Effect of Randomness on Critical Behavior of Spin Models

Renormalization group methods are used to analyze the critical behavior of random Ising models. The Wilson‐Fischer ε‐expansion for the recursion relations for n‐component continuous spin models are developed for randomly inhomogeneous systems. In addition to the usual variables for a homogeneous system there appears a variable which in essence describes local fluctuations in T c . From the structure and stability of the fixed points we conclude that critical exponents are unaffected by randomness for n≳4 but are renormalized by randomness for 1