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progressive stochastic process有什么好的性质? [推广有奖]

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请问一下"progressive stochastic process"怎么理解呢? 它与一般的随机过程(比如可预测的随机过程)相比有哪些不同的性质呢?

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关键词:progressive Stochastic Progress Stochast Process 性质 Process Stochastic progressive

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yyeric 发表于 2009-3-11 01:39:00 |只看作者 |坛友微信交流群

planemath上关于progressive stochastic process的解释:

A stochastic process $ (X_t)_{t\in\mathbb{Z}_+}$ is said to be adapted to a filtration $ (\mathcal{F}_t)$ on the measurable space $ (\Omega,\mathcal{F})$ if $ X_t$ is an $ \mathcal{F}_t$-measurable random variable for each $ t=0,1,\ldots$. However, for continuous-time processes, where the time $ t$ ranges over an arbitrary index set $ \mathbb{T}\subseteq\mathbb{R}$, the property of being adapted is too weak to be helpful in many situations. Instead, considering the process as a map

$\displaystyle X\colon\mathbb{T}\times\Omega\rightarrow\mathbb{R},\ (t,\omega)\mapsto X_t(\omega)$   


it is useful to consider the measurability of $ X$.

The process $ X$ is progressive or progressively measurable if, for every $ s\in\mathbb{T}$, the stopped process $ X^s_t\equiv X_{\min(s,t)}$ is $ \mathcal{B}(\mathbb{T})\otimes\mathcal{F}_s$-measurable. In particular, every progressively measurable process will be adapted and jointly measurable. In discrete time, when $ \mathbb{T}$ is countable, the converse holds and every adapted process is progressive.

A set $ S\subseteq\mathbb{T}\times\Omega$ is said to be progressive if its characteristic function $ 1_S$ is progressive. Equivalently,

$\displaystyle S\cap\left( (-\infty,s]\times\Omega\right)\in\mathcal{B}(\mathbb{T})\otimes\mathcal{F}_s$   


for every $ s\in\mathbb{T}$. The progressively measurable sets form a $ \sigma$-algebra, and a stochastic process is progressive if and only if it is measurable with respect to this $ \sigma$-algebra.

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