Towards the hadron-quark continuity via a topology change in compact stars

We construct a generalized effective field theory approach to dense compact-star matter that exploits the Cheshire Cat Principle for hadron-quark continuity at high density, adhering only to hadronic degrees of freedom, hidden topology and hidden symmetries of QCD. No Landau-Ginzburg-Wilsonian-type phase transition is involved in the range of densities involved. The microscopic degrees of freedom of QCD, i.e., quarks and gluons, possibly intervening at high baryonic density are traded in for fractionalized topological objects. Essential in the description are symmetries invisible in QCD in the matter-free vacuum: Scale symmetry, flavor local symmetry and parity-doubling. The partial emergence of scale symmetry is signaled by a dilatonic scalar in a "pseudo-conformal'' structure. Flavor gauge symmetry manifests with the rho meson mass going toward a Wilsonian RG fixed point identified with the "vector manifestation fixed point (VMFP)'' at which the flavor gauge boson mass goes to zero. Parity doubling is to take place as the quasi-nucleon mass converges to the chiral invariant m(0). The theory with a few controllable parameters accounts satisfactorily for all known properties of normal nuclear matter and makes certain predictions that are drastically different from what is available in the literature. In particular, it provides a topological mechanism, argued to be robust, for the cross-over from soft-to-hard equation of state that predicts the star properties in overall agreement with the presently available data, including the maximum star mass M-max similar to 2.3M(circle dot) and the recent LIGO/Virgo gravity-wave data. What is most glaringly different from all other approaches known, however, is the prediction for the rapid convergence to a sound velocity of star v(s)(2) approximate to 1/3 (in unit c = 1) at a density n greater than or similar to 3n(0), far from the asymptotic density greater than or similar to 50n(0) expected in perturbative QCD. We interpret this to signal the onset of albeit approximate conformal symmetry in dense compact-star matter. We argue that models that properly implement quark degrees of freedom at high densities in the sense of the hadron-quark continuity should, with the parameters fine-tuned, arrive at a qualitatively similar pseudo-conformal structure. The model developed in this paper, if validated by observations, could bring out a new paradigm in nuclear/hadron physics, exploiting ideas ubiquitous in various areas of physics, condensed matter physics, nuclear and particle physics and astrophysics. (C) 2020 Elsevier B.V. All rights reserved.