Abstract
We use the holographic V-QCD models to analyse the physics of dense QCD and neutron stars. Accommodating lattice results for thermodynamics of QCD enables us to make generic predictions for the Equation of State (EoS) of the quark matter phase in the cold and dense regime. We demonstrate that the resulting pressure in V-QCD matches well with a family of neutron-star-matter EoSs that interpolate between state-of-the-art theoretical results for low and high density QCD. After implementing the astrophysical constraints, i.e., the largest known neutron star mass and the recent LIGO/Virgo results for the tidal deformability, we analyse the phase transition between the baryonic and quark matter phases. We find that the baryon density nB at the transition is at least 2.9 times the nuclear saturation density ns. The transition is of strongly first order at low and intermediate densities, i.e., for nB/ns ≲ 7.5.
Highlights
The gauge/gravity duality may provide us with a way forward
We aim at progress in predicting the Equation of State (EoS) of dense QCD matter by using more realistic holographic models, which break conformal symmetry, include confinement, and are able to model the dynamics of real QCD with good precision
We present the numerical results for thermodynamics that stem from extrapolating the holographic EoS down to finite chemical potentials and to zero temperature
Summary
In this work we will be using a class of holographic models for QCD (V-QCD) [8]. These models are effective bottom-up models containing both gluons and dynamical quarks which are fully backreacted to the glue in the Veneziano limit: Nc → ∞ and. In this article we will concentrate on chirally symmetric backgrounds describing the deconfined phase of QCD so that τ = 0. The Ansatz for the metric can be written as ds2 = e2A(r) f (r)−1dr2 − f (r)dt2 + dx2 The thermodynamics in this model has been discussed at zero μ in [21] and at nonzero μ in [22], by using potentials that reproduce various features of QCD at qualitative level. We will compare the predictions of the V-QCD model to lattice data at zero chemical potential. This comparison strongly favors potentials producing phase diagrams with no intermediate (deconfined but chirally broken) phase. In the absence of the intermediate phase, the model will only have nontrivial thermodynamics in the deconfined phase. We will concentrate on analysing the results in this phase in the rest of the article
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