Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Nonlinear Coupling Network to Simulate the Development of the r-mode
  Instablility in Neutron Stars II. Dynamics   Two mechanisms for nonlinear mode saturation of the r-mode in neutron stars
have been suggested: the parametric instability mechanism involving a small
number of modes and the formation of a nearly continuous Kolmogorov-type
cascade. Using a network of oscillators constructed from the eigenmodes of a
perfect fluid incompressible star, we investigate the transition between the
two regimes numerically. Our network includes the 4995 inertial modes up to n<=
30 with 146,998 direct couplings to the r-mode and 1,306,999 couplings with
detuning< 0.002 (out of a total of approximately 10^9 possible couplings).
  The lowest parametric instability thresholds for a range of temperatures are
calculated and it is found that the r-mode becomes unstable to modes with
13<n<15. In the undriven, undamped, Hamiltonian version of the network the rate
to achieve equipartition is found to be amplitude dependent, reminiscent of the
Fermi-Pasta-Ulam problem. More realistic models driven unstable by
gravitational radiation and damped by shear viscosity are explored next. A
range of damping rates, corresponding to temperatures 10^6K to 10^9K, is
considered. Exponential growth of the r-mode is found to cease at small
amplitudes, approximately 10^-4. For strongly damped, low temperature models, a
few modes dominate the dynamics. The behavior of the r-mode is complicated, but
its amplitude is still no larger than about 10^-4 on average. For high
temperature, weakly damped models the r-mode feeds energy into a sea of
oscillators that achieve approximate equipartition. In this case the r-mode
amplitude settles to a value for which the rate to achieve equipartition is
approximately the linear instability growth rate.

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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg