Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perfect transmission and perfect reflection of Bogoliubov quasiparticles
  in a dynamically unstable Bose-Einstein condensate   The Nambu-Goldstone (NG) mode in a Bose-Einstein condensate (BEC) transmits a
potential barrier with probability 1 in the zero-energy limit, which is known
as the anomalous tunneling. In this paper, we investigate the tunneling
properties of quasiparticles in a dynamically unstable BEC. We prepare a
multi-component BEC (binary and spin-1 BEC) in a dynamically unstable state and
solve the tunneling problem of the spin-wave excitation from the condensate. We
find that the perfect transmission occurs even when the BEC is dynamically
unstable if the spin-wave is the NG mode. Here, the mode that exhibits the
perfect transmission is the dynamically unstable spin-wave mode, which is a
pure-imaginary-eigenvalue solution of the Bogoliubov-de Gennes equation. Hence,
we should take the zero-energy limit along not the real axis but the imaginary
axis. We also demonstrate the existence of the perfect reflection of a
dynamically unstable mode at the point where the imaginary part of the
eigenvalue takes its maximum. In this case, the incident and reflected waves
destructively interfere, and the amplitude of the quasiparticle wave function
is strongly suppressed. We numerically confirm that the perfect reflection is a
generic nature of dynamically unstable modes and not related to the NG mode.

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The categories of this paper are: atom-ph
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-th
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg