Entropy production and entropic attractors in black hole fusion and fission

Abstract

We study how black hole entropy is generated and the role it plays in several highly dynamical processes: the decay of unstable black strings and ultraspinning black holes; the fusion of two rotating black holes; and the subsequent fission of the merged system into two black holes that fly apart (which can occur in dimension $D\ge 6$, with a mild violation of cosmic censorship). Our approach uses the effective theory of black holes at $D\to \infty$, but we expect our main conclusions to hold at finite $D$. Black hole fusion is highly irreversible, while fission, which follows the pattern of the decay of black strings, generates comparatively less entropy. In $2\to 1\to 2$ black hole collisions an intermediate, quasi-thermalized state forms that then fissions. This intermediate state erases much of the memory of the initial states and acts as an attractor funneling the evolution of the collision towards a small subset of outgoing parameters, which is narrower the closer the total angular momentum is to the critical value for fission. Entropy maximization provides a very good guide for predicting the final outgoing states. Along our study, we clarify how entropy production and irreversibility appear in the large $D$ effective theory. We also extend the study of the stability of new black hole phases (black bars and dumbbells). Finally, we discuss entropy production through charge diffusion in collisions of charged black holes.

40 pages, 13 figures. v2: small improvements and minor corrections to the text, figures, and references

References in corpus (6)

• Nonlinear Fluid Dynamics from Gravity
• Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship
• Local Fluid Dynamical Entropy from Gravity
• Black Holes as Lumps of Fluid
• Unstable `black branes' from scaled membranes at large $D$
• On the apparent horizon in fluid-gravity duality

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• The large D effective theory of black strings in AdS
• Black hole interactions at large $D$: brane blobology
• Planar Black Holes as a Route to Understanding the Weak Gravity Conjecture
• Lattice Black Branes at Large $D$
• Metric fluctuations in higher-dimensional black holes
• Extremal Instability for Topological Black Holes
• Phase and stability of black strings in Einstein-Gauss-Bonnet theory at large D
• Squashed black holes at large $D$