Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Attractive ultracold bosons in a necklace optical potential   We study the ground state properties of the Bose-Hubbard model with
attractive interactions on a M-site one-dimensional periodic -- necklace-like
-- lattice, whose experimental realization in terms of ultracold atoms is
promised by a recently proposed optical trapping scheme, as well as by the
control over the atomic interactions and tunneling amplitudes granted by
well-established optical techniques. We compare the properties of the quantum
model to a semiclassical picture based on a number-conserving su(M) coherent
state, which results into a set of modified discrete nonlinear Schroedinger
equations. We show that, owing to the presence of a correction factor ensuing
from number conservation, the ground-state solution to these equations provides
a remarkably satisfactory description of its quantum counterpart not only -- as
expected -- in the weak-interaction, superfluid regime, but even in the deeply
quantum regime of large interactions and possibly small populations. In
particular, we show that in this regime, the delocalized, Schroedinger-cat-like
quantum ground state can be seen as a coherent quantum superposition of the
localized, symmetry-breaking ground-state of the variational approach. We also
show that, depending on the hopping to interaction ratio, three regimes can be
recognized both in the semiclassical and quantum picture of the system.

28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs