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Transient Instability of Rapidly Rotating Black Holes
Samuel E. Gralla, Aaron Zimmerman, Peter Zimmerman
We analytically study the linear response of a near-extremal Kerr black hole to external scalar, electromagnetic, and gravitational field perturbations. We show that the energy den…
Horizon Instability of Extremal Kerr Black Holes: Nonaxisymmetric Modes and Enhanced Growth Rate
Marc Casals, Samuel E. Gralla, Peter Zimmerman
We show that the horizon instability of the extremal Kerr black hole is associated with a singular branch point in the Green function at the superradiant bound frequency. We study…
Force-Free Foliations
Geoffrey Compère, Samuel E. Gralla, Alexandru Lupsasca
Electromagnetic field configurations with vanishing Lorentz force density are known as force-free and appear in terrestrial, space, and astrophysical plasmas. We explore a general…
Pulsar Magnetospheres: Beyond the Flat Spacetime Dipole
Samuel E. Gralla, Alexandru Lupsasca, Alexander Philippov
Most studies of the pulsar magnetosphere have assumed a pure magnetic dipole in flat spacetime. However, recent work suggests that the effects of general relativity are in fact of…
Plasma Waves and Jets from Moving Conductors
Samuel E. Gralla, Peter Zimmerman
We consider force-free plasma waves launched by the motion of conducting material through a magnetic field. We develop a spacetime-covariant formalism for perturbations of a unifor…
Inspiral into Gargantua
Samuel E. Gralla, Scott A. Hughes, Niels Warburton
We model the inspiral of a compact object into a more massive black hole rotating very near the theoretical maximum. We find that once the body enters the near-horizon regime the g…