Skip to main content

All Questions

2 votes
2 answers
654 views

Does $\overline{A+B}=\overline A+\overline B$ hold if $\overline A$ and $\overline B$ are compact?

Let us assume that we are working with subsets $A$, $B$ of some topological space $X$ such that also $A+B$ makes sense. (For example, we can have $X=\mathbb R^n$, $X$ could be a topological group, a ...
Martin Sleziak's user avatar
22 votes
4 answers
10k views

Sum of closed and compact set in a TVS

I am trying to prove: $A$ compact, $B$ closed $\Rightarrow A+B = \{a+b | a\in A, b\in B\}$ closed (exercise in Rudin's Functional Analysis), where $A$ and $B$ are subsets of a topological vector space ...
ScroogeMcDuck's user avatar
12 votes
1 answer
4k views

If $A$ and $B$ are compact, then so is $A+B$.

This is an exercise in Chapter 1 from Rudin's Functional Analysis. Prove the following: Let $X$ be a topological vector space. If $A$ and $B$ are compact subsets of $X$, so is $A+B$. My guess: ...
Hui Yu's user avatar
  • 15.1k