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

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 $\ln {\mathcal{B}}_{\text{BBH}}^{\text{Echo}}\simeq -2.9$, indicating that the data favor the BBH hypothesis over our echo-for-wormhole model.