Speaker
Description
Unlike the widely used Walecka-type models for studying nuclear matter properties and neutron star structures, we extended the linear sigma model, originally developed by Schechter and his colleagues, to the baryonic sector to explore dense nucleon systems. This extended framework is termed the baryonic extended linear sigma model (bELSM).
The bELSM incorporates 2-quark and 4-quark configurations to address the P-wave problem of the lowest-lying scalar meson, sigma. Beyond its original purpose, the model offers a systematic way to include delta mesons and hyperons, guided by the chiral symmetry pattern. By employing the relativistic mean field theory, we introduced density effects, revealing a plateau-like behavior of symmetry energy at intermediate densities. This outcome aligns with the FSU-delta model results, where delta mesons were included to resolve inconsistencies between the properties of (^{208})Pb and the tidal deformation of neutron stars observed in GW170817. Notably, the delta meson couplings, including (g_{\delta NN}) and its interactions with sigma, differ significantly from those in Walecka-type models that include delta meson dynamics.
An intriguing discovery is that, when incorporating all possible leading-order terms, the squared sound velocity approaches (1/3) at high densities, following parameters determined by empirical data. As the bELSM encodes the chiral symmetry pattern of QCD, it offers valuable insights into how QCD phenomena impact macroscopic observations.
Additionally, I aim to present some preliminary results for the SU(3) case, as well as introduce an AI-driven platform designed to navigate the complex parameter space of low-energy effective theories and models.
