The Hadwiger-Nelson problem is that of determining the chromatic number of the plane (), defined as the minimum number of colours that can be assigned to the points of the plane so as to prevent any two points unit distance apart from being the same colour. 220 more words

## Tags » Polymath Proposals

#### A new polymath proposal (related to the Riemann Hypothesis) over Tao's blog

(From a post “the music of the primes” by Marcus du Sautoy.)

A new polymath proposal over Terry Tao’s blog who wrote: “Building on the interest expressed in the comments to 90 more words

#### Spontaneous Polymath 14 - A success!

This post is to report an unplanned polymath project, now called polymath 14 that took place over Terry Tao’s blog. A problem was posed by Apoorva Khare was presented and discussed… 9 more words