The Penrose process extracts rotational energy by allowing a fragment with negative stationary Killing energy to enter the black hole while another fragment escapes with more energy than the original body carried.
For a future-directed causal four-momentum crossing a future Killing horizon with generator , the Lorentzian inner product obeys . With and , this is . A massive particle has strict inequality. The same bound follows in the nonextremal quasistationary regime from the Physical-process first law for a rotating black hole and the second law of black-hole mechanics. Negative Killing energy in a Penrose process is allowed, but its angular momentum must satisfy this bound.
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The Penrose process is a theoretical mechanism in general relativity that describes how energy can be extracted from a rotating black hole. Named after the physicist Roger Penrose, who proposed it in 1969, the process exploits the unique features of a rotating black hole, specifically the phenomenon associated with its event horizon and ergosphere. Here's a simplified explanation of how it works: 1. **Rotating Black Hole**: A black hole that rotates is described by the Kerr solution to Einstein's equations.