Fractional strings hypothesis and non-simple laced integrable models

The author discusses the ground state and some elementary excitations of the Bp non-simple laced integrable models. The zeros of the associated Bethe ansatz equations are characterized by a special distribution in the complex plane, which is different from the usual string hypothesis. The introduction of this new solution makes it possible to calculate exactly various properties in the thermodynamic limit. The finite-size corrections to the eigenspectrum strongly suggest that the Bp Wess-Zumino-Witten-Novikov models are the underlying conformal field theory for these non-simple laced models.