3,826 research outputs found
Simulations of some Doubly Stochastic Poisson Point Processes
International audienceComputer simulations of point processes are important either to verify the results of certain theoretical calculations that can be very awkward at times, or to obtain practical results when these calculations become almost impossible. One of the most common methods for the simulation of nonstationary Poisson processes is random thinning. Its extension when the intensity becomes random (doubly stochastic Poisson processes) depends on the structure of this intensity. If the random density takes only discrete values, which is a common situation in many physical problems where quantum mechanics introduces discrete states, it is shown that the thinning method can be applied without error. We study in particular the case of binary density and we present the kind of theoretical calculations that then become possible. The results of various experiments realized with data obtained by simulation show fairly good agreement with the theoretical calculations
Fractional Poisson Fields and Martingales
We present new properties for the Fractional Poisson process and the
Fractional Poisson field on the plane. A martingale characterization for
Fractional Poisson processes is given. We extend this result to Fractional
Poisson fields, obtaining some other characterizations. The fractional
differential equations are studied. We consider a more general Mixed-Fractional
Poisson process and show that this process is the stochastic solution of a
system of fractional differential-difference equations. Finally, we give some
simulations of the Fractional Poisson field on the plane
Testing the existence of clustering in the extreme values
This paper introduces an estimator for the extremal index as the ratio of the number of elements of two point processes defined by threshold sequences un, vn and a partition of the sequence in different blocks of the same size. The first point process is defined by the sequence of the block maxima that exceed un. This paper introduces a thinning of this point process, defined by a threshold vn with vn > un, and with the appealing property that under some mild conditions the ratio of the number of elements of both point processes is a consistent estimator of the extremal index. The method supports a hypothesis test for the extremal index, and hence for testing the existence of clustering in the extreme values. Other advantages are that it allows some freedom to choose un, and it is not very sensitive to the choice of the partition. Finally, the stylized facts found in financial returns (clustering, skewness, heavy tails) are tested via the extremal index, in this case for the DaX return
Stochastic foundations of undulatory transport phenomena: Generalized Poisson-Kac processes - Part I Basic theory
This article introduces the notion of Generalized Poisson-Kac (GPK) processes
which generalize the class of "telegrapher's noise dynamics" introduced by Marc
Kac in 1974, usingPoissonian stochastic perturbations. In GPK processes the
stochastic perturbation acts as a switching amongst a set of stochastic
velocity vectors controlled by a Markov-chain dynamics. GPK processes possess
trajectory regularity (almost everywhere) and asymptotic Kac limit, namely the
convergence towards Brownian motion (and to stochastic dynamics driven by
Wiener perturbations), which characterizes also the long-term/long-distance
properties of these processes. In this article we introduce the structural
properties of GPK processes, leaving all the physical implications to part II
and part III
Nonparametric inference of doubly stochastic Poisson process data via the kernel method
Doubly stochastic Poisson processes, also known as the Cox processes,
frequently occur in various scientific fields. In this article, motivated
primarily by analyzing Cox process data in biophysics, we propose a
nonparametric kernel-based inference method. We conduct a detailed study,
including an asymptotic analysis, of the proposed method, and provide
guidelines for its practical use, introducing a fast and stable regression
method for bandwidth selection. We apply our method to real photon arrival data
from recent single-molecule biophysical experiments, investigating proteins'
conformational dynamics. Our result shows that conformational fluctuation is
widely present in protein systems, and that the fluctuation covers a broad
range of time scales, highlighting the dynamic and complex nature of proteins'
structure.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS352 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Numerical approximation of doubly reflected BSDEs with jumps and RCLL obstacles
We study a discrete time approximation scheme for the solution of a doubly
reflected Backward Stochastic Differential Equation (DBBSDE in short) with
jumps, driven by a Brownian motion and an independent compensated Poisson
process. Moreover, we suppose that the obstacles are right continuous and left
limited (RCLL) processes with predictable and totally inaccessible jumps and
satisfy Mokobodski's condition. Our main contribution consists in the
construction of an implementable numerical sheme, based on two random binomial
trees and the penalization method, which is shown to converge to the solution
of the DBBSDE. Finally, we illustrate the theoretical results with some
numerical examples in the case of general jumps
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