Search for manifestations of spin-torsion coupling

TL;DR

This paper explores how axial vector torsion-spin coupling affects electromagnetic fields within Poincaré gauge theory, deriving modified Maxwell equations, analyzing wave propagation, and setting astrophysical bounds on cosmic torsion.

Contribution

It introduces a comprehensive framework for axial torsion-spin coupling effects, deriving modified Maxwell equations and analyzing electromagnetic wave behavior in torsion fields.

Findings

Electromagnetic wave polarization rotation due to torsion (Faraday effect).

Strong astrophysical bounds on cosmic axial torsion field.

Derived dynamical equations linking torsion and electromagnetic sources.

Abstract

We investigate the axial vector torsion-spin coupling effects in the framework of the Poincar\'e 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.