主 题: The complexity of unknotting
报告人: Prof. Joel Hass (University of California at Davis)
时 间: 2007-11-01 下午 2:40 - 3:40
地 点: 理科一号楼 1303
We look at the complexity of the problem of determining whether
a given curve is knotted or not. This has recently been determined
in joint work with Lagarias and Pippenger. We showed that the Unknotting
problem is in NP. We used this to find an explicit bound
on how many Reidemeister moves are needed to pass between a
diagram of the unknot and a round circle. Finally I will discuss
recent work with Agol and Thurston in which we show that the problem of determining
the genus of a knot in a 3-manifold is NP-complete.
北大老师的评注: Even "Science" is a famous journal, it is not influencial in mathematics.
On the otherhand, if you are interested what kind mathematics may be reported by "Science",
Hass\'s talk is an example.