Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diffractive Nonlinear Geometrical Optics for Variational Wave Equations
  and the Einstein Equations   We derive an asymptotic solution of the vacuum Einstein equations that
describes the propagation and diffraction of a localized, large-amplitude,
rapidly-varying gravitational wave. We compare and contrast the resulting
theory of strongly nonlinear geometrical optics for the Einstein equations with
nonlinear geometrical optics theories for variational wave equations.

37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci