Gravitational lensing by non-self-intersecting vortons

TL;DR

This paper addresses the gravitational lensing signatures of current-carrying vorton loops by using the weak-field thin-lens framework to compare circular vortons, Kibble–Turok–type asymmetric loops, and a novel 123-harmonic vorton class. The authors derive deflection and magnification maps, showing that circular vortons produce a sharp lensing discontinuity that separates a minimally distorted region from an Einstein ring, with the ring coexisting with a near-central image; non-circular vortons with higher-harmonics generate pronounced asymmetries and complex multi-image structures. They demonstrate that frame-dragging introduces asymmetries not present for ordinary NG strings, offering a potential observational discriminant for vorton microphysics and current-carrying cosmic strings in high-resolution surveys. The work emphasizes observational prospects, discusses constraints on $G\mu$, and highlights open questions about non-chiral string models and vorton formation, suggesting that lensing could provide a new window into the physics of superconducting cosmic strings.

Abstract

We investigate the gravitational lensing signatures of vorton configurations, considering the circular vorton, the Kibble-Turok vorton, and a newly proposed class that incorporates simultaneous excitations of the first, second, and third harmonic modes. Working within the weak-field and thin-lens approximations, we demonstrate that circular vortons produce a sharp lensing discontinuity that separates two regions with qualitatively distinct distortions. The corresponding Einstein ring co-exists alongside an almost undistorted source image. This effect is significantly amplified in the case of non-circular vortons, where asymmetries and higher-harmonic deformations amplify the discontinuity and lead to complex image structures. These distinctive lensing patterns offer potential discriminants between different vorton configurations, suggesting that future high-resolution surveys may provide a novel window into the microphysics of current-carrying cosmic strings.

Figures (27)

• Figure 1: Parametric 3D (a, c) and top-view (b, d) curves of Kibble-Turok vorton solutions of various $\kappa$.
• Figure 2: Parametric 3D (a, c) and top-view (b, d) curves of the $123$ vorton solutions of various $\kappa$ and $\beta$.
• Figure 3: Lensing Diagram in the Thin Lens Approximation deLaix:1996vc.
• Figure 4: Deflection vector component $F_1$ (a, b, c) and $F_2$ (d, e, f) from circular Nambu-Goto loop of various $\phi$, illustrated as a heatmap. The maximum and (magnitude of) minimum values of the $F_1$ and $F_2$ component are the same in the respective image. The brighter the color in the heatmap, the larger the deflection in the respective direction. For example, (a) shows large deflection to positive (negative) horizontal direction right to the left (right) of the string, and little to no deflection in the horizontal direction on top of the projection. The plot depicting $F_2$ shows the distribution of vertical deflection.
• Figure 5: Deflection vector magnitude $|\Vec{F}|=\sqrt{F_1^2+F_2^2}$ from circular Nambu-Goto loop for several $\phi$. The brighter the color, the larger the angular deflection magnitude is. Fig. (a) shows the deflection around the outer side of the ring projection is the largest, while no deflection occurs inside the string projection.