Tell me more ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.
up vote 0 down vote favorite

What does $K \Subset U$ mean? I think that $K$ is a compact set with, $K \subset \subset U$ (precompact), where $U$ is an open set. Am I right? Thank you.

share|improve this question
8  
The context would probably help. Did you see this in a book? A paper? Which one? – Zev Chonoles♦ Jul 17 '12 at 20:45
Theorem 1.1 [here][1] [1]: msri.org/attachments/workshops/563/… – user29999 Jul 17 '12 at 20:49
3  
Yes, usually it means that $K$ has compact closure in $U$, see also: mathoverflow.net/questions/43950/meaning-of-subset-notation and looking at the link you gave I'm certain that's what is meant. – t.b. Jul 17 '12 at 20:51
2  
I've always been under the impression that in analysis or PDE contexts, the difference between $\Subset$ and $\subset\subset$ is the difference of using $\langle,\rangle$ versus $<,>$, namely one of typography. (Or, perhaps a better example is using $<<$ versus $\ll$.) – Willie Wong♦ Oct 9 '12 at 10:28

1 Answer

up vote 1 down vote

I have seen $K\subset\subset G$ if $K$ is compact, $G$ is open and $K\subseteq G$. I have seen it used in the context of locally compact topological spaces.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.