Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Closed expression of the interaction kernel in the Bethe-Salpeter
  equation for quark-antiquark bound states   The interaction kernel in the Bethe-Salpeter equation for quark-antiquark
bound states is derived from the Bethe-Salpeter equations satisfied by the
quark-antiquark four-point Green's function. The latter equations are
established based on the equations of motion obeyed by the quark and antiquark
propagators, the four-point Green's function and some other kinds of Green's
functions which follow directly from the QCD generating functional. The B-S
kernel derived is given an exact and explicit expression which contains only a
few types of Green's functions. This expression is not only convenient for
perturbative calculations, but also suitable for nonperturbative
investigations.

36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs