Gruppo di Fisica Statistica

We study the local critical behavior near the free surface of a d-dimensional system with a smooth inhomogeneity induced by a defect of dimension d*≤d-1 located on the surface. The couplings deviate from their bulk critical value by λr⊥-α where r⊥ is the distance to the center of the defect. Using a phenomenological approach, the change in the surface critical exponents is calculated to first order in the perturbation amplitude λ when the system is marginal, i.e., when the decay exponent of the perturbation α is equal to the scaling dimension Δɛ0 of the bulk energy-density operator. Finally, the critical behavior near extended defects in the bulk is compared to the surface case.