Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Three-dimensional gravity and Drinfel'd doubles: spacetimes and
  symmetries from quantum deformations   We show how the constant curvature spacetimes of 3d gravity and the
associated symmetry algebras can be derived from a single quantum deformation
of the 3d Lorentz algebra sl(2,R). We investigate the classical Drinfel'd
double of a "hybrid" deformation of sl(2,R) that depends on two parameters
(\eta,z). With an appropriate choice of basis and real structure, this
Drinfel'd double agrees with the 3d anti-de Sitter algebra. The deformation
parameter \eta is related to the cosmological constant, while z is identified
with the inverse of the speed of light and defines the signature of the metric.
We generalise this result to de Sitter space, the three-sphere and 3d
hyperbolic space through analytic continuation in \eta and z; we also
investigate the limits of vanishing \eta and z, which yield the flat spacetimes
(Minkowski and Euclidean spaces) and Newtonian models, respectively.

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The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci