On MSE I recently asked a question which remained unanswered for a couple of weeks, at which point I cross-posted it on MO where it was answered.

What should be done now with the unanswered question on MSE? Simply add a note directing readers to the MO answer?

Would it be appropriate to answer the MSE question myself, citing the MO answer and perhaps illustrating it with some specific results that flow from it?

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    $\begingroup$ I think Mike's answer below is the best course of action, but in the future, if no one answered the question in MSE, even with possible bounties offered, and a lot of time has passed, you can flag your own question and ask an admin to migrate it to MO. $\endgroup$
    – Ivo Terek
    Dec 30, 2017 at 4:40
  • $\begingroup$ While what @IvoTerek says is possible, I for one, do not really see the point of this type of migration and do not do them. I usually will reply to such a flag by saying that it is better to ask the question there by oneself (with cross-references). $\endgroup$
    – quid Mod
    Jan 7, 2018 at 15:44

1 Answer 1


I would recommend that you answer the question yourself, mostly because it would otherwise go on the Unanswered Questions queue for a silly reason. But also, answers from MathOverflow are not always appropriate for the audience of MathSE. Writing up a version of the answer there that is adapted to the MathSE audience does add value to this site. So adding examples and specific results would be a fine idea. And then since that thorough answer exists on MathOverflow, you don't need to write up a full answer here, but a synopsis with a link would be fine too. So maybe start your answer with something like

I've cross-posted this question to MathOverflow. Here is a summary of the answer given there. ...

And then while you did have to work to adapt your answer, if you still feel uncomfortable gaining some reputation based on the work of the answerer on MathOverflow, then you could mark your answer as community wiki (although I think some users would argue that't not intended use of community wiki).

  • $\begingroup$ This is a quite natural proposal for the OP. Recently I ran through precisely this situation, and you might be interested in the concrete case: The very first math.SE post led to awarding the Tumbleweed badge (it honours having asked a question with zero score, no answers, no comments, and low views for a week) to me. (to be continued) $\endgroup$
    – Hanno
    Jan 1, 2018 at 15:39
  • $\begingroup$ (continued) The revised and abridged Cross-post on MO, posted after a decent waiting time, received an astonishing acceptance and a most helpful answer in particular. After a few days of digestion I sat down to complete the first post with an answer citing the sources and the concretely seeked formula. This was acknowledged by the community (as several upvotes show). Even later I did put the green acceptance check mark on it. $\endgroup$
    – Hanno
    Jan 1, 2018 at 15:39
  • $\begingroup$ This is precisely what I have done in the past at this question. I used community wiki. $\endgroup$ Jan 2, 2018 at 16:58

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