Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Tkachenko Oscillations in Rapidly Rotating Bose-Einstein
  Condensates   We directly image Tkachenko waves in a vortex lattice in a dilute-gas
Bose-Einstein condensate. The low (sub-Hz) resonant frequencies are a
consequence of the small but nonvanishing elastic shear modulus of the
vortex-filled superfluid. The frequencies are measured for rotation rates as
high as 98% of the centrifugal limit for the harmonically confined gas.
Agreement with a hydrodynamic theory worsens with increasing rotation rate,
perhaps due to the increasing fraction of the volume displaced by the vortex
cores. We also observe two low-lying m=0 longitudinal modes at about 20 times
higher frequency.

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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph