Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lochlainn O'Raifeartaigh, Fluids, and Noncommuting Fields   Lochlainn O'Raifeartaigh and his work are recalled; the connection between
fluid mechanics -- his last research topic -- and noncommuting gauge fields is
explained.

8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an