Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recurrence in 2D Inviscid Channel Flow   I will prove a recurrence theorem which says that any $H^s$ ($s>2$) solution
to the 2D inviscid channel flow returns repeatedly to an arbitrarily small
$H^0$ neighborhood. Periodic boundary condition is imposed along the
stream-wise direction. The result is an extension of an early result of the
author [Li, 09] on 2D Euler equation under periodic boundary conditions along
both directions.

13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an