27 Oct
2010
27 Oct
'10
9:27 p.m.
On the same page as the photograph there occurs the following explanation, upon which nobody has previously remarked. << Later Thurston wrote to add: “The letters refer to a word in the free group on three generators, which is the fundamental group of the plane minus the 3 points. If you imagine 3 ‘branch cuts’ going vertically from the three spots, and label them a, b, and c, then as you trace out the word starting from the left inside (I believe) it will trace out the given word, where a