Null Geodesics of Charged Black Holes in String Theory

TL;DR

This paper analyzes null geodesics of charged black holes in heterotic string theory, providing exact solutions in the Einstein frame, circular orbits in the string frame, and applications to photon deflection and quasinormal modes.

Contribution

It offers a comprehensive analysis of null geodesics in heterotic string black holes, including exact solutions and physical implications, which advances understanding of photon trajectories and wave behavior.

Findings

Exact geodesic solutions in Einstein frame using Jacobi-elliptic integrals

Circular geodesics in the string frame

Calculated photon deflection angles and quasinormal modes

Abstract

In this paper, we investigate the null geodesics of the static charged black hole in heterotic string theory. A detailed analysis of the geodesics are done in the Einstein frame as well as in the string frame. In the Einstein frame, the geodesics are solved exactly in terms of the Jacobi-elliptic integrals for all possible energy levels and angular momentum of the photons. In the string frame, the geodesics are presented for the circular orbits. As a physical application of the null geodesics, we have obtained the angle of deflection for the photons and the quasinormal modes of a massless scalar field in the eikonal limit.