When is <psi|AB|theta> equal to <psi|A|theta>*<psi|B|theta>?

[Getterdog]

TL;DR

Sum and product of Dirac operators

Looking at. <psi|AB|theta>, under what conditions would this be equal to <psi|A|theta> * <psi|B|theta> I’m just getting into perturbation theory
and am running into confusing notation. Thanks john

 

[PeroK]

Summary:: Sum and product of Dirac operators

Looking at. <psi|AB|theta>, under what conditions would this be equal to <psi|A|theta> * <psi|B|theta> I’m just getting into perturbation theory
and am running into confusing notation. Thanks john

My first thought is to look at matrix representations.