分数布朗运动驱动的一类随机微分方程的弱解问题
Weak Solutions for Stochastic Differential Equations Driven by Fractional Brownian Motion
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摘要: 本文,我们研究如下分数布朗运动驱动的一类随机微分方程的弱解问题X_t=x+B_t^H+\int_0^tb(s,X_s)\md s,其中B^H=\B_t^H,\,0\leq t\leq T\是Hurst指数为H\in(0,1/2)\cup(1/2,1)的分数布朗运动,b是Borel可测函数且满足线性增长条件|b(t,x)|\leq(1+|x|)f(t),其中x\in\mathbbR且0<t<T, f是非负Borel函数.值得注意的是f是无界的,比如函数f(t)=(T-t)^-\beta或f(t)=t^-\alpha,对于一些0<\alpha,\beta<1无界.这个问题对于分数布朗运动驱动的随机微分方程来说是有意义的.Abstract: Let B^H=\B_t^H,\,0\leq t\leq T\ be a fractional Brownian motion with Hurst index H\in(0,1/2)\cup(1/2,1) and let b be a Borel measurable function such that |b(t,x)|\leq(1+|x|)f(t) for x\in\mathbbR and 0<t<T, where f is a non-negative Borel function. In this note, we consider the existence of a weak solution for the stochastic differential equation of the form X_t=x+B_t^H+\int_0^tb(s,X_s)\md s. It is important to note that f can be unbounded such as f(t)=(T-t)^-\beta and f(t)=t^-\alpha for some 0<\alpha,\beta<1. This question is not trivial for stochastic differential equations driven by fractional Brownian motion.