High-Density Quark Matter in the Cores of Neutron Stars

The dawn of gravitational-wave astronomy has in the past few years opened a new window into the properties of cold and dense matter. In particular, by studying the waveforms emitted by merging neutron-star binanies, one can gain insight into the bulk properties of these dense objects and the behavior of the matter in their cores. It is known that in principle, hadronic matter that is compressed to sufficiently high densities should eventually undergo a deconfinement transition to quark matter; however, due to a lack of first-principles techniques, the exact density where this transition occurs, as well as its precise characteristics, are currently unknown. In this talk, I will show how by combining robust nuclear- and particle-theory input as well as robust astronomical, observational input, we can see evidence for the transition between hadronic and quark matter along the stable neutron-star sequence, indicating that neutron stars probe the transition region of dense QCD. Moreover, I will show that--provided the speed of sound of dense QCD matter is not too extreme--massive neutron stars likely host sizable quark-matter cores, a scenario which is completely consistent with all current observations of these objects.