The axial anomaly and the phases of dense QCD

Abstract

The QCD axial anomaly, by coupling the chiral condensate and BCS pairing fields of quarks in dense matter, leads to a new critical point in the QCD phase diagram [1, 2], which at sufficiently low temperature may terminate the line of phase transitions between chirally broken hadronic matter and color superconducting quark matter. The critical point indicates that matter at low temperature should cross over smoothly from the hadronic to the quark phase, as suggested earlier on the basis of symmetry. We review here the arguments, based on a general Ginzburg–Landau effective Lagrangian, for the existence of the new critical point as well as discuss possible connections between the QCD phase structure and the BEC–BCS crossover in ultracold trapped atomic fermion systems at unitarity and implications for the presence of quark matter in neutron stars.

The QCD Phase Diagram from Chiral Approaches

“…This is a realization of hadron-quark continuity [10] in the Ginzburg-Landau description. Close similarities to the BEC-BCS crossover in ultra-cold atomic systems are also suggestive [11]. …”

Bulk and shear viscosities for the Gribov-Zwanziger plasma

“…The arguments presented in [1,2] suggest that we can use the standard kinetic equation in the relaxation-time approximation (RTA) of the form [18][19][20] …”

Quantum liquids resulting from quark systems with four-quark interaction

“…Let us also remember that the pressure of the vacuum for the NJL model was estimated in [9][10][11] to be 40-50 MeV/fm 3 , which is quite consistent with that obtained in the bag model. It was also demonstrated that there is a region of instability within a certain interval of the Fermi momenta generated by the anomalous behavior of pressure d P/dn < 0 (see also [33][34][35][36]). Figure 10 displays fragments of isotherms shown in Fig.…”

“…If we know the liquid density we obtain the Fermi momentum (P F = 346 MeV) from (35). Applying the identities (37), (38) we have for the particular case b = 0, c = 0 the results C 2 s = 25.3, C 2 v = −0.471, i.e.…”