Typically the CE is introduced as an alteration of the vacuum expectation value of the EM field. Usually papers which calculate the force use this EM field model. My question: The zero point energy should be a superposition of contributions from all field ground states, eg not just the EM field, but say, the Higgs field, the graviton etc. Does anyone know why the EM field is usually picked. Is this one the main contribution to the vacuum perhaps??