Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a possible approach to the variable-mass problem   The mass operator M is introduced as an independent dynamical variable which
is taken as the translation generator P_4 of the inhomogenous De Sitter group.
The classification of representations of the algebra P(1,4) of this group is
performed and the corresponding P(1,4) invariant equations for variable-mass
particles are written out. In this way we have succeeded, in particular, in
uniting the ``external'' and ``internal'' (SU_2) symmetries in a non-trivial
fashion.

29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci