Azimuthal Fermionic Current in the Cosmic String Spacetime Induced by a Magnetic Tube

Abstract

Abstract:In this paper, we calculate the vacuum expectation value of the azimuthal fermionic current, associated with a massive fermionic quantum field in the spacetime of an idealized cosmic string, considering the presence of a magnetic tube of radius a, coaxial to the string. In this analysis three distinct configurations of magnetic field are considered: (i) a magnetic field concentrated on a surface of the tube; (ii) a magnetic field presenting a 1/r radial dependence; and (iii) an homogeneous magnetic field. In order to develop this analysis , we construct the complete set of normalized solution of the Dirac equation in the region outside the tube. By using the mode-sum formula, we show that the azimuthal induced current is formed by two contributions: the first being the current induced by a line of magnetic flux running along the string, and the second, named core-induced current, is induced by the non-vanishing extension of the magnetic tube. The first contribution depends only on the fractional part of the ration of the magnetic flux inside the tube by the quantum one; as to the second contribution, it depends on the total magnetic flux. We specifically analyze the core-induced current in several limits of the parameters and distance to the tube.

Editorial for the Special Issue “The Modern Physics of Compact Stars and Relativistic Gravity 2017”

“…The formation of strings as a result of symmetry breaking in the early Universe and the consequences in modern cosmology and astrophysics is of great interest, both theoretically and observationally. The two articles by M. de Sousa et al [8] and A. Saharian et al [9] deal with cosmic string physics. Both calculate the vacuum expectation values (VEV) in the presence of a single straight cosmic string: The first paper deals with the VEV of the azimuthal current, while the second papers considers the electromagnetic field in various backgrounds.…”