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Weakly turbulent saturation of the nonlinear scalar ergoregion instability
Nils Siemonsen
https://arxiv.org/abs/2510.07467 https://arxiv.org/pdf/2510.07467…

Weakly turbulent saturation of the nonlinear scalar ergoregion instability
We perform time-domain evolutions of the ergoregion instability on a horizonless spinning ultracompact spacetime in scalar theories with potential-type and derivative self-interactions mimicking the nonlinear structure of the Einstein equations. We find that the instability saturates by triggering a weakly turbulent direct cascade, which transfers energy from the most unstable and large-scale modes to small scales. The cascade's nonlinear timescales of each mode are orders of magnitude shorter …