Quasinormal modes and echoes of a double braneworld

TL;DR

This paper investigates the unique gravitational quasinormal modes and echoes of a double braneworld, revealing distinctive spectral features and potential signals for future gravitational wave detection.

Contribution

It introduces a detailed analysis of quasinormal modes and echoes in a double braneworld, highlighting differences from single brane models and potential phenomenological implications.

Findings

Double brane spectrum differs significantly from single brane.

Gravitational echoes appear with large brane splitting.

Long-lived Kaluza-Klein modes cause a beating effect.

Abstract

In this work, we study the gravitational quasinormal modes and the gravitational echoes of a double braneworld. The double braneworld is a kind of split thick brane, which is crucial for addressing the hierarchy problem in the thick brane scenarios. Using the Bernstein spectral method, direct integration method, and asymptotic iteration method, we calculate the quasinormal mode frequencies of the double brane. We find that the quasinormal spectrum is very different from that of the single brane model, especially the high overtone mode. We also perform numerical evolution to study the time-domain properties of the characteristic modes of the double brane. The results show that when the degree of brane splitting is large, gravitational echoes of oscillation attenuation between sub-branes will appear in the thick brane. Furthermore, different long-lived Kaluza-Klein modes interfere with each other, resulting in a beating effect. Compared to a single brane model, the phenomenon of the split double brane is richer, and the lifetime of the massive Kaluza-Klein graviton of the double brane is longer. These phenomena may have potential phenomenological interest. We hope to detect these extra-dimensional signals in future gravitational wave detectors or accelerators.