M. Ruggieri

Chiral crossover, deconfinement, and quarkyonic matter within a Nambu-Jona-Lasinio model with the Polyakov loop

We study the interplay between the chiral and the deconfinement transitions, both at high temperature and high quark chemical potential, by a nonlocal Nambu-Jona-Lasinio model with the Polyakov loop in the mean field approximation and requiring neutrality of the ground state. We consider three forms of the effective potential of the Polyakov loop: two of them with a fixed deconfinement scale, cases I and II, and the third one with a {mu} dependent scale, case III. In cases I and II, at high chemical potential {mu} and low temperature T, the main contribution to the free energy is due to the Z(3)-neutral three-quark states, mimicking the quarkyonic phase of the large N{sub c} phase diagram. On the other hand, in case III the quarkyonic window is shrunk to a small region. Finally we comment on the relations of these results to lattice studies and on possible common prospects. We also briefly comment on the coexistence of quarkyonic and color superconductive phases.

Three flavor Nambu-Jona Lasinio model with Polyakov loop and competition with nuclear matter

We study the phase diagram of the three flavor Polyakov-Nambu-Jona-Lasinio (PNJL) model and, in particular, the interplay between chiral symmetry restoration and deconfinement crossover. We compute chiral condensates, quark densities, and the Polyakov loop at several values of temperature and chemical potential. Moreover we investigate on the role of the Polyakov loop dynamics in the transition from nuclear matter to quark matter.

Equilibrium sequences of nonrotating and rapidly rotating crystalline color-superconducting hybrid stars

The three-flavor crystalline color-superconducting (CCS) phase of quantum chromodynamics (QCD) is a candidate phase for the ground state of cold matter at moderate densities above the density of the deconfinement phase transition. Apart from being a superfluid, the CCS phase has properties of a solid, such as a lattice structure and a shear modulus, and hence the ability to sustain multipolar deformations in gravitational equilibrium. We construct equilibrium configurations of hybrid stars composed of nuclear matter at low, and CCS quark matter at high, densities. Phase equilibrium between these phases is possible only for rather stiff equations of state of nuclear matter and large couplings in the effective Nambu\char22{}Jona-Lasinio Lagrangian describing the CCS state. We identify a new branch of stable CCS hybrid stars within a broad range of central densities which, depending on the details of the equations of state, either bifurcate from the nuclear sequence of stars when the central density exceeds that of the deconfinement phase transition or form a new family of configurations separated from the purely nuclear sequence by an instability region. The maximum masses of our nonrotating hybrid configurations are consistent with the presently available astronomical bounds. The sequences of hybrid configurations that rotate near the mass-shedding limit are found to be more compact and thus support substantially larger spins than their same mass nuclear counterparts.

Chromomagnetic stability of the three flavor Larkin–Ovchinnikov–Fulde–Ferrell phase of QCD

Abstract We compute in the Ginzburg–Landau approximation the gluon Meissner masses for the Larkin–Ovchinnikov–Fulde–Ferrell (LOFF) phase of QCD with three flavors in the kinematical range where it is energetically favored. We find real Meissner masses and therefore chromomagnetic stability.

Electrical neutrality and pion modes in the two flavor Polyakov-Nambu-Jona-Lasinio model

We study the phase diagram and the pion modes in the electrically neutral two flavor Polyakov\char21{}Nambu\char21{}Jona-Lasinio model. One of the main results of this paper is that in the model with massive quarks, when electrical neutrality is required, pions do not condense in the ground state of the model: the isospin chemical potential

Enforced neutrality and color-flavor unlocking in the three-flavor Polyakov-loop Nambu-Jona-Lasinio model

{\ensuremath{\mu}}_{I}=\ensuremath{-}{\ensuremath{\mu}}_{e}/2

Effective gap equation for the inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrel superconductive phase

is always smaller than the value required for pion condensation to occur. Moreover we investigate on the pions and

Spinning supersymmetric Q balls

\ensuremath{\sigma}

Self-consistent evaluation of quark masses in three flavor crystalline color superconductivity

mass spectra. We find that the qualitative behavior of the masses resembles that obtained in the Nambu\char21{}Jona-Lasinio model. We close this paper by studying the intriguing possibility that bound states with the quantum numbers of the pions can be formed above the chiral phase transition.

Neutrality issue in the Polyakov-loop Nambu-Jona-Lasinio model

We study how the charge neutrality affects the phase structure of the three-flavor Polyakov-loop Nambu--Jona-Lasinio (PNJL) model. We point out that, within the conventional PNJL model at finite density, the color neutrality is missing because the Wilson line serves as an external colored field coupled to dynamical quarks. In this paper we heuristically assume that the model may still be applicable. To get color neutrality, one has then to allow nonvanishing color chemical potentials. We study how the quark matter phase diagram in