The Mathematics SE question Can there be an energetically unbounded three-body orbit where escape is impossible due to conservation of angular momentum? was well received and someone had graciously added a +200 bounty to it. It has an associated meta post as well.

One user who is also active here suggested I might post my question here as well but I demurred for fear of cross-posting repercussions.

I understand but I'm uncomfortable cross-posting which is strongly discouraged without special circumstances and a moderator's blessing.

My thoughts are that there's obviously some interest in the question where it is now and moving it (it's currently 21 days old) might deprive readers from seeing the answer, and I have no idea if there is any increased likelihood of a definitive answer here rather than there. But I really am interested in finding out if an answer exists.

What further actions if any should I take?

  • 13
    $\begingroup$ You shouldn't worry about cross-posting at this point: enough time has elapsed. I'm not completely sure that MO is the right home, but I don't think there is harm in trying. $\endgroup$
    – Todd Trimble Mod
    Commented May 26, 2020 at 3:03
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    $\begingroup$ I would include the formula for the angular momentum, at which point the question seems pretty much self-contained and not relying on any physics assumptions. $\endgroup$
    – David Roberts Mod
    Commented May 26, 2020 at 5:52
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    $\begingroup$ I think @ToddTrimble would have said if this were so, so maybe I'm mistaken, but my understanding is that what is discouraged is not ever having a problem on both MSE and MO, but posting it on both fora simultaneously. That is, giving a problem a chance on MSE, but then moving it to MO (if appropriate) if it gets no response, is not an abuse but exactly the way it's meant to work (again, as long as the question is genuinely research-level). $\endgroup$
    – LSpice
    Commented May 26, 2020 at 14:29
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    $\begingroup$ @LSpice thanks for that. A major concern with cross-posting is answer fragmentation, which in this case is not a high risk and once (if) an answer appears on one site I can just start the close process on the other. $\endgroup$
    – uhoh
    Commented May 26, 2020 at 14:49
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    $\begingroup$ @uhoh To help avoid the possibility of answer fragmentation, I suggest you add links between your current question on Math SE and any possible new question on MathOverflow. This way, users can check the question on the other site to see what's been commented on, & possibly answered, with this helping to avoid the user possibly duplicating efforts. $\endgroup$ Commented May 27, 2020 at 6:14
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    $\begingroup$ Thank you all; I will post an edited version in MO in a day or so. $\endgroup$
    – uhoh
    Commented May 27, 2020 at 9:28

1 Answer 1


Gathering comments together into an answer --

There's no problem cross-posting a research-level question from MSE to MO after enough time has passed to give potential answerers a chance to post answers here.

When crossposting from MSE to another stackexchange site, best practice is to post links between the two questions to avoid answer fragmentation and make sure that effort is not duplicated between sites.

  • $\begingroup$ Thank you for the answer, and the reminder; will do so today. $\endgroup$
    – uhoh
    Commented Jun 4, 2020 at 22:22
  • $\begingroup$ @uhoh when you post on MO, it would be helpful to edit your question above and add a link to the new post. $\endgroup$
    – David Roberts Mod
    Commented Jun 5, 2020 at 4:08
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    $\begingroup$ The purpose of this linking is to avoid the situation where the same question has an answer on one of the pages and then someone finds the open question on the other page and spends time thinking about an already answered question. $\endgroup$ Commented Jun 5, 2020 at 6:08

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