Finite-Size Scaling at Yang-Lee Singularities of 2D Discrete Spin Models

We numerically study the Hamiltonian limits of the two dimensional (2D) Ising and 3-state Potts models in complex magnetic fields. From the Phenomenological Renormalization Group, we find the critical field values associated with the Yang-Lee singularity (YLS) in these models. We also determine the low-lying part of the excitation spectrum at the YLS. Finally, we compare the resulting patterns of energy levels to predictions for conformal non-unitary minimal models.