Critical Behavior of the Randomly Spin Diluted 2D Ising Model: A Grand Ensemble Approach

Abstract

The critical behavior of the 2D spin diluted Ising model is investigated by a new method that combines a grand ensemble approach to disordered systems with phenomenological renormalization. We observe a continuous variation of critical exponents with the density $\ensuremath{\rho}$ of magnetic impurities, respecting, however, weak universality in the sense that $\ensuremath{\eta}$ and $\frac{\ensuremath{\gamma}}{\ensuremath{\nu}}$ do not depend on $\ensuremath{\rho}$ while $\ensuremath{\gamma}$ and $\ensuremath{\nu}$ separately do. Our results are in complete agreement with a recent Monte Carlo study.