Narrow Results

We study the nature of charm degrees of freedom near the chiral crossover based on lattice QCD calculations of the second and fourth-order cumulants of charm fluctuations, and their correlations with net baryon number, electric charge, and strangeness fluctuations. We show that below the chiral crossover temperature, $T_{pc}$, the thermodynamics of charm can be very well understood in terms of charmed hadrons. We present evidence that above $T_{pc}$, however, charm quark-like excitations emerge as new degrees of freedom contributing to the partial charm pressure. Nonetheless, up to temperatures as high as 175MeV, charmed hadron-like excitations significantly contribute to the partial charm pressure.

The (1+1)-dimensional bosonized Schwinger model with a generalized gauge-invariant regularization has been studied in a noncommutative scenario. The original commutative model with the indicated regularization revealed the transition from confinement to deconfinement of the fermion.¹⁰ We show that though the introduction of spacetime noncommutativity gives rise to new features in the confinement scenario, it does not affect the deconfining limit.

We review recent progress in lattice QCD at nonzero temperature with emphasis on the calculations of equation of state and the properties of heavy quark–anti-quark pairs at high temperatures. We also briefly discuss the deconfinement and chiral symmetry restoring aspects of the QCD transition at finite temperature.

We consider collective effects in pp-collisions at the LHC energies related to presence of the large orbital angular momentum in the initial state and role of this orbital momentum in the elliptic flow behavior.

We briefly discuss the possible decoherence observed at the LHC emphasizing that the value of the average transverse momentum at can be interpreted as a manifestation of the deviation from the mechanism of the transient state of rotating matter.

Topological ordered phases are gapped states of matter that are characterized by non-local entanglement in their ground state wave functions instead of a local order parameter. In this paper, we review some of the basic results on the entanglement structure of topologically ordered phases. In particular, we focus on the notion and uses of "topological entanglement entropy" in two and higher dimensions, and also briefly review the relation between entanglement spectrum and the spectrum of the physical edge states for chiral topological states. Furthermore, we discuss a curvature expansion for the entanglement entropy which sharpens the nonlocality of topological entanglement entropy.

We discuss a possible explanation of the double-ridge observation in pPb-collisions at the LHC emphasizing that this double structure in the two-particle correlation function can result from the rotation of the transient state of matter.

In this paper, we use a separable gluon propagator model to study the Quantum Chromodynamics (QCD) phase transition at finite temperature and chiral chemical potential. Using this model, we calculate the quark condensate and the chiral susceptibility at finite temperature and chiral chemical potential both in the chiral limit and at finite current quark mass. Based on these, we obtain the QCD phase diagram in the μ₅-T plane.

Following Aharony et al., we analyze the deconfining phase transition in a SU(∞) gauge theory in mean field approximation. The Gross–Witten model emerges as an "ultra"-critical point for deconfinement: while thermodynamically of first order, masses vanish, asymmetrically, at the transition. Potentials for N = 3 are also shown.

Using an effective model for the quantum chromodynamics we study the color deconfinement effects on the chiral transition. We argue that effects of the color deconfinement are important in the chiral limit. As an example we consider in detail the case of two flavors of massless quarks and find that the corresponding chiral transition can be of first order due to the effects of color deconfinement. This is contrary to the conventional expectations that 2-flavor chiral transition is of second order.

In recent papers, a model of a two-sheeted space–time M₄ ×Z₂ was introduced and the quantum dynamics of massive fermions was studied in this framework. In the present study, we show that the physical predictions of the model are perfectly consistent with observations and most importantly, it can solve the puzzling problem of the four-dimensional localization of the fermion species in multidimensional space–times. It is demonstrated that fermion localization on the sheets arises from the combination of the discrete bulk structure and environmental interactions. The mechanism described in this paper can be seen as an alternative to the domain wall localization arising in continuous five-dimensional space–times. Although tightly constrained, motions between the sheets are, however, not completely prohibited. As an illustration, a resonant mechanism through which fermion oscillations between the sheets might occur is described.

Highlights from Brookhaven National Laboratory (BNL) and experiments at the BNL Relativistic Heavy Ion Collider (RHIC) are presented for the years 2011–2013. This review is a combination of lectures which discussed the latest results each year at a three year celebration of the 50th anniversary of the International School of Subnuclear Physics in Erice, Sicily, Italy. Since the first collisions in the year 2000, RHIC has provided nucleus–nucleus and polarized proton–proton collisions over a range of nucleon–nucleon center-of-mass energies from 7.7 GeV to 510 GeV with nuclei from deuterium to uranium, most often gold. The objective was the discovery of the Quark Gluon Plasma, which was achieved, and the measurement of its properties, which were much different than expected, namely a "perfect fluid" of quarks and gluons with their color charges exposed rather than a gas. Topics including quenching of light and heavy quarks at large transverse momentum, thermal photons, search for a QCD critical point as well as measurements of collective flow, two-particle correlations and J/Ψ suppression are presented. During this period, results from the first and subsequent heavy ion measurements at the Large Hadron Collider (LHC) at CERN became available. These confirmed and extended the RHIC discoveries and have led to ideas for new and improved measurements.

