科研之友
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摘要
We investigate QCD at large mu/T by using Z(3)-symmetric SU(3) gauge theory, where mu is the quark-number chemical potential and T is temperature. We impose the flavor-dependent twist boundary condition on quarks in QCD. This QCD-like theory has the twist angle theta as a parameter, and agrees with QCD when theta = 0 and becomes symmetric when theta = 2 pi/3. For both QCD and the Z(3)-symmetric SU(3) gauge theory, the phase diagram is drawn in mu-T plane with the Polyakov-loop extended Nambu-Jona-Lasinio model. In the Z(3)-symmetric SU(3) gauge theory, the Polyakov loop phi is zero in the confined phase appearing at T less than or similar to 200 MeV and mu less than or similar to 300 MeV. The perfectly confined phase never coexists with the color superconducting (CSC) phase, since finite diquark condensate in the CSC phase breaks Z(3) symmetry and then makes f finite phi When mu greater than or similar to 300 MeV, the CSC phase is more stable than the perfectly confined phase at T less than or similar to 100 MeV. Meanwhile, the chiral symmetry can be broken in the perfectly confined phase, since the chiral condensate is Z(3) invariant. Consequently, the perfectly confined phase is divided into the perfectly confined phase without chiral symmetry restoration in a region of mu less than or similar to 300 MeV and T less than or similar to 200 MeV and the perfectly confined phase with chiral symmetry restoration in a region of mu greater than or similar to 300 MeV and 100 less than or similar to T less than or similar to 200 MeV. At low temperature, the basic phase structure of Z(3)-symmetric QCD-like theory remains in QCD. Properties of the sign problem in Z(3)-symmetric theory are also discussed. We discuss a numerical framework to evaluate observables at theta = 0 from those at theta = 2 pi/3.
- 出版日期2016-3-28
