On 3-strand singular pure braid group
Abstract
In this paper, we study the singular pure braid group SPn for n=2,3. We find generators, defining relations and the algebraical structure of these groups. In particular, we prove that SP3 is a semi-direct product SP3=̃V3⋋ℤ, where ̃V3 is an HNN-extension with base group ℤ2∗ℤ2 and cyclic associated subgroups. We prove that the center Z(SP3) of SP3 is a direct factor in SP3.