转化方式。。

转换

这是个很重要的概念。measure是测度，可以是个高深的概念（专门有研究此的“测度论”），change of measure就是改变测度，比如：从real world测度换到risk neutral测度。与此相关的东东是：Radon-Nikodym derivative，Girsanov's theorem，理解了这两个能让你多了解change of measure。

抱歉，我说不太清楚，因为我的理论知识不够扎实。可以GOOGLE一下上面的名词，不过，需要数学基础好才能看得懂那些解释。不过，论坛里有这方面的高手，你也可等看他们的回复。

测度改变~~~
找本实变的书看看。

Since in the real physical measure, every asset has different expected return. So it is not possible to pricing them in physical measure. But if the no arbitrage condition holds, you can change the probability space into a risk neutral measure, so that every asset grows in risk free rate under this measure so that you can discount the expected payoff with risk free rate. In the real world, you can't do that.

This is a mathematical method, very basic while important in derivative pricing. It has a close link with martingale, PDE and SDE. A more general name is change of numeraire. LZ should be very familiar to this method other wise, you can not say you study derivatives.

hope help~