Converting mixed phase into hadrons

We study the transition of expanding QCD matter from the mixed to the hadronic phase and its effects on the transverse flow of hadrons. In the transverse expansion a rarefaction shock develops. Physically allowed values of the energy densities and flow velocities at the shock front are determined. The transverse rapidity of the flow is determined as a function of pion multiplicity. We show that the lifetime of the mixed phase is by and large determined by the longitudinal expansion and is not appreciably affected by the transverse rarefaction, thus making long lifetimes for the entire system possible.     

FeMnNi合金冲击相变与卸载逆相变历程研究

采用VISAR测试技术,将正向加载和逆向加载实验相结合,研究了不同加载压力下FeMnNi合金的冲击相变和卸载逆相变历程.结果表明:冲击加载压力与冲击相变阈值之差小于逆相变阈值时,即0＜σp-σt＜σn,FeMnNi合金发生α→ε相变,加载段呈现弹性波、塑性波和相变波三波结构,塑性波在自由面反射稀疏波使FeMnNi合金完...     

Field-theoretical treatment of the liquid-vapor phase transition in nuclear systems

The liquid-vapor phase transition in hot nuclear matter is investigated in a field-theoretical approach employing euclidean-space (imaginary time) path-integral techniques. This approach allows us to study the nucleation due to both quantum and thermodynamic fluctuations. The bubbles of the new phase appear as instanton solutions of the euclidean-space field equations. The critical bubble sizes and associated transition probabilities are calculated. We examine the temperature and density values for which a phase transition may develop in hot nuclear matter produced in the course of a heavy-ion reaction.     

Density dependence of nucleon radius and mass in the global color symmetry model of QCD with a sophisticated effective gluon propagator

Making use of the global color symmetry model (GCM) at finite chemical potential and with a sophisticated effective gluon propagator, the density dependence of the bag constant, the total energy and the radius of a nucleon in nuclear matter is investigated. A maximal nuclear matter density for the existence of the bag with three quarks confined within is given as about 8 times the normal nuclear matter density. The calculated results indicate that, before the maximal density is reached, the bag constant and the total energy of a nucleon decrease, and the radius of a nucleon increases, with the increasing of the nuclear matter density. As the maximal nuclear matter density is reached, the mass and the bag constant of the nucleon vanish and the radius becomes infinite suddenly. It manifests that a phase transition from nucleons to quarks takes place. Meanwhile, shortening the interaction range among quarks can induce the phase transition to happen easier.     

FeMnNi合金高压加卸载历程测量和相变层裂分析

 采用VISAR和X光联合测试技术,利用等厚对称和逆向碰撞法测量了FeMnNi合金高压加卸载历程和相变层裂信息。加载过程中,FeMnNi合金样品发生α→ε相转变,相变波速大于塑性波速,在撞击面上相变波与塑性波合并成单一相变波;卸载过程中,FeMnNi合金样品可能发生了逆相变,形成了除合并相变波在自由面反射中心稀疏波R以外的两道卸载波S1和S2。等厚对称高压加载下,FeMnNi合金样品发生了二次层裂。分析中心稀疏波R、卸载波S1和S2在样品中的传播作用过程,发现样品发生冲击相变和卸载逆转变是导致其等厚对称高压加载下发生二次层裂行为的主要原因。     

冲击加载下FeMnNi合金相变和层裂特性实验研究(英文)

采用激光速度干涉仪(VISAR)、X射线衍射(XRD)和扫描电镜(SEM)联合测试技术,利用等厚对称加载和逆向加载实验,研究了Fe MnNi合金的冲击相变和层裂行为。结果发现:加载压力大于6.5 GPa时,Fe MnNi合金样品发生α→ε相变;中心稀疏波的卸载作用使内压力降至4~5 GPa时,Fe MnNi合金样品发生ε→α逆相变,并伴有卸载稀疏冲击波形成。分析Fe MnNi合金样品中塑性波、相变波、稀疏波和稀疏冲击波的传播作用过程,发现加载压力大于其相变应力时,等厚对称加载下Fe MnNi合金存在产生层裂行为的物理机制。     

Soliton and multiphonon microdynamics of thermal conductivity of plutonium and uranium in the temperature range of martensitic phase transitions

The microdynamics of nonlinear crystal lattice vibrations of Pu and U at temperatures of martensitic phase transitions has been studied. Using the Lenard-Jones potential, the dynamic equations are solved when the energy is transferred by solitons. The synchronism of solitons and the energy flux peaks demonstrates the staccato-effect. The temperature dependences of the thermal conductivity have maxima at the phase transitions. A spectral analysis shows that the main heat transfer is provided by rarefaction solitons. Upon the martensitic transition, the spectral density is transformed with “ignition” of the high-frequency region. The spectral density demonstrates maxima of the quasi-biphonon type.     

