Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collisional Fragmentation is Not a Barrier to Close-in Planet Formation   Collisional fragmentation is shown to not be a barrier to rocky planet
formation at small distances from the host star. Simple analytic arguments
demonstrate that rocky planet formation via collisions of homogeneous
gravity-dominated bodies is possible down to distances of order the Roche
radius ($r_\mathrm{Roche}$). Extensive N-body simulations with initial bodies
${\gtrsim}1700$ km that include plausible models for fragmentation and merging
of gravity-dominated bodies confirm this conclusion and demonstrate that rocky
planet formation is possible down to ${\sim}$1.1 $r_\mathrm{Roche}$. At smaller
distances, tidal effects cause collisions to be too fragmenting to allow mass
build-up to a final, dynamically stable planetary system. We argue that even
differentiated bodies can accumulate to form planets at distances that are not
much larger than $r_\mathrm{Roche}$.

21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex