# Examining the Kerr Metric through Wave Fronts of Null Geodesics

## TL;DR

This paper investigates the structure of wave fronts of null geodesics in Kerr spacetime, revealing complex caustic formations and cusps that enhance understanding of gravitational lensing effects.

## Contribution

It introduces a wave front analysis of null geodesics in Kerr metric, revealing non-symmetric collapses and caustic structures not fully characterized before.

## Key findings

- Wave fronts develop tube-like structures with cusps.
- Cusps trace out astroidal caustic tubes.
- Wave front approach complements existing lensing analyses.

## Abstract

We examine the singularities of the wave fronts of null geodesics from point sources in the Kerr Metric. We find that the wave fronts develop a tube like structure that collapses non-symmetrically, leading to cusp features in the wave front singularities. As the wave front advances, the cusps trace out an astroidal shaped caustic tube, which had been discovered previously using lens mapping and geodesic deviation methods. Thus, the wave front approach in this study helps to complete a picture of caustics and gravitational lensing in the Kerr geometry.