Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The superconducting gap in the Hubbard model and the two gap energy
  scales in high-Tc cuprates   Recent excperiments (ARPES, Raman) suggest the presence of two distinct
energy gaps in high-Tc superconductors (HTSC), exhibiting different doping
dependences. Results of a variational cluster approach to the superconducting
state of the two-dimensional Hubbard model are presented which show that this
model qualitatively describes this gap dichotomy: One gap (antinodal) increases
with less doping, a behavior long considered as reflecting the general gap
behavior of the HTSC. On the other hand, the near-nodal gap does even slightly
decrease with underdoping. An explanation of this unexpected behavior is given
which emphasizes the crucial role of spin fluctuations in the pairing
mechanism.

9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
2
The categories of this paper are: math