Scalar-Field Wave Dynamics and Quasinormal Modes of the Teo Rotating Wormhole

TL;DR

This paper analyzes scalar wave perturbations and quasinormal modes of the rotating Teo wormhole, revealing unique spectral signatures and differences from Kerr black holes, influenced by rotation and boundary conditions.

Contribution

It provides the first detailed computation of QNM spectra for the rotating Teo wormhole, highlighting distinctive features compared to black holes and exploring superradiance potential.

Findings

QNM frequencies decrease with increasing spin, indicating longer-lived modes.

Teo wormhole exhibits partial reflection and one-sided mode splitting.

No classical superradiance observed due to absence of horizon.

Abstract

We investigate scalar field perturbations of the rotating Teo wormhole. We also compute the quasinormal mode (QNM) spectrum using first order WKB approximation. After separation of variables, we obtain a Schroedinger type radial equation and a smooth barrier potential which is shaped by the localized frame-dragging effects of the wormhole throat. This barrier potential provides damped oscillatory modes for the range of spins that were examined. The QNM spectrum shows a coherent and monotonic dependence on rotation. As the spin increases, both the oscillating frequency of the scalar wave and its damping rate decrease, which indicates progressively longer lived modes in the absence of absorption due to a horizon. We have verified the correspondence in the Eikonal limit, by obtaining the radius of the photon ring, its orbital frequency, and the Lyaponov exponent. Next, we compared the Teo wormhole QNM with that of the Kerr black hole QNM to find that the Kerr QNM is dictated by absorption at the horizon and they also exhibit symmetric pro-grade retrograde mode splitting, whereas the Teo wormhole QNM shows a stronger, and spatially confined response to spin. The Teo wormhole also exhibit partial reflection at the throat and a very distinct one-sided mode splitting which rapidly saturates as the spin increases. Additionally, the rotating Teo wormhole allows an ergoregion with the possibility of frequency kinematics compatible with superradiance. Due to the absence of an event horizon or a dissipative boundary, there is no evidence of classical superradiant amplification that was seen in Kerr. The results we obtained clearly demonstrates how rotation and boundary conditions jointly shape wave propagation in horizonless compact objects. They also provide certain characteristic spectral signatures that can be used to distinguish rotating wormhole spacetimes from rotating black hole spacetimes.