Last changed Wed Aug 29 13:31:01 BST 2001
We are grateful to David Wright who produced a number of pictures in connection with our paper inserttitle .
The current document was written by David Wright, to explain what he had done. His document has since been
lightly edited by David Epstein. The original form of the document was produced using latex2html by Nikos Drakos.
The Trace slice
For downloading, the source of this document is in
These correspond to traces
(using the upper case convention for inverses).
We use a boundary tracing method for exploring the values of for which such a group is discrete. The p/q word in a and b is defined by
We solve in order of p/q for values of where wp/q has trace 2.
The resulting plot of is below, for cusps ranging from -3/1 just off to the left to 3/1 just off to the right.
epstein-lset.epsi is a large file (around 30Mb). The advantage of taking a look at it with a PostScript viewer, like ghostscript or gv, is that David Wright's program computes the limit set in circular order. The limit set is naturally the continuous image of a circle. In the viewer, the picture appears comparatively slowly, and you see a movie of the image in the plane of a point on the circle. This enables one to see the map, rather than just the image of the map.