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 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.

Highlights

  • In fundamental theoretical physics, there are a number of principles that are assumed, and, among them, one of the most important is the principle of covariance, stating that the form of physical laws must be independent from the coordinate system employed to write them

  • 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

  • There are a number of principles that are assumed, and, among them, one of the most important is the principle of covariance, stating that the form of physical laws must be independent from the coordinate system employed to write them

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Summary

Introduction

There are a number of principles that are assumed, and, among them, one of the most important is the principle of covariance, stating that the form of physical laws must be independent from the coordinate system employed to write them. The single most important one may be that Einstein gravity was first published in the year 1916 when no spin was known and, despite being insightful to set the torsion tensor to zero, when Dirac came with a theory of spinors comprising an intrinsic spin in 1928, the successes of Einstein theory of gravity were already too great to make anyone wonder about the possibility of modifying it This is no scientific reason to hinder research, but, sociologically, it can be easy to understand why one would not lightly go to look beyond something good, Universe 2021, 7, 305 especially today that the successes of the Einstein theory of gravitation have become practically complete. A third section will be about studying limiting situations that can allow us to get even more information about the torsion–spin coupling

Torsion Gravity for Spinor Fields
Geometry and Its Matter Content
Tensor and Gauge Fields
Spinorial Fields
Covariant Field Equations
Torsion-Spin Interactions
Torsion and Spinor Decomposition
Torsion as Axial-Vector Massive Field
Torsion–Spinor Binding
Limiting Situations
Massive Cases
Effective Approximation
Non-Relativistic Limit
Massless Case
Two: Basic Applications
Consequences of Spin
Singularity Avoidance
Pauli Exclusion
Positive Energy
Macroscopic Limit
Particles and Cosmology
Conclusions

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