Null Geodesics in a Magnetically Charged Stringy Black Hole Spacetime

TL;DR

This paper investigates the paths of light around a magnetically charged black hole in string theory, analyzing effective potentials, possible orbits, and photon frequency shifts, and compares these with other black hole types.

Contribution

It provides a detailed analysis of null geodesics and photon frequency shifts in magnetically charged stringy black hole spacetime, highlighting differences from electrically charged and Schwarzschild black holes.

Findings

No stable circular orbits outside the event horizon for massless particles.

Distinct photon frequency shifts compared to other black hole spacetimes.

Differences in geodesic behavior influenced by magnetic charge and dilaton field.

Abstract

We study the geodesic motion of massless test particles in the background of a magnetic charged black hole spacetime in four dimensions in dilaton-Maxwell gravity. The behaviour of effective potential in view of the different values of black hole parameters is analysed in the equatorial plane. The possible orbits for null geodesics are also discussed in detail in view of the different values of the impact parameter. We have also calculated the frequency shift of photons in this spacetime. The results obtained are then compared with those for the electrically charged stringy black hole spacetime and the Schwarzschild black hole spacetime. It is observed that there exists no stable circular orbit outside the event horizon for massless test particles.