3 research outputs found
Near Horizon Limits of Massless BTZ and Their CFT Duals
We consider the massless BTZ black hole and show that it is possible to take
its "near horizon" limit in two distinct ways. The first one leads to a null
self-dual orbifold of AdS3 and the second to a spacelike singular AdS3/Z_K
orbifold in the large K limit, the "pinching orbifold". We show that from the
dual 2d CFT viewpoint, the null orbifold corresponds to the p^+=0 sector of the
Discrete Light-Cone Quantisation (DLCQ) of the 2d CFT where a chiral sector of
the CFT is decoupled, while the pinching orbifold corresponds to taking an
infinite mass gap limit in both the right and left sectors of the 2d CFT,
essentially leaving us with the states L_0=\bar L_0=c/24 only. In the latter
case, one can combine the near horizon limit with sending the 3d Planck length
l_P to zero, or equivalently the dual CFT central charge c to infinity. We
provide preliminary evidence that in that case some nontrivial dynamics may
survive the limit.Comment: 22 pages, no figures, v2: minor improvements, references adde
EVH Black Holes, AdS3 Throats and EVH/CFT Proposal
Within class of generic black holes there are extremal black holes (with
vanishing Hawking temperature T) and vanishing horizon area Ah, but with finite
Ah/T ratio,the Extremal Vanishing Horizon (EVH) black holes. We study the near
horizon limit of a four dimensional EVH black hole solution to a generic
(gauged) Einstein-Maxwell dilaton theory and show that in the near horizon
limit they develop a throat which is a pinching orbifold limit of AdS3. This is
an extension of the well known result for extremal black holes the near horizon
limit of which contains an AdS2 throat. We show that in the near EVH near
horizon limit the pinching AdS3 factor turns to a pinching BTZ black hole and
that this near horizon limit is indeed a decoupling limit. We argue that the
pinching AdS3 or BTZ orbifold is resolved if the near horizon limit is
accompanied by taking the 4d Newton constant G4 to zero such that the
Bekenstein-Hawking entropy S = Ah/(4G4) remains finite. We propose that in this
limit the near horizon EVH black hole is dual to a 2d CFT. We provide pieces of
evidence in support of the EVH/CFT correspondence and comment on its connection
to the Kerr/CFT proposal and speculations how the EVH/CFT may be used to study
generic e.g. Schwarzchild-type black holes.Comment: 31 pages, 3 figures, JHEP styl