Critical behavior of the randomly spin diluted 2D Ising model: A grand ensemble approach

The critical behavior of the 2D spin-diluted Ising model is investigated by a new method which combines a grand ensemble approach to disordered systems with phenomenological renormalization. We observe a continuous variation of critical exponents with the density ρ of magnetic impurities, respecting, however, weak universality in the sense that η and γ/ν do not depend on ρ while γ and ν separately do. Our results are in complete agreement with a recent Monte Carlo study.