ATOMIC BOMBS ARE FAKE! IT'S ALL BECAUSE OF THE JEWS!
Oh, wait ... I'm not Eleven11. Anyway.
I've often read about how Germany could have developed the atomic bomb, but many things kept them back, not in the least improper mathematics on the part of their physicists. IIRC they got an equation wrong or something, and thus proclaimed atomic weaponry as "impossible."
WI that was circulated out into the mathematical community? Simply put, what if Germany and everyone else (US, UK, USSR, etc.) thought that atomic bombs were mathematically impossible, and thus fantasy? I suppose some things in WWII would have progressed differently, such as the Japanese surrender, but what else would have changed?
I don't think it'd be plausible for people to believe atomic weaponry to be impossible for forever, so WI mathematicians fix the equations later on ITTL? So, let's say that instead of in the 1940s, Manhattan Project-esque programs spring up in the 1950s or early 1960s? Would the later development change anything, and how much would depend on who got the bomb first?