= Random-walk derivation of stellar relaxation
{title2=$t_{\mathrm{rel}}\sim0.1(N/\ln N)t_{\mathrm{cross}}$}
<Small-angle gravitational encounters> occur at rate $2\pi b\,db\,nu$ and supply kicks $2Gm/(bu)$. Independent kick variances add to $d\langle\Delta v^2\rangle/dt=8\pi G^2m^2n\ln\Lambda/u$. Setting the accumulated variance to $u^2$ and using virial scaling gives a <stellar relaxation time> of order $0.1N/\ln N$ <stellar crossing times>, with the coefficient dependent on profile and crossing convention.
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