Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hydrodynamically-bound states of a pair of microrollers: a dynamical
  system insight   Recent work has identified persistent cluster states which were shown to be
assembled and held together by hydrodynamic interactions alone [Driscoll
\textit{et al.} (2017) Nature Physics, 13(4), 375]. These states were seen in
systems of colloidal microrollers; microrollers are colloidal particles which
rotate about an axis parallel to the floor and generate strong, slowly
decaying, advective flows. To understand these bound states, we study a simple,
yet rich, model system of two microrollers. Here we show that pairs of
microrollers can exhibit hydrodynamic bound states whose nature depends on a
dimensionless number, denoted $B$, that compares the relative strength of
gravitational forces and external torques. Using a dynamical system framework,
we characterize these various states in phase space and analyze the
bifurcations of the system as $B$ varies. In particular, we show that there is
a critical value, $B^*$, above which active flows can beat gravity and lead to
stable motile orbiting, or "leapfrog", trajectories, reminiscent of the
self-assembled motile structures, called "critters", observed by Driscoll
\textit{et al}. We identify the conditions for the emergence of these
trajectories and study their basin of attraction. This work shows that a wide
variety of stable bound states can be obtained with only two particles.
  Our results aid in understanding the mechanisms that lead to spontaneous
self-assembly in hydrodynamic systems, such as microroller suspensions, as well
as how to optimize these systems for particle transport.

5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas