TITLE: A nice result for an sub-area I am not working in
QUESTION [6 upvotes]: I have recently come across a (recent) problem in a different sub-area, by a well-established mathematician, that he deems likely to be intractable, but to which I have found a particularly nice proof (at least I believe so) using the techniques well known in my own sub-area. I think the result itself has a particularly illuminating interpretation so I would like to get it published somehow, but since I am not familiar with the sub-area nor particularly interested in working in it (by which I simply mean I am not suitable for the sub-area), would the best recourse be to contact the author and ask him to write a paper together on the result?

REPLY [9 votes]: Probably more like: Contact the author, and ask for his reaction.  It could be: "Great, let me help you publish it".  Or it could be: "You made the following well-nown error."