English

The group $G_{n}^{2}$ with a parity and with points

Geometric Topology 2016-05-03 v1

Abstract

In~\cite{Ma} Manturov studied groups GnkG_{n}^{k} for fixed integers nn and kk such that k<nk<n. In particular, Gn2G_{n}^{2} is isomorphic to the group of free braids of nn-stands. In~\cite{KiMa} Manturov and the author studied an invariant valued in free groups not only for free braids but also for free tangles, which is derived from the group Gn2G_{n}^{2}. On the other hands, in~\cite{FeMa} Manturov and Fedoseev studied groups Br2nBr_{2}^{n} of virtual braids with parity and groups BrdnBr_{d}^{n} of virtual braids with dots. They showed that there is a monomorphism from Br2nBr_{2}^{n} to BrdnBr_{d}^{n} and it is deduced that a parity of the braid can be represented by a geometric object, dots on strands. In this paper we study Gn2G_{n}^{2} with structures, which are corresponded to parity and points on a braid, which are denoted by Gn,p2G_{n,p}^{2} and Gn,d2G_{n,d}^{2}, respectively. In section 3, it is proved that there is a monomorphism from Gn2G_{n}^{2} to Gn,p2G_{n,p}^{2} and that there is a monomorphism from Gn,p2G_{n,p}^{2} to Gn,d2G_{n,d}^{2}. By the homomorphism from Gn2G_{n}^{2} to Gn,p2G_{n,p}^{2}, it can be deduced that a given parity of a braid has geometric representation, which is the number of points on the braid. In section 4, it can be proved that for each element β\beta in Gn,d2G_{n,d}^{2}, an element in Gn+12G_{n+1}^{2} obtained by adding another strand by tracing points on β\beta. That is, a parity of free braid of nn-stands is represented not only by points on strands, but also by an n+1n+1-th strand. Conversely, for a braid of n+1n+1-strands, a braid of nn-strands is obtained by deleting one strand of the braid of n+1n+1-strand. Finally, we will simply discuss about the way to adjust the previous observations to know whether a given braid is Brunnian or not.

Keywords

Cite

@article{arxiv.1605.00073,
  title  = {The group $G_{n}^{2}$ with a parity and with points},
  author = {S. Kim},
  journal= {arXiv preprint arXiv:1605.00073},
  year   = {2016}
}