M. T. Homer Reid MIT Home Page
Physics Problems Research teaching My Music About Me Miscellany


Computing Casimir Energies, Forces, and Torques with scuff-cas2d

scuff-cas2d is a command-line utility very similar to scuff-cas3d, but with the difference that it computes Casimir interactions among quasi-2D objects instead of compact 3D objects. (A quasi-2D object is an object of infinite extent in one spatial dimension, which we take to be the z dimension, and constant cross section in the transverse (xy) dimensions.)

Actually, scuff-cas2d is not really part of the scuff-em suite, but more of a standalone code that is bundled together with the scuff-em distribution because of its similarity to scuff-cas3d. The main distinction is that, instead of using RWG basis functions to describe surface currents, scuff-cas2d uses a different type of basis function, which I call ``two-dimensional rooftop'' (TDRT) functions. (See Chapter 7 of my PhD thesis for more info on TDRT functions and the implementation of scuff-cas2d.) This means that scuff-cas2d -- in contrast to scuff-cas3d and all other codes in the scuff-em suite -- does not use the scuff-em core library or the usual .scuffgeo file format for scuff-em geometries. Instead, for quasi-2D geometries there is a slightly different file format and a slightly different procedure for generating meshed geometries. These details are discussed in the tutorial and in the reference sections below.

scuff-cas2d computes Casimir energies and forces per unit length for a collection of quasi-2D objects, at various displacements and rotations of the objects. The basic flow of a scuff-cas2d run goes something like this:

  1. You create a 2D mesh file for each distinct object in your geometry. (scuff-cas2d doesn't do the meshing for you; you use external software like GMSH or COMSOL for that.)
  2. You create a simple text file that lists all the objects in your geometry and specifies their frequency-dependent material properties. (As noted above, the format of this file is similar, but not identical, to that of the usual .scuffgeo files used to define three-dimensional scuff-em geometries).
  3. You create a second simple text file containing a list of transformations to be applied to the geometry, where each transformation is a series of displacements and rotations applied to one or more of the objects in your geometry.
  4. You run scuff-cas2d with appropriate command-line options to compute Casimir energies and forces per unit length for your geometry under each of the transformations you described.
  5. Finally, you interpret the variety of output files that scuff-cas2d emits. In general the one you will care most about is the .out file, which simply lists the computed energy and force per unit length at each of the transformations you specified.

The documentation for scuff-cas2d is divided into the following sections.

scuff-cas2d Documentation
1. A Tutorial Introduction to scuff-cas2d
2. scuff-cas2d Command-Line Reference
3. scuff-cas2d Input File Reference
4. scuff-cas2d Output File Reference
5. A Compendium of scuff-cas2d Examples

Core Library

Computing Casimir Energies, Forces, and Torques with scuff-cas2D, by Homer Reid
Last Modified: 11/16/16