Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of the vortex-particle complexes bound to the free surface of
  superfluid helium   We present an experimental and theoretical study of the 2D dynamics of
electrically charged nanoparticles trapped under a free surface of superfluid
helium in a static vertical electric field. We focus on the dynamics of
particles driven by the interaction with quantized vortices terminating at the
free surface. We identify two types of particle trajectories and the associated
vortex structures: vertical linear vortices pinned at the bottom of the
container and half-ring vortices travelling along the free surface of the
liquid.

2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg