Atom —— Measure Theory

Atom 是测度论中的一个概念。

In mathematics, more precisely in measure theory, an atom is a measurable set which has positive measure and contains no set of smaller positive measure. A measure which has no atoms is called non-atomic or atomless.

简单来说，如果可测集是 atom，那么对于，，就有。如果一个测度不存在 atom，就说这个测度是 non-atomic或者atomless。

这个概念在概率论里面有一个很直观的例子，就是当不可数时，如果存在，这样的概率空间，显然不太好，所以有时候会给概率空间加上 atomless 的条件！

参考：

• https://en.wikipedia.org/wiki/Atom_(measure_theory)
• https://en.wikipedia.org/wiki/Probability_space