Derivative-expansion approach to the interaction between close surfaces

Abstract

The derivative-expansion approach to the calculation of the interaction between two surfaces is a generalization of the proximity force approximation, a technique in widespread use in different areas of physics. The derivative expansion has so far been applied to seemingly unrelated problems in different areas; it is our principal aim here to present the approach in its full generality. To that end, we introduce a unified setting, which is independent of any particular application, provide a formal derivation of the derivative expansion in that general setting, and study some of its properties. With a view toward the possible application of the derivative expansion to other areas, like nuclear and colloidal physics, we also discuss the relation between the derivative expansion and some time-honored uncontrolled approximations used in these contexts. By putting them under similar terms as in the derivative expansion, we believe that the path is open to the calculation of next-to-leading-order corrections also for these contexts. We also review some results obtained within the derivative expansion, by applying it to different concrete examples and highlighting some important points.