I asked the question

"Which sets occur as boundaries of other sets in topological spaces?"

on MathStackExchange on June 23, thinking that the answer is probably known, but there are no answers yet. Is this sufficient reason to ask it again on Mathoverflow? Am I likely to get answers then?

  • $\begingroup$ It seems you got an answer. Now, you might not be satisfied with the answer, but this can also mean that the questions was not quite clear. $\endgroup$
    – user9072
    Jul 9, 2014 at 8:54
  • $\begingroup$ @quid No, there are no answers yet, only a comment (and some other deleted comments, now integrated into the question). $\endgroup$ Jul 9, 2014 at 11:06
  • $\begingroup$ I meant the partial answer given in a comment. $\endgroup$
    – user9072
    Jul 9, 2014 at 12:28
  • $\begingroup$ Seems like this meta question has provoked another helpful comment - maybe not necessary. $\endgroup$
    – user25199
    Jul 9, 2014 at 12:33
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    $\begingroup$ Why was this downvoted? Irrespective of whether it’s appropriate to move the question to MO, it is appropriate and on-topic to inquire about it here on meta. $\endgroup$ Jul 9, 2014 at 19:20
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    $\begingroup$ The comment I made on MSO implies that spaces with the required property must be perfect. I think one can show that this is also sufficient for $T_0$ second-countable spaces (that is, if $X$ is $T_0$ second-countable, then every closed subset of $X'$ is a boundary of a subset of $X$, even one with an empty interior). However, it seems to me that the question may be rather nontrivial in full generality, and that it is fine to re-ask it on MO. $\endgroup$ Jul 9, 2014 at 21:43
  • $\begingroup$ @Emil Good point. I agree the question looks fine for MO, preferably with a link here. $\endgroup$
    – user25199
    Jul 10, 2014 at 10:27
  • $\begingroup$ I think that @EmilJeřábek comment shows that a revised version of the question would be fine. Why not instead of migrating it ask a question taking the information obtained via comment(answers) into account, linking to oiriginal and the meta question. Or if you really want to migrate it, edit it beforehand. $\endgroup$
    – user9072
    Jul 10, 2014 at 17:23
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    $\begingroup$ @quid, EmilJerabek, Carl Thanks for the responses, I am reposting it here on MO. $\endgroup$ Jul 10, 2014 at 20:31
  • 1
    $\begingroup$ @quid By the way, by migrating I have always meant just copying the post manually and reposting, with revisions. Is there another way of making that happen? $\endgroup$ Jul 10, 2014 at 20:33
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    $\begingroup$ Yes. In fact "migration" is a particular technical term in the Stack Exchange network. See meta.stackexchange.com/questions/10249/… $\endgroup$
    – user9072
    Jul 10, 2014 at 22:05


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