Sean Vig's 2011 GSOC Project

Developing Wigner-3nj Symbols in SymPy

Moving Beyond First Coupling Iteration

In the last week, one of the main things I did was to submit a pull request for the coupled spin machinery that I have been working on. This pull request can be seen here. This implements the coupling and uncoupling operations for states and operators and how these states and operators interact for coupling of two spin states. This pull still has some kinks to work out and some details to iron out, but should be finished up soon.

Moving beyond this pull, the rest of this week has been in working on modifying the coupling methods developed in this pull and making them work for an arbitrary number of spin spaces. The current idea will be to pass a tuple of j values which are to be coupled instead of passing j1 and j2 parameters. While this would work, it would be nice to be able to define how the terms are coupled, noting that the order of how the spaces are coupled matter in determining the coefficients and what will be diagonal in the basis of the coupled states. The current way I am working the coupling is to couple j1 and j2, then couple this to j3, etc. I have currently changed the all the methods to accept the tuple of j values, however, the coupling and uncoupling methods have not been changed to accept arbitrary numbers of spaces. Most of this week has been thinking and trying to determine a good way to implement this machinery that scales to arbitrary numbers of spaces. While it is not directly necessary for dealing with spin states, I will likely also implement Wigner-6j/9j/12j coefficients in, which will be very similar to the Wigner-3j symbols that were implemented with the Clebsch-Gordan coefficients.

While I am starting to work on this final component of my project, it will be a close call as to whether or not it can get pushed in time to make it in before the end of the project, which will be in just 2 weeks. The initial coupling stuff should get in, but this will be a much closer call. That said, I will definitely see this last part of the project into master.