Spinodal instabilities in symmetric nuclear matter within a density-dependent relativistic mean-field approach

Danışman, Betül
The nuclear matter liquid-gas phase transition is expected to be a signal of nuclear spinodal instabilities as a result of density fluctuations. Nuclear spinodal instabilities in symmetric nuclear matter are studied within a stochastic relativistic density-dependent model in semi-classical approximation. We use two parameterization for the Lagrange density, DDME1 and TW sets. The early growth of density fluctuations is investigated by employing relativistic Vlasov equation based on QHD and discussed the cluster size of the condensations from the early growth of density correlation functions. Expectations are that hot nuclear matter behaves unstable around ρb ≈ ρ0/4 (below the saturation density) and at low temperatures. We therefore present our results at low temperature T=1 MeV and at higher temperature T=5 MeV, and also at a lower initial baryon density ρb = 0.2 ρ0 and a higher value ρb = 0.4 ρ0 where unstable behavior is within them. Calculations in density-dependent model are compared with the other calculations obtained in a relativistic non-linear model and in a Skyrme type nonivrelativistic model. Our results are consistent with them. Qualitatively similar results show that the physics of the quantities are model-independent. The size of clusterization is estimated in two ways, by using half-wavelength of the most unstable mode and from the width of correlation function at half maximum. Furthermore, the average speed of condensing fragments during the initial phase of spinodal decomposition are determined by using the current density correlation functions.


Spinodal instabilities in nuclear matter in a stochastic relativistic mean-field approach
Ayik, S.; Yılmaz Tüzün, Özgül; Er, N.; Gokalp, A.; Ring, P. (American Physical Society (APS), 2009-09-01)
Spinodal instabilities and early growth of baryon density fluctuations in symmetric nuclear matter are investigated in the basis of the stochastic extension of the relativistic mean-field approach in the semiclassical approximation. Calculations are compared with the results of nonrelativistic calculations based on Skyrme-type effective interactions under similar conditions. A qualitative difference appears in the unstable response of the system: the system exhibits most unstable behavior at higher baryon d...
Spinodal instabilities in symmetric nuclear matter within a nonlinear relativistic mean-field approach
Acar, Fatma; Yılmaz, Osman; Department of Physics (2011)
Spinodal instability mechanism and early development of density fluctuations for symmetric nuclear matter at finite temperature are studied. A stochastic extension of Walecka-type relativistic mean-field model including non-linear self-interactions of scalar mesons with NL3 parameter set is employed in the semi-classical approximation. The growth rates of unstable collective modes are investigated below the normal density and at low temperatures. The system exhibits most unstable behavior in longer wave len...
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Ayik, S.; Yilmaz, B.; Yılmaz, Osman; Umar, A. S. (2019-07-01)
Employing a quantal diffusion description based on the stochastic mean-field approach, we analyze the mass distribution of the primary fragments in the collisions of the Xe-136 + Pb-208 system at the bombarding energy E-c.m. = 526 MeV. This quantal approach provides a good description of the primary fragment distribution without any adjustable parameter, including the effects of shell structure
Quantum statistical effects on fusion dynamics of heavy ions
Ayik, S; Yilmaz, B; Gokalp, A; Yılmaz, Osman; Takigawa, N (American Physical Society (APS), 2005-05-01)
To describe the fusion of two very heavy nuclei at near barrier energies, a generalized Langevin approach is proposed. The approach incorporates the quantum statistical fluctuations in accordance with the fluctuation and dissipation theorem. It is illustrated that the quantum statistical effects introduce an enhancement of the formation of a compound nucleus, though the quantum enhancement is somewhat less pronounced as indicated in the previous calculations.
RPA instabilities in finite nuclei at low density
Jacquot, B; Colonna, M; Ayik, S; Chomaz, P (Elsevier BV, 1997-05-12)
Early development of the instabilities in a dilute nuclear source is investigated using a finite temperature quantal RPA approach for different systems, The growth rates of the unstable collective modes are determined by solving a dispersion relation, which is obtained by parametrizing the transition density in terms of its multipole moments. Under typical conditions of a dilute finite system at moderate temperatures the dispersion relation exhibits an ultraviolet cut-off. As a result, only a finite number ...
Citation Formats
B. Danışman, “Spinodal instabilities in symmetric nuclear matter within a density-dependent relativistic mean-field approach,” M.S. - Master of Science, Middle East Technical University, 2011.