Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coherent tunnelling through two quantum dots with Coulomb interaction   The coherent conductance and current is calculated through two quantum dots
using the Hubbard model for a single level per spin. The occurrence of negative
differential conductance is demonstrated. The Ohmic conductance is calculated
for dots with equally spaced levels. Transport is determined by matching energy
levels, even when they do not occur at the charge degeneracy points.

15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat