Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mechanical alignment of suprathermally rotating grains   It is shown that mechanical alignment of grains can be efficient for grains
rotating suprathermally, i.e. with kinetic energy substantially exceeding $k$
(the Boltzmann constant) over any temperature in the system. The paper studies
suprathermal rotation caused by H$_{2}$ formation and the alignment that takes
place due to crossover events. Gaseous bombardment in the course of a crossover
as well as both gaseous friction and poisoning of active sites are shown to
produce alignment. The first type of alignment happens due to the angular
momentum deposited by a corpuscular flux with a grain, the second is caused by
the change of the mean time back to crossover due to the interaction with a
gaseous flux. We show that the two processes act as to decrease the grain cross
section in respect to the flux and we find the Rayleigh reduction factor for
the joint action of the two processes as well as the range of applicability of
each of the processes. Our study indicates that mechanical alignment can be
more widely spread than it is generally accepted.

30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio