Evanescent black holes

Abstract

A renormalizable theory of quantum gravity coupled to a dilaton and conformal matter in two spacetime dimensions is analyzed. The theory is shown to be exactly solvable classically. Included among the exact classical solutions are configurations describing the formation of a black hole by collapsing matter. The problem of Hawking radiation and back reaction of the metric is analyzed to leading order in a I/N expansion, where N is the number of matter fields. The results suggest that the collapsing matter radiates away all of its energy before an event horizon has a chance to form, and black holes thereby disappear from the quantum-mechanical spectrum. It is argued that the matter asymptotically approaches a zero-energy "bound state" which can carry global quantum numbers and that a unitary S matrix including such states should exist.

Graded Poisson-sigma models and dilaton-deformed 2D supergravity algebra

“…It is neither linear nor does it represent a drastic simplification compared to the algebra of constraints G I . In particular it is not obvious to interpret the general result as a deformed Neuveu-Schwarz or Ramond algebra 6 . It rather reflects in a cumbersome way the large arbitrariness in the gPSM as derived by the fermionic extension from a PSM.…”

“…They include effective theories of direct physical interest, like reduced d-dimensional Einstein theories and the extensions thereof (Einstein-deSitter, Jordan-Brans-Dicke theories [1][2][3][4][5]), but also theories suggested by stringy arguments [6] 1 . On the other hand, supersymmetric extensions of gravity [8][9][10][11] are believed to be a crucial ingredient for a consistent solution of the problem how to quantize gravity in the framework of string/brane theory [12][13][14].…”

“…with the CGHS model [6] as the formal limit d → ∞. The Jackiw-Teitelboim model [32][33][34][35][36] corresponds to 8) and the bosonic part of the simplest non-trivial 2d supergravity model of Howe [37] -after the correct identification of the dilaton with one of the components of the superfield [38]becomes…”

“…The most interesting models are described by potentials of type 6) where e.g. spherically reduced gravity from d dimensions is given by [28][29][30][31] …”

Little string thermodynamics

“…In particular the thermal behavior of LSTs has been addressed by various authors. It was argued in the work of [12] that the LSTs at finite temperature can be realized in terms of the CGHS black hole [10]. As a consequence of this the holographic prescription of [6] implies that the finite temperature LST is holographically dual to string theory on the CHS tube [11] capped off by a horizon (the two-dimensional cigar geometry in Euclidean metric), along with a SU(2) WZW model with level prescribed by the number of NS5-branes and a free CFT for the longitudinal directions of the brane.…”