谈谈自然科学和社会科学的“大交叉”(二)

On the "Grand-Crossover" of Natural and Social Sciences (Ⅱ)

突变是一种临界现象。它发生在某一个参数缓慢变化达到特定值的时刻。突变前后系统的状态有质的差异，会出现或消失某些对称和有序。这里考虑出现新的有序状态的情形。刻画新的有序或对称状态的一个或一组参数称为序参数。序参数从旧状态中的零值．连续变化或跃变到新状态中的非零值。这种变化情形最为有趣。任意小的非零值代表新的对称和有序。这个零与非零的差异、有和无的差异，决定临界现象的突变性。“不是西风压倒东风，就是东风压倒西风”。新相一旦出现，就决定了系统的性质。

Some concepts of non--equilibrium statistical physics and nonlinear science may find their applications to social science. In fact. many social phenomena are manifestations of general features of complex systems. In this article, we will briefly introduce how to describe characteristics of complex systems, and outline how to apply them to humanity studies in China.