Gravitational lensing by Reissner-Nordstr\"om black holes with topological defects

TL;DR

This paper investigates how topological defects like global monopoles and cosmic strings influence gravitational lensing by Reissner-Nordström black holes, revealing increased deflection angles in weak gravitational fields.

Contribution

It introduces a geometrical method to compute deflection angles considering topological defects, extending previous models to include these spacetime features.

Findings

Deflection angle increases with topological defects.

Optical Gaussian curvature is calculated using the Gauss-Bonnet theorem.

Weak limit approximation yields leading terms of deflection angle.

Abstract

Using a new geometrical approach introduced by Gibbons and Werner we study the deflection angle by Reissner-Nordstr\"{o}m black holes in the background spacetimes with a global monopole and a cosmic string. By calculating the corresponding optical Gaussian curvature and applying the Gauss-Bonnet theorem to the optical metric we find the leading terms of the deflection angle in the weak limit approximation. We find that the deflection angle increases due to the presence of topological defects.