Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density-matrix functionals for pairing in mesoscopic superconductors   A functional theory based on single-particle occupation numbers is developed
for pairing. This functional, that generalizes the BCS approach, directly
incorporates corrections due to particle number conservation. The functional is
benchmarked with the pairing Hamiltonian and reproduces perfectly the energy
for any particle number and coupling.

17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat