Ricerc@Sapienza

Neutron Stars (NSs) are extremely compact objects, in wich matter reaches extreme conditions that are inaccessible by Earth-based experiments. To improve the present understanding of the properties of NS matter encoded the Equation of State (EOS)--that is, the relation linking pressure and energy density--one has to resort largely to the astrophysical data that are being collected by the rapidly evolving multimessenger astronomy. Gravitational waves (GWs) from a binary NS merger were first detected in event GW170817, and the upcoming third generation of GW detectors are even more promising. Moreover, missions aimed at studying the NS radius, such as NICER, have already provided measurements that point to a bright future. In general, matter in the inner region of a cold NS can be modelled as a charge-neutral perfect fluid consisting of nucleons and leptons in beta equilibrium, in which strong interactions dominate nucleon-nucleon forces. It has been also pointed out, however,that a phase transition to more exotic forms of matter, leading to the appearance of, e.g., strange baryons or even deconfined quarks, could eventually take place in the innermost region of massive NSs.

In order to study these two scenarios, we plan to (i) develop a novel EOS of nuclear matter--obtained from a microscopic dynamical model using the formalism of Correlated Basis Functions (CBF)--and (ii) investigate how a physically motivated quark extension would be connected to it. We will adopt a fully Bayesian framework to constrain the properties of both phases using astrophysical data. Thermal effects, relevant in the merger and post-merger stages of NS cohalescence, will be also studied using a suitable generalisation of the formalism.