Kerr black holes are, in theory, the spacetime region outside of a black hole. Kerr black holes were first proposed in 1963, and for nearly 60 were not mathematically proven to have stability. In other words, an inevitably perturbance to a Kerr black hole.
Relying on proof by contradiction, on May 30 three researchers posted online a 912page paper a mathematical analysis to show "that slowly rotating Kerr black holes are indeed stable."^{[1]}
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