The sound velocity $v_s$ and dimensionless tidal deformability $\mathrm{\Lambda }$ 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 $v_s=1/\sqrt{3}$, the so-called conformal sound velocity, set in at a density relevant to compact stars $\gtrsim 2n_0$ where $n_0$ is the normal nuclear matter density, can accommodate all presently established nuclear matter and compact-star properties including the maximum star-mass constraint $\simeq 2.3M_{\odot }$. 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 $2.0\lesssim n_{1/2}/n_0\lesssim 4.0$ commensurate with a possible change of degrees of freedom from hadrons.

• Received 28 November 2018
• Revised 25 January 2019

DOI:https://doi.org/10.1103/PhysRevD.100.114003