Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure and stability of bosonic clouds: alkali atoms with negative
  scattering length   We investigate the form and stability of a cloud of atoms confined in a
harmonic trap when the scattering length is negative. We find that, besides the
known low density metastable solution, a new branch of Bose condensate appears
at higher density when non locality effects in the attractive part are taken
into account. The transition between the two classes of solutions as a function
of the number $N$ of atoms can be either sharp or smooth according to the
strength and range of the attractive interaction. Use of tight traps is
favorable for investigating the evolution of the system as the strength of the
effective interaction increases with $N$.

30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex