Speaker
Description
Most current neutron star EoS inferences are intentionally agnostic: they reconstruct the cold beta-equilibrated pressure-density relation without committing to a microscopic composition. This is appropriate for masses, radii, and tidal deformabilities. Still, it leaves out quantities that depend on the off-equilibrium energy functional, such as composition, frozen sound speeds, direct-Urca thresholds, buoyancy, and transport inputs. Therefore, we developed a framework that, under the nucleonic hypothesis, remains agnostic about the effective microphysics by using a flexible metamodel for the energy density as a function of density and asymmetry: The aim is not to replace fully agnostic inference, but to provide a composition-aware null model that can be validated against alternative parametrisations in the same way as barotropic frameworks are compared today. This new framework may be useful both for Bayesian inference of composition-sensitive observables and as a compact alternative to tabulated EoSs in simulations, with finite-temperature extensions under development.
Based on: "An Asymptotically Causal Metamodel for Neutron Star Equations of State", Montefusco et al. (2026), https://arxiv.org/abs/2604.00196