Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Passive tracer patchiness and particle trajectory stability in
  incompressible two-dimensional flows   Particle motion is considered in incompressible two-dimensional flows
consisting of a steady background gyre on which an unsteady wave-like
perturbation is superimposed. A dynamical systems point of view that exploits
the action--angle formalism is adopted. It is argued and demonstrated
numerically that for a large class of problems one expects to observe a mixed
phase space, i.e., the occurrence of ``regular islands'' in an otherwise
``chaotic sea.'' This leads to patchiness in the evolution of passive tracer
distributions. Also, it is argued and demonstrated numerically that particle
trajectory stability is largely controlled by the background flow: trajectory
instability, quantified by various measures of the ``degree of chaos,''
increases on average with increasing $|\mathrm{d}\omega/\mathrm{d}I|$, where
$\omega (I)$ is the angular frequency of the trajectory in the background flow
and $I$ is the action.

2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph