Figure 27

Figure 27: Instantaneous wave fronts in the spacetime of a non-transparent string of finite radius r* with k = 0.8 and a = 0. The picture shows in 3-dimensional space the intersections of the light cone of Figure 24 with three hypersurfaces t = constant, at values t1 > t2 > t3. The vertical coordinate is the z-coordinate which was suppressed in Figure 24. Only one half of each instantaneous wave front is shown so that one can look into its interior. There is a transverse self-intersection (cut locus) but no caustic.