Is $S_2$ a sigma algebra?

Asked May 14 '19 at 07:22

Active May 14 '19 at 07:22

Viewed 44 times

In this discussion $\sigma$ -algebra is the smallest collection of sets which...

Dave asks whenever $S_2$ is an algebra, but later he observes that “It would be if we only took finite unions and intersections”, which I don’t really understand.

Could you provide me an example why it is not a sigma algebra?

asked May 14 '19 at 07:22

Laura

I don't see why $S_2$ must be closed under complement. But, I don't understand the original accepted answer either. – Violapterin May 14 '19 at 07:58
Answered, for example, here (keyword: Borel hierarchy). – mihaild May 14 '19 at 08:17

Is $S_2$ a sigma algebra?

0 Answers0