Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long time existence for a two-dimensional strongly dispersive Boussinesq
  system   We prove a long time existence result for the solutions of a two-dimensional
Boussinesq system modeling the propagation of long, weakly nonlinear water
waves. This system is exceptional in the sense that it is the only
  linearly well-posed system in the (abcd) family of Boussinesq systems whose
eigenvalues of the linearized system have nontrivial zeroes. This new
difficulty is solved by the use of "good unknowns " and of normal form
techniques.

5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom