Computations on U and V when they do not commute.
We have f=U+U−1+V+V−1. Exp is the exponential map: ef=Σ∞m=0fnn!. U and V do not commute and we have UmVn=eimnVnUm for any m,n integer. I want to find the constant term for the expression ∂2e−f/2∂2ef. We have ∂2f=V−V−1.
Is there any program in which I can compute it?
What is (mathematically) ∂2? Is it a derivation? (So that we can formally extend it to a polynomial to a series in f...) Is there really exp(imn) the twisting factor?