Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effects of Ohmic and ambipolar diffusion on the formation and evolution
  of the first cores, protostars and circumstellar discs   We investigate the formation and evolution of a first core, protostar, and
circumstellar disc with a three-dimensional non-ideal (including both Ohmic and
ambipolar diffusion) radiation magnetohydrodynamics simulation. We found that
the magnetic flux is largely removed by magnetic diffusion in the first core
phase and that the plasma $\beta$ of the centre of the first core becomes
large, $\beta>10^4$. Thus, proper treatment of first core phase is crucial in
investigating the formation of protostar and disc. On the other hand, in an
ideal simulation, $\beta\sim 10$ at the centre of the first core. The
simulations with magnetic diffusion show that the circumstellar disc forms at
almost the same time of protostar formation even with a relatively strong
initial magnetic field (the value for the initial mass-to-flux ratio of the
cloud core relative to the critical value is $\mu=4$). The disc has a radius of
$r \sim 1$ AU at the protostar formation epoch. We confirm that the disc is
rotationally supported. We also show that the disc is massive ($Q\sim 1$) and
that gravitational instability may play an important role in the subsequent
disc evolution.

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The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph