Quantal description of spinodal instabilities in asymmetric nuclear matter

---

Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: FATMA ACAR ÇAKIRÇA

Danışman: OSMAN YILMAZ

Özet:

Spinodal instability mechanism and early development of density fluctuations for asymmetric hot nuclear matter produced in heavy-ion collisions are investigated in non-relativistic and relativistic stochastic mean-field approaches. In relativistic approach, a stochastic extension of the relativistic mean-field approximation based on non-linear Walecka model employed in a quantal framework. The mediator rho meson is added to the Walecka model in order to investigate the isospin dependence of the system. The growth rates of the unstable collective modes are calculated and the boundary of the spinodal region is obtained from the phase diagram for different initial conditions at different asymmetries. In general, growth of instabilities becomes slower with increasing charge asymmetry. The baryon density correlation function that includes information about the initial size of the condensing fragments is also calculated for the collective modes. In the non-relativistic framework, a complete treatment of density correlation functions is presented by including collective modes and non-collective modes as well. The growth of density fluctuations in the spinodal region of asymmetric nuclear matter is investigated in the stochastic mean-field approach based on Skyrme-type effective interactions. It is possible to derive nearly analytical expression for the density correlation function in the linear response limit of the stochastic mean-field approach, which involves a counter integration over the complex frequency plane. In order to provide a complete description of the correlation function,we evaluate collective and also non-collective poles in numerical calculations. These investigations will allow us to obtain more accurate information about the condensation mechanism and early evolution of liquid-gas phase transformation of nuclear matter.