18.11. SineGordon and non-unitary models a. Find the value of for which the S-matrix element S(1,1)()

18.11. Sine–Gordon and non-unitary models

a. Find the value of ξ for which the S-matrix element S(1,1)(θ) of the Sine–Gordon model coincides with the S-matrix of the Yang–Lee model. Explain why the restriction of the Sine–Gordon model produces a negative residue at the pole

θ = 2πi/3.

b. Generalize the result above, finding the value of ξ that leads to the equality of the S-matrices S(n,m)(θ) of the Sine–Gordon model with those of the integrable deformation of the minimal non-unitary modelsM2,2n+1.