Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Electric-Dipole Representation in Atomic Physics   The unitary transformation that leads from the minimal-coupling description
to the electric-dipole one is analysed in detail. The momentum cut-off function
f(k), which is understood in the definition of such a transformation, is
obtained explicitly by use of the variational method. We give an expression for
f(k) in terms of the electron-density and of the mean-squared value of the
electric-dipole moment of the atom in its ground state. A relevant consequence
concerns the van der Waals interaction, whose long-distance behaviour turns out
to be proportional to R^{-8} .

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The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys