Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with examples
Search options not deleted
user 61536
For questions requesting examples of a certain structure or phenomenon
4
votes
Accepted
Semi-metrizable spaces with countable chain condition
There exists a counterexample, that is, a non-separable semi-metrizable space with ccc, which can be constructed as follows. Consider the countable power $\mathbb Z^\omega$ of the group of integers. F …
- 41.8k
5
votes
Accepted
How could I see quickly that this space is not normal?
Theorem. A dense subspace $X$ of the Tychonoff cube $[0,1]^\kappa$ is not normal if $X$ contains an uncountable closed discrete subspace $D$ such that each $x\in D$ has finite support $\mathrm{supp}(x …
- 41.8k
5
votes
Accepted
Let $X$ be a Lindelof, perfectly normal, $\sigma$-space. Must $X$ be separable?
If a $\sigma$-space $X$ is Lindelof, then it is paracompact and by Theorem 4.4 of Gruenhage's survey "Generalized Metric Spaces" in the "Hanbook of Set-Theoretic Topology", $X$ has countable network a …
- 41.8k
4
votes
Proofs without words
The picture below proves (without words) that it is possible to draw the classical Desargues configuration $D_{10}$ using points in the set $\{-3,-2,-1,0,1,2,3\}^2$. This picture was produced by Alex …