In his last published paper, Alan Turing was pondering on knots and how to decide whether a given knot diagram is actually the ‘unknot’, which means that by moving the knot around, you could deform it to a round circle. As he wrote in 1954:
"No systematic method is yet known by which one can tell whether two knots are the same" - 'Solvable and Unsolvable Problems'
Nearly 70 years later Marc Lackenby has made a breakthrough of Gordian proportions. Marc presented his results at a seminar at UC Davis this week. Full story here.
Bulletin category