Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Convective instability and mass transport of diffusion layers in a
  Hele-Shaw geometry
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys