Echoes from Asymmetric Wormholes and Black Bounce

TL;DR

This paper studies how asymmetry in wormholes and black bounce spacetimes affects field perturbations, revealing echo signals and potential instabilities linked to effective potential shapes.

Contribution

It investigates the impact of spacetime asymmetry on quasinormal modes and echoes, providing new insights into stability and signal features in asymmetric wormhole and black bounce backgrounds.

Findings

Echo signals are present in some wormhole cases.

Asymmetry causes asymmetry in effective potentials.

Negative potentials may indicate instability, but this can be affected by asymmetry.

Abstract

The time evolution of the field perturbations in the wormhole and black bounce backgrounds are investigated. We find that the asymmetry of spacetime results in the asymmetry of the effective potential of the perturbed equation. The quasinormal modes are strongly dependent on the shapes of the effective potentials. Specifically, the signals of echoes arise in some wormhole cases and reflect the asymmetric properties of wormholes. We examine the features of echoes within different circumstances. Besides, the negative values of effective potentials usually imply the instability of the system. By analyzing some specific metrics, we find that the negative regions of effective potentials are enclosed by the black hole horizons in these cases. But this statement could be broken in asymmetric cases.