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4. Nuclear Physics (CSN3)

Neutron star and dense nuclear matter with phenomenological short distance repulsion.

by Jesper Leong (University of Adelaide, Australia)

Aula Salvini (LNF)

Aula Salvini



The nuclear equation of state is well known at the low-density from the study of finite nuclear. Conversely, perturbative QCD describes nuclear matter existing as deconfined quark-gluon plasma when the densities become extremely high. However, the intermediate range is yet to be determined. To nuclear theorist neutron stars are interesting because their core densities sit precisely in this region. Measurements of their mass, radii and now the tidal deformability help constrain the nuclear equation of state. The highest mass stars are now observed to be over 2 solar masses with the possibility of reaching 2.3. What is interesting is that hadronic models, subjected to beta equilibrium, should not predict the existence of heavy neutron stars due to the appearance of hyperons. Hyperons are thought to appear around 3-4 times saturation density and rob pressure generated via neutron degeneracy. This in turn lowers the maximum mass in which the theory can predict. The observation of heavy neutron stars suggest that additional repulsion must be present if one is to reasonably presume strange baryons in the cores of heavy neutron stars.  
In this presentation I will describe in more detail the hyperon crisis and the relevant physics for high density repulsion within the framework of the quark-meson-coupling model (QMC).