Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nucleon-pair approximation with matrix representation   In this paper, we propose an approach of the nucleon-pair approximation
(NPA), in which the collective nucleon pairs are represented in terms of
antisymmetric matrices, and commutations between nucleon pairs are given by
using matrix multiplication that avoids angular-momentum couplings and
recouplings. Therefore the present approach significantly simplifies the NPA
computation. Furthermore, it is formulated on the same footing with and without
isospin.

29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin