Interior metric and ray-tracing map in the firework black-to-white hole transition

Understand

The possibility that a black hole could tunnel into a white hole has recently received attention.

• Here we present a metric that improves the 'firework' metric: it describes the entire process and solves the Einstein equations everywhere except on a small transition surface that corresponds to the quantum tunnelling.
• We compute the corresponding ray-tracing map from past infinity to future infinity explicitly.