Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Failure of standard approximations of the exchange coupling in
  nanostructures   We calculate the exchange coupling for a double dot system using a novel,
numerically exact yet efficient technique, based on finite-element methods.
Specifically, we evaluate the exchange coupling both for a quasi-one and a
two-dimensional system, also including an applied magnetic field. Our numerical
results provide a stringent test for standard approximation schemes (e.g.,
Heitler-London, Hund-Mulliken, Hubbard), and they show that the standard
methods do not have reliable predictive power for real quantum-dot systems.

21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph