English

On extensions of the standard representation of the braid group to the singular braid group

Representation Theory 2025-04-15 v1

Abstract

For an integer n2n \geq 2, set BnB_n to be the braid group on nn strands and SBnSB_n to be the singular braid group on nn strands. SBnSB_n is one of the important group extensions of BnB_n that appeared in 1998. Our aim in this paper is to extend the well-known standard representation of BnB_n, namely ρS:BnGLn(Z[t±1])\rho_S:B_n \to GL_n(\mathbb{Z}[t^{\pm 1}]), to SBnSB_n, for all n2n \geq 2, and to investigate the characteristics of these extended representations as well. The first major finding in our paper is that we determine the form of all representations of SBnSB_n, namely ρS:SBnGLn(Z[t±1])\rho'_S: SB_n \to GL_n(\mathbb{Z}[t^{\pm 1}]), that extend ρS\rho_S, for all n2n\geq 2. The second major finding is that we find necessary and sufficient conditions for the irreduciblity of the representations of the form ρS\rho'_S of SBnSB_n, for all n2n\geq 2. We prove that, for t1t\neq 1, the representations of the form ρS\rho'_S are irreducible and, for t=1t=1, the representations of the form ρS\rho'_S are irreducible if and only if a+c1.a+c\neq 1. The third major result is that we consider the virtual singular braid group on nn strands, VSBnVSB_n, which is a group extension of both BnB_n and SBnSB_n, and we determine the form of all representations ρS:VSB2GL2(Z[t±1])\rho''_S: VSB_2 \to GL_2(\mathbb{Z}[t^{\pm 1}]), that extend ρS\rho_S and ρS\rho'_S; making a path toward finding the form of all representations ρS:VSBnGLn(Z[t±1])\rho''_S: VSB_n \to GL_n(\mathbb{Z}[t^{\pm 1}]), that extend ρS\rho_S and ρS\rho'_S, for all n3n\geq 3.

Keywords

Cite

@article{arxiv.2504.09256,
  title  = {On extensions of the standard representation of the braid group to the singular braid group},
  author = {Mohamad N. Nasser},
  journal= {arXiv preprint arXiv:2504.09256},
  year   = {2025}
}