Sound velocity and tidal deformability in compact stars

The sound velocity vs and dimensionless tidal deformability Λ are analyzed using the pseudo-conformal model we developed before. In contrast to the conclusion obtained in the previous works in the literature, our model with the upper bound of the sound velocity vs=1/3, the so-called conformal sound velocity, set in at a density relevant to compact stars ≳2n0 where n0 is the normal nuclear matter density, can accommodate all presently established nuclear matter and compact-star properties including the maximum star-mass constraint ≃2.3 M⊙. This observation is associated with a possible emergence of pseudoconformal structure in compact star matter-in which the trace of energy-momentum tensor is a nearly density-independent nonzero constant-brought in by a topology change at 2.0≲n1/2/n0≲4.0 commensurate with a possible change of degrees of freedom from hadrons.