Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collinear velocity relaxation of two spheres in a viscous incompressible
  fluid   Collinear velocity relaxation of two spheres immersed in a viscous
incompressible fluid is studied on the basis of an approximate expression for
the retarded hydrodynamic interaction. After a sudden impulse applied to one
sphere, the other one instantaneously starts to move as well, with amplitude
determined by the added mass effect. The velocities of both spheres eventually
decay with a t^{-3/2} long-time tail, but the relative velocity decays with a
t^{-5/2} long-time tail. The three relaxation functions are approximated by
simple expressions involving only a small number of poles in the complex square
root of frequency plane.

10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg