Evidence of cosmic strings by the observation of the alignment of quasar polarization axes on Mpc scale

Abstract

The recently found alignment of the polarization axes (PA) of quasars in large quasar groups (LQGs) on Mpc scales can be explained by general relativistic cosmic string networks. By considering the cosmic string as a result of spontaneous symmetry breaking of the gauged U(1) abelian Higgs model with topological charge [Formula: see text], many stability features of [Formula: see text]-vortex solutions of superconductivity can be taken over. Decay of the high multiplicity ([Formula: see text]) super-conducting vortex into a lattice of [Formula: see text] vortices of unit magnetic flux is energetically favorable. The temporarily broken axial symmetry will leave an imprint of a preferred azimuthal-angle on the lattice. The stability of the lattice depends critically on the parameters of the model, especially when gravity comes into play. In order to handle the strong nonlinear behavior of the time-dependent coupled field equations of gravity and the scalar-gauge field, we will use a high-frequency approximation scheme to second order on a warped 5D axially symmetric spacetime with the scalar-gauge field residing on the brane. We consider different winding numbers for the subsequent orders of perturbations of the scalar field. A profound contribution to the energy–momentum tensor comes from the bulk spacetime and can be understood as “dark”-energy. The cosmic string becomes super-massive by the contribution of the 5D Weyl tensor on the brane and the stored azimuthal preferences will not fade away. During the recovery to axial symmetry, gravitational and electro-magnetic radiation will be released. The perturbative appearance of a nonzero energy–momentum component [Formula: see text] can be compared with the phenomenon of bifurcation along the Maclaurin–Jacobi sequence of equilibrium ellipsoids of self-gravitating compact objects, signaling the onset of secular instabilities. There is a kind of similarity with the Goldstone-boson modes of spontaneously broken symmetries of continuous groups. The recovery of the SO(2) symmetry from the equatorial eccentricity takes place on a time-scale comparable with the emission of gravitational waves. The emergent azimuthal-angle dependency in our model can be used to explain the aligned PA in LQGs on Mpc scales. Spin axis direction perpendicular to the major axes of LQGs when the richness decreases can be explained as a second-order effect in our approximation scheme by the higher multiplicity terms. The preferred directions are modulo [Formula: see text], with [Formula: see text] being an integer dependent on the [Formula: see text]th order of approximation. When more data of quasars of high redshift becomes available, one could prove that the alignment emerged after the symmetry breaking scale and must have a cosmological origin. The effect of the warp factor on the second-order perturbations could also be an indication of the existence of extra large dimensions.