Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Combinatorial Geometry of Q-Gorenstein Quasi-Homogeneous Surface
  Singularities   The main result of this paper is a construction of fundamental domains for
certain group actions on Lorentz manifolds of constant curvature. We consider
the simply connected Lie group G~, the universal cover of the group SU(1,1) of
orientation-preserving isometries of the hyperbolic plane. The Killing form on
the Lie group G~ gives rise to a bi-invariant Lorentz metric of constant
curvature. We consider a discrete subgroup Gamma_1 and a cyclic discrete
subgroup Gamma_2 in G~ which satisfy certain conditions. We describe the
Lorentz space form Gamma_1\G~/Gamma_2 by constructing a fundamental domain for
the action of the product of Gamma_1 and Gamma_2 on G~ by (g,h)*x=gxh^{-1}.
This fundamental domain is a polyhedron in the Lorentz manifold G~ with totally
geodesic faces. For a co-compact subgroup the corresponding fundamental domain
is compact. The class of subgroups for which we construct fundamental domains
corresponds to an interesting class of singularities. The bi-quotients of the
form Gamma_1\G~/Gamma_2 are diffeomorphic to the links of quasi-homogeneous
Q-Gorenstein surface singularities.

0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol