Firewall black holes and echoes from an action principle

Understand

It is often said that there is no gravity theory based on local action principles giving rise to firewall black hole solutions.

• Additionally, Guo and Mathur 2022 (2205.10921) have cast doubt on the observability of firewall echoes due to closed trapped surface produced by backreaction of macroscopic in-falling wave packets.
• In this paper, we bring Einstein-Maxwell-Dilaton action as a toy model that serves as counterexample to these assertions.
• Actions with Maxwell and dilaton fields emerge from several fundamental theories, such as the low energy limit of (super) string theory or Kaluza-Klein compactifications.