On twist positive braids with the 2-variable link invariant: 3-braids of width 2
Abstract
The possible 2-variable link polynomial PL(v,z) for an oriented link L, which has width 2 in the variable v, is studied, where width of PL(v,z) is the minimal number of strands allowed by the index bound. It is shown that if the 2-variable link invariant PL(v,z) for an oriented link L has width k in the variable v, then it is the same as the polynomial of a closed k-braid, k=1,2. Also a complete list of 3- braids of width 2, which close to knots, are given. Consequently it is shown that PL(v,z) determines ˆβ for the full 3-braid β. Finally, the 2-variable polynomial for the non-full 3-braid is calculated.