Is GW190521 a gravitational wave echo of wormhole remnant from another universe?

TL;DR

This paper investigates whether GW190521 could be a single echo pulse from a wormhole remnant formed by BBHs in another universe and connected to ours. It develops a toy Schwarzschild-like Morris–Thorne wormhole model in which the postmerger ringdown partially tunnels through a throat, producing an initial echo that is detectable as a short burst; the first echo is modeled with a sine-Gaussian template and compared to the LVK BBH waveform using SNR calculations and Bayesian evidence. The analysis finds a network SNR of about $14.5$ for the echo model, close to the BBH result of about $15.6$, but the Bayesian comparison yields $\ln \mathcal{B}^{\text{Echo}}_{\text{BBH}} \simeq -2.9$, favoring the standard BBH interpretation; this underscores the need for more comprehensive waveform templates (including spin and subsequent echoes) to robustly test the hypothesis. Overall, the work provides a proof-of-principle for testing wormhole-echo scenarios in short-duration GW bursts and highlights both the potential and the current limitations of such exotic interpretations.

Abstract

A particularly compelling aspect of the GW190521 event detected by the LIGO--Virgo--KAGRA (LVK) collaboration is that it has an extremely short duration, and lacks a clearly identifiable inspiral phase usually observed in the binary black holes (BBHs) coalescence. In this work, we hypothesize that GW190521 might represent a single, isolated gravitational wave (GW) echo pulse from the wormhole, which is the postmerger remnant of BBHs in another universe and connected to our universe through a throat. The ringdown signal after BBHs merged in another universe can pass through the throat of wormhole and be detected in our universe as a short-duration echo pulse. Our analysis results indicate that our model yields a network signal-to-noise ratio comparable to that of the standard BBHs merger model reported by the LVK collaboration. For GW190521, Bayesian model selection yields $\ln \mathcal{B}^{\text{Echo}}_{\text{BBH}} \simeq -2.9$, indicating that the data favor the BBH hypothesis over our echo-for-wormhole model.

Figures (4)

• Figure 1: Schematic of the echo interpretation of GW190521. Top: A binary black hole merger forms a wormhole. Bottom: The black mirror barriers represent a wormhole connecting two universes. A portion of the merger-generated ringdown GWs enters the wormhole. These GW modes operates between mirror barriers due to the reflections of barriers, and certain modes tunnel through the right-side barrier into our universe, leading to a series of echoes in our universe. The first echo pulse (blue arrow) was observed as GW190521.
• Figure 2: The posterior distribution of parameters for our echo-for-wormhole model. In this analysis, the sky location was fixed to the best-fit values reported by ZFT19abanrhr.
• Figure 3: The maximum-likelihood waveform reconstructions for the LIGO Livingston (L1) detector in the time-domain with the GPS time. The left panel shows the result for our echo-for-wormhole model (Red), while the right panel corresponds to the BBHs model (Orange) using the IMRPhenomXPHM waveform.
• Figure 4: The posterior distribution of intrinsic parameters and luminosity distance for the standard BBHs IMR event with IMRPhenomXPHM waveform. This distribution is consistent with the result reported by the LVK collaboration for GW190521 using the same waveform model Estelles:2021jnz.