Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density-Wave Instability and Collective Modes in a Bilayer System of
  Dipolar Bosons   We consider a bilayer of dipolar bosons in which the polarization of dipoles
are perpendicular to the planes. Using accurate static structure factor $S(q)$
data from hypernetted-chain calculation for single layer dipolar bosons we
construct effective screened interactions for intralayer particles. We adopt
the random-phase approximation for interlayer interactions. We study the
instability of the homogeneous bilayer system against the formation of density
waves by investigating the poles of the density-density response function. The
dispersion of collective modes of this system also signals the density-wave
instability. We also investigate the effect of counterflow on the collective
mode dispersion and on the density-wave instability and discuss the
dissipationless superfluid drag effect in the presence of a background
velocity.

34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int