Figure 4

Figure 4: Penrose diagrams of Schwarzschild-Vaidya metrics for which the mass function M (v) vanishes for v < 0 [137]. The space-time metric is flat in the past of v = 0 (i.e., in the shaded region). In the left panel, as v tends to infinity, M vanishes and M tends to a constant value M0. The space-like dynamical horizon H, the null event horizon E, and the time-like surface r = 2M0 (represented by the dashed line) all meet tangentially at + i. In the right panel, for v > v0 we have M = 0. Space-time in the future of v = v0 is isometric with a portion of the Schwarzschild space-time. The dynamical horizon H and the event horizon E meet tangentially at v = v 0. In both figures, the event horizon originates in the shaded flat region, while the dynamical horizon exists only in the curved region.