Black Holes Trapped by Ghosts

TL;DR

This paper reveals a new nonlinear phase in black hole relaxation involving a saddle-node ghost, which causes a delay before the linear regime and produces distinctive quiescence-burst signals in gravitational waves.

Contribution

It uncovers a previously unknown nonlinear regime in black hole dynamics governed by a saddle-node ghost, extending understanding beyond linear perturbation theory.

Findings

Identification of a long-lived nonlinear bottleneck controlled by a saddle-node ghost.

Discovery of a universal power-law timescale for the delay before linearity.

Prediction of a quiescence-burst signature in gravitational-wave signals.

Abstract

Violent cosmic events, from black hole mergers to stellar collapses, often leave behind highly excited black hole remnants that inevitably relax to equilibrium. The prevailing view, developed over decades, holds that this relaxation is rapidly filtered into a linear regime, establishing linear perturbation theory as the bedrock of black hole spectroscopy and a key pillar of gravitational-wave physics. Here we unveil a distinct nonlinear regime that transcends the traditional paradigm: before the familiar linear ringdown, an intrinsically nonlinear, long-lived bottleneck can dominate the evolution. This stage is controlled by a saddle-node ghost in phase space, which traps the remnant and delays the onset of linearity by a timescale obeying a universal power-law. The ghost imprints a distinctive quiescence-burst signature on the emitted radiation: a prolonged silence followed by a violent burst and a delayed ringdown. Rooted in the bifurcation topology, it extends naturally to neutron and boson stars, echoing a topological universality shared with diverse nonlinear systems in nature. Our results expose a missing nonlinear chapter in gravitational dynamics and identify ghost-induced quiescence-burst patterns as clear targets for future observations.