Science at the Sabha 2018

Knots and braids are familiar to us all from childhood. How do we tell one knot from another? How many knots are there? Given a tangled loop of string, is it really knotted or can we open it up without having to cut it? I will try to explain how mathematicians think about these questions. Besides being of intrinsic interest, answers to such questions have applications to subjects as varied as cryptology and the structure of DNA