Hydrodynamics of a quark-gluon plasma undergoing a phase transition

We present a new method for solving the relativistic hydrodynamic equations. This method allows a simple and reliable numerical treatment of shock waves. We check its accuracy in one-dimensional problems for which analytical solutions are known. Then we apply it to a 3-dimensional calculation of the evolution of a quark-gluon plasma, assuming cylindrical symmetry and longitudinal boost invariance. We treat the hadronization as a first-order phase transition and study the effects of this phase transition on the final distributions of particles. In particular, we analyse the possible correlations between particle multiplicities and transverse momenta which might signal the occurrence of such a phase transition in heavy ion collisions.     

Effect of hadronic hard-core radius on the phase transition to an interacting quark-gluon plasma

The effect of volume corrections on the equations of state for the hadron gas by treating nucleons and antinucleons as hard-core particles or bags is studied. Its consequences on the critical values of temperatureT and chemical potential μ _B of the phase transition from a gas of finite sized hadrons to an interacting quark matter are explored.     

Bubble collisions in the cosmological quark-hadron phase transition

Assuming that a first-order QCD phase transition occured in the very early universe, we investigate the growth and collisions of hadron bubbles in the thin-wall approximation. We also discuss a mechanism of baryon number concentration.     

Axion oscillations and the quark-hadron phase transition

We consider the possibility that the quark-hadron phase transition occurs when the axion field passes through the minimum of its potential during its oscillation cycle. If this were to occur, the axion field would gain no energy from the associated increase in mass thus permitting the cosmological bound on the axion decay constant to be raised. However, we find that the probability of this happening is small.     

Constraints for critical temperature of the phase transition into the quark-gluon plasma

Low temperature of the phase transition into the quark-gluon plasma correspond to low values of the bag model constant and to absolutely stable strange quark matter. Some of the observed pulsars are identified quite reliably as neutron stars. If strange matter is stable, the central density of these pulsars is to be smaller that critical density of the phase transition into the nonstrange quark matter. The nonstrange quark matter being formed turns to more stable strange matter on a weak interaction timescale converting neutron stars into strange stars. The requirement of stability of old and newly born neutron stars is used to constrain the bag model constant and the critical temperature of the phase transition into the quark-gluon plasma at zero chemical potential.     

The phase transition to the quark-gluon plasma and its effect on hydrodynamic flow

It is shown that in ideal relativistic hydrodynamics a phase transition from hadron to quark and gluon degrees of freedom in the nuclear matter equation of state leads to a minimum in the excitation function of the transverse collective flow.     

Cosmological quark-hadron phase transition and formation of isothermal density fluctuations

The dynamical process of the cosmological quark-hadron phase transition is investigated under the assumption of a weakly first-order phase transition. In particular the characteristic mass of these nuggets is determined to be smaller than 10¹⁹ g, using a spatial correlation function of the trapped quark phase. Furthermore, the possibility of these nuggets being left as isothermal baryonic clouds with very high density (δϱ_b/ϱ_b ∼ 5.0×10¹²) after evaporation is pointed out, and its cosmological implications are discussed.     

Model of deconfinement phase transition in baryonic quark-gluon bag system

A model of phase transition between baryonic hadron and quark-gluon matter is elaborated. The spectrum of baryonic colourless bags is found. It is shown that the constraint of bag colourlessness is decisive for the phase transition to be realized.     

Scaling properties of hadron production in the Ising model for quark-hadron phase transition

Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory is reexamined in the Ising model, so that spatial fluctuations during the transition can be taken into account. Although the dimension of the physical system is 2, as will be argued, bothd=2 andd=4 Ising systems are studied, the latter being theoretically closer to the Ginzberg-Landau theory. The normalized factorial momentsF _q are used to quantify multiplicity fluctuations, and the scaling exponentν is used to characterize the scaling properties. It is found by simulation on the Ising lattice thatν becomes a function of the temperatureT nearT _c . The average value ofν over a range ofT<T _c agrees with the value of 1.3 derived analytically from the Ginzberg-Landau theory. Thus the implications of the mean-field theory are not invalidated by either the introduction of spatial fluctuations or the restriction to a 2D system.     

Spatially modulated phase in the holographic description of quark-gluon plasma

We present a string theory construction of a gravity dual of a spatially modulated phase. Our earlier work shows that the Chern-Simons term in the five-dimensional Maxwell theory destabilizes the Reissner-Nordstr?m black holes in anti-de Sitter space if the Chern-Simons coupling is sufficiently high. In this Letter, we show that a similar instability is realized on the world volume of 8-branes in the Sakai-Sugimoto model in the quark-gluon plasma phase. Our result suggests a new spatially modulated phase in quark-gluon plasma when the baryon density is above 0.8Nf fm(-3) at temperature 150 MeV.     

Effect of pre-existing baryon inhomogeneities on the dynamics of quark-hadron transition

Baryon number inhomogeneities may be generated during the epoch when the baryon asymmetry of the universe is produced, e.g. at the electroweak phase transition. These lumps will have a lower temperature than the background. Also the value ofT _c will be different in these regions. Since a first-order quark-hadron (Q–H) transition is susceptible to small changes in temperature, we investigate the effect of the presence of such baryonic lumps on the dynamics of the Q–H transition. We find that the phase transition is delayed in these lumps for significant overdensities. Consequently, we argue that baryon concentration in these regions grows by the end of the transition. We mention some models which may give rise to such high baryon overdensities before the Q–H transition.     

Mott effect and J/\psi dissociation at the quark-hadron phase transition

We investigate the in-medium modification of pseudoscalar and vector mesons in a QCD-motivated chiral quark model by solving the Dyson-Schwinger equations for quarks and mesons at finite temperature for a wide mass range of meson masses, from light ( , ) to open-charm (D, D ^*) states. At the chiral/deconfinement phase transition, the quark-antiquark bound states enter the continuum of unbound states and become broad resonances (hadronic Mott effect). We calculate the in-medium cross-sections for charmonium dissociation due to collisions with light hadrons in a chiral Lagrangian approach, and show that the D- and D ^*-meson spectral broadening lowers the threshold for charmonium dissociation by - and -mesons. This leads to a step-like enhancement in the reaction rate. We suggest that this mechanism for enhanced charmonium dissociation may be the physical mechanism underlying the anomalous suppression observed by NA50.Received: 30 September 2002, Published online: 22 October 2003PACS: 05.20.Dd Kinetic theory - 12.38.Mh Quark-gluon plasma - 14.40.-n Mesons - 25.75.Nq Quark deconfinement, quark-gluon plasma production, and phase transitions