Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Light self-trapping in a large cloud of cold atoms   We show that, for a near-resonant propagating beam, a large cloud of cold
87Rb atoms acts as a saturable Kerr medium and produces self-trapping of light.
By side fluorescence imaging we monitor the transverse size of the beam and,
depending on the sign of the laser detuning with respect to the atomic
transition, we observe self-focusing or -defocusing, with the waist remaining
stationary for an appropriate choice of parameters. We analyze our observations
by using numerical simulations based on a simple 2-level atom model.

8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph