Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconducting fluctuations in small grains - the Universal Hamiltonian
  and the reduced BCS model   Small superconducting grains are discussed in the frameworks of both the
reduced BCS Hamiltonian and the Universal Hamiltonian. It is shown that
fluctuations of electrons in levels far from the Fermi energy dominate
superconducting properties in small and ultrasmall grains. Experimental
consequences related to the spin susceptibility and persistent currents of
grains and rings with weak electron-electron interactions are discussed.

36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph