A note on the Penrose process in rotating regular black holes

Abstract

We investigate the Penrose process of energy extraction in the context of rotating regular black holes. For the Neves-Saa class of regular black hole solutions, which includes the Bardeen, Hayward and Fan-Wang spacetimes as special cases, the extraction efficiency is bounded above by the known value for Kerr spacetime. However, in the case of a new rotating regular black hole which does not have a Schwarzschild singular limit for zero rotation, the extraction efficiency can indeed become very large, as shown in our analysis here.

Figures (9)

• Figure 1: Variation of the static limit surface (solid red) together with the inner and outer horizon (solid black) of the Bardeen $(3,2,a)$, Hayward $(3,3,a)$ and Fan-Wang $(3,1,a)$ rotating spacetimes for various choices of $a$ and $g$. Solid: outer, Dashed: inner.
• Figure 2: Variation of ergo-region (region between solid red and solid black) for rotating regular black holes with $p=3$ and various $q$ values is shown, for $a=0.4M$ and $g=0.2M$.
• Figure 3: Graph of ergo-region (region between solid red and solid black) for rotating regular black holes with $q=3$ and various $p$ values, for $a=0.8M$ and $g=0.2M$.
• Figure 4: The allowed values of $a/M$ and $g/M$ for which an outer horizon exists in the rotating Bardeen black hole (left). The right subfigure shows the variation of the maximum energy extraction efficiency with $a/M$ and $g/M$.
• Figure 5: The allowed values of $a/M$ and $g/M$ for which an outer horizon exists in the rotating Fan-Wang black hole (left). The right subfigure shows the variation of the maximum energy extraction efficiency with $a/M$ and $g/M$.