We investigate Abelian and monopole contributions to spatial string tension in the deconfined phase of finite temperature SU(2) gauge theory without imposing any gauge fixing conditions. Lattice calculations of non-Abelian and Abelian spatial string tensions from the Wilson action at gauge coupling $\beta =2.74$ and lattice volume $24^3\times N_t$$(N_t=\{24,8,6,4,2\})$ show that these string tensions agree with each other within error bars at any adopted value of $N_t$, which implies Abelian dominance. From measurements of non-Abelian, Abelian and monopole forces that arise from the corresponding spatial string tension, furthermore, we find the tendency that the monopole contribution to the spatial string tension can be almost as large as the non-Abelian and Abelian ones. The temperature dependence of the calculated non-Abelian and Abelian spatial string tensions allows us to conclude that the concept of dimensional reduction holds both for non-Abelian and Abelian sectors at temperatures higher than twice the critical temperature.

In addition to the gauge charges, a new charge degree of freedom is identified in the deconfined phase in the lattice Ising gauge theory. While applying to the hydrogen-bonded ferroelectrics, the new charge is essentially the electric charge, leading to the divergent dielectric susceptibility. The new degree of freedom paves an experimentally accessible way to identify the deconfined phase in the lattice Ising gauge theory.

Results on bulk particle observables, from a hybrid approach to relativistic heavy-ion collisions, are presented over a wide range of beam energies from E_lab = 2 - 160 A GeV. In this model a hydrodynamic phase is integrated into a hadronic transport model. This setup enables us to study the effect of the equation of state of hot and dense nuclear matter on different observables from heavy-ion collider experiments. In addition we present a study on density fluctuations at a phase transition in the framework of chiral fluid dynamics.

Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this work we present a selection of reaction observables in dissipative collisions particularly sensitive to the isovector part of the interaction, i.e.to the symmetry term of the nuclear Equation of State (EoS). At low energies the behavior of the symmetry energy around saturation influences dissipation and fragment production mechanisms. We will first discuss the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation during the charge equilibration in fusion and deep-inelastic collisions. Important Iso - EOS are stressed. Reactions induced by unstable ¹³²Sn beams appear to be very promising tools to test the sub-saturation Isovector EoS. New Isospin sensitive observables are also presented for deep-inelastic, fragmentation collisions and Isospin equilibration measurements (Imbalance Ratios).

The high density symmetry term can be derived from isospin effects on heavy ion reactions at relativistic energies (few AGeV range), that can even allow a "direct" study of the covariant structure of the isovector interaction in the hadron medium. Rather sensitive observables are proposed from collective flows and from pion/kaon production. The possibility of the transition to a mixed hadron-quark phase, at high baryon and isospin density, is finally suggested. Some signatures could come from an expected "neutron trapping" effect. The importance of studying violent collisions with radioactive beams from low to relativistic energies is finally stressed.

Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. High Energy Collisions are studied in order to access nuclear matter properties at high density. Particular attention is devoted to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent covariant transport simulations built on effective field theories we are testing isospin observables ranging from nucleon/cluster emissions, collective flows (in particular the elliptic, squeeze out, part) and meson production. The possibility to shed light on the controversial neutron/proton effective mass splitting in asymmetric matter is also stressed.

The "symmetry" repulsion at high baryon density will also lead to an "earlier" hadron-deconfinement transition in n-rich matter. The phase transition of hadronic to quark matter at high baryon and isospin density is analyzed. Nonlinear relativistic mean field models are used to describe hadronic matter, and the MIT bag model is adopted for quark matter. The boundaries of the mixed phase and the related critical points for symmetric and asymmetric matter are obtained. Isospin effects appear to be rather significant. The binodal transition line of the (T,ρ_B) diagram is lowered in a region accessible to heavy ion collisions in the energy range of the new planned FAIR/NICA facilities. Some observable effects of the mixed phase are suggested, in particular a neutron distillation mechanism. Theoretically a very important problem appears to be the suitable treatment of the isovector part of the interaction in effective QCD lagrangian approaches.

The relative multiplicities for hadron production in different high energy collisions are in general well described by an ideal gas of all hadronic resonances, except that under certain conditions, strange particle rates are systematically reduced. We show that the suppression factor ${\gamma }_s$, accounting for reduced strange particle rates in $pp$, $pA$ and $AA$ collisions at different collision energies, becomes a universal function when expressed in terms of the initial entropy density $s_0$ or the initial temperature $T$ of the produced thermal medium. It is found that ${\gamma }_s$ increases from about 0.5 to 1.0 in a narrow temperature range around the quark–hadron transition temperature $T_c\simeq 160$MeV. Strangeness suppression thus disappears with the onset of color deconfinement; subsequently, full equilibrium resonance gas behavior is attained.

Recent extensive data from the beam energy scan of the STAR collaboration at BNL-RHIC provide the basis for a detailed update for the universal behavior of the strangeness suppression factor ${\gamma }_s$ as function of the initial entropy density as proposed in our recent paper (P. Castorina, S Plumari and H. Satz, Int. J. Mod. Phys. E26 (2017) 1750081, arXiv:1709.02706 [nucl-th]).

In this talk I summarize our current understanding of quarkonium states above deconfinement based on phenomenological and lattice QCD studies.