Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phonon instability and self-organized structures in multi-layer stacks
  of confined dipolar Bose-Einstein condensates in optical lattices   In calculations to date [1,2] of multi-layer stacks of dipolar condensates,
created in one-dimensional optical lattices, the condensates have been assumed
to be two-dimensional. In a real experiment, however, the condensates do not
extend to infinity in the oblate direction, but have to be confined by a trap
potential, too. By three-dimensional numerical simulations of this realistic
experimental situation we find a crucial dependence of the phonon instability
boundary on the number of layers. Moreover, near the boundary of the phonon
instability, a variety of structured ground-state wave functions emerges, which
may indicate the onset of a roton instability [3,4].

16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom