Search

Abstract This review aims at providing an extensive discussion of modern constraints relevant for dense and hot strongly interacting matter. It includes theoretical first-principle results from lattice and perturbative QCD, as well as chiral effective field theory results. From the experimental side, it includes heavy-ion collision and low-energy nuclear physics results, as well as observations from neutron stars and their mergers. The validity of different constraints, concerning specific conditions and ranges of applicability, is also provided.

In this Letter, we present a new, weakly model-dependent test for “standard” equation-of-state (EoS) models that disfavor sharp and strong phase transitions by using NS mass and radius observations. We show the radii of two NSs observed by NICER (PSR J0740+6620 and PSR 0030+0451) are correlated if these two NSs are built upon standard EoS models. The radii of NSs with different masses are sensitive to the pressures at different densities, and the pressures at different densities are strongly correlated in standard EoS models. We further show that the correlation of the NS radii can be significantly weakened when additional degrees of freedom concerning the first-order phase transitions are added into the EoSs. We propose a new quantity, D _L , which measures the extent to which the linear correlation of the radii of two NSs is weakened. Our method gives a 48% identification probability (with a 5% false alarm rate) of finding beyond-standard EoS models in NICER observations. Future observations with higher measurement accuracy can confirm or rule out this identification. Our method is generalizable to any pair of NS masses and can be employed with other sets of observations in the future.