Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collective suppression of optical hyperfine pumping in dense clouds of
  atoms in microtraps   We observe a density-dependent collective suppression of optical pumping
between the hyperfine ground states in an array of submicrometer-sized clouds
of cold rubidium atoms. The suppressed Raman transition rate can be explained
by strong resonant dipole-dipole interactions that are enhanced by increasing
atom density. The observations are consistent with stochastic electrodynamics
simulations that incorporate the effects of the nonlinear population transfer
via internal atomic levels embedded in a coupled-dipole model.

33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn