Tagging - 2017-12-03

2:48 AM

To be honest, I thought that the name Riesz representation theorem is commonly used for Hilbert space and for C(X). This is also how it is used on Wikipedia: Riesz representation theorem and Riesz–Markov–Kakutani representation theorem.

Google search for riesz representation theorem for lp spaces suggests that this is used too. But it is question for somebody more knowledgeable of this area how common it actually is.

The same search in Google Books also returns some books which use this phrase.

@JohnMa I have asked this also in Modern Abstract Analysis chatroom (the room was called Functional Analysis before - the scope of the room was expanded recently). Perhaps somebody there might be able to answer this.

Feeds

6:21 AM

1

Q: Limit for number of questions where tag can be added by tag-creator soon after the creation of tag

Occasionally we have seen a situation like this: A user creates a new tag. The tag is then discussed on meta and the consensus is that the tag is not suitable and should be completely removed. However, it takes some time until somebody notices the tag and brings up the issue on meta. And then the...

Martin Sleziak

This was posted partly as a reaction to the situation I have seen quite recently - a tag which was ony a few hours old and it already had over 50 questions. (Even if the tag turns out to be useful and remains on the site, this seems to me a bit excessive.) — Martin Sleziak 7 mins ago

Martin Sleziak

7:09 AM

And I will add that not too long ago there was a discussion involving a tag that had over 100 questions after a few days. (But at least this is a bit less extreme than the example mentioned in the previous comment.) Since I want to keep this discussion general, I have not linked to these specific instances. (However, the users who follow situations with new tags can probably easily guess which tags I am talking about.) — Martin Sleziak 11 secs ago

It is probably clear for anybody who visits this room. (And the specific instances are not that relevant for general discussion - other than they provide evidence that this actually happens.) In any case, I meant the tags riesz-representation-theorem and birthday.

16 hours ago, by Martin Sleziak

Wow! The tag riesz-representation-theorem was created today and it already has 67 question.

For my money, when a single user introduces a tag and then throws over a 100 questions into it within the span of three days... that's either badge gaming for Taxonomist, or just a naive (but nonetheless blatant) ignorance of protocol as to how new tag should be introduced: via some discussion on meta. Especially when the said user has over 80k points. — Asaf Karagila Nov 20 at 20:35

I am aware of the fact that recently I have posted quite a lot questions about tags. (And this might be contra-productive, since if we have too many new questions on meta, only a few get attention.) But with the exception of the question about (tag-removed) I was mainly reacting to a tag which was created by somebody else.

in Modern Abstract Analysis, 1 min ago, by Michael Greinecker

@MartinSleziak I have seen this use of Riesz representation theorem before- and I too was puzzled.

Thanks for the response @MichaelGreinecker. What do you think about this new tag?

Will it be useful? What should be the scope (should it include Lp-spaces?)

This was quid's reaction to the riesz-representation-theorem tag.

16 hours ago, by quid

@MartinSleziak that's a bit strange, but maybe the tag itself is not too bad.

I am bit reluctant to create yet another tag-related post on meta (be it as a separate question or as an answer in tag management thread) - since we had a lot of tag-related posts on meta recently. (To great extent, I am the person to blame for that.)

I can imagine that this tag might actually be useful.

Michael Greinecker

I'm not sure about the usefulness, but thematically the broad interpretation seems to be okay. But for the L_p-case, I would point it out in a question as in: math.stackexchange.com/questions/2002008/…

Martin Sleziak

> I'm just looking for references about Riesz representation theorem for $L^p$ spaces and consequences.

You pointed out that question as an example that users on this site commonly use this meaning of Riesz representation theorem?

Michael Greinecker

The problem is that the result is too advanced for there being something like an expert on doing "Riesz representation theorem problems" on problems set. Even in the dual of spaces of continuus functions versions, many differences exist. How general compact spaces are used? Maybe local compactness and compactly supported functions? Baire vs. Borel measures?

Martin Sleziak

BTW I have added dual-spaces tag (and made some other tag-adjustments) to the question in you r link.

Michael Greinecker

@MartinSleziak Maybe not commonly, but it is used. It falls within the general theme of representing dual spaces, so it is not totally strange to have it under the same umbrella.But I'm not sure the tag serves any use.

Martin Sleziak

7:24 AM

The fact that there are various minor variations of this theorem (or, more specifically, of the C(X)-version) seems to me an argument in favor of the tag.

Re: But I'm not sure the tag serves any use. This is exactly why it would be nicer to see some discussion about a new tag on meta before it grows to something like 50 or 100 questions.

Of course, if we look on how many new tags are created, if every new tag was discussed on meta, almost no other questions would be visible there among tag discussions.

Michael Greinecker

@MartinSleziak I'm not sure how people use tagging in general. I sometimes use tags to focus on seeing only material relevant to me when I'm in a hurry and there I use less specific tags. At the same time, this tag would probably not create too much noise.

Martin Sleziak

I'll have to go offline for a bit. Thanks for joining the discussion about the tag.

Michael Greinecker

Sure, see you around! And thanks for putting as much effort into greasing the tagging system!

Martin Sleziak

9:27 AM

BTW the tag (dual-spaces) is relatively new, too. It was created in April by Marios Gretsas‌. (It seems that he used to have username capo.)

John Ma

10:15 AM

This tag is actually way better than the old [duality theorems](https://math.stackexchange.com/questions/tagged/duality-theorems) which is a
completely mess. I will purpose to get rid of it, but may be later since there is so much tagging going on on meta recently.

Martin Sleziak

2:50 PM

There was a discussion about duality-theorems tag on meta. With no answers.

18

Q: What is [duality-theorem] for?

There are several concepts of duality in mathematics. There is the duality in the sense of category theory, and there is duality in optimization, and there is duality in order theory (which is closer to the one in category theory, I believe). I don't know too much about these topics, so I can't ...

discussion tagging

I think the tag is unsalvageable. Keeping Poincaré duality, linear program duality, and dual Banach spaces under the same tag defies common sense. (Not to mention the categorical stuff, which defies common sense on its own.) I'd say delete the tag. It shall be neither mine nor yours. — 40 votes Jul 18 '13 at 13:44

@JohnMa Maybe when you decide to post about then duality-theorems tags on meta, you can post it as the answer to the above question. Since the discussion which is there so far already suggests some support of the removal of that tag. (But the discussion was so far only in the comments, nobody posted an answer.)

Although there is an advantage in posting a new question, too. (Since the old question has no chance to get into the community-bulletin, which means that it receives a bit less attention than a fresh question.)

Still, posting the suggestion as an answer is at least a possibility which is worth considering.

John Ma

10:30 PM

@MartinSleziak Probably I will give an answer there. I do not expect a lengthy discussion since the situation is clearly bad. Thanks for the link!

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$Mathematics$ Tagging