I don't get it. Do you have a simpler way to explain what the term "self-coupled" means in this context. What are the alternatives to being "self-coupled"? Did you mean to say that the force is constant with distance or proportional to distance. The former was the case I thought applied. Is the strong force proportional to distance? The strong force is proportional to distance, not constant with distance.
By "self-coupled", I mean that the strong force interacts via the strong force. Imagine what optics would be like, if every photon carried an electromagnetic charge.
The strong force is proportional to distance, not constant with distance.
I anticipate that there might be some ambiguity in this quote. If we take the Cornell potential for the Quark-Antiquark in QCD it is V = Ar for "large" r (that is greater than 1 fm = 10 to minus 15 m) in addition to this there is a Coulumb term that we can skip here. This leads to quark confinement, since the string tension, A = 0.85 GeV/fm (=1.4kN~ 15 tons!), means that the string will always break and create quark-antiquark pairs if one tries to separate strongly interacting particles. i.e. the quarks are confined.
This is a phenomenological potential and the string part is not, as yet, derivable from the fundamental theory of QCD, although numerical calculations and plausibility arguments suggest that QCD is in agreement with the observations. i.e. the Quark-Antiquark potential is linear for large r (>1fm). Other potentials are as well used to describe this but the Cornell potential seems both to be simple and give good results.
The force is the derivative of the potential, thus the quote should be
The strong force potential is proportional to distance and the strong force force is constant.
Thanks for inspiring me to check this.
Here is a nice presentation of QCD:
http://www.phys.cmu.edu/halld/talks/morningstar_col_2001.ppt Warning 3.5 MB!