On String S-matrix, Bound States and TBA

Understand

The study of finite J effects for the light-cone AdS superstring by means of the Thermodynamic Bethe Ansatz requires an understanding of a companion 2d theory which we call the mirror model.

• It is obtained from the original string model by the double Wick rotation.
• The S-matrices describing the scattering of physical excitations in the string and mirror models are related to each other by an analytic continuation.
• We show that the unitarity requirement for the mirror S-matrix fixes the S-matrices of both theories essentially uniquely.