Sometimes, there is an absolute limit on the number of terms an officeholder can serve, while, in other cases, the restrictions are merely on the number of consecutive terms.
For example, Maxwell's Equations would always be capitalized, while quantum mechanics is usually un-capitalized. I searched half a dozen sites for an answer to this but found no clue about a rule. So go either way that makes you happy, but (most of all) be consistent.
Quantum electrodynamics, commonly referred to as QED, is a quantum field theory of the electromagnetic force. Taking the example of the force between two electrons, the classical theory of electromagnetism would describe it as arising from the electric field produced by each electron at the position of the other.