Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Instabilities and the Formation of Small-Scale Structures in Planetary
  Nebulae   Recent observations have revealed the presence of a variety of small-scale
``micro-structures'' in Planetary Nebulae images. I discuss numerical
hydrodynamics models of planetaries and outline the formation and growth of
instabilities that may be seen in these models. It is possible that these may
be the forerunners of some of the observed small-scale structures.

11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin