O-BTZ: Orientifolded BTZ Black Hole

Understand

Banados-Teitelboim-Zanelli (BTZ) black holes are constructed by orbifolding AdS3 geometry by boost transformations of its O(2,2) isometry group.

• Here we construct a new class of solutions to AdS3 Einstein gravity, orientifolded BTZ or O-BTZ for short, which in general, besides the usual BTZ orbifolding, involve orbifolding (orientifolding) by a Z_2 part of O(2,2) isometry group.
• This Z_2 is chosen such that it changes the orientation on AdS3 while keeping the orientation on its 2D conformal boundary.
• O-BTZ solutions exhaust all un-oriented AdS3 black hole solutions, as BTZ black holes constitute all oriented AdS3 black holes.