We fix $d \geq 2$ and denote $\mathcal S$ the semi-group of $d \times d$ matrices with non negative entries. We consider a sequence $(A_n, B_n)_{n \geq 1} $ of i. i. d. random variables with values in $\mathcal S\times \mathbb R_+^d$ and study the asymptotic behavior of the Markov chain $(X_n)_{n \geq 0}$ on $ \mathbb R_+^d$ defined by:
\[
\forall n \geq 0, \qquad X_{n+1}=A_{n+1}X_n+B_{n+1},
\] where $X_0$ is a fixed random variable. We assume that the Lyapunov exponent of the matrices $A_n$ equals $0$ and prove, under quite general hypotheses, that there exists a unique (infinite) Radon measure $λ$ on $(\mathbb R^+)^d$ which is invariant for the chain $(X_n)_{n \geq 0}$. The existence of $λ$ relies on a recent work by T.D.C. Pham about fluctuations of the norm of product of random matrices . Its unicity is a consequence of a general property, called "local contractivity", highlighted about 20 years ago by M. Babillot, Ph. Bougerol et L. Elie in the case of the one dimensional affine recursion .
Recurrence of multidimensional affine recursions in the critical case
Laboratoire d’Analyse et de Mathématiques Appliquées UMR 8050, Université Gustave Eiffel, Université Paris-Est Créteil, CNRS(应用分析与数学实验室 UMR 8050,巴黎东克雷泰伊大学,古斯塔夫·埃菲尔大学,法国国家科学研究中心);Institut Denis Poisson UMR 7013, Université de Tours, Université d’Orléans, CNRS(丹尼斯·普瓦松研究所 UMR 7013,图尔大学,奥尔良大学,法国国家科学研究中心)
On the tails of the invariant measure for multidimensional affine stochastic recursions in the critical case
Univ Bretagne Sud, CNRS UMR 6205, LMBA(南布列塔尼大学);Universität Hildesheim, Institut für Mathematik und Angewandte Informatik(希尔德斯海姆大学);State Key Laboratory of Mathematical Sciences, Academy of Mathematics and Systems Science, Chinese Academy of Sciences(中国科学院数学与系统科学研究院)
Affine processes on $\mathbb{R}_+^n \times \mathbb{R}^n$ and multiparameter time changes
给出了仿射过程的一种时变状态空间$\mathbb{R}_+^m\times \mathbb{R}^n$构造方法。这些过程在Duffie,Filipović and Schachermayer,2003中得到了系统的研究,因为它们包含了有趣的过程类,如Lévy过程、带移民的连续分支过程和Ornstein-Uhlenbeck类型。该构造基于多维Lévy过程的(基本)连续泛函,这意味着Lévy过程的极限定理(几乎必然和分布)可以继承到仿射过程。该结构可以解释为一个多参数的时变方案或作为一个(随机)常微分方程驱动的不连续函数。特别是,我们提出了基于欧拉法求解相关的不连续常微分方程,这是收敛的仿射过程的逼近方案。