I am trying to derive the evolution operator for a time dependent Hamiltonian which satisfies the commutator $$[H(t_1), H(t_2)]=I f(t_1,t_2)$$ Where $I$ is the identity operator, and $f(t_1,t_2)$ is an arbitrary function of the time parameters which maps to the complex numbers.
I am aware of a derivation which uses the Magnus expansion, an exponential operator expansion in nested commutators of the Hamiltonian, but I am trying to derive it using the Dyson series expansion.
