We compute numerically the mass spectrum and the specific free energy for the T = T c Ising model with nonzero magnetic field in the scaling limit. The results are in good agreement with the proposed exact S-matrix.
We compute the spectrum and several critical amplitudes of the two dimensional Ising model in a magnetic field with the transfer matrix method. The three lightest masses and their overlaps with the spin and the energy operators are computed on lattices of a width up to L=21. In extracting the continuum results we also take into account the corrections to scaling due to irrelevant operators. In contrast with previous Monte Carlo simulations our final results are in perfect agreement with the predictions of S-matrix and conformal field theory. We also obtain the amplitudes of some of the subleading corrections, for which no S-matrix prediction has yet been obtained.
The two-dimensional tricritical Ising model with an order parameter perturbation is studied using two different lattice models. The mass spectrum is found to be the same as in the 2D Ising model with a magnetic field. Results for the scaling functions are in agreement with universality and for the lowest mass a relationship with the scaling function of the Ising model is observed. The numerical results do not support a recent proposal of Dotsenko on the dynamical generation of extra terms in the perturbative calculation of scaling functions.