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13 papers
Short Communications
Random partitions of sets
V. N. Sachkov Moscow
Abstract:
Let
$\mathfrak A_m$ be a set of
$m$ elements and each its partition into subsets be equiprobable. Let
$\xi_l$ be the number of subsets of power
$l$ in the random partition. Then the vector
$$
((\xi_{i_1}-\lambda_{i_1})/\sqrt{\lambda_{i_1}},\dots,(\xi_{i_k}-\lambda_{i_k})/\sqrt{\lambda_{i_k}}),
$$
where
$\lambda_l=r^l/l!$,
$r$ being the unique real root of the equation
$re^r=m$, is shown to be asymptotically normal as
$m\to\infty$ with unit variances and independent components. The limit distributions of
$\mu_m$ and
$\nu_m$ are studied,
$\mu_m$ $(\nu_m)$ being the greatest (least) power in the random partition of
$\mathfrak A_m$. The first is shown to be close to a double exponential distribution in a neighbourhood of point
$er$, the second to be the degenerate distribution with the unit mass at point 1.
Received: 14.02.1973