2:29 AM
There are various questions where $(x+A)\cap A$ appears. For example, Proof that $(a+A)\cap A=\varnothing$ if $A$ is countable or questions about Steinhaus theorem.
Would apply here? I know that it is typically for $A+B$, but $a+B$ is a special case.

5 hours later…
7:08 AM
There are several post on main about various selection principles in general topology. Would be suitable for them? Or some of them?
In mathematics, the theory of selection principles deals with the possibility of obtaining mathematically significant objects by selecting elements from sequences of sets. The studied properties mainly include covering properties, measure- and category-theoretic properties, and local properties in topological spaces, especially functions spaces. Often, the characterization of a mathematical property using a selection principle is a nontrivial task leading to new insights on the characterized property. == Background and definitions == In 1924, Karl Menger introduced the following basis property...

1 hour later…
8:11 AM
in Math Mods' Office, 7 hours ago, by quid
One more (final for now) thought: if anything the syn should go in the other direction. It's hardly ever a good idea to map tags from general to special, as it can result in mistags.

1 hour later…
9:13 AM
The tag was created here by learnmore. I do not think we should create new meta-tags without discussion on meta, so I have removed it.

1 hour later…
10:14 AM
Should questions about various ordinal spaces (I am not sure whether that's correct name) such as $[0,\omega_1)$ or $[0,\omega_1]$ with order topology be tagged also with ?
7

In the definition of a manifold $M$, we have the following conditions: For some fixed $n$, $M$ is locally homeomorphic to $\mathbb{R}^d$. $M$ is connected, second countable, and Hausdorff. Now, with this definition, it is a well-known theorem that $M$ can be embedded in $\mathbb{R}^{2n+1}$. I...

4

Let $\omega_1$ be the first uncountable ordinal. Let $L$ denote $\omega_1 \times [0,1)$ with the order topology and smallest element removed. How can we show this space is not second countable?

4 hours later…
1:58 PM
0

After much delay, I have today removed the topology⇒general-topology tag synonym. This means that as of now topology is a perfectly acceptable stand-alone tag. Topology, of course, is also a wide ranging field of study, and I feel that the topology tag by itself often won't adequately narrow down...

1 hour later…
3:11 PM
So the tag - which has been mentioned also here a few times - has been removed.
8

Update. The subspaces tag has been removed thanks to a friendly neighbourhood Community Manager. There's another possibility that hasn't been mentioned in the OP, and the one I would prefer: kill it! I don't see subspaces as a tag that will ever be consistently used, and not something that ...

### Removal of (subspaces) tag

yesterday, 1 day total – 40 messages, 4 users, 0 stars

Bookmarked 56 mins ago by Martin Sleziak