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Results tagged with gn.general-topology
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user 2757
Continuum theory, point-set topology, spaces with algebraic structure, foundations, dimension theory, local and global properties.
4
votes
Accepted
Can I detect the point of impact without looking at it?
Andrew's comments showed me that in my first answer I was misunderstanding several aspects of his question. Since I am still not entirely sure that I am capturing the spirit of the problem, let be be …
- 23.8k
3
votes
Can I detect the point of impact without looking at it?
The answer is that everything can be recovered, if $f$ is chosen suitably!
There are $2^{\aleph_0}$ possibilities for $c$, so we can fix an injection $c \mapsto u_c$ from the set of possible $c$ into …
- 23.8k
28
votes
What are interesting families of subsets of a given set?
Even families of subsets closed under unions are interesting. The following conjecture of Peter Frankl has been open for 31 years:
Let $A$ be a finite set, and let $\mathcal{F}$ be a collection o …
- 23.8k