Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: String theory on three dimensional black holes   We investigate the string theory on three dimensional black holes discovered
by Ba\~{n}ados, Teitelboim and Zanelli in the framework of conformal field
theory. The model is described by an orbifold of the $\widetilde{SL}(2,R)$ WZW
model. The spectrum is analyzed by solving the level matching condition and we
obtain winding modes. We then study the ghost problem and show explicit
examples of physical states with negative norms. We discuss the tachyon
propagation and the target space geometry, which are irrelevant to the details
of the spectrum. We find a self-dual T-duality transformation reversing the
black hole mass. We also discuss difficulties in string theory on curved
spacetime and possibilities to obtain a sensible string theory on three
dimensional black holes. This work is the first attempt to quantize a string
theory in a black hole background with an infinite number of propagating modes.

3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat