Bifurcation and global continuation of travelling-rotating Schr\"odinger maps on the sphere

We study travelling-rotating solutions of the Schrödinger map equation into the sphere, viewed as tangent profiles of rigid vortex filaments.

Two first integrals reduce the profile equation to a scalar cubic equation for the vertical component, giving an elliptic-function description and explicit closure conditions.

We prove bifurcation from the equatorial branch at $\lambda_k=R\sqrt{k^2-1}$, $k\ge2$, and establish a global continuation alternative inside the regular non-polar class.

The possible boundary mechanisms are pole contact, vertical collapse, and double-root degeneration.

Numerical continuation of the equatorial branches suggests convergence to the north-pole boundary.

Up to gauge, the reconstructed vortex filaments are of Kida type.