Reaching percolation and conformal limits in neutron stars

TL;DR

This paper uses multimessenger constraints to analyze the dense matter inside neutron stars, showing that the speed of sound approaches conformal limits and relates to QCD deconfinement, with implications for critical phenomena.

Contribution

It provides a statistical analysis of neutron star matter properties, linking the speed of sound and trace anomaly to conformal limits and QCD deconfinement conditions.

Findings

Speed of sound approaches conformal values at neutron star centers.

Peak of the speed of sound aligns with deconfinement densities.

Fluctuations suggest critical behavior beyond neutron star densities.

Abstract

Generating an ensemble of equations of state that fulfill multimessenger constraints, we statistically determine the properties of dense matter found inside neutron stars (NSs). We calculate the speed of sound and trace anomaly and demonstrate that they are driven towards their conformal values at the center of maximally massive NSs. The local peak of the speed of sound is shown to be located at values of the energy and particle densities which are consistent with deconfinement and percolation conditions in QCD matter. We also analyze fluctuations of the net-baryon number density in the context of possible remnants of critical behavior. We find that the global maxima of the variance of these fluctuations emerge at densities beyond those found in the interiors of NSs.