Independent Operators for Interacting Electrons

Operators which add an electron to an interacting system and satisfy the time-independent Heisenberg equation are independent in the sense that they are completely decoupled from one another. The energies of these operators describe the electronic structure of the system and can be used to determine energies of interacting many electron states. This is illustrated with a calculation of the gap in a Hubbard model for a cubic crystal of s-electrons.