Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phoretic and hydrodynamic interactions of weakly-confined autophoretic
  particles   Phoretic particles self-propel using self-generated physico-chemical
gradients at their surface. Within a suspension, they interact hydrodynamically
by setting the fluid around them into motion, and chemically by modifying the
chemical background seen by their neighbours. While most phoretic systems
evolve in confined environments due to buoyancy effects, most models focus on
their interactions in unbounded flows. Here, we propose a first model for the
interaction of phoretic particles in Hele-Shaw confinement and show that in
this limit, hydrodynamic and phoretic interactions share not only the same
scaling but also the same form, albeit in opposite directions. In essence, we
show that phoretic interactions effectively reverse the sign of the
interactions that would be obtained for swimmers interacting purely
hydrodynamically. Yet, hydrodynamic interactions can not be neglected as they
significantly impact the magnitude of the interactions. This model is then used
to analyse the behaviour of a suspension. The suspension exhibits swirling and
clustering collective modes dictated by the orientational interactions between
particles, similar to hydrodynamic swimmers, but here governed by the surface
properties of the phoretic particle; the reversal in the sign of the
interaction tends to slow down the swimming motion of the particles.

15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph