Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Planet formation in stellar binaries II: overcoming the fragmentation
  barrier in alpha Centauri and gamma Cephei-like systems   Planet formation in small-separation (~20 AU) eccentric binaries such as
gamma Cephei or alpha Centauri is believed to be adversely affected by the
presence of the stellar companion. Strong dynamical excitation of planetesimals
by the eccentric companion can result in collisional destruction (rather than
growth) of 1-100 km objects, giving rise to the "fragmentation barrier" for
planet formation. We revise this issue using a novel description of secular
dynamics of planetesimals in binaries, which accounts for the gravity of the
eccentric, coplanar protoplanetary disk, as well as gas drag. By studying
planetesimal collision outcomes we show, in contrast to many previous studies,
that planetesimal growth and subsequent formation of planets (including gas
giants) in AU-scale orbits within ~20 AU separation binaries may be possible,
provided that the protoplanetary disks are massive (>10^{-2}M_\odot) and only
weakly eccentric (disk eccentricity <0.01). These requirements are compatible
with both the existence of massive (several M_J) planets in gamma Cep-like
systems and the results of recent simulations of gaseous disks in eccentric
binaries. Terrestrial and Neptune-like planets can also form in lower-mass
disks at small (sub-AU) radii. We find that fragmentation barrier is less of a
problem in eccentric disks which are apsidally aligned with the binary orbit.
Alignment gives rise to special locations, where (1) relative planetesimal
velocities are low and (2) the timescale of their drag-induced radial drift is
long. This causes planetesimal pileup at such locations in the disk and
promotes their growth.

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The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess