Null Hypersurface Caustics, Closed Null Curves, and Super-Entropy

Abstract

Recently it was discovered that null hypersurfaces can develop caustics outside the event horizon of super-entropic Kerr-AdS black holes, in contrast to the usual Kerr-AdS case. In this work we explore a few more examples of black hole spacetimes in which such exterior caustics can develop. If a closed null curve is present, e.g., in the case of Taub-NUT and the "transunital" Kerr-AdS spacetimes, then it coincides with a null hypersurface caustic (NHC) of a minimal separation parameter. Thus a spacetime on the verge of forming closed timelike curves could develop a caustic. Known examples of super-entropic black holes also have exterior NHC, although such spacetimes are free of closed null/timelike curves. Nevertheless the relationship between closed causal curves, NHC, and super-entropy is not straightforward. This is best illustrated with the BTZ black string, which for some choices of the warp factor in the extra dimension and the value of the charge, can be super-entropic. However, even those that are not super-entropic can admit NHC outside the horizon.

Improved the discussion on ultra-spinning Kerr-Sen-AdS Black Hole in Sec.III(A) with new figures

References in corpus (25)

• Black hole chemistry: thermodynamics with Lambda
• Black Hole Enthalpy and an Entropy Inequality for the Thermodynamic Volume
• The First Law of Thermodynamics for Kerr-Anti-de Sitter Black Holes
• Rotating Charged Black Hole Solution in Heterotic String Theory
• General Kerr-NUT-AdS Metrics in All Dimensions
• Super-Entropic Black Holes
• SOME PROPERTIES OF THE KERR SOLUTION TO LOW ENERGY STRING THEORY
• Four-dimensional black holes with unusual horizons
• Ultraspinning limits and super-entropic black holes
• Quasinormal modes of massive fermions in Kerr spacetime: Long-lived modes and the fine structure
• Kerr-de Sitter Black Holes with NUT Charges
• Quasi-Spherical Light Cones of the Kerr Geometry
• Thermodynamic Volumes for AdS-Taub-NUT and AdS-Taub-Bolt
• Are ultra-spinning Kerr-Sen-AdS${}_4$ black holes always super-entropic ?
• Shadows of charged rotating black holes: Kerr-Newman versus Kerr-Sen
• Covariant double-null dynamics: $(2+2)$-splitting of the Einstein equations
• Instability of Super-Entropic Black Holes in Extended Thermodynamics
• Are Superentropic black holes superentropic?
• Null hypersurfaces in Kerr-(A)dS spacetimes
• Holographic dual of a time machine
• Cosmic Censorship for AdS${}_5$-Kerr
• Closed timelike curves and the second law of thermodynamics
• "Twisted" black holes are unphysical
• Twisted Black Hole Is Taub-NUT
• Local and Global Analytic Solutions for a Class of Characteristic Problems of the Einstein Vacuum Equations in the "Double Null Foliation Gauge"

Cited by in corpus (8)

• Topological classes of thermodynamics of rotating AdS black holes
• Light Deflection Angle by Superentropic Black Holes
• Null hypersurface caustics for high dimensional superentropic black holes
• Thermodynamic Instability of $3D$ Einstein-Born-Infeld AdS Black Holes
• Shadowless rapidly rotating yet not ultraspinning Kerr-AdS${}_4$ and Kerr-Newman-AdS${}_4$ black holes
• Dimensional structure of thermodynamic topology in ultraspinning Kerr-AdS black holes
• Null hypersurface caustics and super-entropic black holes
• Ultra-spinning Chow's black holes in six-dimensional gauged supergravity and their properties