Experimental investigation of adiabatic evaporation waves in superheated refrigerants

Propagation of adiabatic evaporation waves arising while refrigerants R-11 rapidly transit to metastable state due to depressurization in the rarefaction wave is experimentally investigated. New regularities of the interphase surface dynamics and the influence of interphase heat and mass transfer in propagation of adiabatic evaporation waves are obtained. It has been found that the phase transition in metastable liquid occurs in the conditions of developing multiscale turbulence in liquid and vapor phases under dynamic action of a vapor flow on the interphase surface and convective heat supply to the zone of high-intensity phase transition. The surface phase transition was visualized by a rapid video camera, its pulsating character is revealed and its properties are determined.     

Phase transition to hyperon matter in neutron stars

Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R approximately equal 8 km.     

Nuclear matter at high density: Phase transitions,multiquark states,and supernova outbursts

Phase transition from hadronic matter to quark-gluon matter is discussed for various regimes of temperature and baryon number density. For small and medium densities, the phase transition is accurately described in the framework of the Field Correlation Method, whereas at high density predictions are less certain and leave room for the phenomenological models. We study formation of multiquark states (MQS) at zero temperature and high density. Relevant MQS components of the nuclear matter can be described using a previously developed formalism of the quark compound bags (QCB). Partialwave analysis of nucleon-nucleon scattering indicates the existence of 6QS which manifest themselves as poles of P matrix. In the framework of the QCB model, we formulate a self-consistent system of coupled equations for the nucleon and 6QS propagators in nuclear matter and the G matrix. The approach provides a link between high-density nuclear matter with the MQS components and the cumulative effect observed in reactions on the nuclei, which requires the admixture of MQS in the wave functions of nuclei kinematically. 6QS determines the natural scale of the density for a possible phase transition into theMQS phase of nuclear matter. Such a phase transition can lead to dynamic instability of newly born protoneutron stars and dramatically affect the dynamics of supernovae. Numerical simulations show that the phase transition may be a good remedy for the triggering supernova explosions in the spherically symmetric supernovamodels. A specific signature of the phase transition is an additional neutrino peak in the neutrino light curve. For a Galactic core-collapse supernova, such a peak could be resolved by the present neutrino detectors. The possibility of extracting the parameters of the phase of transition from observation of the neutrino signal is discussed also.     

Effects of Density-Dependent Quark Mass on Phase Diagram of Color-Flavor-Locked Quark Matter

Considering the density dependence of quark mass, we investigate the phase transition between the (unpaired) strange quark matter and the color-flavor-locked matter, which are supposed to be two candidates for the ground state of strongly interacting matter. We find that if the current mass of strange quark ms is small, the strange quark matter remains stable unless the baryon density is very high. If ms is large, the phase transition from the strange quark matter to the color-flavor-locked matter in particular to its gapless phase is found to be different from the results predicted by previous works. A complicated phase diagram of three-flavor quark matter is presented, in which the color-flavor-locked phase region is suppressed for moderate densities.     

Relativistic shocks in the systems containing domains with anomalous equation of state and quark baryonic matter hadronization

Theoretical basis for general stability criterion of relativistic shocks in baryonic matter is proposed. Different formulations of shock mechanical stability are considered and applied to the analysis of rarefaction shock hadronization transition.     

Quark matter formation in dense stellar objects

It is expected that at very large densities and/or temperatures a quark-hadron phase transition takes place. Lattice QCD calculations at zero baryon density indicate that the transition occurs at T _c ∼ 150–170 MeV. The transition is likely to be second order or a cross over phenomenon. Although not much is known about the density at which the phase transition takes place at small temperatures, it is expected to occur around the nuclear densities of few times nuclear matter density. Also, there is a strong reason to believe that the quark matter formed after the phase transition is in colour superconducting phase. The matter densities in the interior of neutron stars being larger than the nuclear matter density, the neutron star cores may possibly consist of quark matter which may be formed during the collapse of supernova. Starting with the assumption that the quark matter, when formed consists of predominantly u and d quarks, we consider the evolution of s quarks by weak interactions in the present work. The reaction rates and time required to reach the chemical equilibrium are computed here. Our calculations show that the chemical equilibrium is reached in about 10⁻⁷ seconds. Further more during the equilibration process enormous amont of energy is released and copious numbers of neutrinos are produced. Implications of these on the evolution of supernovae will be discussed.     

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.     

Relativistic shocks in the systems containing domains with anomalous equation of state and quark baryonic matter hadronization

Theoretical basis for general stability criterion of relativistic shocks in baryonic matter is proposed. Different formulations of shock mechanical stability are considered and applied to the analysis of rarefaction shock hadronization transition.     

Phase transition and the nucleon as a soliton in the Nambu-Jona-Lasinio model at finite temperature and density

We study some bulk thermodynamical characteristics, meson properties and the nucleon as a baryon-number-one soliton in hot quark matter in the NJL model as well as in hot nucleon matter in a hybrid NJL model in which the Dirac sea of quarks is combined with a Fermi sea of nucleons. In both cases, working in the mean-field approximation, we find a chiral phase transition from the Goldstone to the Wigner phase. At finite density the chiral order parameter and the constituent quark mass have a non-monotonic temperature dependence — at finite temperatures not close to the critical one they are less affected than in cold matter. Whereas quark matter is rather soft against thermal fluctuations and the corresponding chiral phase transition is smooth, nucleon matter is much stiffer and the chiral phase transition is very sharp. The thermodynamical variables show large discontinuities which is an indication for a first-order phase transition. We solve the B = 1 solitonic sector of the NJL model in the presence of external hot quark and nucleon media. In the hot medium at intermediate temperature the soliton is more bound and less swelled than in the case of cold matter. At some critical temperature, which for nucleon matter coincides with the critical temperature for the chiral phase transition, we find no more a localized solution. According to this model scenario one should expect a sharp phase transition from nucleon to quark matter.     

Particle clustering and Mott transition in nuclear matter at finite temperature (II): Self-consistent ladder Hartree-Fock approximation and model calculations for cluster abundances and the phase diagram

Hot nuclear matter is described in terms of a quantum statistical approach. A self-consistent ladder Hartree-Fock approximation is derived in order to achieve a simultaneous treatment of free nucleons, douterons and higher clusters. In this approximation the effect of the correlated medium on the cluster abundances is studied. The Mott mechanism is pointed out in which clusters are destructed for densities beyond the Mott density. Cluster abundances and a phase diagram are calculated by means of a model calculation based on a simplified Skyrme interaction. The role of the higher clusters in calculating the phase diagram is investigated. The possible existence of a first-order phase transition in hot nuclear matter is discussed.     

Rarefaction wave and gravitational equilibrium in a two-phase liquid-vapor medium

The problems studied in this paper involve the action of laser radiation or a particle beam on a condensed material. Such an interaction produces a hot corona, and the recoil momentum accelerates the cold matter. In the coordinate frame tied to the accelerated target, the acceleration is equivalent to the acceleration of gravity. For this reason, the density distribution ρ is hydrostatic in the zeroth approximation. In this paper the structure of such a flow is studied for a two-phase equation of state. It is shown that instead of a power-law density profile, which obtains for a constant specific-heat ratio, a complicated distribution containing a region with a sharp variation of ρ arises. Similar characteristics of the density profile arise with isochoric heating of matter by an ultrashort laser pulse and the subsequent expansion of the heated layer. The formation of a rarefaction wave and the interaction of oppositely propagating rarefaction waves in a two-phase medium are studied. It is very important to take account of the two-phase nature of the material, since conditions (p _a ∼1 Mbar) are often realized under which the foil material comes after expansion into the two-phase region of the phase diagram. Zh. éksp. Teor. Fiz. 115, 2091–2105 (June 1999)     

Hydrodynamics and Platoon Formation for a Totally Asymmetric Exclusion Model with Particlewise Disorder

We consider a one-dimensional totally asymmetric exclusion model with quenched random jump rates associated with the particles, and an equivalent interface growth process on the square lattice. We obtain rigorous limit theorems for the shape of the interface, the motion of a tagged particle, and the macroscopic density profile on the hydrodynamic scale. The theorems are valid under almost every realization of the disordered rates. Under suitable conditions on the distribution of jump rates the model displays a disorder-dominated low-density phase where spatial inhomogeneities develop below the hydrodynamic resolution. The macroscopic signature of the phase transition is a density discontinuity at the front of the rarefaction wave moving out of an initial step-function profile. Numerical simulations of the density fluctuations ahead of the front suggest slow convergence to the predictions of a deterministic particle model on the real line, which contains only random velocities but no temporal noise.