Invariant and group theoretical integrations over the U(n) group
S. Aubert, C. S. Lam · Journal of Mathematical Physics · 2004
In a previous article, an “invariant method” to calculate monomial integrals over the U(n) group was introduced. In this paper, we study the more traditional group-theoretical method, and compare its strengths and weaknesses with those of the invariant method. As a result, we are able to introduce a “hybrid method” which combines the respective strengths of the other two methods. There are many examples in the paper illustrating how each of these methods works.