Equations of State of Superdense Nuclear Matter for Use in Neutron Star Merger Simulations

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The observation of the first binary neutron star merger named GW170817 using LIGO and VIRGO led the scientific community into the era of multi-messenger astronomy with gravitational waves. Numerical relativity simulations have shown that the pressure-density relationship (known as equation of state) of hot and dense matter plays a fundamental role in simulating the collisions of neutron stars. Neutron stars are up to twice as massive as our Sun but are typically only around 20 kilometers across. At such extraordinary densities, atomic nuclei collapse, and neutrons and protons are squeezed so tightly together that they may disintegrate into a plasma made of up and down quarks, which are the most fundamental building blocks of matter. The goal of this project is to determine a comprehensive set of state-of-the art models for the equation of state of superdense nuclear matter for use by researchers working on neutron-star merger simulations. In particular, the group will investigate the role of quarks for neutron-star mergers and identify possible signals by means of which quarks may register themselves in the gravitational-wave signals produced by merging neutron stars. The models for the equation of state will be made available to the community at online services (CompOSE, StellarCollapse). Graduate and undergraduate students at San Diego State University will be trained in areas of physics which are richly interdisciplinary and enrich their educational experience beyond what they learn in the classroom.The overarching goal of this project is to determine a comprehensive set of state-of-the art models for the equation of state of hot and dense nuclear matter for use by researchers working on neutron-star merger simulations. Contemporary effective field theoretical models, i.e., the relativistic density-dependent Hartree (DDRMF) model and the (local and the non-local) 3-flavor Polyakov-Nambu-Jona-Lasinio (3PNJL) model, will be used to accomplish this goal. The DDRMF is a versatile and numerically tractable nuclear many-body theory well suited for studies of dense and dense hadronic matter. The 3PNJL model is an effective model of quantum chromodynamics which allows for a contemporary modeling of quark matter. It provides a functional and numerically tractable approach to quantum chromodynamics. The model accounts for the dynamical breaking of chiral symmetry and mimics quark confinement via the Polyakov-loop potential. Quark deconfinement at zero and finite temperature will be studied using both the Gibbs and Maxwell condition for phase equilibrium. The strongest, currently possible constraints from nuclear theory, nuclear experiment, and astrophysics will be used to fix the parameters of the effective field theories and test the validity of the equations of state.This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.