Schwarzschild Black Hole Turbulence: Scalar Probe

TL;DR

This paper investigates how scalar perturbations around a Schwarzschild black hole can lead to energy redistribution and turbulence-like cascades, using averaging methods and mode interactions to understand instability mechanisms.

Contribution

It introduces a coupled mode framework to analyze near-resonant interactions and identifies dominant energy transfer routes in black hole perturbations.

Findings

Difference-frequency interactions dominate at high multipole numbers.

Instability regions ('tongues') depend on detuning and drive energy transfer.

Provides a quantitative mechanism for turbulence signatures in black hole ringdowns.

Abstract

We explore how perturbations of a Schwarzschild black hole can redistribute energy among scalar modes and seed turbulent like cascades. We make use of the van der Pol-Krylov-Bogoliubov averaging method and derive coupled mode equations that describe near-resonant interactions between neighbouring multipoles. We compare two routes to instability, namely the difference-frequency mixing between adjacent modes and the diagonal (Mathieu) self-modulation channel. We show that, at high multipole number (eikonal limit), the difference-frequency route dominates and drives a one-way cascade from higher to lower frequencies. We chart the corresponding instability regions ("tongues") and quantify their detuning dependence. The framework provides a simple, quantitative mechanism for energy transfer in black hole ringdowns and clarifies when and how turbulent signatures can arise within linear probes on a weakly perturbed background.