Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The N-representability problem, the pseudo-spectral decomposition of
  antisymmetric 1-body operators, and collective behaviour   The pseudo--spectral decomposition of an $N$--particle antisymmetric 1--body
positive--semidefinite operator that corresponds to the canonical convex
decomposition into the extreme elements of the dual cone of the set of fermion
$N$--representable $1$--density operators has been derived. An attempt at
constucting a mathematical model for collective behaviour of a system of
$N$--fermions that originates from the pseudo--spectral decomposition is
presented.

1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