  We study nonlinear sigma model, especially Skyrme model without twist and
Skyrme model with twist: twisted Skyrmion string. Twist term, $mkz$, is
indicated in vortex solution. Necessary condition for stability of vortex
solution has consequence that energy of vortex is minimum and scale-free
(vortex solution is neutrally stable to changes in scale). We find numerically
that the value of vortex minimum energy per unit length for twisted Skyrmion
string is $20.37\times 10^{60}~\text{eV/m}$.
