Hebrew University topology and geometry seminar

Abstract: A Brunnian braid is a braid that becomes trivial after removing any one of its strands. We describe algebraically the group of Brunnian braids on a general surface, assuming that the surface is not a sphere or projective plane. In the latter exceptional cases the group of Brunnian braids is described by an algebraic procedure together with the homotopy groups of a 2-sphere. A braid is Cohen if it remains the same (not necessary trivial) after deleting any one of its strands. We give some partial results connected with Cohen braids from our work in progress.