10733730
Nucleon flow and fragment flow in heavy ion reactions.
The collective flow of nucleons and that of fragments in the [sup 12]C+[sup 12]C reaction below 150 MeV/nucleon are calculated with the antisymmetrized version of molecular dynamics combined with the statistical decay calculation. The density dependent Gogny force is used as the effective interaction. The calculated balance energy is about 100 MeV/nucleon, which is close to the observed value. Below the balance energy, the absolute value of the fragment flow is larger than that of nucleon flow, which is also in accordance with data. The dependence of the flow on the stochastic collision cross section and its origin are discussed. All the results are naturally understood by introducing the concept of two components of flow: the flow of dynamically emitted nucleons and the flow of the nuclear matter which contributes to both the flow of fragments and the flow of nucleons due to the statistical decay.
119187846
Hot hadron-quark mixed phase including hyperons
We study the hadron-quark phase transition with the finite-size effects at finite temperature. For the hadron phase, we adopt a realistic equation of state in the framework of the Brueckner-Hartree-Fock theory including hyperons. The properties of the mixed phase are clarified by considering the finite-size effects under the Gibbs conditions. We find that the equation of state becomes softer than that at zero temperature for some density region. We also find that the equation of state gets closer to that given by the Maxwell construction. Moreover, the number of hyperons is suppressed by the presence of quarks. These are characteristic features of the hadron-quark mixed phase, and should be important for many astrophysical phenomena such as mergers of binary neutron stars.
119341714
Quark deconfinement transition in hyperonic matter
Abstract We discuss the properties of the hadron–quark mixed phase in compact stars using a realistic equation of state of hyperonic matter and the MIT bag model. We find that the equation of state of the mixed phase is similar to that given by the Maxwell construction, but that the mixed phase becomes mechanically unstable if the surface tension of the interface between the two pure phases is strong enough. The composition of the mixed phase is very different from that of the Maxwell construction; in particular, hyperons are completely suppressed.
2937697
Critical phenomena in finite systems
We discuss the dynamics of finite systems within molecular dynamics models. Signatures of a critical behavior are analyzed and compared to experimental data both in nucleus-nucleus and metallic cluster collisions. We suggest the possibility to explore the instability region via tunneling. In this way we can obtain fragments at very low temperatures and densities. We call these fragments quantum drops.
10929692
Extension of quantum molecular dynamics and its application to heavy-ion collisions.
In order to treat low-energy heavy-ion reactions, we make an extension of quantum molecular dynamics method. A phenomenological Pauli potential is introduced into effective interactions to approximate the nature of the Fermion many-body system. We treat the widths of nucleon wave-packets as time-dependent dynamical variables. With these modifications, our model can well describe the ground-state properties in wide mass range. Improvements due to the extension are also obtained in the nucleus-nucleus collision calculations.
33155232
Simulation of transitions between "pasta" phases in dense matter.
Calculations of equilibrium properties of dense matter predict that at subnuclear densities nuclei can be rodlike or slablike. To investigate whether transitions between phases with nonspherical nuclei can occur during the collapse of a star, we perform quantum molecular dynamic simulations of the compression of dense matter. We have succeeded in simulating the transitions between rodlike and slablike nuclei and between slablike nuclei and cylindrical bubbles. Our results strongly suggest that nonspherical nuclei can be formed in the inner cores of collapsing stars.
34447702
Collective modes in hot and dense matter.
We propose a model for a relativistic many-body system at finitetemperature in the framework of thermo field dynamics, which is a real-timeformalism of finite-temperature field theory. Our model contains the scalar(sigma) and the vector (..omega..) mesons as well as the Dirac nucleon. Thefull propagator and self-energy for each particle are presented in terms ofspectral representations. The Feynman rules for a perturbation expansion areshown. They are applied to the study of collective modes in hot and densematter within the random-phase approximation. The dispersion relations of thelongitudinal and transverse collective modes in the meson branch arecalculated. We also estimate the effective meson mass which is defined as theenergy needed to create one meson at rest in extreme matter. The effects ofvacuum fluctuations are also examined. They contribute a fair amount to thecollective modes through the effective nucleon mass.