Search

The effect of Lorentz invariance breaking on the production rate and the equation of state at finite temperature is investigated in the frame of 3 theory. The invariance breaking significantly changes the off-shell degree at high temperatures.

A recently developed expansion method for analytically solving the ground states of strongly coupling Schrodinger equations by Friedberg, Lee, and Zhao is extended to excited states and applied to power-law central forces for which scaling properties are proposed. As examples for application of the extended method, the Hydrogen atom problem is resolved and the low-lying states of Yukawa potential are approximately obtained.

Meson corrections on the chiral condensate up to next-to-leading order in a 1/Nc expansion at finite densityare investigated in the NJL model with explicit chiral symmetry breaking. Compared with mean-field results, the chiralphase transition is still of the first order while the properties near the critical density for chiral phase transition are foundto change significantly.

The decay process σ → ππ at high temperature and density and its relation with chiral phase transition are discussed in the framework of the Nambu–Jona-Lasinio model. The decay rate for the process σ → ππ is calculated in the whole temperature and density region. The contribution of the final state pion statistics to the decay rate is discussed. The maximum decay rate at different chemical potentials is computed. Finally, we investigate the relation between the starting point of the decay process and the critical point of the first-order chiral phase transition.

In the chiral symmetry breaking phase described by the NJL model at quark level, along with the chiral symmetry restoration the ratio of shear viscosity to entropy density η/s drops down monotonously and reaches the minimum at the critical point, while the ratio of bulk viscosity to entropy density ζ/s behaves oppositely.

In color superconductor the gluon condensate drops down at moderate density but goes up at high density and can even exceed its vacuum value when the density is high enough.

Meson-nucleon scatterings are investigated in an SU(3) × SU(3) σ model with scalar, vector, pseudoscalar and pseudovector couplings between mesons and baryons. From the calculation of effective coupling constants, sigma terms and s-wave scattering lengths for πN and K+N scatterings in the tree approximation, we find that the pseudoscalar coupling dominates s- and u-channel baryon Born terms, and the cancellation between the scalar and vector interactions leads to reasonable meson-nucleon scattering properties.

We investigate nucleon mass splitting at finite isospin chemical potential in the frame of two flavor Nambu--Jona-Lasinio model. It is analytically proved that, in the phase with explicit isospin symmetry breaking the proton mass decreases and the neutron mass increases linearly in the isospin chemical potential., Comment: 3 pages and no figures

A more general expression for the quark propagator including both chiral and diquark condensates has been derived by using energy projectors. This makes it possible to study the phase transition from the hadron phase to the colour-superconductivity phase in the moderate baryon density region by using the Feynman diagrammatic method or the Green function method.

Colour superconductivity is investigated in the frame of a two flavour instanton-induced model. The ratio of diquark to quark-antiquark coupling constants is restricted to be c/(Nc-1) with 1≤c≤2.87 and controls the formation region and amplitude of colour superconductivity. While the finite current quark mass changes the chiral transition significantly, it does not considerably change the colour superconductivity.

The relation between the formation time and the intranuclear cascading in high-energy hA collisions is discussed. By comparing the final-state rapidity distribution obtained from a simple model with the experimental data, the appropriate formation time is estimated as about 1 fm.

The energy, target-mass, and rapidity-window independence or approximate independence of the multiplicity moments in high-energy nucleus-nucleus collisions are analyzed. It is pointed out that all of these properties are due to nuclear geometry. It is proved under general conditons that, when the target mass is not extremely light and the rapidity window not very narrow, the normalized moments of multiplicity are approximately equal to that of the number of participating nucleons. The calculated results for both minimum-bias and central events agree with recent experimental data.

Intranuclear cascade, one of the most important non-linear effects in high energy nucleus-nucleus collisions, is investigated, its influence on the target mass dependence of the distributions of final state particles is discussed. Using hydrodynamical model to treat non-linear effects, the main features of the rapidity distributions and their dependence on the target mass are naturally explained. The results of numerical calculation for16O-A central collisions at 60 and 200A GeV agree with the existing data.

The rapidity distributions of shower particles in high-energy nucleus-nucleus collisions are investigated and compared with that in hadron-hadron and hadron-nucleus collisions. The remarkable difference in the correlation between rapidity distribution and multiplicity in the three cases, as well as the scaling of rapidity distribution in the target region and the nonscaling of the same distribution in the central region, are explained.