We discuss a characterization of the centered Gaussian distribution which can
be read from results of Archimedes and Maxwell, and relate it to Charles
Stein's well-known characterization of the same distribution. These
characterizations fit into a more general framework involving the beta-gamma
algebra, which explains some other characterizations appearing in the Stein's
method literature.
The beta-Bernoulli process provides a Bayesian nonparametric prior for models
involving collections of binary-valued features. A draw from the beta process
provides an infinite collection of probabilities in the unit interval, and a
draw from the Bernoulli process turns these into binary-valued features. Recent
work has shown how to derive stick-breaking representations for the beta
process, by analogy to Sethuraman's derivation of a stick-breaking
representation for the Dirichlet process.
This article provides an overview of recent work on descriptions and
properties of the convex minorant of random walks and L\'evy processes which
summarize and extend the literature on these subjects.
This article contains both a point process and a sequential description of
the greatest convex minorant of Brownian motion on a finite interval. We use
these descriptions to provide new analysis of various features of the convex
minorant such as the set of times where the Brownian motion meets its minorant.
The equivalence of the these descriptions is non-trivial, which leads to many
interesting identities between quantities derived from our analysis. The
sequential description can be viewed as a Markov chain for which we derive some
fundamental properties.
We offer a unified approach to the theory of convex minorants of L\'evy
processes with continuous distributions. New results include simple and
explicit constructions of the convex minorant of a L\'evy process, on both
finite and infinite time intervals, and of a Poisson point process of
excursions above the convex minorant up to an independent exponential time. The
Poisson-Dirichlet distribution of parameter 1 is shown to be the universal law
of ranked lengths of excursions of a L\'evy process with continuous
distributions above its convex minorant on the interval $[0,1]$.
We provide a representation of the maximal difference between a standard
Brownian bridge and its concave majorant on the unit interval, from which we
deduce expressions for the distribution and density functions and moments of
this difference. This maximal difference has an application in nonparametric
statistics where it arises in testing monotonicity of a density or regression
curve.
We provide a representation of the maximal difference between a standard
Brownian bridge and its concave majorant on the unit interval, from which we
deduce expressions for the distribution and density functions and moments of
this difference. This maximal difference has an application in nonparametric
statistics where it arises in testing monotonicity of a density or regression
curve.
We use a natural ordered extension of the Chinese Restaurant Process to grow
a two-parameter family of binary self-similar continuum fragmentation trees. We
provide an explicit embedding of Ford's sequence of alpha model trees in the
continuum tree which we identified in a previous article as a distributional
scaling limit of Ford's trees. In general, the Markov branching trees induced
by the two-parameter growth rule are not sampling consistent, so the existence
of compact limiting trees cannot be deduced from previous work on the sampling
consistent case.
We prove a long-standing conjecture which characterises the Ewens-Pitman
two-parameter family of exchangeable random partitions, plus a short list of
limit and exceptional cases, by the following property: for each $n = 2,3,
>...$, if one of $n$ individuals is chosen uniformly at random, independently
of the random partition $\pi_n$ of these individuals into various types, and
all individuals of the same type as the chosen individual are deleted, then for
each $r > 0$, given that $r$ individuals remain, these individuals are
partitioned according to $\pi_r'$ for some sequence of rando
We develop some theory of spinal decompositions of discrete and continuous
fragmentation trees. Specifically, we consider a coarse and a fine spinal
integer partition derived from spinal tree decompositions. We prove that for a
two-parameter Poisson--Dirichlet family of continuous fragmentation trees,
including the stable trees of Duquesne and Le Gall, the fine partition is
obtained from the coarse one by shattering each of its parts independently,
according to the same law.