SURFACE CRITICAL-BEHAVIOR OF INHOMOGENEOUS SEMI-INFINITE SYSTEMS

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* less-than-or-equal-to d - 1 located on the surface. The couplings deviate from their bulk critical value by lambda-r(perpendicular-to -alpha) where r(perpendicular-to) 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 lambda when the system is marginal, i.e., when the decay exponent of the perturbation alpha is equal to the scaling dimension DELTA(epsilon)0 of the bulk energy-density operator. Finally, the critical behavior near extended defects in the bulk is compared to the surface case.