Unified weak and strong coupling framework for nuclear matter and neutron stars
Niko Jokela (Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014, Finland, Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FIN-00014, Finland); Matti Järvinen (The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978, Israel, Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea, Asia Pacific Center for Theoretical Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea); Govert Nijs (Institute for Theoretical Physics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands); Jere Remes (Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014, Finland, Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FIN-00014, Finland)
Ab initio methods using weakly interacting nucleons give a good description of condensed nuclear matter up to densities comparable to the nuclear saturation density. At higher densities strong interactions between overlapping nucleons become important; we propose that the interactions will continuously switch over to follow a holographic model in this region. In order to implement this, we construct hybrid equations of state (EOSs) where various models are used for low-density nuclear matter, and the holographic V-QCD model is used for nonperturbative high-density nuclear matter as well as for quark matter. We carefully examine all existing constraints from astrophysics of compact stars and discuss their implications for the hybrid EOSs. Thanks to the stiffness of the V-QCD EOS for nuclear matter, we obtain a large family of viable hybrid EOSs passing the constraints. We find that quark matter cores in neutron stars are unstable due to the strongly first-order deconfinement transition and predict bounds on the tidal deformability as well as on the radius of neutron stars. By relying on universal relations, we also constrain characteristic peak frequencies of gravitational waves produced in neutron star mergers.
