Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a motion equation for two particles in relativistic quantum mechanics   The purpose of the present note is to propose, in the framework of
relativistic quantum mechanics, a new Poincare-invariant equation for two
particles with masses m_1, m_2 and spin s_1=s_2=1/2. It is a first-order linear
differential equation for the eight-component wave function. With the help of
this equation the description of the motion of two-particle systems is reduced
to the description of one-particle systems in the (1+6)-dimensional Minkowski
space which can be in two spin states (s=0 or s=1).

16
The categories of this paper are: stat
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex