  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 palpable 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 non-perturbative 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.
