The dilute A${}_4$ model, the E${}_7$ mass spectrum and the tricritical Ising model

Abstract

The exact perturbation approach is used to derive the (seven) elementary correlation lengths and related mass gaps of the two-dimensional dilute A${}_4$ lattice model in regime 2- from the Bethe ansatz solution. This model provides a realisation of the integrable $\varphi (1,2)$ perturbation of the c=7/10 conformal field theory, which is known to describe the off-critical thermal behaviour of the tricritical Ising model. The E${}_7$ masses predicted from purely elastic scattering theory follow in the approach to criticality. Universal amplitudes for the tricritical Ising model are calculated.

24 pages, LaTeX, submitted to Journal of Mathematical Physics. One paragraph added and some minor typos corrected