A few months ago, Gil Kalai got in touch to suggest that it was time to revisit Polymath5, the attempt to prove the Erdős discrepancy problem. I agreed, but we have both been rather busy in the interim, so it is only now that we are ready. One of the things that Gil did was write three posts, which I shall be putting up as guest posts, the first one today and the others over the next few days. I hope that people who contributed to the project the first time round will consider having another go, and that people who didn’t, but would be interested, will find that they can use the wiki that we created to record our progress to get up to speed with what is already known. Once Gil’s posts are up, I’ll probably write a post myself, and I hope that some serious work might start in early September. I always felt that when the original attempt petered out, it was just a kind of loss of energy that individual mathematicians often feel, rather than the result of hitting a brick wall. And just as having a break from a problem is often useful for individuals, I hope it will turn out to be for this polymath project. If it doesn’t, then maybe I’ll do something I meant to do much earlier, which is write up in paper form the progress that has already been made. (Of course, if I do that, then anybody is free to contribute to the writing.)
If you want to look at some of the earlier posts, they are collected together in the polymath5 category on this blog.