International Journal of Modern Physics E

The contributions of the pion-cloud to the magnetic moments of the nucleon octet is investigated in a chiral symmetric independent-quark model. The effective potential representing phenomenologically the confining interaction due to the non-perturbative multigluon mechanism is taken in the form . The pion-nucleon coupling constant comes out to be 14.43, as compared to the experimental value 14.1. The results obtained for the magnetic moments of the octet baryons, after incorporating the centre-of-mass motion and the low-order pionic corrections, agree reasonably with the experiment.

We derive an explicit expression for the one-body dissipation which includes effects from the mixing through the neck of the velocity distributions associated to each of the colliding nuclei. This expression may be considered a generalization of the window dissipation formula that covers the transition between the mononuclear and dinuclear regimes.

Nonlinear excitations of nuclear density are considered in the framework of semiclassical nonlinear nuclear hydrodynamics. Possible types of stationary nonlinear waves in nuclear media are analysed using Nonlinear Schrödinger equation of fifth order and classified using a simple mechanical picture. It is shown that a rich spectrum of nonlinear oscillations in one-dimensional nuclear medium exist.

An expression for the optical potential is obtained in the nuclear matter approximation while taking into account the rearrangement potential for the generalized two-particle density-dependent Skyrme forces. The rearrangement potential influence on the nucleon-nucleus scattering is investigated. It is shown that two- and three-particle Skyrme forces are not equivalent in calculating the imaginary part of the optical potential. The intensity of the optical potential (both its real and imaginary parts) appears to be decreased considerably when the rearrangement potential is taken into account. As a result the dependence of scattering phase shifts on the incident nucleons energy is changed markedly.

The information entropy of a nuclear density distribution is calculated for a number of nuclei. Various phenomenological models for the density distribution using different geometries are employed. Nuclear densities calculated within various microscopic mean field approaches are also employed. It turns out that the entropy increases from crude phenomenological models to more sophisticated (microscopic) ones. It is concluded that the larger the information entropy, the better the quality of the nuclear density distribution. An alternative approach is also examined: the net information content, i.e. the sum of information entropies in position and momentum space S_r+S_k. It is indicated that S_r+S_k is a maximum, when the best fit to experimental data of the density and momentum distributions is attained.

The properties of baryonic matter have been investigated at finite density and temperature using different models. The variation of baryon masses and fractional number densities with baryon density and temperature obtained from different models have been compared. The quark hadron phase transition have been studied using Chiral Colour Dieletric (CCD) model in the quark sector. No phase transition have been observed for the different variants of the Zimanyi-Moszkowski models below T=60 MeV.

We present an approach to derive a relativistic kinetic equation of the Vlasov type. Our approach is especially reliable for the description of quantum field systems with many internal degrees of freedom. The method is based on the Heisenberg picture and leads to a kinetic equation which fulfills the conservation laws. We apply the approach to the standard Walecka Lagrangian and an effective chiral Lagrangian.

A quadrupole boson Hamiltonian is considered within a time dependent variational formalism. The trial functions are coherent states with respect to the quadrupole bosons and . The character, chaotic or regular, of the classical trajectories are studied, in terms of both the Poincaré surface of sections and maximal Lyapunov exponents, as a function of energy and an order parameter B, the coefficient of the third order boson term. A peculiar feature concerning the behavior of chaos and order in the range of large energies is pointed out. Quantizing the classical energy function one obtains an operator whose spectrum is analyzed in terms of level spacing distribution, Some classical and quantal features of the chaotic motion are possibly related.