Symmetry energy in the KIDS framework and extension to quarkionic matter

Abstract

Abstract Recent and ongoing laboratory experiments on nuclei and astronomical observations of neutron stars and gravitational waves offer valuable information on the symmetry energy and its dependence on the baryonic density ρ, S(ρ). Analytical models abound for the behavior of S(ρ) in the nucleonic regime. At high densities, however, extrapolations from the nucleonic regime become unreliable and the functional form of S(ρ) should be properly adjusted. Conveniently, the pseudoconformal symmetry emergent in dense, topologically altered nuclear matter suggests a simple expression for the energy per baryon in terms of ρ. Here, I consider a rudimentary interpolation between the Korea-IBS-Daegu-SKKU (KIDS) nucleonic equation of state (EoS) and a pseudo-conformal one at zero temperature. I assume for simplicity that the conformal limit is reached abruptly, but under continuous energy and pressure. Application to neutron stars suggestes that a crossover to quarkionic matter can lead to more compact stars or even heavier stars, depending on the precise form of the nucleonic EoS and on the order of the transition to quarkionic matter. These results are in line with previous studies of hybrid EoSs and represent only a “baby step” to further explorations with hybrid-KIDS EoSs.