Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Population-imbalance instability in a Bose-Hubbard ladder in the
  presence of a magnetic flux   We consider a two-leg Bose-Hubbard ladder in the presence of a magnetic flux.
We make use of Gross-Pitaevskii, Bogoliubov, bosonization, and renormalization
group approaches to reveal a structure of ground-state phase diagrams in a
weak-coupling regime relevant to cold atom experiments. It is found that except
for a certain flux $\phi=\pi$, the system shows different properties as
changing hoppings, which also leads to a quantum phase transition similar to
the ferromagnetic XXZ model. This implies that population-imbalance instability
occurs for certain parameter regimes. On the other hand, for $\phi=\pi$, it is
shown that an umklapp process caused by commensurability of a magnetic flux
stabilizes a superfluid with chirality and the system does not experience such
a phase transition.

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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: econ