Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Variational Principle Directly on the Coherent Pair Condensate. I. the
  BCS Case
9
The categories of this paper are: nlin
2
The categories of this paper are: math
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph