PUB - Publikationen an der Universität Bielefeld

We present a numerical calculation of the Lee -Yang and Fisher zeros of the 2D Ising model using multipoint Pade approximants. We perform simulations for the 2D Ising model with ferromagnetic couplings both in the absence and in the presence of a magnetic field using a cluster spin -flip algorithm. We show that it is possible to extract genuine signature of Lee -Yang and Fisher zeros of the theory through the poles of magnetization and specific heat, using the multipoint Pade method. We extract the poles of magnetization using Pade approximants and compare their scaling with known results. We verify the circle theorem associated to the well known behavior of Lee -Yang zeros. We present our finite volume scaling analysis of the zeros done at T 1 / 4 T c for a few lattice sizes, extracting to a good precision the (combination of) critical exponents fib. The computation at the critical temperature is performed after the latter has been determined via the study of Fisher zeros, thus extracting both fi c and the critical exponent nu. Results already exist for extracting the critical exponents for the Ising model in two and three dimensions making use of Fisher and Lee -Yang zeros. In this work, multipoint Pade is shown to be competitive with this respect and thus a powerful tool to study phase transitions.