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Correlations between bulk parameters in relativistic and nonrelativistic hadronic mean-field models

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 Publication date 2015
  fields Physics
and research's language is English




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In this work, we study the arising of correlations among some isoscalar ($K_o$, $Q_o$, and $I_o$) and isovector ($J$, $L_o$, $K_{sym}^o$, $Q_{sym}^o$, and $I_{sym}^o$) bulk parameters in nonrelativistic and relativistic hadronic mean-field models. For the former, we investigate correlations in Skyrme and Gogny parametrizations, as well as in the nonrelativistic (NR) limit of relativistic point-coupling models. We provide analytical correlations among bulk parameters for the NR limit, discussing the conditions in which they are linear ones. Based on a recent study [B. M. Santos et al., Phys. Rev. C 90, 035203 (2014)], we also show that some correlations presented in the NR limit are reproduced for relativistic models presenting cubic and quartic self-interactions in the scalar field $sigma$, mostly studied in this work in the context of the relativistic framework. We also discuss how the crossing points, observed in the density dependence of some bulk parameters, can be seen as a signature of linear correlations between the specific bulk quantity presenting the crossing, and its immediately next order parameter.



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Relativistic mean-field (RMF) models have been widely used in the study of many hadronic frameworks because of several important aspects not always present in nonrelativistic models, such as intrinsic Lorentz covariance, automatic inclusion of spin, appropriate saturation mechanism for nuclear matter, causality and, therefore, no problems related to superluminal speed of sound. With the aim of identifying the models which best satisfy well known properties of nuclear matter, we have analyzed $263$ parameterizations of seven different types of RMF models under three different sets of constraints related to symmetric nuclear matter, pure neutron matter, symmetry energy, and its derivatives. One of these (SET1) is formed of the same constraints used in a recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we analyzed $240$ Skyrme parameterizations. The results pointed to $2$ models consistent with all constraints. By using another set of constraints, namely, SET2a, formed by the updat
The present work starts by providing a clear identification of correlations between critical parameters ($T_c$, $P_c$, $rho_c$) and bulk quantities at zero temperature of relativistic mean-field models (RMF) presenting third and fourth order self-interactions in the scalar field $sigma$. Motivated by the nonrelativistic version of this RMF model, we show that effective nucleon mass ($M^*$) and incompressibility ($K_o$), at the saturation density, are correlated with $T_c$, $P_c$, and $rho_c$, as well as, binding energy and saturation density itself. We verify agreement of results with previous theoretical ones regarding different hadronic models. Concerning recent experimental data of the symmetric nuclear matter critical parameters, our study allows a prediction of $T_c$, $P_c$ and $rho_c$ compatible with such values, by combining them, through the correlations found, with previous constraints related to $M^*$ and $K_o$. An improved RMF parametrization, that better agrees with experimental values for $T_c$, is also indicated.
We analyze the localization properties of two-body correlations induced by pairing in the framework of relativistic mean field (RMF) models. The spatial properties of two-body correlations are studied for the pairing tensor in coordinate space and for the Cooper pair wave function. The calculations are performed both with Relativistic-Hatree-Bogoliubov (RHB) and RMF+Projected-BCS (PBCS) models and taking as examples the nuclei $^{66}$Ni, $^{124}$Sn and $^{200}$Pb. It is shown that the coherence length have the same pattern as in previous non-relativistic HFB calculations, i.e., it is maximum in the interior of the nucleus and drops to a minimum in the surface region. In the framework of RMF+PBCS we have also analysed, for the particular case of $^{120}$Sn, the dependence of the coherence length on the intensity of the pairing force. This analysis indicates that pairing is reducing the coherence length by about 25-30 $%$ compared to the RMF limit.
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