Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Active Model H: Scalar Active Matter in a Momentum-Conserving Fluid   We present a continuum theory of self-propelled particles, without alignment
interactions, in a momentum-conserving solvent. To address phase separation we
introduce a scalar concentration field $\phi$ with advective-diffusive
dynamics. Activity creates a contribution
$\Sigma_{ij}=-\zeta((\partial_i\phi)(\partial_j\phi)-(\nabla\phi)^{2}\delta_{ij}/d)$
to the deviatoric stress, where $\zeta$ is odd under time reversal and $d$ is
the number of spatial dimensions; this causes an effective interfacial tension
contribution that is negative for contractile swimmers. We predict that domain
growth then ceases at a length scale where diffusive coarsening is balanced by
active stretching of interfaces, and confirm this numerically. Thus the
interplay of activity and hydrodynamics is highly nontrivial, even without
alignment interactions.

20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph