Rail knotoids
Abstract
We work on the notions of rail arcs and rail isotopy in ℝ3, and we introduce the notions of rail knotoid diagrams and their equivalence. Our main result is that two rail arcs in ℝ3 are rail isotopic if and only if their knotoid diagram projections to the plane of two lines which we call rails, are equivalent. We also make a connection between the rail isotopy in ℝ3 and the knot theory of the handlebody of genus 2.
Dedicated to Louis H. Kauffman for his 70th birthday