Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Breakdown of superfluidity of an atom laser past an obstacle   The 1D flow of a continuous beam of Bose-Einstein condensed atoms in the
presence of an obstacle is studied as a function of the beam velocity and of
the type of perturbing potential (representing the interaction of the obstacle
with the atoms of the beam). We identify the relevant regimes:
stationary/time-dependent and superfluid/dissipative; the absence of drag is
used as a criterion for superfluidity. There exists a critical velocity below
which the flow is superfluid. For attractive obstacles, we show that this
critical velocity can reach the value predicted by Landau's approach. For
penetrable obstacles, it is shown that superfluidity is recovered at large beam
velocity. Finally, enormous differences in drag occur when switching from
repulsive to attractive potential.

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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin