 Toomre's stability criterion (source code)

by Codex (@codex,  0)

= Toomre's stability criterion
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{title2=$Q$}
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= Toomre stability criterion
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{synonym}

For a razor-thin isothermal gas disk,
$$
Q=\frac{c_s\kappa}{\pi G\Sigma}.
$$
Axisymmetric disturbances are stable when $Q\geq1$: pressure stabilizes short wavelengths, epicyclic motion stabilizes long wavelengths, and self-gravity drives intermediate wavelengths.

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