On the day a proof outran its readers
Copyright: Sanjay Basu The proof nobody read O n a Friday afternoon last November, an autonomous system called Aristotle was handed a problem Paul Erdős had posed roughly thirty years earlier. Six hours later it produced a proof. The proof was a long file of Lean 4 code, full of lemmas that no human had read. Verification took about a minute. Somewhere in the middle of those six hours, Aristotle did something the working mathematics community had quietly failed to do for a generation. It noticed that the problem, as published in the official list of Erdős open problems, had a small gap in its statement. A hypothesis was missing. With the hypothesis added back in, the question reduced cleanly to a corollary of Brown’s criterion, and Aristotle proved that version. The hard version, the one Erdős presumably meant to ask, is still open. You can read the Lean file. It is on GitHub. I have looked at it. I cannot really tell you what it says. The kernel of Lean, the small piece of trusted cod...