Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cold Collision Frequency Shift of an Optical Spectrum of a Trapped Gas   We develop an exact sum rule that relates the spectral shift of a trapped gas
undergoing cold collisions to measurable quantities of the system. The method
demonstrates the dependence of the cold collision frequency shift on the
quantum degeneracy of the gas and facilitates extracting scattering lengths
from the data. We apply the method to analyzing spectral data for magnetically
trapped hydrogen atoms and determine the value of the $1S-2S$ scattering
length.

10
The categories of this paper are: q-bio
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The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
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The categories of this paper are: eess
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc