Editorial

3 pages, 174 KiB

Open AccessEditorial

Editorial for the Special Issue “Torsion-Gravity and Spinors in Fundamental Theoretical Physics”

by Luca Fabbri

Universe 2023, 9(6), 269; https://doi.org/10.3390/universe9060269 - 04 Jun 2023

Viewed by 839

The Einsteinian theory of gravitation is among the best-established theories ever conceived in physics [...] Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

Research

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12 pages, 297 KiB

Open AccessArticle

Torsionally-Induced Stability in Spinors

by Luca Fabbri

Universe 2023, 9(2), 73; https://doi.org/10.3390/universe9020073 - 30 Jan 2023

Cited by 2 | Viewed by 692

Abstract

We consider the role of the torsion axial-vector played in the dynamics of the Dirac spinor fields: we show that the torsional correction entails effects that render regular the otherwise singular spinorial matter field distribution. Comments about consequences for physics are eventually given. [...] Read more.

We consider the role of the torsion axial-vector played in the dynamics of the Dirac spinor fields: we show that the torsional correction entails effects that render regular the otherwise singular spinorial matter field distribution. Comments about consequences for physics are eventually given. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

13 pages, 350 KiB

Open AccessArticle

Search for Manifestations of Spin–Torsion Coupling

by Mariya Iv. Trukhanova, Pavel Andreev and Yuri N. Obukhov

Universe 2023, 9(1), 38; https://doi.org/10.3390/universe9010038 - 06 Jan 2023

Cited by 2 | Viewed by 1270

Abstract

We investigate the axial vector spin–torsion coupling effects in the framework of the Poincaré gauge theory of gravity with the general Yang–Mills type Lagrangian. The dynamical equations for the “electric” and “magnetic” components of the torsion field variable are obtained in the general [...] Read more.

We investigate the axial vector spin–torsion coupling effects in the framework of the Poincaré gauge theory of gravity with the general Yang–Mills type Lagrangian. The dynamical equations for the “electric” and “magnetic” components of the torsion field variable are obtained in the general form and it is shown that the helicity density and the spin density of the electromagnetic field appear as the physical sources. The modified Maxwell’s equations for the electromagnetic field are derived, and the electromagnetic wave propagation under the action of the uniform homogeneous torsion field is considered. We demonstrate the Faraday effect of rotation of the polarization for such a wave and establish the strong bound on the possible cosmic axial torsion field from the astrophysical data. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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13 pages, 405 KiB

Open AccessArticle

Big Bang Nucleosynthesis Constraints on f (T, T_G) Gravity

by Petros Asimakis, Emmanuel N. Saridakis, Spyros Basilakos and Kuralay Yesmakhanova

Universe 2022, 8(9), 486; https://doi.org/10.3390/universe8090486 - 14 Sep 2022

Cited by 3 | Viewed by 1221

Abstract

We confront

f (T, T_{G})

gravity, with big bang nucleosynthesis (BBN) requirements. The former is obtained using both the torsion scalar, as well as the teleparallel equivalent of the Gauss–Bonnet term, in the Lagrangian, resulting to modified Friedmann equations [...] Read more.

We confront

f (T, T_{G})

gravity, with big bang nucleosynthesis (BBN) requirements. The former is obtained using both the torsion scalar, as well as the teleparallel equivalent of the Gauss–Bonnet term, in the Lagrangian, resulting to modified Friedmann equations in which the extra torsional terms constitute an effective dark energy sector. We calculate the deviations of the freeze-out temperature

T_{f}

, caused by the extra torsion terms in comparison to

Λ

CDM paradigm. Then, we impose five specific

f (T, T_{G})

models and extract the constraints on the model parameters in order for the ratio

| Δ T_{f} / T_{f} |

to satisfy the observational BBN bound. As we find, in most of the models the involved parameters are bounded in a narrow window around their general relativity values as expected, asin the power-law model, where the exponent n needs to be

n ≲ 0.5

. Nevertheless, the logarithmic model can easily satisfy the BBN constraints for large regions of the model parameters. This feature should be taken into account in future model building. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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23 pages, 1503 KiB

Open AccessArticle

A Possible Explanation of Dark Matter and Dark Energy Involving a Vector Torsion Field

by Graeme W. Milton

Universe 2022, 8(6), 298; https://doi.org/10.3390/universe8060298 - 25 May 2022

Cited by 2 | Viewed by 1520

Abstract

A simple gravitational model with torsion is studied, and it is suggested that it could explain the dark matter and dark energy in the universe. It can be reinterpreted as a model using the Einstein gravitational equations where spacetime has regions filled with [...] Read more.

A simple gravitational model with torsion is studied, and it is suggested that it could explain the dark matter and dark energy in the universe. It can be reinterpreted as a model using the Einstein gravitational equations where spacetime has regions filled with a perfect fluid with negative energy (pressure) and positive mass density, other regions containing an anisotropic substance that in the rest frame (where the momentum is zero) has negative mass density and a uniaxial stress tensor, and possibly other “luminal” regions where there is no rest frame. The torsion vector field is inhomogeneous throughout spacetime, and possibly turbulent. Numerical simulations should reveal whether or not the equations are consistent with cosmological observations of dark matter and dark energy. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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14 pages, 350 KiB

Open AccessArticle

Quantum Hydrodynamics of Spinning Particles in Electromagnetic and Torsion Fields

by Mariya Iv. Trukhanova and Yuri N. Obukhov

Universe 2021, 7(12), 498; https://doi.org/10.3390/universe7120498 - 15 Dec 2021

Cited by 2 | Viewed by 1823

Abstract

We develop a many-particle quantum-hydrodynamical model of fermion matter interacting with the external classical electromagnetic and gravitational/inertial and torsion fields. The consistent hydrodynamical formulation is constructed for the many-particle quantum system of Dirac fermions on the basis of the nonrelativistic Pauli-like equation obtained [...] Read more.

We develop a many-particle quantum-hydrodynamical model of fermion matter interacting with the external classical electromagnetic and gravitational/inertial and torsion fields. The consistent hydrodynamical formulation is constructed for the many-particle quantum system of Dirac fermions on the basis of the nonrelativistic Pauli-like equation obtained via the Foldy–Wouthuysen transformation. With the help of the Madelung decomposition approach, the explicit relations between the microscopic and macroscopic fluid variables are derived. The closed system of equations of quantum hydrodynamics encompasses the continuity equation, and the dynamical equations of the momentum balance and the spin density evolution. The possible experimental manifestations of the torsion in the dynamics of spin waves is discussed. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

20 pages, 337 KiB

Open AccessArticle

Can a Chameleon Field Be Identified with Quintessence?

by A. N. Ivanov and M. Wellenzohn

Universe 2020, 6(12), 221; https://doi.org/10.3390/universe6120221 - 26 Nov 2020

Cited by 4 | Viewed by 1706

Abstract

In the Einstein–Cartan gravitational theory with the chameleon field, while changing its mass independently of the density of its environment, we analyze the Friedmann–Einstein equations for the Universe’s evolution with the expansion parameter a being dependent on time only. We analyze the problem [...] Read more.

In the Einstein–Cartan gravitational theory with the chameleon field, while changing its mass independently of the density of its environment, we analyze the Friedmann–Einstein equations for the Universe’s evolution with the expansion parameter a being dependent on time only. We analyze the problem of an identification of the chameleon field with quintessence, i.e., a canonical scalar field responsible for dark energy dynamics, and for the acceleration of the Universe’s expansion. We show that since the cosmological constant related to the relic dark energy density is induced by torsion (Astrophys. J.2016, 829, 47), the chameleon field may, in principle, possess some properties of quintessence, such as an influence on the dark energy dynamics and the acceleration of the Universe’s expansion, even in the late-time acceleration, but it cannot be identified with quintessence to the full extent in the classical Einstein–Cartan gravitational theory. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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19 pages, 321 KiB

Open AccessArticle

On the Role of Einstein–Cartan Gravity in Fundamental Particle Physics

by Carl F. Diether III and Joy Christian

Universe 2020, 6(8), 112; https://doi.org/10.3390/universe6080112 - 05 Aug 2020

Cited by 7 | Viewed by 4150

Abstract

Two of the major open questions in particle physics are: (1) Why do the elementary fermionic particles that are so far observed have such low mass-energy compared to the Planck energy scale? (2) What mechanical energy may be counterbalancing the divergent electrostatic and [...] Read more.

Two of the major open questions in particle physics are: (1) Why do the elementary fermionic particles that are so far observed have such low mass-energy compared to the Planck energy scale? (2) What mechanical energy may be counterbalancing the divergent electrostatic and strong force energies of point-like charged fermions in the vicinity of the Planck scale? In this paper, using a hitherto unrecognised mechanism derived from the non-linear amelioration of the Dirac equation known as the Hehl–Datta equation within the Einstein–Cartan–Sciama–Kibble (ECSK) extension of general relativity, we present detailed numerical estimates suggesting that the mechanical energy arising from the gravitationally coupled self-interaction in the ECSK theory can address both of these questions in tandem. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

Review

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63 pages, 561 KiB

Open AccessReview

Fundamental Theory of Torsion Gravity

by Luca Fabbri

Universe 2021, 7(8), 305; https://doi.org/10.3390/universe7080305 - 18 Aug 2021

Cited by 14 | Viewed by 2040

Abstract

In this work, we present the general differential geometry of a background in which the space–time has both torsion and curvature with internal symmetries being described by gauge fields, and that is equipped to couple spinorial matter fields having spin and energy as [...] Read more.

In this work, we present the general differential geometry of a background in which the space–time has both torsion and curvature with internal symmetries being described by gauge fields, and that is equipped to couple spinorial matter fields having spin and energy as well as gauge currents: torsion will turn out to be equivalent to an axial-vector massive Proca field and, because the spinor can be decomposed in its two chiral projections, torsion can be thought as the mediator that keeps spinors in stable configurations; we will justify this claim by studying some limiting situations. We will then proceed with a second chapter, where the material presented in the first chapter will be applied to specific systems in order to solve problems that seems to affect theories without torsion: hence the problem of gravitational singularity formation and positivity of the energy are the most important, and they will also lead the way for a discussion about the Pauli exclusion principle and the concept of macroscopic approximation. In a third and final chapter, we are going to investigate, in the light of torsion dynamics, some of the open problems in the standard models of particles and cosmology which would not be easily solvable otherwise. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

24 pages, 406 KiB

Open AccessReview

Some Mathematical Aspects of f(R)-Gravity with Torsion: Cauchy Problem and Junction Conditions

by Stefano Vignolo

Universe 2019, 5(12), 224; https://doi.org/10.3390/universe5120224 - 06 Dec 2019

Cited by 5 | Viewed by 2249

Abstract

We discuss the Cauchy problem and the junction conditions within the framework of

f (R)

-gravity with torsion. We derive sufficient conditions to ensure the well-posedness of the initial value problem, as well as general conditions to join together on a [...] Read more.

We discuss the Cauchy problem and the junction conditions within the framework of

f (R)

-gravity with torsion. We derive sufficient conditions to ensure the well-posedness of the initial value problem, as well as general conditions to join together on a given hypersurface two different solutions of the field equations. The stated results can be useful to distinguish viable from nonviable

f (R)

-models with torsion. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

22 pages, 312 KiB

Open AccessReview

On the Mathematics of Coframe Formalism and Einstein–Cartan Theory—A Brief Review

by Manuel Tecchiolli

Universe 2019, 5(10), 206; https://doi.org/10.3390/universe5100206 - 27 Sep 2019

Cited by 11 | Viewed by 3454

Abstract

This article is a review of what could be considered the basic mathematics of Einstein–Cartan theory. We discuss the formalism of principal bundles, principal connections, curvature forms, gauge fields, torsion form, and Bianchi identities, and eventually, we will end up with Einstein–Cartan–Sciama–Kibble field [...] Read more.

This article is a review of what could be considered the basic mathematics of Einstein–Cartan theory. We discuss the formalism of principal bundles, principal connections, curvature forms, gauge fields, torsion form, and Bianchi identities, and eventually, we will end up with Einstein–Cartan–Sciama–Kibble field equations and conservation laws in their implicit formulation. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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