= Turbulent mixing of a secularly unstable dust layer
{title2=$s\sim2\pi\epsilon G\sigma_0|k|/\Omega-Dk^2$}
<Turbulence> can raise dust random speeds, increase layer thickness and mix density enhancements by <eddy diffusion>, delaying <secular gravitational instability>. On sufficiently long wavelengths, weak-drag growth is proportional to $|k|$, whereas simple diffusive damping is proportional to $k^2$. Thus diffusion alone need not remove all long-wave growth in an infinite idealization, although finite size and lifetime can make it ineffective. Coherent turbulent concentration can also increase local <surface density>, so the net effect requires a stochastic transport model.
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