Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stability and structure of an anisotropically trapped dipolar
  Bose-Einstein condensate: angular and linear rotons   We study theoretically Bose-Einstein condensates with polarized dipolar
interactions in anisotropic traps. We map the parameter space by varying the
trap frequencies and dipolar interaction strengths and find an irregular-shaped
region of parameter space in which density-oscillating condensate states occur,
with maximum density away from the trap center. These density-oscillating
states may be biconcave (red-blood-cell-shaped), or have two or four peaks. For
all trap frequencies, the condensate becomes unstable to collapse for
sufficiently large dipole interaction strength. The collapse coincides with the
softening of an elementary excitation. When the condensate mode is
density-oscillating, the character of the softening excitation is related to
the structure of the condensate. We classify these excitations by linear and
angular characteristics. We also find excited solutions to the Gross-Pitaevskii
equation, which are always unstable.

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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex