Magnetic correlation length and universal amplitude of the lattice E8 Ising model

Abstract

The perturbation approach is used to derive the exact correlation length ξ of the dilute AL lattice models in regimes 1 and 2 for L odd. In regime 2 the A3 model is the E8 lattice realization of the two-dimensional Ising model in a magnetic field h at T = Tc. When combined with the singular part fs of the free energy the result for the A3 model gives the universal amplitude fsξ2 = 0.061 728 . . . as h → 0 in precise agreement with the result obtained by Delfino and Mussardo via the form-factor bootstrap approach. Show more