This is not a question of authorship, à la Rembrandt. Rather, to be blunt, the question is: is this person
the founder of modern algebraic geometry? Is it the creator of the étale fundamental group who hands over bottles to acolytes in a bar-fight
before being felled by J. Dufilho:
Is it the divinely inspired inventor of crystalline cohomology who threatens to strangle the rentière Mouaque?
When I wrote a post about Zazie dans le métro (quite a while ago), I mentioned the fact that googling had revealed a claim that Grothendieck had appeared in the movie version of that book, which was filmed by Louis Malle in 1960. Since I recently bought the DVD version of the movie, I’ve been trying to clarify if this is true or not.
First of all, in true old-fashioned style, there are no extendedly exhaustive credits at the end, so the only way to know if he is there is to recognize him. The claim mentioned that Grothendieck was supposed to play “the bar tender”. But this is clearly not the case, if interpreted in terms of the most important bar tender, Turandot, who is a fairly important character (and appears in the credits).
However, there are other bars in the movie, and in particular, there is this long scene at the end where a late onion-soup party degenerates into a general fight with about a hundred waiters involved. This is where the above character appears, and being the only bald character, he is very visible. So: is that really Grothendieck? The photographs I can find of him from around that time are not very good, and I’m terrible at recognizing people from pictures, so maybe other readers will have a more convincing and definitive opinion. Mine is rather that it’s probably not Grothendieck, but it’s easy to guess how someone seeing the movie just once, with this fast-moving scene and this very obvious character, might have decided that it was a good story… [Note that the fact that the bald waiter does not wear glasses, whereas Grothendieck did, may not be very significant (how good does your eyesight need to be to throw bottles around?).]