nLab extremal black hole




For a charged and/or rotating black hole (Kerr spacetime, Reissner-Nordstrom spacetime, Kerr-Newman spacetime) there is a minimum possible mass for given charge and angular momentum. When this minimum is attained, one hence speaks of an extremal black hole.


Near horizon geometry and JT gravity

The near horizon geometry of extremal black holes in dd dimensional spacetime is anti de Sitter spacetime AdS 2AdS_{2} (KLR 07, AGJST 06, AY 07, ANT 07).

The AdS 2×S d2AdS_2 \times S^{d-2} near horizon geometry of near-extremal black holes is well approximated by Jackiw-Teitelboim gravity (NSST 18, MTV 18).



  • Tatsuo Azeyanagi, Tatsuma Nishioka, Tadashi Takayanagi, Near Extremal Black Hole Entropy as Entanglement Entropy via AdS 2/CFT 1AdS_2/CFT_1, Phys.Rev.D77:064005,2008 (arXiv:0710.2956)

  • Sean Carroll, Matthew C. Johnson, Lisa Randall, Extremal limits and black hole entropy, JHEP 0911:109,2009 (arXiv:0901.0931)

  • Ashoke Sen, Extremal black holes, talk slides 2009 (pdf)

See also

BH entropy

On black hole entropy of (near-)extremal black holes:

Near-horizon geometry and JT gravity

Discussion of the near horizon geometry

  • Hari K. Kunduri, James Lucietti, Harvey S. Reall, Near-horizon symmetries of extremal black holes, Class.Quant.Grav.24:4169-4190,2007 (arXiv:0705.4214)

  • Dumitru Astefanesei, Kevin Goldstein, Rudra P. Jena, Ashoke Sen, Sandip P. Trivedi, Rotating Attractors, JHEP 0610:058,2006 (arXiv:hep-th/0606244)

  • Dumitru Astefanesei, Hossein Yavartanoo, Stationary black holes and attractor mechanism, Nucl.Phys.B794:13-27,2008 (arXiv:0706.1847)

via JT gravity:

  • Pranjal Nayak, Ashish Shukla, Ronak M Soni, Sandip P. Trivedi, V. Vishal, On the Dynamics of Near-Extremal Black Holes (arXiv:1802.09547)

  • Upamanyu Moitra, Sandip P. Trivedi, V. Vishal, Near-Extremal Near-Horizons (arXiv:1808.08239)

Actual observation

Observational signature:

  • Minyong Guo, Niels A. Obers, Haopeng Yan, Observational signature of near-extremal Kerr-like black holes in a modified gravity theory at the Event Horizon Telescope, Phys. Rev. D 98, 084063 (2018) (arXiv:1806.05249)

Actual observation:

Last revised on July 20, 2022 at 17:12:35. See the history of this page for a list of all contributions to it.