Tidal Disruption in Topological Solitons and the Emergence of an Effective Horizon

TL;DR

This paper investigates how particles and strings behave in horizonless spacetimes that mimic black holes, revealing that they experience extreme tidal forces and instabilities similar to those near horizons, supporting the idea of effective horizon emergence.

Contribution

It demonstrates that horizonless topological solitons can replicate black hole absorption features and exhibit horizon-like tidal effects, providing new insights into quantum gravity models.

Findings

Particles follow Schwarzschild-like trajectories but face extreme tidal forces near the cap.

Strings experience tidal instabilities that trap them, preventing escape.

The onset of instabilities depends on the Kaluza-Klein scale, string scale, and mass.

Abstract

We compute the dynamics of particles and strings falling into smooth horizonless spacetimes that match the Schwarzschild black hole but replace its horizon with a smooth cap in supergravity. The cap consists of a regular topological structure formed by the deformations of extra compact dimensions. We show that infalling particles follow Schwarzschild-like trajectories down to the cap, but experience rapidly growing tidal forces that reach extreme values. In addition, infalling strings encounter a region of tidal instability localized at the cap, where transverse modes are excited. This stringy excitation drains their kinetic energy, resulting in tidal trapping. We demonstrate that the onset and strength of this instability depend sensitively on the Kaluza-Klein scale, the string scale, and the mass of the spacetime, ensuring that strings cannot escape the cap region. These results show that horizonless geometries can reproduce key features of black hole absorption while maintaining regularity at the horizon scale, offering compelling evidence for the emergence of effective horizon-like behavior from topological spacetime structures.