Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Grain Alignment in Molecular Clouds   One of the most informative techniques of studying magnetic fields in
molecular clouds is based on the use of starlight polarization and polarized
emission arising from aligned dust. How reliable the interpretation of the
polarization maps in terms of magnetic fields is the issue that the grain
alignment theory addresses.
  I briefly review basic physical processes involved in grain alignment.

33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn