Correlation functions near modulated and rough surfaces.

In a system with long-ranged correlations, the behavior of correlation functions is sensitive to the presence of a boundary. We show that surface deformations strongly modify this behavior as compared to a flat surface. The modified near surface correlations can be measured by scattering probes. To determine these correlations, we develop a perturbative calculation in the deformations in height from a flat surface. Detailed results are given for a regularly patterned surface, as well as for a self-affinely rough surface with roughness exponent zeta. By combining this perturbative calculation in height deformations with the field-theoretic renormalization-group approach, we also estimate the values of critical exponents governing the behavior of the decay of correlation functions near a self-affinely rough surface. We find that for the interacting theory, a large enough zeta can lead to a different surface critical behavior. We also provide scaling relations between roughness induced critical exponents for thermodynamic surface quantities.