divergences in supergravity are softened with respect to non-supersymmetric gravity, it does not seem to be a finite theory. Therefore, it has to be understood as an effective “low-energy” theory describing the interactions of the light degrees of freedom of some underlying quantum theory, which is supposed to be the superstring. Supergravity encodes superstring large-scale dynamics even in limits in which a superstring consistent formulation is missing.

The objective of this Special Issue of Symmetry is to address diverse aspects of gravity theories beyond general relativity under different perspectives, in the direction of a deeper understanding of open questions regarding gravitational interaction, also in relation to other fundamental forces. Both research and review papers are welcomed.

Potential topics covering, but not limited to, the following subheadings are deemed suitable for submission: modified (alternative) theories of gravity, supergravity models, group theoretical aspects and solutions; gravity in dimensions other than four and in non-relativistic regimes; spacetime symmetries, supersymmetry in superspace, and cohomological properties of the latter; gauge/gravity duality and applications; and gravitation and cosmology.

Dr. Lucrezia Ravera
Guest Editor

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Keywords

  • spacetime symmetries
  • classical and quantum aspects of gravity
  • modified gravity
  • metric-affine gravity
  • gravity in dimensions other than four
  • superspace and cohomology
  • supergravity models
  • AdS/CFT correspondence
  • black holes in gravity and supergravity
  • gravitation and cosmology

Published Papers (4 papers)

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Research

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19 pages, 727 KiB  
Article
Reconstruction of Scalar-Torsion Gravity Theories from the Physical Potential of a Scalar Field
by Sergei V. Chervon and Igor V. Fomin
Symmetry 2023, 15(2), 291; https://0-doi-org.brum.beds.ac.uk/10.3390/sym15020291 - 20 Jan 2023
Cited by 4 | Viewed by 1117
Abstract
We consider scalar-torsion gravity theories based on the exact solutions of a physical type of potential for cosmological inflationary models based on the non-minimal coupling of a scalar field and torsion. We analyzed the inflationary models with different types of inflationary dynamics and [...] Read more.
We consider scalar-torsion gravity theories based on the exact solutions of a physical type of potential for cosmological inflationary models based on the non-minimal coupling of a scalar field and torsion. We analyzed the inflationary models with different types of inflationary dynamics and corresponding scalar field parameters. Such an approach allows us to consider different physical potentials and types of scalar-torsion gravity theories in the context of the realization of both stages of accelerated expansion of the universe. We also considered the correspondence surrounding the proposed inflationary models and the observational constraints on the parameters of cosmological perturbations. Full article
(This article belongs to the Special Issue Modified Gravity, Supergravity and Cosmological Applications)
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25 pages, 430 KiB  
Article
Space, Matter and Interactions in a Quantum Early Universe Part I: Kac–Moody and Borcherds Algebras
by Piero Truini, Alessio Marrani, Michael Rios and Klee Irwin
Symmetry 2021, 13(12), 2342; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13122342 - 06 Dec 2021
Cited by 1 | Viewed by 1904
Abstract
We introduce a quantum model for the universe at its early stages, formulating a mechanism for the expansion of space and matter from a quantum initial condition, with particle interactions and creation driven by algebraic extensions of the Kac–Moody Lie algebra e9 [...] Read more.
We introduce a quantum model for the universe at its early stages, formulating a mechanism for the expansion of space and matter from a quantum initial condition, with particle interactions and creation driven by algebraic extensions of the Kac–Moody Lie algebra e9. We investigate Kac–Moody and Borcherds algebras, and we propose a generalization that meets further requirements that we regard as fundamental in quantum gravity. Full article
(This article belongs to the Special Issue Modified Gravity, Supergravity and Cosmological Applications)
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14 pages, 731 KiB  
Article
Space, Matter and Interactions in a Quantum Early Universe. Part II: Superalgebras and Vertex Algebras
by Piero Truini, Alessio Marrani, Michael Rios and Klee Irwin
Symmetry 2021, 13(12), 2289; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13122289 - 01 Dec 2021
Cited by 1 | Viewed by 1098
Abstract
In our investigation on quantum gravity, we introduce an infinite dimensional complex Lie algebra gu that extends e9. It is defined through a symmetric Cartan matrix of a rank 12 Borcherds algebra. We turn gu into a Lie superalgebra [...] Read more.
In our investigation on quantum gravity, we introduce an infinite dimensional complex Lie algebra gu that extends e9. It is defined through a symmetric Cartan matrix of a rank 12 Borcherds algebra. We turn gu into a Lie superalgebra sgu with no superpartners, in order to comply with the Pauli exclusion principle. There is a natural action of the Poincaré group on sgu, which is an automorphism in the massive sector. We introduce a mechanism for scattering that includes decays as particular resonant scattering. Finally, we complete the model by merging the local sgu into a vertex-type algebra. Full article
(This article belongs to the Special Issue Modified Gravity, Supergravity and Cosmological Applications)
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Review

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41 pages, 535 KiB  
Review
Metric-Affine Myrzakulov Gravity Theories
by Nurgissa Myrzakulov, Ratbay Myrzakulov and Lucrezia Ravera
Symmetry 2021, 13(10), 1855; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13101855 - 03 Oct 2021
Cited by 13 | Viewed by 1813
Abstract
In this paper, we review the so-called Myrzakulov Gravity models (MG-N, with N = I, II, …, VIII) and derive their respective metric-affine generalizations (MAMG-N), discussing also their particular sub-cases. The field equations of the theories are obtained by regarding the metric tensor [...] Read more.
In this paper, we review the so-called Myrzakulov Gravity models (MG-N, with N = I, II, …, VIII) and derive their respective metric-affine generalizations (MAMG-N), discussing also their particular sub-cases. The field equations of the theories are obtained by regarding the metric tensor and the general affine connection as independent variables. We then focus on the case in which the function characterizing the aforementioned metric-affine models is linear and consider a Friedmann-Lemaître–Robertson–Walker background to study cosmological aspects and applications. Historical motivation for this research is thoroughly reviewed and specific physical motivations are provided for the aforementioned family of alternative theories of gravity. Full article
(This article belongs to the Special Issue Modified Gravity, Supergravity and Cosmological Applications)
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