Re: Quantum Commutator

*To*: mathgroup at smc.vnet.net*Subject*: [mg85325] Re: Quantum Commutator*From*: "Eric R. Bittner" <bittner at uh.edu>*Date*: Wed, 6 Feb 2008 01:25:49 -0500 (EST)

Dear Dick, I'm sorry this is sort of late in the post, but I just came across your query looking for similar software using Google. As it turns out, a bit of digging through my own quantum mechanics course notes yields a nice solution. There's a nice relation you my wish to exploit in calculating quantum commutators. I believe it's originally due to Dirac. In essence, if you have quantum operators A(p,q) and B(p,q) as functions of the quantum p & q operators, then [A,B] = i hbar {A,B} where {A,B} is the classical poisson bracket. This is easy to code in Mathematica! In addition you can generalize this to any set of canonical variables, for example the boson operators a & a^\dagger. For example, if you have operators A(a,a^\dagger) and B(a,a^\dagger) then [A(a,a^\dagger), B(a,a^\dagger)] = i hbar (\partial_a A \partial_{a^\dagger}B- \partial_{a^\dagger}A\partial_a B For fermions, you need to modifiy this to take in to account Pauli exclusion, but that's simple since you can relate the commutator to the anti-commutator. Cheers! Eric B.