# SIS

## Seminar

### Spectral curve for the Heisenberg ferromagnet and AdS/CFT

Seminar Room 1, Newton Institute

#### Abstract

Highly spinning classical strings on R x S^3 are described by the Landau-Lifshitz model or equivalently by the Heisenberg ferromagnet in the thermodynamic limit. The spectrum of this model can be given in terms of spectral curves. In this talk we study the issue of stability, i.e. whether any given admissible spectral curve can actually be realized as a solution to the discrete Bethe equations. In particular, what about those classical string solutions which have unstable excitation modes? Are they physical or not? We also find and explore the general two-cut solution whose moduli-space shows a surprisingly rich structure.