Echoes of novel black-bounce spacetimes

TL;DR

This paper investigates electromagnetic and scalar field evolution in novel black-bounce spacetimes, revealing characteristic gravitational wave echoes that depend on the spacetime parameters, and distinguishes different spacetime states through their echo signals.

Contribution

It provides the first detailed analysis of electromagnetic and scalar field echoes in black-bounce spacetimes, linking echo signals to spacetime parameters and transitions.

Findings

Echo signals appear only when a > 2M.

Echo signals transform into quasinormal ringdowns at a threshold parameter value.

Distinct echo characteristics differentiate black holes and wormholes.

Abstract

Gravitational wave echoes can be used as a significant observable to understand the properties of black holes horizon. In addition, echoes would also closely relate to the unique properties of compact objects. In this work we study the evolution of electromagnetic field and scalar field under the background of novel black-bounce spacetimes. Our results show an obvious echoes signal that can characterize the properties of novel black-bounce spacetimes, and a detailed analysis about the characteristics of the echoes signal is given. By studying the quasinormal ringdown of the three states of novel black-bounce spacetimes, including black holes in $0<a<2 M$, the one-way wormhole in $a=2M$ and the traversable wormhole in $a>2 M$, we find that the echoes signal only appears when $a>2M$ in this spacetime, but when the parameter $a$ increases to a threshold, the echoes signal will be transformed into a quasinormal ringdown of the two-way traversable wormhole.