Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Relaxation of spins due to a magnetic field gradient, revisited;
  Identity of the Redfield and Torrey theories
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
16
The categories of this paper are: stat
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga