5:56 AM
Wouldn't a better name for tag used for questions about Monster group?
I have noticed the tag when looking for suitable tags for the recently bumped question: The Monster Group uses in mathematical physics. The tag-excerpt says at the moment:
> Questions about the Monster group, the largest of the sporadic simple groups. This group acts as symmetries on a vertex operator algebra whose graded dimension is the elliptic $j$-function.

1 hour later…
6:59 AM
The tag is (at least to me) one of the tags where it is unclear when to use it. But I guess it would be suitable for: Reference request: Oldest calculus, real analysis books with exercises?
> Questions in which books play a key-role, such as questions on antique books, e-books, difference between various editions of a book, etc. For questions asking for recommendations of books on some subject the tag textbook-recommendation is often more suitable.
2

Per the title, what are some of the oldest calculus, real analysis books out there with exercises? Maybe there are some hidden gems from before the 20th century out there. Edit. Unsolved exercises are fine.

1 hour later…
8:13 AM
@MartinSleziak The tag no longer exists. Since I do not see it in the revision history I suppose it was removed by the automated process which removed the tags with single occurrence if they are at least 6 months old.
No other questions which had this tag in the past: data.stackexchange.com/mathoverflow/query/910476/… Not even among the deleted questions: data.stackexchange.com/mathoverflow/query/883845/…
Feb 17 at 8:08, by Martin Sleziak
It seems that falls into the same category as some other problematic tags - , , , , , . I have mentioned some of them before: https://chat.stackexchange.com/transcript/10243/2017/11/30
From the tags mentioned in the above message, only , and exist at the moment.

5 hours later…
12:49 PM
@MartinSleziak That question is now deleted - only the copy on Mathematics remained: The ways of covering a 4×44×44\times 4 square by 1×21×21\times 2 colored dominoes.

1 hour later…
1:56 PM
@MartinSleziak I see that Arun Debray already suggested synonym qft $\to$ quantum-field-theory. mathoverflow.net/tags/synonyms Let's hope there will be enough user who notice the synonym and vote for it.

8 hours later…
9:57 PM
The tags and perhaps should probably be added to the question: Pontriagin reflexivity of the character group. Still I am not sure what to choose as the top-level tag.
6

For an Abelian topological group $G$ by $G^{\wedge}$ we denote the Pontryagin dual of $G$, i.e. the group of continuous homomorphisms $G\to\mathbb T:=\{z\in\mathbb C:|z|=1\}$. The group $G^{\wedge}$ is endowed with the topology of uniform convergence on compact subsets of $G$. A topological group...