Nuclear matter equation of state and astrophysics

Abstract

Neutron-star masses, radii, and inspiral tidal deformabilities now provide quantitative constraints on the cold equation of state (\eos), favoring relatively soft matter around one to two times nuclear saturation density and substantial stiffening at larger density. These bulk constraints, however, do not uniquely determine the microscopic composition of the stellar core. Hyperons, deconfined quarks, quarkyonic matter, and strong first-order phase transitions remain viable possibilities. This article summarizes the present multimessenger status and emphasizes the next challenge---a unified description of strongly interacting matter across catalyzed neutron stars, binary mergers, and heavy-ion collisions. Recent results presented at SQM2026, including new constraints on hyperon interactions and advances in multidimensional equation-of-state modeling, highlight the complementary experimental and theoretical inputs required for this program. The MUSES Calculation Engine provides modular software infrastructure for connecting these inputs to astrophysical and heavy-ion applications.