Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spiral and never-settling patterns in active suspensions   We present a combined numerical and analytical study of pattern formation in
an active system where particles align, possess a density-dependent motility,
and are subject to a logistic reaction. This is a model for suspensions of
reproducing bacteria, but it can also represent, in the ordered phase,
actomyosin gels in vitro or in vivo. In the disordered phase, we find that
motility suppression and growth compete to yield stable or blinking patterns,
which, when dense enough, acquire internal orientational ordering, to yield
asters or spirals. In the ordered phase, the reaction term leads to previously
unobserved never-settling patterns which can provide a simple framework to
understand the formation of motile and spiral patterns in actin.

24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th