Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Regge calculus: a unique tool for numerical relativity   The application of Regge calculus, a lattice formulation of general
relativity, is reviewed in the context of numerical relativity. Particular
emphasis is placed on problems of current computational interest, and the
strengths and weaknesses of the lattice approach are highlighted. Several new
and illustrative applications are presented, including initial data for the
head on collision of two black holes, and the time evolution of vacuum
axisymmetric Brill waves.

3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg