Spin and New Physical Field

A complete geometric unification of gravity and electromagnetism is proposed by considering two aspects of torsion: its relation to spin established in Einstein--Cartan theory and the possible interpretation of the torsion trace as the electromagnetic potential. Starting with a Lagrangian built of Dirac spinors, orthonormal tetrads, and a complex rather than a real linear connection we define an extended spinor derivative by which we obtain not only a very natural unification...

The studies of the generalized Einstein Lagrangian densities without torsion are extended to those of the more generalized Lagrangian densities with torsion. The properties of the more generalized Lagrangian densities are studied systematically and thoroughly. The dynamical laws of a gravitational system such as the gravitational field equations, the conservation laws of the energy-momentum tensor densities, the conservation laws of the spin densities and the equations of mot...

In the framework of Covariant Canonical Gauge Theory of Gravity (CCGG), the dynamics of the arising torsion field is analyzed. Since the action is quadratic in the Riemann tensor and therefore also in the derivative of the torsion, torsion is no longer identical to spin density as in the Einstein-Cartan theory but propagates dynamically. It is shown in this paper, that in the weak torsion limit, the torsion axial vector field obeys a wave equation with an effective mass term,...

One of the greatest unsolved issues of the physics of this century is to find a quantum field theory of gravity. According to a vast amount of literature unification of quantum field theory and gravitation requires a gauge theory of gravity which includes torsion and an associated spin field. Various models including either massive or massless torsion fields have been suggested. We present arguments for a massive torsion field, where the probable rest mass of the correspondin...

A theory of gravity with torsion is examined in which the torsion tensor is constructed from the exterior derivative of an antisymmetric rank two potential plus the dual of the gradient of a scalar field. Field equations for the theory are derived by demanding that the action be stationary under variations with respect to the metric, the antisymmetric potential, and the scalar field. A material action is introduced and the equations of motion are derived. The correct conserva...

We review many quantum aspects of torsion theory and discuss the possibility of the space-time torsion to exist and to be detected. The paper starts, in Chapter 2, with an introduction to the classical gravity with torsion, that includes also interaction of torsion with matter fields. In Chapter 3, the renormalization of quantum theory of matter fields and related topics, like renormalization group, effective potential and anomalies, are considered. Chapter 4 is devoted to th...

It is known that General Relativity ({\bf GR}) uses a Lorentzian Manifold $(M_4;g)$ as a geometrical model of the physical spacetime. The metric $g$ is required to satisfy Einstein's equations. Since the 1960s many authors have tried to generalize this model by introducing torsion. In this paper we discuss the present status of torsion in a theory of gravity. Our conclusion is that the general-relativistic model of the physical spacetime is sufficient for the all physical app...

In general relativity the affine connection is required to be symmetric so torsion is zero while according to the Einsten- Cartan's theory torsion is connected to the spin tensor as expressed by the Cartan's equations. We consider the theory of spinors in general relativity in the light of the results of Einstein Cartan's theory.In general relativity the affine connection is required to be symmetric so torsion is zero while according to the Einsten- Cartan's theory torsion is...

Whether torsion plays or not a role in the description of the gravitational interaction is a problem that can only be solved by experiment. This is, however, a difficult task: since there are different possible interpretations for torsion, there is no a model-independent way to look for it. In these notes, two different possibilities will be reviewed, their consistency analyzed, and the corresponding experimental outputs briefly discussed.

We propose four simple Lagrangians for gravity models with dynamical torsion which are free from ghosts and tachyons. The torsion propagates two massive or massless particles of spin 1^\pm and 0^\pm besides the massless graviton 2^+ propagated by metric.