Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolution of the vorticity-area density during the formation of coherent
  structures in two-dimensional flows   It is shown: 1) that in two-dimensional, incompressible, viscous flows the
vorticity-area distribution evolves according to an advection-diffusion
equation with a negative, time dependent diffusion coefficient and 2) how to
use the vorticity-streamfunction relations, i.e., the so-called scatter-plots,
of the quasi-stationary coherent structures in order to quantify the
experimentally observed changes of the vorticity distribution moments leading
to the formation of these structures.

18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg