Shima

The color charges and the electric ones are corresponding to two different spaces. The former is according to the interaction of quarks and gluons and the latter is due to the interaction of quarks and photon. Although we don't usually consider the electric interactions in the QCD lagrangian because the electromagnetic force is not strong, quarks carry both charges which are relating to two different symmetry groups: U(1)_{electromagnetism} and SU(3)_{color} both are local symmetries. A proton consists of two valence Up quarks (everyone with +2/3 electric charge) and one valence Down quark (with -1/3 electric charge). You can see that the proton charge is equal to +1.

There are 8 gluons which carry color and anti-color charges as the exchange particles for the strong forces. You can find some details here: http://en.wikipedia.org/wiki/Gluon

Thank you a lot for sharing your thoughts

Sorry I had a typo : E= J / sigma is true.

I guess that the quark matter is wholly color singlet and so stable, since the original baryon matter which converted to quark matter is colorless. But since a cooper pair of two quarks has a net color charge, some stability conditions must be imposed in a color superconducting phase. This is usually done by means of color chemical potentials (as the Lagrange multipliers), and as a result this phase is color singlet also. I don't know whether we need a long range interaction to have some kind of conductivity or a short one. To have a flow of charged particles (no matter what kind of charge we mean) the system must be in the weak interaction region. In the case of dense baryon matter where the nucleons overlap, the strong interaction is so weak that the quarks can flow freely, or jump from a nucleon to its neighboring nucleon. This may mean the color current. I think you want to remind us that the color force is short range and this is the reason why we can not excite the color conductivity with external tools. I agree with you, but I can make an analogy of the Ohm's law (( E=\sigma J, \sigma is the conductivity)) for the quark matter. To excite a color current we must impose an external Chromo-Electric field. But the main question left : What is this kind of gauge Variant electric field ? Is it measurable? How can we made it?

To Schrodinger's hat and questionposter, Thanks for your replies. I couldn't find anything about the " color resistivity " concept through the scientific articles and also in Wikipedia. Imagine that we have the definition of "color conductivity" with the flow of (colorful) quarks in a quark matter system. Now we should be able to describe something like insulators or conductors. What kind of interaction can oppose the quarks flow? Anyway I think these conceptions are not physically meaningful, whilst we don't have any gauge invariant quantity as the color resistivity or color current (which in color superconductors must be a supercurrent). Am I right?

Is Color Superconducting phase really superconductor? What would be the meaning of " Color Conductivity " or " Color Resistivity " there ?