I have a question about the history of two important results from the eighties in symplectic geometry. In both cases it seems that important results were developed (almost) simultaneously by different people, which I find quiet remarkable and unusual. I would be interested in knowing if the corresponding researchers were aware of each other, working on the same projects, and if so at what stage of their project they did become aware of the other one. (Highly hypothetical: do you think that these days people accept more easily to publish a joint paper in such a situation?)
There is the convexity result by Atiyah, Michael F., Convexity and commuting Hamiltonians, Bull. Lond. Math. Soc. 14, 1-15 (1982). ZBL0482.58013. and by Guillemin, V.; Sternberg, S., Convexity properties of the moment mapping, Invent. Math. 67, 491-513 (1982). ZBL0503.58017. Both articles have been published in the same year... of course, it takes some time to get a paper published and there was also nothing like the arxiv to maybe have a better idea of the developments.
I'm also surprised because the localization result Duistermaat, J. J.; Heckman, G. J., On the variation in the cohomology of the symplectic form of the reduced phase space, Invent. Math. 69, 259-268 (1982). ZBL0503.58015. was published the same year, followed by Berline, Nicole; Vergne, Michele, Zeros d’un champ de vecteurs et classes characteristiques équivariantes, Duke Math. J. 50, 539-549 (1983). ZBL0515.58007., which seems to describe a similar thing.
I admit that I do not have a very precise question, but if anybody could give some insight on how so many interesting things developed in such a short time by different authors, I would be extremely interested.