Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure and Melting of Two-Species Charged Clusters in a Parabolic
  Trap   We consider a system of charged particles interacting with an unscreened
Coulomb repulsion in a two-dimensional parabolic confining trap. The static
charge on a portion of the particles is twice as large as the charge on the
remaining particles. The particles separate into a shell structure with those
of greater charge situated farther from the center of the trap. As we vary the
ratio of the number of particles of the two species, we find that for certain
configurations, the symmetry of the arrangement of the inner cluster of
singly-charged particles matches the symmetry of the outer ring of
doubly-charged particles. These matching configurations have a higher melting
temperature and a higher thermal threshold for intershell rotation between the
species than the nonmatching configurations.

29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph