Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time-dependent modeling of extended thin decretion disks of critically
  rotating stars   During their evolution massive stars can reach the phase of critical rotation
when a further increase in rotational speed is no longer possible. Direct
centrifugal ejection from a critically or near-critically rotating surface
forms a gaseous equatorial decretion disk. Anomalous viscosity provides the
efficient mechanism for transporting the angular momentum outwards. The outer
part of the disk can extend up to a very large distance from the parent star.
We study the evolution of density, radial and azimuthal velocity, and angular
momentum loss rate of equatorial decretion disks out to very distant regions.
We investigate how the physical characteristics of the disk depend on the
distribution of temperature and viscosity. We calculated stationary models
using the Newton-Raphson method. For time-dependent hydrodynamic modeling we
developed the numerical code based on an explicit finite difference scheme on
an Eulerian grid including full Navier-Stokes shear viscosity. The sonic point
distance and the maximum angular momentum loss rate strongly depend on the
temperature profile and are almost independent of viscosity. The rotational
velocity at large radii rapidly drops accordingly to temperature and viscosity
distribution. The total amount of disk mass and the disk angular momentum
increase with decreasing temperature and viscosity. The time-dependent
one-dimensional models basically confirm the results obtained in the stationary
models as well as the assumptions of the analytical approximations. Including
full Navier-Stokes viscosity we systematically avoid the rotational velocity
sign change at large radii. The unphysical drop of the rotational velocity and
angular momentum loss at large radii (present in some models) can be avoided in
the models with decreasing temperature and viscosity.

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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: econ