Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Future stability of the $1+3$ Milne model for Einstein-Klein-Gordon
  system   We study the small perturbations of the $1+3$-dimensional Milne model for the
Einstein-Klein-Gordon (EKG) system. We prove the nonlinear future stability,
and show that the perturbed spacetimes are future causally geodesically
complete. For the proof, we work within the constant mean curvature (CMC) gauge
and focus on the $1+3$ splitting of the Bianchi-Klein-Gordon equations.
Moreover, we treat the Bianchi-Klein-Gordon equations as evolution equations
and establish the energy scheme in the sense that we only commute the
Bianchi-Klein-Gordon equations with the spatially covariant derivatives while
the normal derivative is not allowed.

28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg