A geometric interpretation of the normal closure of the braid group Bn in the braid group of the torus Bn(T)
Abstract
It had been proved by Birman and Goldberg that the normal closure of the pure braid group Pn(D) in the pure braid group of the torus Pn(T) is the commutator subgroup [Pn(T),Pn(T)]. In this paper, we are going to study the case of full braid groups: i.e. the normal closure of Bn(D) in Bn(T), which turns out to have an interesting geometric description.