Comment on Dark Matter Capture in Neutron Stars with Exotic Phases

In this short paper, we argue the issue on dark matter capture in neutron stars. After summarizing the whole scenario and the introduction of previous studies along this line, we propose some potentially important effects due to the appearance of exotic phases such as neutron superfluidity, meson condensation and quark superconductivity. Those effects might be sizable and alter the previous results.

Renormalized vs Nonrenormalized Chiral Transition in a Magnetic Background

We study analytically the chiral phase transition for hot quark matter in presence of a strong magnetic background, focusing on the existence of a critical point at zero baryon chemical potential and nonzero magnetic field. We build up a Ginzburg-Landau effective potential for the chiral condensate at finite temperature, computing the coefficients of the expansion within a chiral quark-meson model. Our conclusion is that the existence of the critical point at finite $bm B$ is very sensitive to the way the ultraviolet divergences of the model are treated. In particular, we find that after renormalization, no chiral critical point is present in the phase diagram. On the other hand, such a critical point there exists when the ultraviolet divergences are not removed by a proper renormalization of the thermodynamic potential.

The Critical End Point of Quantum Chromodynamics Detected by Chirally Imbalanced Quark Matter

We suggest the idea, supported by concrete calculations within chiral models, that the critical endpoint of the phase diagram of Quantum Chromodynamics with three colors can be detected, by means of Lattice simulations of grand-canonical ensembles with a chiral chemical potential, $mu_5$, conjugated to chiral charge density. In fact, we show that a continuation of the critical endpoint of the phase diagram of Quantum Chromodynamics at finite chemical potential, $mu$, to a critical end point in the temperature-chiral chemical potential plane, is possible. This study paves the way of the mapping of the phases of Quantum Chromodynamics at finite $mu$, by means of the phases of a fictitious theory in which $mu$ is replaced by $mu_5$.

Magnetic Susceptibility of the Quark Condensate and Polarization from Chiral Models

We compute the magnetic susceptibility of the quark condensate and the polarization of quarks at zero temperature and in a uniform magnetic background. Our theoretical framework consists of two chiral models that allow to treat self-consistently the spontaneous breaking of chiral symmetry: the linear $sigma-$model coupled to quarks, dubbed quark-meson model, and the Nambu-Jona-Lasinio model. We also perform analytic estimates of the same quantities within the renormalized quark-meson model, both in the regimes of weak and strong fields. Our numerical results are in agreement with the recent literature; moreover, we confirm previous Lattice findings, related to the saturation of the polarization at large fields.

Chiral symmetry restoration and deconfinement in strong magnetic fields

I review recent results obtained within chiral effective models, on the phase structure of hot quark matter in a strong magnetic background. After a brief introduction, I focus on the results obtained within two chiral models improved with the Polyakov loop. The models differ for the content of interactions, but both of them are tuned to reproduce Lattice QCD thermodynamics at zero and imaginary chemical potential. One of them takes into account an explicit Polyakov loop dependence of the coupling; the other one neglects this contribution, but takes into account multi-quark interactions. A comparison between the phase diagrams of the two models is presented.

Collective modes in the color flavor locked phase

We study the low energy effective action for the collective modes of the color flavor locked phase of QCD. This phase of matter has long been known to be a superfluid because by picking a phase its order parameter breaks the quark-number $U(1)_B$ symmetry spontaneously. We consider the modes describing fluctuations in the magnitude of the condensate, namely the Higgs mode, and in the phase of the condensate, namely the Nambu-Goldstone (or Anderson-Bogoliubov) mode associated with the breaking of $U(1)_B$. By employing as microscopic theory the Nambu-Jona Lasinio model, we reproduce known results for the Lagrangian of the Nambu-Goldstone field to the leading order in the chemical potential and extend such results evaluating corrections due to the gap parameter. Moreover, we determine the interaction terms between the Higgs and the Nambu-Goldstone field. This study paves the way for a more reliable study of various dissipative processes in rotating compact stars with a quark matter core in the color flavor locked phase.

Phase diagram of hot quark matter under magnetic field

In this talk, I review the computation of the phase diagram of hot quark matter in strong magnetic field, at zero baryon density, within an effective model of Quantum Chromodynamics.

Dressed Polyakov loop and phase diagram of hot quark matter under magnetic field

We evaluate the dressed Polyakov loop for hot quark matter in strong magnetic field. To compute the finite temperature effective potential, we use the Polyakov extended Nambu-Jona Lasinio model with eight-quark interactions taken into account. The bare quark mass is adjusted in order to reproduce the physical value of the vacuum pion mass. Our results show that the dressed Polyakov loop is very sensitive to the strenght of the magnetic field, and it is capable to capture both the deconfinement crossover and the chiral crossover. Besides, we compute self-consistently the phase diagram of the model. We find a tiny split of the two aforementioned crossovers as the strength of the magnetic field is increased. Concretely, for the largest value of magnetic field investigated here, $eB=19 m_pi^2$, the split is of the order of $10%$. A qualitative comparison with other effective models and recent Lattice results is also performed.

Non-topological Domain Walls in a Model with Broken Supersymmetry

We study non-topological, charged planar walls (Q-walls) in the context of a particle physics model with supersymmetry broken by low-energy gauge mediation. Analytical properties are derived within the flat-potential approximation for the flat-direction raising potential, while a numerical study is performed using the full two-loop supersymmetric potential. We analyze the energetics of finite-size Q-walls and compare them to Q-balls, non-topological solitons possessing spherical symmetry and arising in the same supersymmetric model. This allow us to draw a phase diagram in the charge-transverse length plane, which shows a region where Q-wall solutions are more stable than Q-balls.

Dielectric correction to the Chiral Magnetic Effect

We derive an electric current density $j_{em}$ in the presence of a magnetic field $B$ and a chiral chemical potential $mu_5$. We show that $j_{em}$ has not only the anomaly-induced term $propto mu_5 B$ (i.e. Chiral Magnetic Effect) but also a non-anomalous correction which comes from interaction effects and expressed in terms of the susceptibility. We find the correction characteristically dependent on the number of quark flavors. The numerically estimated correction turns out to be a minor effect on heavy-ion collisions but can be tested by the lattice QCD simulation.