Superradiant instabilities of rotating black branes and strings

By V. Cardoso, Shijun Yoshida. 2005

161 citations recorded by the source corpus.

Black branes and strings are generally unstable against a certain sector of gravitational perturbations. This is known as the Gregory-Laflamme instability. It has been recently argued [1], [2] that there exists another general instability affecting many rotating extended black objects. This instability is in a sense universal, in that it is triggered by any massless field, and not just gravitational perturbations. Here we investigate this novel mechanism in detail. For this instability to work, two ingredients are necessary: (i) an ergo-region, which gives rise to superradiant amplification of waves, and (ii) ``bound'' states in the effective potential governing the evolution of the particular mode under study. We show that the black brane Kerr4×Rp is unstable against this mechanism, and we present numerical results for instability timescales for this case. On the other hand, and quite surprisingly, black branes of the form Kerrd×Rp are all stable against this mechanism for d > 4. This is quite an unexpected result, and it stems from the fact that there are no stable circular orbits in higher dimensional black hole spacetimes, or in a wave picture, that there are no bound states in the effective potential. We also show that it is quite easy to simulate this instability in the laboratory with acoustic black branes.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/77f3541d6c71a19d61e078c475a5339363ca1315

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Citations in the corpus

Superradiance: Energy Extraction, Black-Hole Bombs and Implications for Astrophysics and Particle Physics (2015, background): “For a BH with mass M , the shortest instability time scale is τ ∼ ( M 106M ) yr for a ultralight scalar [279, 343, 10, 100, 11], and shorter for vector [10, 99, 100] and tensor fields [11] for which superradiance is more efficient (cf.”
Constraining the mass of dark photons and axion-like particles through black-hole superradiance (2018, background): “Detailed calculations for the instability rate for scalar fields was done in [33, 34] and highly accurate numerical results will be given in section 2.”
Superradiance (2015, background): “The details need, of course, a careful consideration of the corresponding perturbation equations; nevertheless such conclusions hold for several different scenarios [354, 14, 79, 355, 350], as we discuss in more detail in the next sections.”
Instability of the massive Klein-Gordon field on the Kerr spacetime (2007, background): “Our numerical results are consistent with earlier studies [12, 17, 20, 51].”
Black holes with only one Killing field (2011, background): “There is a superradiant instability for massive scalars only in four dimensions [22].”