The main objectives of the polymath8 project, initiated back in June, were to understand the recent breakthrough paper of Zhang establishing an infinite number of prime gaps bounded by a fixed constant $latex {H}&fg=000000$, and then to lower that value of $latex {H}&fg=000000$ as much as possible. After a large number of refinements, optimisations, and other modifications to Zhang’s method, we have now lowered the value of $latex {H}&fg=000000$ from the initial value of $latex {70,000,000}&fg=000000$ down to (provisionally) $latex {4,680}&fg=000000$, as well as to the slightly worse value of $latex {14,994}&fg=000000$ if one wishes to avoid any reliance on the deep theorems of Deligne on the Weil conjectures.

As has often been the case with other polymath projects, the pace has settled down subtantially after the initial frenzy of activity; in particular, the values of $latex {H}&fg=000000$ (and other key parameters, such as $latex {k_0}&fg=000000$, $latex {\varpi}&fg=000000$…