Roles of axial anomaly on neutral quark matter with color superconducting phase

Abstract

We investigate effects of the axial anomaly term with a chiral-diquark coupling on the phase diagram within a two-plus-one-flavor Nambu-Jona-Lasinio (NJL) model under the charge-neutrality and $\beta$-equilibrium constraints. We find that when such constraints are imposed, the new anomaly term plays a quite similar role as the vector interaction does on the phase diagram, which the present authors clarified in a previous work. Thus, there appear several types of phase structures with multiple critical points at low temperature $T$, although the phase diagrams with intermediate-$T$ critical point(s) are never realized without these constraints even within the same model Lagrangian. This drastic change is attributed to an enhanced interplay between the chiral and diquark condensates due to the anomaly term at finite temperature; the u-d diquark coupling is strengthened by the relatively large chiral condensate of the strange quark through the anomaly term, which in turn definitely leads to the abnormal behavior of the diquark condensate at finite $T$, inherent to the asymmetric quark matter. We note that the critical point from which the crossover region extends to zero temperature appears only when the strength of the vector interaction is larger than a critical value. We also show that the chromomagnetic instability of the neutral asymmetric homogenous two-flavor color superconducting(2CSC) phase is suppressed and can be even completely cured by the enhanced diquark coupling due to the anomaly term and/or by the vector interaction.

15 pages, 5 figures, typos corrected, new references and some statements added

References in corpus (15)

• Color superconductivity in dense quark matter
• The QCD phase diagram at nonzero quark density
• Inhomogeneous phases in the Nambu-Jona-Lasino and quark-meson model
• New Critical Point Induced by the Axial Anomaly in Dense QCD
• 2+1 Flavor Polyakov--Nambu--Jona-Lasinio Model at Finite Temperature and Nonzero Chemical Potential
• Phase structure, collective modes, and the axial anomaly in dense QCD
• Vector interaction, charge neutrality and multiple chiral critical point structures
• Multiple Critical Points in Effective Quark Models
• Number of the QCD critical points with neutral color superconductivity
• The axial anomaly and the phases of dense QCD
• Role of two-flavor color superconductor pairing in a three-flavor Nambu--Jona-Lasinio model with axial anomaly
• Stable gapless superconductivity at strong coupling
• Gluonic phases, vector condensates, and exotic hadrons in dense QCD
• Chromomagnetic instability in two-flavor quark matter at nonzero temperature
• $X$ Meson aka ${\eta }^{\prime }$ and Kobayashi-Maskawa-'t Hooft Six-quark Vertex -- $U(1{)}_A$ Anomaly and Generalized Nambu-Jona-Lasinio Model --