Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The extended Hubbard model applied to study the pressure effects for
  High Temperature Superconductors   We make use of a BCS type approach based on the extended Hubbard Hamiltonian
to study the superconductor transition and to give a microscopic interpre-
tation of the pressure effects on Tc in high temperature superconductors. This
novel method suggests that the applied pressure causes an increase of the
superconducting gap and this effect is explored in order to explain the
variations of Tc. Our approach is therefore beyond the scope of previously
phenomenological models which basically postulate a pressure-induced charge
transfer and an intrinsic term linear on the pressure. We obtain a microscopic
interpretation of this intrinsic term and a general expansion of Tc in terms of
the pressure. To demonstrate the efficiency of the method we apply it to the
experimental data of the Hg-base superconductors.

22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs