Poisson-Dirichlet distribution
= Poisson-Dirichlet distribution
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The Poisson-Dirichlet family consists of laws of decreasing random mass partitions $(p_i)$ with $\sum_i p_i=1$. Its two-parameter notation is $PD(\alpha,\theta)$, with $0\le\alpha<1$ and $\theta>-\alpha$. The conventional one-parameter <probability distribution> $PD(\theta)$ means $PD(0,\theta)$, for $\theta>0$, and can be constructed from normalized gamma jumps.