Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Einstein's equations in Ashtekar's variables constitute a symmetric
  hyperbolic system   We show that the 3+1 vacuum Einstein field equations in Ashtekar's variables
constitutes a first order symmetric hyperbolic system for arbitrary but fixed
lapse and shift fields, by suitable adding to the system terms proportional to
the constraint equations.

8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin