Color-flavor locking

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Color-flavor locking (CFL) is a phenomenon that is expected to occur in ultra-high-density quark matter. The quarks form Cooper pairs, whose color properties are correlated with their flavor properties in a symmetric pattern. According to the standard model of particle physics, the color-flavor-locked phase is the highest density phase of three-flavor matter.

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[edit] Color-flavor-locked Cooper pairing

If each quark is represented as \psi^\alpha_i, with color index α taking values 1,2,3 corresponding to red, green, and blue, and flavor index i taking values 1,2,3 corresponding to up, down, and strange, then the color-flavor locked pattern of Cooper pairing is [1]

\langle \psi^\alpha_i C \gamma_5 \psi^\beta_j \rangle \propto \delta^\alpha_i\delta^\beta_j - \delta^\alpha_j\delta^\beta_i = \epsilon^{\alpha\beta A}\epsilon_{ij A}

This means that a Cooper pair of an up quark and a down quark must have colors red and green, and so on. This pairing pattern is special because it leaves a large unbroken symmetry group.

[edit] Physical properties

The CFL phase has several remarkable properties,

There are several variants of the CFL phase, representing distortions of the pairing structure in response to external stresses such as a difference between the mass of the strange quark and the mass of the up and down quarks.

[edit] Further reading

  • M. Alford, K. Rajagopal, T. Schäfer, A. Schmitt, "Color superconductivity in dense quark matter", arxiv:0709.4635, to be published in Reviews of Modern Physics.

[edit] References

  1. ^ M. Alford, K. Rajagopal and F. Wilczek, "QCD at Finite Baryon Density: Nucleon Droplets and Color Superconductivity" arxiv:hep-ph/9711395, published as Phys. Lett. B422, 247 (1998).