Pfhorrest wrote:My question for the physicists here is whether the unification of the electromagnetic and nuclear forces means that W and Z bosons and gluons are all just different kinds of excitations of the same field as photons, i.e. The electromagnetic field. Or are the fields themselves somehow split at lower energies? How does that work?
There is a single electroweak field, and photons, W bosons, and Z bosons are all excitations of that field. However, at low energies, we can treat it as being two different fields - the electromagnetic field and the weak field, with photons being excitations of the EM part and the W and Z of the weak part. It's kind of like how in classical E&M, there is a single electromagnetic field, but you can also talk sensibly about just the 'electric field' or just the 'magnetic field'.
But remember, the strong force is not unified with the electroweak in the Standard Model, so gluons are excitations of a different field. There are theories in which the strong and electroweak forces are unified, called Grand Unified Theories or GUTs, but so far we haven't seen direct evidence (like proton decay or supersymmetric particles) for any of them.
The next level beyond that is what is called a Theory of Everything, which would be a theory in which those three forces and gravity are all unified into a single field. Note, though, a difference between gravity and the strong force: in the case of the strong force, we do have a quantum theory of the force (QCD), it just isn't unified with the electroweak as a single field; whereas we don't have a separate quantum theory of gravity at all.
rmsgrey wrote:I'm not a physicist, but my understanding is that there isn't an electromagnetic field, but a fog of virtual photons that interact with charged particles and each other, producing much the same effects as the classical EM field - at short ranges, you encounter more of the virtual photons, so the effects are stronger, producing the inverse-square effect. So when photons split off from other exchange particles, the "fields" also become distinct.
Actually, there are fundamental fields. In a quantum field theory, each particle is an excitation of a quantized field. One of the slightly confusing things about modern physics is that you can switch back and forth between thinking of things as particles and as fields.