Showing papers by "Barbara Martinucci published in 2015"

Compound Poisson process with a Poisson subordinator

Abstract: A compound Poisson process whose randomized time is an independent Poisson process is called a compound Poisson process with Poisson subordinator We provide its probability distribution, which is expressed in terms of the Bell polynomials, and investigate in detail both the special cases in which the compound Poisson process has exponential jumps and normal jumps Then for the iterated Poisson process we discuss some properties and provide convergence results to a Poisson process The first-crossing time problem for the iterated Poisson process is finally tackled in the cases of (i) a decreasing and constant boundary, where we provide some closed-form results, and (ii) a linearly increasing boundary, where we propose an iterative procedure to compute the first-crossing time density and survival functions

Compound Poisson process with a Poisson subordinator

Abstract: A compound Poisson process whose randomized time is an independent Poisson process is called compound Poisson process with Poisson subordinator. We provide its probability distribution, which is expressed in terms of the Bell polynomials, and investigate in detail both the special cases in which the compound Poisson process has exponential jumps and normal jumps. Then for the iterated Poisson process we discuss some properties and provide convergence results to a Poisson process. The first-crossing-time problem for the iterated Poisson process is finally tackled in the cases of (i) a decreasing and constant boundary, where we provide some closed-form results, and (ii) a linearly increasing boundary, where we propose an iterative procedure to compute the first-crossing-time density and survival functions.

A fractional counting process and its connection with the Poisson process

Abstract: We consider a fractional counting process with jumps of amplitude $1,2,\ldots,k$, with $k\in \mathbb{N}$, whose probabilities satisfy a suitable system of fractional difference-differential equations. We obtain the moment generating function and the probability law of the resulting process in terms of generalized Mittag-Leffler functions. We also discuss two equivalent representations both in terms of a compound fractional Poisson process and of a subordinator governed by a suitable fractional Cauchy problem. The first occurrence time of a jump of fixed amplitude is proved to have the same distribution as the waiting time of the first event of a classical fractional Poisson process, this extending a well-known property of the Poisson process. When $k=2$ we also express the distribution of the first passage time of the fractional counting process in an integral form. Finally, we show that the ratios given by the powers of the fractional Poisson process and of the counting process over their means tend to 1 in probability.

A review on symmetry properties of birth-death processes

Abstract: In this paper we review some results on time-homogeneous birth-death processes. Specifically, for truncated birth-death processes with two absorbing or two reflecting endpoints, we recall the necessary and sufficient conditions on the transition rates such that the transition probabilities satisfy a spatial symmetry relation. The latter leads to simple expressions for first-passage-time densities and avoiding transition probabilities. This approach is thus thoroughly extended to the case of bilateral birth-death processes, even in the presence of catastrophes, and to the case of a two-dimensional birth-death process with constant rates.

Fractional growth process with two kinds of jumps

Abstract: We consider a suitable fractional jump process describing growth phenomena, that may be viewed as a counting process characterized by 2 kinds of jumps with size 1 and 2. We obtain the probability generating function and the probability law of the process, expressed in terms of the generalized Mittag-Leffler function. The mean, variance, and squared coefficient of variation are also provided.

On a fractional jump process with two kinds of jumps and its connection with the Poisson process

Abstract: We consider a fractional jump process with jumps of size 1 and 2, whose probabilities satisfy a fractional extension of the difference-differential equations $$ \dfrac{\mathrm{d}p_{k}(t) }{\mathrm{d}t } =\lambda_{2}p_{k-2}(t)+\lambda_{1}p_{k-1}(t)-(\lambda_{1}+\lambda_{2})p_{k}(t), \quad k\geq 0, \;\; t>0. $$ We obtain the probability law of the resulting process in terms of generalized Mittag-Leffler functions. We also discuss two equivalent representations both in terms of a subordinator governed by a suitable fractional Cauchy problem, and of a compound fractional Poisson process. The first occurrence time of a jump of fixed amplitude is proved to have the same distribution as the waiting time of the first event of a classical fractional Poisson process, this extending a well-known result for the Poisson process. We also express the distribution of the first passage time of the fractional jump process in an integral form that involves the joint distribution of the classical fractional Poisson process. Finally, we show that the ratios given by the powers of the jump process over their means converge in probability to 1.