Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the structure and spectrum of classical two-dimensional clusters with
  a logarithmic interaction potential   We present a numerical study of the effect of the repulsive logarithmic
inter-particle interaction on the ground state configuration and the frequency
spectrum of a confined classical two-dimensional cluster containing a finite
number of particles. In the case of a hard wall confinement all particles form
one ring situated at the boundary of the potential. For a general r^n
confinement potential, also inner rings can form and we find that all
frequencies lie below the frequency of a particular mode, namely the
breathing-like mode. An interesting situation arises for the parabolic confined
system(i.e. n=2). In this case the frequency of the breathing mode is
independent of the number of particles leading to an upper bound for all
frequencies. All results can be understood from Earnshaw's theorem in two
dimensions. In order to check the sensitivity of these results, the spectrum of
vortices in a type II superconductor which, in the limit of large penetration
depths, interact through a logarithmic potential, is investigated.

12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat