Search

We describe a multi-messenger interpretation of GW170817, which yields a robust lower limit on NS radii. This excludes NSs with radii smaller than about 10.7 km and thus rules out very soft nuclear matter. We stress the potential of this type of constraints when future detections become available. For instance, a very similar argumentation may yield an upper bound on the maximum mass of nonrotating NSs. We also discuss simulations of NS mergers, which undergo a first-order phase transition to quark matter. We point out a different dynamical behavior. Considering the gravitational-wave signal, we identify an unambiguous signature of the QCD phase transition in NS mergers. We show that the occurrence of quark matter through a strong first-order phase transition during merging leads to a characteristic shift of the dominant postmerger frequency. The frequency shift is indicative for a phase transition if it is compared to the postmerger frequency which is expected for purely hadronic EoS models. A very strong deviation of several 100 Hz is observed for hybrid EoSs in an otherwise tight relation between the tidal deformability and the postmerger frequency. In future events the tidal deformability will be inferred with sufficient precision from the premerger phase, while the dominant postmerger frequency can be obtained when current detectors reach a higher sensitivity in the high-frequency range within the next years. Finally, we address the potential impact of a first-order phase transition on the electromagnetic counterpart of NS mergers. Our simulations suggest that there would be no significant qualitative differences between a system undergoing a phase transition to quark matter and purely hadronic mergers. The quantitative differences are within the spread which is found between different hadronic EoS models. This implies on the one hand that GW170817 is compatible with a possible transition to quark matter. On the other hand these considerations show that it may not be easy to identify quantitative differences between purely hadronic mergers and events in which quark matter occurs considering solely their electromagnetic counterpart or their nucleosynthesis products. [ABSTRACT FROM AUTHOR]

We discuss the possible phase structure of strongly interacting matter in the regime of high densities and low temperatures where the quarks are expected to be in a color superconducting state. We focus on the additional constraints imposed by the requirement of electric and color neutrality which is essential for the description of neutron star interiors. To that end we employ a 3-flavor NJL-type quark model, which treats the diquark condensates and the quark-antiquark condensates on an equal footing. The resulting phase diagram at zero temperature and the various independent chemical potentials turns out to be very rich, containing at least five different color superconducting phases. We search for regions of electrically and color neutral matter and also discuss the possibility of mixed phases with zero net charge. Neglecting surface and Coulomb effects we find nine different mixed phases with up to four components. Preliminary estimates indicate, however, that the mixed phases become unstable if surface and Coulomb effects are included. [ABSTRACT FROM AUTHOR]