Microphysics of compact-star matter: nuclear correlations and constraints across densities

Although compact stars are commonly regarded as laboratories of high-density matter, their consistent modeling also relies critically on the description of nuclear matter from dilute conditions up to densities around saturation. In neutron-rich matter, microscopic constraints from ab initio calculations at sub-saturation densities can be incorporated into flexible phenomenological descriptions of the nuclear equation of state and combined with other sources of information within a Bayesian framework, illustrating the impact of low-density nuclear physics on neutron-star crust properties. Across this density range, a further challenge arises from nuclear correlations: light nuclear clusters can form and, at finite temperature, remain relevant over a wide region of the phase diagram. Their properties are strongly modified by the surrounding medium through Pauli blocking, ultimately leading to their Mott dissolution. I will discuss recent developments aimed at incorporating these effects within density-functional approaches, focusing on their impact on the composition, equation of state, and thermodynamic response of stellar matter under conditions relevant to proto-neutron stars and neutron-star merger remnants. The broader goal is to combine this phenomenological modeling, informed also by constraints from nuclear experiments, with microscopic benchmarks, toward a more consistent description of compact-star matter.