Title
A Tale of Three Couplings: Poisson–Dirichlet and GEM Approximations for Random Permutations
Abstract
For a random permutation of $n$ objects, as $n \to \infty$, the process giving the proportion of elements in the longest cycle, the second-longest cycle, and so on, converges in distribution to the Poisson–Dirichlet process with parameter 1. This was proved in 1977 by Kingman and by Vershik and Schmidt. For soft reasons, this is equivalent to the statement that the random permutations and the Poisson–Dirichlet process can be coupled so that zero is the limit of the expected $\ell_1$ distance between the process of cycle length proportions and the Poisson–Dirichlet process. We investigate how rapid this metric convergence can be, and in doing so, give two new proofs of the distributional convergence.One of the couplings we consider has an analogue for the prime factorizations of a uniformly distributed random integer, and these couplings rely on the ‘scale-invariant spacing lemma’ for the scale-invariant Poisson processes, proved in this paper.
Year
DOI
Venue
2006
10.1017/S0963548305007054
Combinatorics, Probability & Computing
Keywords
DocType
Volume
cycle length proportion,gem approximations,distributional convergence,metric convergence,random permutation,random integer,dirichlet process,random permutations,scale-invariant spacing lemma,scale-invariant poisson,second-longest cycle,longest cycle
Journal
15
Issue
ISSN
Citations 
1-2
0963-5483
0
PageRank 
References 
Authors
0.34
1
3
Name
Order
Citations
PageRank
Richard Arratia118221.00
A. D. Barbour26518.58
simon tavare322924.40