Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A variational principle for three-dimensional water waves over Beltrami
  flows   We consider steady three-dimensional gravity-capillary water waves with
vorticity propagating on water of finite depth. We prove a variational
principle for doubly periodic waves with relative velocities given by Beltrami
vector fields, under general assumptions on the wave profile.

11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an