Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamically triggered star formation in giant molecular clouds   A Lagrangian, particle-based numerical method (tree code gravity plus
smoothed particle hydrodynamics) was used to simulate clump-clump collisions
occurring within GMCs.
  The collisions formed shock-compressed layers, out of which condensed
approximately co-planar protostellar discs of 7-60 solar masses and 500-1000AU
radius. Binary and multiple systems were the usual final state. Lower mass
objects were also produced, but commonly underwent disruption or merger. Such
objects occasionally survived by being ejected via a three-body slingshot event
resulting from an encounter with a binary system.
  Varying the impact parameter, b, altered the processes by which the
protostellar systems formed. At low b a single central disc formed initially,
and was then spun-up by an accretion flow, causing it to produce secondaries
via rotational instabilities. At mid b the shocked layer w hich formed
initially broke up into fragments, and discs were then formed via fragment
merger. At large b single objects formed within the compressed leading edge of
each clump. These became unbound from each other as b was increased further.
  The effect of changing numerical factors was examined by : (i) colliding
clumps which had been re-oriented before the collision (thus altering the
initial particle noise), and (ii) by quadrupling the number of particles in
each clump (thus increasing the resolution of the simulation). Both changes
were found to affect the small-scale details of a collision, but leave the
large scale morphology largely unaltered.
  It was concluded that clump-clump collisions provide a natural mechanism by
which multiple protostellar systems may form.

36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
18
The categories of this paper are: econ