Abstract
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.
Highlights
The era of multimessenger astrophysics has enabled theorists working on neutron stars (NSs) to scrutinize their models against new available data
The low-density equations of state (EOSs) was given by a selection of well-established models of nuclear matter, whereas the EOS for both the dense nuclear and quark matter was given by the holographic V-QCD model
We found that all known astronomical bounds can be satisfied if the nuclear matter becomes strongly coupled at one-to-two nuclear saturation densities as described by holography
Summary
The era of multimessenger astrophysics has enabled theorists working on neutron stars (NSs) to scrutinize their models against new available data. An alternate approach is to relax the stringent rules stemming from string theory and to take a more phenomenological bottomup approach: Follow the rules of gauge-gravity duality as closely as possible but allow some freedom in model building Such an effective holographic framework for dense and cold QCD matter has been studied recently in [14,15,16,17] based on models introduced in [18,19,20,21], i.e., improved holographic QCD and V-QCD. In this article we will continue this work by carrying out a detailed analysis of the hybrid EOSs. The goal is to explore all remaining freedom in this construction, arising from the uncertainties in the nuclear matter model as well as the model dependence of the holographic approach, while taking into account the known constraints to the EOS coming from the LIGO/Virgo observations and NS mass measurements. The paper is supplemented with two appendixes containing technical details and discussion on the adiabatic index
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
