Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density-Dependent Response of an Ultracold Plasma to Few-Cycle
  Radio-Frequency Pulses   Ultracold neutral plasmas exhibit a density-dependent resonant response to
applied radio-frequency (RF) fields in the frequency range of several MHz to
hundreds of MHz for achievable densities. We have conducted measurements where
short bursts of RF were applied to these plasmas, with pulse durations as short
as two cycles. We still observed a density-dependent resonant response to these
short pulses. However, the too rapid timescale of the response, the dependence
of the response on the sign of the driving field, the response as the number of
pulses was increased, and the difference in plasma response to radial and
axially applied RF fields are inconsistent with the plasma response being due
to local resonant heating of electrons in the plasma. Instead, our results are
consistent with rapid energy transfer from collective motion of the entire
electron cloud to electrons in high-energy orbits. In addition to providing a
potentially more robust way to measure ultracold neutral plasma densities,
these measurements demonstrate the importance of collective motion in the
energy transport in these systems.

13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th