Event № 664

Given two closed embedded curves on a surface we say that they are at distance one if they intersect at two points or less. This defines a metric on a family of loops by considering the shortest chain of elements at distance one. By choosing various surfaces and families of curves one can obtain metric spaces with very diverse and rich geometry.

Despite the elementary construction this metric seems to be nearly unexplored. At the same time it is related to some important metrics (e.g. Hofer's metric, fragmentation metric, etc) on groups of diffeomorphisms of the surface. I will discuss [few] examples where the geometry is understood and will describe [lots of] those where nothing is known.

No symplectic preliminaries are assumed for this talk.