Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Onset of cavity deformation upon subsonic motion of a projectile in a
  fluid complex plasma   We study deformation of a cavity around a large projectile moving with
subsonic velocity in the cloud of small dust particles. To solve this problem,
we employ the Navier--Stokes equation for a compressible fluid with due regard
for friction between dust particles and atoms of neutral gas. The solutions
shows that due to friction, the pressure of dust cloud at the boundary of the
cavity behind the projectile can become negative, which entails formation of a
microscopic void free from dust particles -- the cavity deformation.
Corresponding threshold velocity is calculated, which is found to decrease with
increasing cavity size. Measurement of such velocity makes it possible to
estimate the static pressure inside the dust cloud.

34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th