Semi-classical description of spinodal instabilities of asymmetric nuclear matter in a relativistic stochastic model

Saatçi, Selen
A hot and dense nuclear matter expands and cools down. It may enter the spinodal region, where uniform matter is mechanically unstable. Small amplitude density fluctuations grow rapidly and leads to formation of nuclear clusters, called nuclear multifragmentation process. It is considered that the spinodal instability provides a dynamical mechanism for liquid-gas phase transformation of nuclear matter. In this work, the spinodal dynamics of the asymmetric nuclear matter is studied within the stochastic extension of the relativistic mean field approximation based on a nonlinear Walecka Model. The early growth of the density fluctuations and the primary size of the condensation regions are investigated in the semi-classical limit. The mediator rho meson is added to the Walecka model in order to generate the isospin dependence of the nuclear matter. The growth rates of the most unstable modes are determined with the corresponding shortest growth times. In order the specify the temperature and isospin asymmetry dependence of the system, the calculations are implemented for different initial conditions at different asymmetries. The most unstable activity is occurred in the symmetric nuclear matter and decreases as the system becomes richer in neutrons. The baryon density correlation function is also presented as a function of the distance between two space points and the early size of the condensing regions are determined. The results are found to be consistent with the ranges of the dispersion relation for the most unstable modes. Also, the boundary of the spinodal region is evaluated for the cases with different asymmetries and the isospin dependence of the nuclear matter is observed in this way.
Citation Formats
S. Saatçi, “Semi-classical description of spinodal instabilities of asymmetric nuclear matter in a relativistic stochastic model,” M.S. - Master of Science, Middle East Technical University, 2013.