Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin and charge gaps in the one-dimensional Kondo-lattice model with
  Coulomb interaction between conduction electrons   The density-matrix renormalization-group method is applied to the
one-dimensional Kondo-lattice model with the Coulomb interaction between the
conduction electrons. The spin and charge gaps are calculated as a function of
the exchange constant $J$ and the Coulomb interaction $U_c$. It is shown that
both the spin and charge gaps increase with increasing $J$ and $U_c$. The spin
gap vanishes in the limit of $J \rightarrow 0$ for any $U_c$ with an
exponential form, $\Delta_s\propto \exp{[-1/\alpha (U_c) J \rho]}$. The
exponent, $\alpha (U_c)$, is determined as a function of $U_c$. The charge gap
is generally much larger than the spin gap. In the limit of $J \rightarrow 0$,
the charge gap vanishes as $\Delta_c=\frac{1}{2}J$ for $U_c=0$ but for a finite
$U_c$ it tends to a finite value, which is the charge gap of the Hubbard model.

34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn