Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Calculation of collective modes for the Bose-Hubbard model with
  confinement   The collective excitations in the Bose-Hubbard model in a trap are studied by
means of numerical diagonalization in one dimension. The strength function is
calculated for monopole and dipole perturbations, and moments of the strength
function are utilized in order to obtain information about the collective
behavior under external forces. In the superfluid regime, the spectrum is found
to be exhausted by one single frequency, while in systems that contain a Mott
insulating plateau several frequencies are excited. An explanation of recent
experimental findings in terms of a Mott plateau is suggested.

15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas