Speaker
Description
Describing nuclear matter across the extreme range of densities, temperatures, and isospin asymmetries encountered in astrophysical environments remains a challenge. This is particularly critical for binary neutron star mergers, where both dense matter and clusterized low-density phases influence observable signals. In addition, r-process nucleosynthesis in the ejecta requires reliable nuclear structure inputs for thousands of neutron-rich nuclei.
We build on the Brussels-Skyrme-on-a-Grid (BSkG) framework, which provides a unified and accurate description of nuclear structure and neutron star matter, including nuclear masses and fission barriers. Focusing on the BSkG4 parameterization [1], we construct a new finite-temperature equation of state (EoS) covering the range of conditions encountered in merger simulations.
At sub-saturation densities, we describe inhomogeneous matter within a temperature-dependent extended Thomas-Fermi (TETF) approach [2], enabling a consistent semi-classical treatment of nuclei embedded in a nucleon fluid. This approach captures the composition and thermodynamics of clusterized matter in an efficient and accurate framework.
We implement the resulting EoS in numerical-relativity simulations of binary neutron star mergers using the BAM code [3] and present first exploratory results. We discuss the impact of the new microphysics on the properties of the ejecta and related observables, including neutrino emission and kilonova signals. These results illustrate the role of a consistent nuclear physics description in multi-messenger astrophysics.
[1] G. Grams, N. Shchechilin, A. Sanchez-Fernandez, W. Ryssens, N. Chamel, and S. Goriely. EPJA, 61, 35, (2025).
[2] G. Grams, N. Shchechilin, T. Diverrès, A. Fantina, N. Chamel, and F. Gulminelli. Universe 11, 6 (2025).
[3] H. Gieg, F. Schianchi, M. Ujevic, and T. Dietrich, PRD 112, 023036 (2025).