As an aside note, from some discussion in chat you had recently (including the one with me), I have to say that I admire your patience quid.

@quid I have promised you to post a question about deletions on meta. I would be glad if you had a look on a draft of the question before I post it: math.meta.stackexchange.com/questions/20430/…

I have formulated the question only about incorrect answers. (There already is highly upvoted Willie Wong's post about deleting questions: Are we too trigger-happy about deleting (relatively) new posts?)

You mentioned your concern about deletions on meta - I decided not to include this here, since it seems to me that these are two different issue. (But I agree with you that deletions of meta post - especially if the reason for deletion is disagreement - is not a good trend and it probably should be brought up on meta, too.)

I did not want to make the post too inflammatory or accusatory. (Already the topic is quite controversial and likely to bring some heated exchanges.)

So I have decided not to link to crude - although it is related to the post. (That could be perceived as accusing particular group of users.)

Although some points raised in arjafi's answer (superdownvotes, way to get 1 reputation point back) are perhaps related, but they are not to important and they would also link this very directly to a recent controversy.

In any case, I'd be grateful if you have a look and let me know what you think and whether there are some improvements I can make to the question.

If you think that there is a reason to discuss this in a private room rather then here, feel free to move the messages to some private room. (But since the plan is to post on meta anyway, there is probably no need to do that.)

And, of course, if you think that now there is too much going on on meta and it would be better to postpone this discussion and ask such question later, I am find with that, too.

Hi @MichaelGreinecker - about our previous tag discussion: It seems that tag for semicontinuous functions has some support, but I would probably wait a week or two to see whether somebody else joins the discussion. (Or at least to see whether more votes are added to see what the consensus there is.)

But I suppose it is eventually going created. (And it will be the tag excluding multifunctions.)

@MartinSleziak Sure, it seems to be not the most controversial meta issue. There is no hurry.

I have added a few brief remarks there about relation of semicontinuity of multifunctions to Vietoris topology: chat.stackexchange.com/transcript/3740/2017/11/23

This is also a way how we can related semicontinuity of multifunctions and continuity fo functions.

Similarly as you explained this relation is your answer:

> But if we treat a function as a special case of a multi-valued functions, all semi-continuity notions for multi-valued-functions boil down to ordinary continuity (but not upper-or semi-continuity).

I see that you peeked into functional analysis chat room.

It would be nice to get this room going.

Thank you. Btw: I have noted that the tag "multi-valued functions" excludes empty-valued functions. I think it would be desirable to make this more general.

So far it seems that most of conversations in functional analysis chat room is BAYMAX asking questions and me answering (if I know that answer, which often is not the case). It would be nice to see some other users interested in this area in that room.

@MichaelGreinecker Probably that tag-info deserves rewrite.

I think it is very hard to get a math-topic-room going that is not just the tutoring complement to the main site.

But at least minor change along these lines would be a quick fix: "Some source also allow empty values."

And if somebody experienced in the topic wants to add more substantial improvements, they can edit the tag-info when they have more time.

@MichaelGreinecker Well, Homotopy Theory room on MO is a great example of room around one topic which works.

Since functional analysis room had more activity recently, it was noticed by a few users. But most of them only had a look what is going on in the room.

Here on Math.SE, Set theory room was very active for some period. But again, it was mainly because single user who kept that room active.

I'll check out what makes the homotopy-room work. Having actual discussions on FAwould be great. I'll also think about new wording for multivalued-functions.

Well, probably the thing why it works is that there are many users who are interested in the topic and who discuss there.

For example, I would be of no use in functional analysis chat room for any discussion beyond relatively basic topics.

And, in fact, when I tried to answer some questions there, I saw that even on basics I am quite often a bit on shaky grounds.

@MichaelGreinecker This was advice I got from a user active in Homotopy Theory chat room:

The whole conversation can be seen here: chat.stackexchange.com/transcript/9755/2013/11/14 and chat.stackexchange.com/transcript/9755/2013/11/15

Perhaps something like this might be a reasonable question on meta: "How to make a chat room successful?"

@MartinSleziak I'm wondering if one couldn't braden the topic a bit. While I learned some topics in FA in more depth than what people usually learn in a first course (ordered vector spaces and vector measures), I'm blissfuly ignorant of other more well known topics (spectral theory, operator algebras). Maybe one can broaden the topic a bit.

I can think of users on MSE I associate with set theory, general topology, or probability theory, but there isn't really anyone I think of as a primary functional analyst. Maybe the user with the frequently changing names.

I have also collected my thoughts on things which might improve chances of chat room to get active in this answer.

I think that if the room description is "functional analysis" i ti sclear that it includes spectral theory and operator algebra.s

I have added you among room owners. (Which is merely a symbolic gesture - a moderator automatically can do everything what a RO can do.)

I know, I was rather thinking about somewhat more abstract analysis. It might be easier to get a critical mass of interested competent users then.

Anyway, if you have some reasonable additions to the room topic, feel free to add it.

That is a clever move: Now I feel obliged to check in more often. ;-)

Don't feel obliged. In fact, you can by a few clicks remove yourself from room ownership if you wish to.

@MichaelGreinecker Do you mean something like adding harmonic analysis?

I have to admit that I have only very basic idea what this area is about. (Although it certainly looks interesting.)

Yes. Something like a room for the mixture of topics known as "Real Analysis" in graduate textbooks

Well, there also is Calculus and Analysis chat room.

It has rather general description: "For questions about calculus, real analysis, functional analysis,Complex analysis ... "

In fact the reason I asked for functional analysis room to be unfrozen was that I was having conversations with one or two users about functional analysis in the Calculus and Analysis chatroom. (So it seemed reasonable to have a room for this specific topic.)

I think the important part would be to exclude the calculus part.

So you think about separate room for real and harmonic analysis? (Or perhaps with addition of functional analysis.)

As in Calculus and Analysis would be for more elementary topics and this one would be somewhat similar but more advanced?

I'm not sure about an appropriate name, but something like modern abstract analysis.

Yes, more advanced topics. The area I would feel most comfortable myself is probably measure theory.

BTW it seems that there was previously measure theory room.

@MichaelGreinecker Ok, so the question is whether still keep functional analysis as a separate chatroom and this would be a new room. Or whether this would be expansion of the current functional analysis room.

Admittedly, we probably already have quite a lot of rooms.

The room you suggest - modern abstract analysis - would include stuff such as real analysis, functional analysis, harmonic analysis, measure theory.

The measure theory room was probably great when t.b. was a regular, but he stopped posting in '15.

Yes, that is the knd of breath I would be thinking of.

Yes, and t.b. would certainly be able to contribute to discussions about functional analysis.

@MichaelGreinecker So my suggestion would be change room topic like this. And room name you suggested (Modern abstract analysis) seems quite ok to me.

And let us consider this as an experiment.

It is possible that only topics from functional analysis will be discussed there.

I'm in. I would commit to hanging around there a bit.

Or if at some point the room users of that room have feeling that it is better to have a separate room for functional analysis again, they can be divided.

Will you edit room topic? Or should we do this later as not to interrupt BAYMAX who is currently asking about some problem related to compact operators there?

It would be great if some topic becam so big that it would need its own room.

I can think about a description, post it here and then I can copy&paste it over there later.

How about: "Modern Abstract Analysis: For functional analysis, measure theory, and related areas."

Let's go with that. We can always edit it further of we have some reasonable ideas.

We could then change the room description in the List of chatrooms to: "Modern Abstract Analysis (Originally started as functional analysis chatroom, later expanded to include topics from measure theory and other related areas.)"

Perhaps I could mention in the post on meta also advanced real analysis? Harmonic analysis?

Or just leave this at the shorter description I've given above?

The longer description seems to be fine and not excessive.

Re: I'm blissfuly ignorant of other more well known topics (spectral theory, operator algebras).

These are among the topics I would be very glad to learn more about. From what I heard, Banach algebras seem quite useful.

I have a rather strange math education. I'm a trained economist. Even though I know some rather advanced stuff, there are basics in areas such as complex analysis that I lack completely. This makes learning some topics fairly hard.

@MartinSleziak looks good to me. I might have phrased some things slightly differently, for example, the one answer on meta.se seems more nuanced to me. But that's not a problem. we seem to have slightly different views and this is noticeable. In the end it might just be about adding a modifier.

But it's fine as is. I think.

Hi quid.

By the one answer on meta you mean that I somehow misrepresented what is said in one of the links to meta.SE i've provided?

We are talking about this part, right?

> On the other hand, on meta.SE I read that wrong answers should actually be downvoted, not deleted: Why shouldn't I delete wrong answers?. (Also: What can be done with a blatantly wrong answer to a popular question? and When should I delete an answer?)

I have expanded that paragraph a bit:

> On the other hand, on meta.SE I read that wrong answers should actually be downvoted, not deleted. At least in the case that the answer is actually an attempt to answer the question, but it is incorrect. (As opposed to "not an answer'.) See:

Sorry, I'll have to go to the laundry room. But I'll be back maybe in 10 minutes.

Anyway, the main question is whether the current version seems at least more-or-less ok. If yes, maybe I could post it.

And a secondary question is whether it is ok to post it now. (But probably postponing it does not change too much. Although there are more active discussions on meta than usually, I might be one of the people to blame.)

@MartinSleziak Adam Lear discusses three notions of "wrong" that I'd paraphrase as (a) 'unrelated', (b) 'correct but not good', (c) 'incorrect' Then it is said, for (a) deleted, for (b) don't delete and for (c) it's not so clear but usually downvote. I think we are mostly discussing votes on type c, and I do not see that answer saying one should not delete those in egregious cases.

But that's maybe something I could expand on in an answer.

Ok, so I'll post it in the current form. After all, some details can be fine-tuned after the post, if needed.

Yes, sounds good to me.

Done: Should wrong answers be deleted?